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Diffstat (limited to 'gnu/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp')
| -rw-r--r-- | gnu/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp | 3538 |
1 files changed, 0 insertions, 3538 deletions
diff --git a/gnu/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/gnu/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp deleted file mode 100644 index fef051aa1b7..00000000000 --- a/gnu/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp +++ /dev/null @@ -1,3538 +0,0 @@ -//===- InstructionCombining.cpp - Combine multiple instructions -----------===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// InstructionCombining - Combine instructions to form fewer, simple -// instructions. This pass does not modify the CFG. This pass is where -// algebraic simplification happens. -// -// This pass combines things like: -// %Y = add i32 %X, 1 -// %Z = add i32 %Y, 1 -// into: -// %Z = add i32 %X, 2 -// -// This is a simple worklist driven algorithm. -// -// This pass guarantees that the following canonicalizations are performed on -// the program: -// 1. If a binary operator has a constant operand, it is moved to the RHS -// 2. Bitwise operators with constant operands are always grouped so that -// shifts are performed first, then or's, then and's, then xor's. -// 3. Compare instructions are converted from <,>,<=,>= to ==,!= if possible -// 4. All cmp instructions on boolean values are replaced with logical ops -// 5. add X, X is represented as (X*2) => (X << 1) -// 6. Multiplies with a power-of-two constant argument are transformed into -// shifts. -// ... etc. -// -//===----------------------------------------------------------------------===// - -#include "InstCombineInternal.h" -#include "llvm-c/Initialization.h" -#include "llvm-c/Transforms/InstCombine.h" -#include "llvm/ADT/APInt.h" -#include "llvm/ADT/ArrayRef.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/None.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/ADT/TinyPtrVector.h" -#include "llvm/Analysis/AliasAnalysis.h" -#include "llvm/Analysis/AssumptionCache.h" -#include "llvm/Analysis/BasicAliasAnalysis.h" -#include "llvm/Analysis/CFG.h" -#include "llvm/Analysis/ConstantFolding.h" -#include "llvm/Analysis/EHPersonalities.h" -#include "llvm/Analysis/GlobalsModRef.h" -#include "llvm/Analysis/InstructionSimplify.h" -#include "llvm/Analysis/LoopInfo.h" -#include "llvm/Analysis/MemoryBuiltins.h" -#include "llvm/Analysis/OptimizationRemarkEmitter.h" -#include "llvm/Analysis/TargetFolder.h" -#include "llvm/Analysis/TargetLibraryInfo.h" -#include "llvm/Analysis/ValueTracking.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/CFG.h" -#include "llvm/IR/Constant.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DIBuilder.h" -#include "llvm/IR/DataLayout.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/Function.h" -#include "llvm/IR/GetElementPtrTypeIterator.h" -#include "llvm/IR/IRBuilder.h" -#include "llvm/IR/InstrTypes.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/Intrinsics.h" -#include "llvm/IR/LegacyPassManager.h" -#include "llvm/IR/Metadata.h" -#include "llvm/IR/Operator.h" -#include "llvm/IR/PassManager.h" -#include "llvm/IR/PatternMatch.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/Use.h" -#include "llvm/IR/User.h" -#include "llvm/IR/Value.h" -#include "llvm/IR/ValueHandle.h" -#include "llvm/Pass.h" -#include "llvm/Support/CBindingWrapping.h" -#include "llvm/Support/Casting.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Compiler.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/DebugCounter.h" -#include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/KnownBits.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Transforms/InstCombine/InstCombine.h" -#include "llvm/Transforms/InstCombine/InstCombineWorklist.h" -#include "llvm/Transforms/Utils/Local.h" -#include <algorithm> -#include <cassert> -#include <cstdint> -#include <memory> -#include <string> -#include <utility> - -using namespace llvm; -using namespace llvm::PatternMatch; - -#define DEBUG_TYPE "instcombine" - -STATISTIC(NumCombined , "Number of insts combined"); -STATISTIC(NumConstProp, "Number of constant folds"); -STATISTIC(NumDeadInst , "Number of dead inst eliminated"); -STATISTIC(NumSunkInst , "Number of instructions sunk"); -STATISTIC(NumExpand, "Number of expansions"); -STATISTIC(NumFactor , "Number of factorizations"); -STATISTIC(NumReassoc , "Number of reassociations"); -DEBUG_COUNTER(VisitCounter, "instcombine-visit", - "Controls which instructions are visited"); - -static cl::opt<bool> -EnableCodeSinking("instcombine-code-sinking", cl::desc("Enable code sinking"), - cl::init(true)); - -static cl::opt<bool> -EnableExpensiveCombines("expensive-combines", - cl::desc("Enable expensive instruction combines")); - -static cl::opt<unsigned> -MaxArraySize("instcombine-maxarray-size", cl::init(1024), - cl::desc("Maximum array size considered when doing a combine")); - -// FIXME: Remove this flag when it is no longer necessary to convert -// llvm.dbg.declare to avoid inaccurate debug info. Setting this to false -// increases variable availability at the cost of accuracy. Variables that -// cannot be promoted by mem2reg or SROA will be described as living in memory -// for their entire lifetime. However, passes like DSE and instcombine can -// delete stores to the alloca, leading to misleading and inaccurate debug -// information. This flag can be removed when those passes are fixed. -static cl::opt<unsigned> ShouldLowerDbgDeclare("instcombine-lower-dbg-declare", - cl::Hidden, cl::init(true)); - -Value *InstCombiner::EmitGEPOffset(User *GEP) { - return llvm::EmitGEPOffset(&Builder, DL, GEP); -} - -/// Return true if it is desirable to convert an integer computation from a -/// given bit width to a new bit width. -/// We don't want to convert from a legal to an illegal type or from a smaller -/// to a larger illegal type. A width of '1' is always treated as a legal type -/// because i1 is a fundamental type in IR, and there are many specialized -/// optimizations for i1 types. Widths of 8, 16 or 32 are equally treated as -/// legal to convert to, in order to open up more combining opportunities. -/// NOTE: this treats i8, i16 and i32 specially, due to them being so common -/// from frontend languages. -bool InstCombiner::shouldChangeType(unsigned FromWidth, - unsigned ToWidth) const { - bool FromLegal = FromWidth == 1 || DL.isLegalInteger(FromWidth); - bool ToLegal = ToWidth == 1 || DL.isLegalInteger(ToWidth); - - // Convert to widths of 8, 16 or 32 even if they are not legal types. Only - // shrink types, to prevent infinite loops. - if (ToWidth < FromWidth && (ToWidth == 8 || ToWidth == 16 || ToWidth == 32)) - return true; - - // If this is a legal integer from type, and the result would be an illegal - // type, don't do the transformation. - if (FromLegal && !ToLegal) - return false; - - // Otherwise, if both are illegal, do not increase the size of the result. We - // do allow things like i160 -> i64, but not i64 -> i160. - if (!FromLegal && !ToLegal && ToWidth > FromWidth) - return false; - - return true; -} - -/// Return true if it is desirable to convert a computation from 'From' to 'To'. -/// We don't want to convert from a legal to an illegal type or from a smaller -/// to a larger illegal type. i1 is always treated as a legal type because it is -/// a fundamental type in IR, and there are many specialized optimizations for -/// i1 types. -bool InstCombiner::shouldChangeType(Type *From, Type *To) const { - // TODO: This could be extended to allow vectors. Datalayout changes might be - // needed to properly support that. - if (!From->isIntegerTy() || !To->isIntegerTy()) - return false; - - unsigned FromWidth = From->getPrimitiveSizeInBits(); - unsigned ToWidth = To->getPrimitiveSizeInBits(); - return shouldChangeType(FromWidth, ToWidth); -} - -// Return true, if No Signed Wrap should be maintained for I. -// The No Signed Wrap flag can be kept if the operation "B (I.getOpcode) C", -// where both B and C should be ConstantInts, results in a constant that does -// not overflow. This function only handles the Add and Sub opcodes. For -// all other opcodes, the function conservatively returns false. -static bool MaintainNoSignedWrap(BinaryOperator &I, Value *B, Value *C) { - OverflowingBinaryOperator *OBO = dyn_cast<OverflowingBinaryOperator>(&I); - if (!OBO || !OBO->hasNoSignedWrap()) - return false; - - // We reason about Add and Sub Only. - Instruction::BinaryOps Opcode = I.getOpcode(); - if (Opcode != Instruction::Add && Opcode != Instruction::Sub) - return false; - - const APInt *BVal, *CVal; - if (!match(B, m_APInt(BVal)) || !match(C, m_APInt(CVal))) - return false; - - bool Overflow = false; - if (Opcode == Instruction::Add) - (void)BVal->sadd_ov(*CVal, Overflow); - else - (void)BVal->ssub_ov(*CVal, Overflow); - - return !Overflow; -} - -/// Conservatively clears subclassOptionalData after a reassociation or -/// commutation. We preserve fast-math flags when applicable as they can be -/// preserved. -static void ClearSubclassDataAfterReassociation(BinaryOperator &I) { - FPMathOperator *FPMO = dyn_cast<FPMathOperator>(&I); - if (!FPMO) { - I.clearSubclassOptionalData(); - return; - } - - FastMathFlags FMF = I.getFastMathFlags(); - I.clearSubclassOptionalData(); - I.setFastMathFlags(FMF); -} - -/// Combine constant operands of associative operations either before or after a -/// cast to eliminate one of the associative operations: -/// (op (cast (op X, C2)), C1) --> (cast (op X, op (C1, C2))) -/// (op (cast (op X, C2)), C1) --> (op (cast X), op (C1, C2)) -static bool simplifyAssocCastAssoc(BinaryOperator *BinOp1) { - auto *Cast = dyn_cast<CastInst>(BinOp1->getOperand(0)); - if (!Cast || !Cast->hasOneUse()) - return false; - - // TODO: Enhance logic for other casts and remove this check. - auto CastOpcode = Cast->getOpcode(); - if (CastOpcode != Instruction::ZExt) - return false; - - // TODO: Enhance logic for other BinOps and remove this check. - if (!BinOp1->isBitwiseLogicOp()) - return false; - - auto AssocOpcode = BinOp1->getOpcode(); - auto *BinOp2 = dyn_cast<BinaryOperator>(Cast->getOperand(0)); - if (!BinOp2 || !BinOp2->hasOneUse() || BinOp2->getOpcode() != AssocOpcode) - return false; - - Constant *C1, *C2; - if (!match(BinOp1->getOperand(1), m_Constant(C1)) || - !match(BinOp2->getOperand(1), m_Constant(C2))) - return false; - - // TODO: This assumes a zext cast. - // Eg, if it was a trunc, we'd cast C1 to the source type because casting C2 - // to the destination type might lose bits. - - // Fold the constants together in the destination type: - // (op (cast (op X, C2)), C1) --> (op (cast X), FoldedC) - Type *DestTy = C1->getType(); - Constant *CastC2 = ConstantExpr::getCast(CastOpcode, C2, DestTy); - Constant *FoldedC = ConstantExpr::get(AssocOpcode, C1, CastC2); - Cast->setOperand(0, BinOp2->getOperand(0)); - BinOp1->setOperand(1, FoldedC); - return true; -} - -/// This performs a few simplifications for operators that are associative or -/// commutative: -/// -/// Commutative operators: -/// -/// 1. Order operands such that they are listed from right (least complex) to -/// left (most complex). This puts constants before unary operators before -/// binary operators. -/// -/// Associative operators: -/// -/// 2. Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. -/// 3. Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. -/// -/// Associative and commutative operators: -/// -/// 4. Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. -/// 5. Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. -/// 6. Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" -/// if C1 and C2 are constants. -bool InstCombiner::SimplifyAssociativeOrCommutative(BinaryOperator &I) { - Instruction::BinaryOps Opcode = I.getOpcode(); - bool Changed = false; - - do { - // Order operands such that they are listed from right (least complex) to - // left (most complex). This puts constants before unary operators before - // binary operators. - if (I.isCommutative() && getComplexity(I.getOperand(0)) < - getComplexity(I.getOperand(1))) - Changed = !I.swapOperands(); - - BinaryOperator *Op0 = dyn_cast<BinaryOperator>(I.getOperand(0)); - BinaryOperator *Op1 = dyn_cast<BinaryOperator>(I.getOperand(1)); - - if (I.isAssociative()) { - // Transform: "(A op B) op C" ==> "A op (B op C)" if "B op C" simplifies. - if (Op0 && Op0->getOpcode() == Opcode) { - Value *A = Op0->getOperand(0); - Value *B = Op0->getOperand(1); - Value *C = I.getOperand(1); - - // Does "B op C" simplify? - if (Value *V = SimplifyBinOp(Opcode, B, C, SQ.getWithInstruction(&I))) { - // It simplifies to V. Form "A op V". - I.setOperand(0, A); - I.setOperand(1, V); - // Conservatively clear the optional flags, since they may not be - // preserved by the reassociation. - if (MaintainNoSignedWrap(I, B, C) && - (!Op0 || (isa<BinaryOperator>(Op0) && Op0->hasNoSignedWrap()))) { - // Note: this is only valid because SimplifyBinOp doesn't look at - // the operands to Op0. - I.clearSubclassOptionalData(); - I.setHasNoSignedWrap(true); - } else { - ClearSubclassDataAfterReassociation(I); - } - - Changed = true; - ++NumReassoc; - continue; - } - } - - // Transform: "A op (B op C)" ==> "(A op B) op C" if "A op B" simplifies. - if (Op1 && Op1->getOpcode() == Opcode) { - Value *A = I.getOperand(0); - Value *B = Op1->getOperand(0); - Value *C = Op1->getOperand(1); - - // Does "A op B" simplify? - if (Value *V = SimplifyBinOp(Opcode, A, B, SQ.getWithInstruction(&I))) { - // It simplifies to V. Form "V op C". - I.setOperand(0, V); - I.setOperand(1, C); - // Conservatively clear the optional flags, since they may not be - // preserved by the reassociation. - ClearSubclassDataAfterReassociation(I); - Changed = true; - ++NumReassoc; - continue; - } - } - } - - if (I.isAssociative() && I.isCommutative()) { - if (simplifyAssocCastAssoc(&I)) { - Changed = true; - ++NumReassoc; - continue; - } - - // Transform: "(A op B) op C" ==> "(C op A) op B" if "C op A" simplifies. - if (Op0 && Op0->getOpcode() == Opcode) { - Value *A = Op0->getOperand(0); - Value *B = Op0->getOperand(1); - Value *C = I.getOperand(1); - - // Does "C op A" simplify? - if (Value *V = SimplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) { - // It simplifies to V. Form "V op B". - I.setOperand(0, V); - I.setOperand(1, B); - // Conservatively clear the optional flags, since they may not be - // preserved by the reassociation. - ClearSubclassDataAfterReassociation(I); - Changed = true; - ++NumReassoc; - continue; - } - } - - // Transform: "A op (B op C)" ==> "B op (C op A)" if "C op A" simplifies. - if (Op1 && Op1->getOpcode() == Opcode) { - Value *A = I.getOperand(0); - Value *B = Op1->getOperand(0); - Value *C = Op1->getOperand(1); - - // Does "C op A" simplify? - if (Value *V = SimplifyBinOp(Opcode, C, A, SQ.getWithInstruction(&I))) { - // It simplifies to V. Form "B op V". - I.setOperand(0, B); - I.setOperand(1, V); - // Conservatively clear the optional flags, since they may not be - // preserved by the reassociation. - ClearSubclassDataAfterReassociation(I); - Changed = true; - ++NumReassoc; - continue; - } - } - - // Transform: "(A op C1) op (B op C2)" ==> "(A op B) op (C1 op C2)" - // if C1 and C2 are constants. - Value *A, *B; - Constant *C1, *C2; - if (Op0 && Op1 && - Op0->getOpcode() == Opcode && Op1->getOpcode() == Opcode && - match(Op0, m_OneUse(m_BinOp(m_Value(A), m_Constant(C1)))) && - match(Op1, m_OneUse(m_BinOp(m_Value(B), m_Constant(C2))))) { - BinaryOperator *NewBO = BinaryOperator::Create(Opcode, A, B); - if (isa<FPMathOperator>(NewBO)) { - FastMathFlags Flags = I.getFastMathFlags(); - Flags &= Op0->getFastMathFlags(); - Flags &= Op1->getFastMathFlags(); - NewBO->setFastMathFlags(Flags); - } - InsertNewInstWith(NewBO, I); - NewBO->takeName(Op1); - I.setOperand(0, NewBO); - I.setOperand(1, ConstantExpr::get(Opcode, C1, C2)); - // Conservatively clear the optional flags, since they may not be - // preserved by the reassociation. - ClearSubclassDataAfterReassociation(I); - - Changed = true; - continue; - } - } - - // No further simplifications. - return Changed; - } while (true); -} - -/// Return whether "X LOp (Y ROp Z)" is always equal to -/// "(X LOp Y) ROp (X LOp Z)". -static bool leftDistributesOverRight(Instruction::BinaryOps LOp, - Instruction::BinaryOps ROp) { - // X & (Y | Z) <--> (X & Y) | (X & Z) - // X & (Y ^ Z) <--> (X & Y) ^ (X & Z) - if (LOp == Instruction::And) - return ROp == Instruction::Or || ROp == Instruction::Xor; - - // X | (Y & Z) <--> (X | Y) & (X | Z) - if (LOp == Instruction::Or) - return ROp == Instruction::And; - - // X * (Y + Z) <--> (X * Y) + (X * Z) - // X * (Y - Z) <--> (X * Y) - (X * Z) - if (LOp == Instruction::Mul) - return ROp == Instruction::Add || ROp == Instruction::Sub; - - return false; -} - -/// Return whether "(X LOp Y) ROp Z" is always equal to -/// "(X ROp Z) LOp (Y ROp Z)". -static bool rightDistributesOverLeft(Instruction::BinaryOps LOp, - Instruction::BinaryOps ROp) { - if (Instruction::isCommutative(ROp)) - return leftDistributesOverRight(ROp, LOp); - - // (X {&|^} Y) >> Z <--> (X >> Z) {&|^} (Y >> Z) for all shifts. - return Instruction::isBitwiseLogicOp(LOp) && Instruction::isShift(ROp); - - // TODO: It would be nice to handle division, aka "(X + Y)/Z = X/Z + Y/Z", - // but this requires knowing that the addition does not overflow and other - // such subtleties. -} - -/// This function returns identity value for given opcode, which can be used to -/// factor patterns like (X * 2) + X ==> (X * 2) + (X * 1) ==> X * (2 + 1). -static Value *getIdentityValue(Instruction::BinaryOps Opcode, Value *V) { - if (isa<Constant>(V)) - return nullptr; - - return ConstantExpr::getBinOpIdentity(Opcode, V->getType()); -} - -/// This function predicates factorization using distributive laws. By default, -/// it just returns the 'Op' inputs. But for special-cases like -/// 'add(shl(X, 5), ...)', this function will have TopOpcode == Instruction::Add -/// and Op = shl(X, 5). The 'shl' is treated as the more general 'mul X, 32' to -/// allow more factorization opportunities. -static Instruction::BinaryOps -getBinOpsForFactorization(Instruction::BinaryOps TopOpcode, BinaryOperator *Op, - Value *&LHS, Value *&RHS) { - assert(Op && "Expected a binary operator"); - LHS = Op->getOperand(0); - RHS = Op->getOperand(1); - if (TopOpcode == Instruction::Add || TopOpcode == Instruction::Sub) { - Constant *C; - if (match(Op, m_Shl(m_Value(), m_Constant(C)))) { - // X << C --> X * (1 << C) - RHS = ConstantExpr::getShl(ConstantInt::get(Op->getType(), 1), C); - return Instruction::Mul; - } - // TODO: We can add other conversions e.g. shr => div etc. - } - return Op->getOpcode(); -} - -/// This tries to simplify binary operations by factorizing out common terms -/// (e. g. "(A*B)+(A*C)" -> "A*(B+C)"). -Value *InstCombiner::tryFactorization(BinaryOperator &I, - Instruction::BinaryOps InnerOpcode, - Value *A, Value *B, Value *C, Value *D) { - assert(A && B && C && D && "All values must be provided"); - - Value *V = nullptr; - Value *SimplifiedInst = nullptr; - Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); - Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); - - // Does "X op' Y" always equal "Y op' X"? - bool InnerCommutative = Instruction::isCommutative(InnerOpcode); - - // Does "X op' (Y op Z)" always equal "(X op' Y) op (X op' Z)"? - if (leftDistributesOverRight(InnerOpcode, TopLevelOpcode)) - // Does the instruction have the form "(A op' B) op (A op' D)" or, in the - // commutative case, "(A op' B) op (C op' A)"? - if (A == C || (InnerCommutative && A == D)) { - if (A != C) - std::swap(C, D); - // Consider forming "A op' (B op D)". - // If "B op D" simplifies then it can be formed with no cost. - V = SimplifyBinOp(TopLevelOpcode, B, D, SQ.getWithInstruction(&I)); - // If "B op D" doesn't simplify then only go on if both of the existing - // operations "A op' B" and "C op' D" will be zapped as no longer used. - if (!V && LHS->hasOneUse() && RHS->hasOneUse()) - V = Builder.CreateBinOp(TopLevelOpcode, B, D, RHS->getName()); - if (V) { - SimplifiedInst = Builder.CreateBinOp(InnerOpcode, A, V); - } - } - - // Does "(X op Y) op' Z" always equal "(X op' Z) op (Y op' Z)"? - if (!SimplifiedInst && rightDistributesOverLeft(TopLevelOpcode, InnerOpcode)) - // Does the instruction have the form "(A op' B) op (C op' B)" or, in the - // commutative case, "(A op' B) op (B op' D)"? - if (B == D || (InnerCommutative && B == C)) { - if (B != D) - std::swap(C, D); - // Consider forming "(A op C) op' B". - // If "A op C" simplifies then it can be formed with no cost. - V = SimplifyBinOp(TopLevelOpcode, A, C, SQ.getWithInstruction(&I)); - - // If "A op C" doesn't simplify then only go on if both of the existing - // operations "A op' B" and "C op' D" will be zapped as no longer used. - if (!V && LHS->hasOneUse() && RHS->hasOneUse()) - V = Builder.CreateBinOp(TopLevelOpcode, A, C, LHS->getName()); - if (V) { - SimplifiedInst = Builder.CreateBinOp(InnerOpcode, V, B); - } - } - - if (SimplifiedInst) { - ++NumFactor; - SimplifiedInst->takeName(&I); - - // Check if we can add NSW flag to SimplifiedInst. If so, set NSW flag. - // TODO: Check for NUW. - if (BinaryOperator *BO = dyn_cast<BinaryOperator>(SimplifiedInst)) { - if (isa<OverflowingBinaryOperator>(SimplifiedInst)) { - bool HasNSW = false; - if (isa<OverflowingBinaryOperator>(&I)) - HasNSW = I.hasNoSignedWrap(); - - if (auto *LOBO = dyn_cast<OverflowingBinaryOperator>(LHS)) - HasNSW &= LOBO->hasNoSignedWrap(); - - if (auto *ROBO = dyn_cast<OverflowingBinaryOperator>(RHS)) - HasNSW &= ROBO->hasNoSignedWrap(); - - // We can propagate 'nsw' if we know that - // %Y = mul nsw i16 %X, C - // %Z = add nsw i16 %Y, %X - // => - // %Z = mul nsw i16 %X, C+1 - // - // iff C+1 isn't INT_MIN - const APInt *CInt; - if (TopLevelOpcode == Instruction::Add && - InnerOpcode == Instruction::Mul) - if (match(V, m_APInt(CInt)) && !CInt->isMinSignedValue()) - BO->setHasNoSignedWrap(HasNSW); - } - } - } - return SimplifiedInst; -} - -/// This tries to simplify binary operations which some other binary operation -/// distributes over either by factorizing out common terms -/// (eg "(A*B)+(A*C)" -> "A*(B+C)") or expanding out if this results in -/// simplifications (eg: "A & (B | C) -> (A&B) | (A&C)" if this is a win). -/// Returns the simplified value, or null if it didn't simplify. -Value *InstCombiner::SimplifyUsingDistributiveLaws(BinaryOperator &I) { - Value *LHS = I.getOperand(0), *RHS = I.getOperand(1); - BinaryOperator *Op0 = dyn_cast<BinaryOperator>(LHS); - BinaryOperator *Op1 = dyn_cast<BinaryOperator>(RHS); - Instruction::BinaryOps TopLevelOpcode = I.getOpcode(); - - { - // Factorization. - Value *A, *B, *C, *D; - Instruction::BinaryOps LHSOpcode, RHSOpcode; - if (Op0) - LHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op0, A, B); - if (Op1) - RHSOpcode = getBinOpsForFactorization(TopLevelOpcode, Op1, C, D); - - // The instruction has the form "(A op' B) op (C op' D)". Try to factorize - // a common term. - if (Op0 && Op1 && LHSOpcode == RHSOpcode) - if (Value *V = tryFactorization(I, LHSOpcode, A, B, C, D)) - return V; - - // The instruction has the form "(A op' B) op (C)". Try to factorize common - // term. - if (Op0) - if (Value *Ident = getIdentityValue(LHSOpcode, RHS)) - if (Value *V = tryFactorization(I, LHSOpcode, A, B, RHS, Ident)) - return V; - - // The instruction has the form "(B) op (C op' D)". Try to factorize common - // term. - if (Op1) - if (Value *Ident = getIdentityValue(RHSOpcode, LHS)) - if (Value *V = tryFactorization(I, RHSOpcode, LHS, Ident, C, D)) - return V; - } - - // Expansion. - if (Op0 && rightDistributesOverLeft(Op0->getOpcode(), TopLevelOpcode)) { - // The instruction has the form "(A op' B) op C". See if expanding it out - // to "(A op C) op' (B op C)" results in simplifications. - Value *A = Op0->getOperand(0), *B = Op0->getOperand(1), *C = RHS; - Instruction::BinaryOps InnerOpcode = Op0->getOpcode(); // op' - - Value *L = SimplifyBinOp(TopLevelOpcode, A, C, SQ.getWithInstruction(&I)); - Value *R = SimplifyBinOp(TopLevelOpcode, B, C, SQ.getWithInstruction(&I)); - - // Do "A op C" and "B op C" both simplify? - if (L && R) { - // They do! Return "L op' R". - ++NumExpand; - C = Builder.CreateBinOp(InnerOpcode, L, R); - C->takeName(&I); - return C; - } - - // Does "A op C" simplify to the identity value for the inner opcode? - if (L && L == ConstantExpr::getBinOpIdentity(InnerOpcode, L->getType())) { - // They do! Return "B op C". - ++NumExpand; - C = Builder.CreateBinOp(TopLevelOpcode, B, C); - C->takeName(&I); - return C; - } - - // Does "B op C" simplify to the identity value for the inner opcode? - if (R && R == ConstantExpr::getBinOpIdentity(InnerOpcode, R->getType())) { - // They do! Return "A op C". - ++NumExpand; - C = Builder.CreateBinOp(TopLevelOpcode, A, C); - C->takeName(&I); - return C; - } - } - - if (Op1 && leftDistributesOverRight(TopLevelOpcode, Op1->getOpcode())) { - // The instruction has the form "A op (B op' C)". See if expanding it out - // to "(A op B) op' (A op C)" results in simplifications. - Value *A = LHS, *B = Op1->getOperand(0), *C = Op1->getOperand(1); - Instruction::BinaryOps InnerOpcode = Op1->getOpcode(); // op' - - Value *L = SimplifyBinOp(TopLevelOpcode, A, B, SQ.getWithInstruction(&I)); - Value *R = SimplifyBinOp(TopLevelOpcode, A, C, SQ.getWithInstruction(&I)); - - // Do "A op B" and "A op C" both simplify? - if (L && R) { - // They do! Return "L op' R". - ++NumExpand; - A = Builder.CreateBinOp(InnerOpcode, L, R); - A->takeName(&I); - return A; - } - - // Does "A op B" simplify to the identity value for the inner opcode? - if (L && L == ConstantExpr::getBinOpIdentity(InnerOpcode, L->getType())) { - // They do! Return "A op C". - ++NumExpand; - A = Builder.CreateBinOp(TopLevelOpcode, A, C); - A->takeName(&I); - return A; - } - - // Does "A op C" simplify to the identity value for the inner opcode? - if (R && R == ConstantExpr::getBinOpIdentity(InnerOpcode, R->getType())) { - // They do! Return "A op B". - ++NumExpand; - A = Builder.CreateBinOp(TopLevelOpcode, A, B); - A->takeName(&I); - return A; - } - } - - return SimplifySelectsFeedingBinaryOp(I, LHS, RHS); -} - -Value *InstCombiner::SimplifySelectsFeedingBinaryOp(BinaryOperator &I, - Value *LHS, Value *RHS) { - Instruction::BinaryOps Opcode = I.getOpcode(); - // (op (select (a, b, c)), (select (a, d, e))) -> (select (a, (op b, d), (op - // c, e))) - Value *A, *B, *C, *D, *E; - Value *SI = nullptr; - if (match(LHS, m_Select(m_Value(A), m_Value(B), m_Value(C))) && - match(RHS, m_Select(m_Specific(A), m_Value(D), m_Value(E)))) { - bool SelectsHaveOneUse = LHS->hasOneUse() && RHS->hasOneUse(); - BuilderTy::FastMathFlagGuard Guard(Builder); - if (isa<FPMathOperator>(&I)) - Builder.setFastMathFlags(I.getFastMathFlags()); - - Value *V1 = SimplifyBinOp(Opcode, C, E, SQ.getWithInstruction(&I)); - Value *V2 = SimplifyBinOp(Opcode, B, D, SQ.getWithInstruction(&I)); - if (V1 && V2) - SI = Builder.CreateSelect(A, V2, V1); - else if (V2 && SelectsHaveOneUse) - SI = Builder.CreateSelect(A, V2, Builder.CreateBinOp(Opcode, C, E)); - else if (V1 && SelectsHaveOneUse) - SI = Builder.CreateSelect(A, Builder.CreateBinOp(Opcode, B, D), V1); - - if (SI) - SI->takeName(&I); - } - - return SI; -} - -/// Given a 'sub' instruction, return the RHS of the instruction if the LHS is a -/// constant zero (which is the 'negate' form). -Value *InstCombiner::dyn_castNegVal(Value *V) const { - Value *NegV; - if (match(V, m_Neg(m_Value(NegV)))) - return NegV; - - // Constants can be considered to be negated values if they can be folded. - if (ConstantInt *C = dyn_cast<ConstantInt>(V)) - return ConstantExpr::getNeg(C); - - if (ConstantDataVector *C = dyn_cast<ConstantDataVector>(V)) - if (C->getType()->getElementType()->isIntegerTy()) - return ConstantExpr::getNeg(C); - - if (ConstantVector *CV = dyn_cast<ConstantVector>(V)) { - for (unsigned i = 0, e = CV->getNumOperands(); i != e; ++i) { - Constant *Elt = CV->getAggregateElement(i); - if (!Elt) - return nullptr; - - if (isa<UndefValue>(Elt)) - continue; - - if (!isa<ConstantInt>(Elt)) - return nullptr; - } - return ConstantExpr::getNeg(CV); - } - - return nullptr; -} - -static Value *foldOperationIntoSelectOperand(Instruction &I, Value *SO, - InstCombiner::BuilderTy &Builder) { - if (auto *Cast = dyn_cast<CastInst>(&I)) - return Builder.CreateCast(Cast->getOpcode(), SO, I.getType()); - - assert(I.isBinaryOp() && "Unexpected opcode for select folding"); - - // Figure out if the constant is the left or the right argument. - bool ConstIsRHS = isa<Constant>(I.getOperand(1)); - Constant *ConstOperand = cast<Constant>(I.getOperand(ConstIsRHS)); - - if (auto *SOC = dyn_cast<Constant>(SO)) { - if (ConstIsRHS) - return ConstantExpr::get(I.getOpcode(), SOC, ConstOperand); - return ConstantExpr::get(I.getOpcode(), ConstOperand, SOC); - } - - Value *Op0 = SO, *Op1 = ConstOperand; - if (!ConstIsRHS) - std::swap(Op0, Op1); - - auto *BO = cast<BinaryOperator>(&I); - Value *RI = Builder.CreateBinOp(BO->getOpcode(), Op0, Op1, - SO->getName() + ".op"); - auto *FPInst = dyn_cast<Instruction>(RI); - if (FPInst && isa<FPMathOperator>(FPInst)) - FPInst->copyFastMathFlags(BO); - return RI; -} - -Instruction *InstCombiner::FoldOpIntoSelect(Instruction &Op, SelectInst *SI) { - // Don't modify shared select instructions. - if (!SI->hasOneUse()) - return nullptr; - - Value *TV = SI->getTrueValue(); - Value *FV = SI->getFalseValue(); - if (!(isa<Constant>(TV) || isa<Constant>(FV))) - return nullptr; - - // Bool selects with constant operands can be folded to logical ops. - if (SI->getType()->isIntOrIntVectorTy(1)) - return nullptr; - - // If it's a bitcast involving vectors, make sure it has the same number of - // elements on both sides. - if (auto *BC = dyn_cast<BitCastInst>(&Op)) { - VectorType *DestTy = dyn_cast<VectorType>(BC->getDestTy()); - VectorType *SrcTy = dyn_cast<VectorType>(BC->getSrcTy()); - - // Verify that either both or neither are vectors. - if ((SrcTy == nullptr) != (DestTy == nullptr)) - return nullptr; - - // If vectors, verify that they have the same number of elements. - if (SrcTy && SrcTy->getNumElements() != DestTy->getNumElements()) - return nullptr; - } - - // Test if a CmpInst instruction is used exclusively by a select as - // part of a minimum or maximum operation. If so, refrain from doing - // any other folding. This helps out other analyses which understand - // non-obfuscated minimum and maximum idioms, such as ScalarEvolution - // and CodeGen. And in this case, at least one of the comparison - // operands has at least one user besides the compare (the select), - // which would often largely negate the benefit of folding anyway. - if (auto *CI = dyn_cast<CmpInst>(SI->getCondition())) { - if (CI->hasOneUse()) { - Value *Op0 = CI->getOperand(0), *Op1 = CI->getOperand(1); - if ((SI->getOperand(1) == Op0 && SI->getOperand(2) == Op1) || - (SI->getOperand(2) == Op0 && SI->getOperand(1) == Op1)) - return nullptr; - } - } - - Value *NewTV = foldOperationIntoSelectOperand(Op, TV, Builder); - Value *NewFV = foldOperationIntoSelectOperand(Op, FV, Builder); - return SelectInst::Create(SI->getCondition(), NewTV, NewFV, "", nullptr, SI); -} - -static Value *foldOperationIntoPhiValue(BinaryOperator *I, Value *InV, - InstCombiner::BuilderTy &Builder) { - bool ConstIsRHS = isa<Constant>(I->getOperand(1)); - Constant *C = cast<Constant>(I->getOperand(ConstIsRHS)); - - if (auto *InC = dyn_cast<Constant>(InV)) { - if (ConstIsRHS) - return ConstantExpr::get(I->getOpcode(), InC, C); - return ConstantExpr::get(I->getOpcode(), C, InC); - } - - Value *Op0 = InV, *Op1 = C; - if (!ConstIsRHS) - std::swap(Op0, Op1); - - Value *RI = Builder.CreateBinOp(I->getOpcode(), Op0, Op1, "phitmp"); - auto *FPInst = dyn_cast<Instruction>(RI); - if (FPInst && isa<FPMathOperator>(FPInst)) - FPInst->copyFastMathFlags(I); - return RI; -} - -Instruction *InstCombiner::foldOpIntoPhi(Instruction &I, PHINode *PN) { - unsigned NumPHIValues = PN->getNumIncomingValues(); - if (NumPHIValues == 0) - return nullptr; - - // We normally only transform phis with a single use. However, if a PHI has - // multiple uses and they are all the same operation, we can fold *all* of the - // uses into the PHI. - if (!PN->hasOneUse()) { - // Walk the use list for the instruction, comparing them to I. - for (User *U : PN->users()) { - Instruction *UI = cast<Instruction>(U); - if (UI != &I && !I.isIdenticalTo(UI)) - return nullptr; - } - // Otherwise, we can replace *all* users with the new PHI we form. - } - - // Check to see if all of the operands of the PHI are simple constants - // (constantint/constantfp/undef). If there is one non-constant value, - // remember the BB it is in. If there is more than one or if *it* is a PHI, - // bail out. We don't do arbitrary constant expressions here because moving - // their computation can be expensive without a cost model. - BasicBlock *NonConstBB = nullptr; - for (unsigned i = 0; i != NumPHIValues; ++i) { - Value *InVal = PN->getIncomingValue(i); - if (isa<Constant>(InVal) && !isa<ConstantExpr>(InVal)) - continue; - - if (isa<PHINode>(InVal)) return nullptr; // Itself a phi. - if (NonConstBB) return nullptr; // More than one non-const value. - - NonConstBB = PN->getIncomingBlock(i); - - // If the InVal is an invoke at the end of the pred block, then we can't - // insert a computation after it without breaking the edge. - if (InvokeInst *II = dyn_cast<InvokeInst>(InVal)) - if (II->getParent() == NonConstBB) - return nullptr; - - // If the incoming non-constant value is in I's block, we will remove one - // instruction, but insert another equivalent one, leading to infinite - // instcombine. - if (isPotentiallyReachable(I.getParent(), NonConstBB, &DT, LI)) - return nullptr; - } - - // If there is exactly one non-constant value, we can insert a copy of the - // operation in that block. However, if this is a critical edge, we would be - // inserting the computation on some other paths (e.g. inside a loop). Only - // do this if the pred block is unconditionally branching into the phi block. - if (NonConstBB != nullptr) { - BranchInst *BI = dyn_cast<BranchInst>(NonConstBB->getTerminator()); - if (!BI || !BI->isUnconditional()) return nullptr; - } - - // Okay, we can do the transformation: create the new PHI node. - PHINode *NewPN = PHINode::Create(I.getType(), PN->getNumIncomingValues()); - InsertNewInstBefore(NewPN, *PN); - NewPN->takeName(PN); - - // If we are going to have to insert a new computation, do so right before the - // predecessor's terminator. - if (NonConstBB) - Builder.SetInsertPoint(NonConstBB->getTerminator()); - - // Next, add all of the operands to the PHI. - if (SelectInst *SI = dyn_cast<SelectInst>(&I)) { - // We only currently try to fold the condition of a select when it is a phi, - // not the true/false values. - Value *TrueV = SI->getTrueValue(); - Value *FalseV = SI->getFalseValue(); - BasicBlock *PhiTransBB = PN->getParent(); - for (unsigned i = 0; i != NumPHIValues; ++i) { - BasicBlock *ThisBB = PN->getIncomingBlock(i); - Value *TrueVInPred = TrueV->DoPHITranslation(PhiTransBB, ThisBB); - Value *FalseVInPred = FalseV->DoPHITranslation(PhiTransBB, ThisBB); - Value *InV = nullptr; - // Beware of ConstantExpr: it may eventually evaluate to getNullValue, - // even if currently isNullValue gives false. - Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i)); - // For vector constants, we cannot use isNullValue to fold into - // FalseVInPred versus TrueVInPred. When we have individual nonzero - // elements in the vector, we will incorrectly fold InC to - // `TrueVInPred`. - if (InC && !isa<ConstantExpr>(InC) && isa<ConstantInt>(InC)) - InV = InC->isNullValue() ? FalseVInPred : TrueVInPred; - else { - // Generate the select in the same block as PN's current incoming block. - // Note: ThisBB need not be the NonConstBB because vector constants - // which are constants by definition are handled here. - // FIXME: This can lead to an increase in IR generation because we might - // generate selects for vector constant phi operand, that could not be - // folded to TrueVInPred or FalseVInPred as done for ConstantInt. For - // non-vector phis, this transformation was always profitable because - // the select would be generated exactly once in the NonConstBB. - Builder.SetInsertPoint(ThisBB->getTerminator()); - InV = Builder.CreateSelect(PN->getIncomingValue(i), TrueVInPred, - FalseVInPred, "phitmp"); - } - NewPN->addIncoming(InV, ThisBB); - } - } else if (CmpInst *CI = dyn_cast<CmpInst>(&I)) { - Constant *C = cast<Constant>(I.getOperand(1)); - for (unsigned i = 0; i != NumPHIValues; ++i) { - Value *InV = nullptr; - if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) - InV = ConstantExpr::getCompare(CI->getPredicate(), InC, C); - else if (isa<ICmpInst>(CI)) - InV = Builder.CreateICmp(CI->getPredicate(), PN->getIncomingValue(i), - C, "phitmp"); - else - InV = Builder.CreateFCmp(CI->getPredicate(), PN->getIncomingValue(i), - C, "phitmp"); - NewPN->addIncoming(InV, PN->getIncomingBlock(i)); - } - } else if (auto *BO = dyn_cast<BinaryOperator>(&I)) { - for (unsigned i = 0; i != NumPHIValues; ++i) { - Value *InV = foldOperationIntoPhiValue(BO, PN->getIncomingValue(i), - Builder); - NewPN->addIncoming(InV, PN->getIncomingBlock(i)); - } - } else { - CastInst *CI = cast<CastInst>(&I); - Type *RetTy = CI->getType(); - for (unsigned i = 0; i != NumPHIValues; ++i) { - Value *InV; - if (Constant *InC = dyn_cast<Constant>(PN->getIncomingValue(i))) - InV = ConstantExpr::getCast(CI->getOpcode(), InC, RetTy); - else - InV = Builder.CreateCast(CI->getOpcode(), PN->getIncomingValue(i), - I.getType(), "phitmp"); - NewPN->addIncoming(InV, PN->getIncomingBlock(i)); - } - } - - for (auto UI = PN->user_begin(), E = PN->user_end(); UI != E;) { - Instruction *User = cast<Instruction>(*UI++); - if (User == &I) continue; - replaceInstUsesWith(*User, NewPN); - eraseInstFromFunction(*User); - } - return replaceInstUsesWith(I, NewPN); -} - -Instruction *InstCombiner::foldBinOpIntoSelectOrPhi(BinaryOperator &I) { - if (!isa<Constant>(I.getOperand(1))) - return nullptr; - - if (auto *Sel = dyn_cast<SelectInst>(I.getOperand(0))) { - if (Instruction *NewSel = FoldOpIntoSelect(I, Sel)) - return NewSel; - } else if (auto *PN = dyn_cast<PHINode>(I.getOperand(0))) { - if (Instruction *NewPhi = foldOpIntoPhi(I, PN)) - return NewPhi; - } - return nullptr; -} - -/// Given a pointer type and a constant offset, determine whether or not there -/// is a sequence of GEP indices into the pointed type that will land us at the -/// specified offset. If so, fill them into NewIndices and return the resultant -/// element type, otherwise return null. -Type *InstCombiner::FindElementAtOffset(PointerType *PtrTy, int64_t Offset, - SmallVectorImpl<Value *> &NewIndices) { - Type *Ty = PtrTy->getElementType(); - if (!Ty->isSized()) - return nullptr; - - // Start with the index over the outer type. Note that the type size - // might be zero (even if the offset isn't zero) if the indexed type - // is something like [0 x {int, int}] - Type *IndexTy = DL.getIndexType(PtrTy); - int64_t FirstIdx = 0; - if (int64_t TySize = DL.getTypeAllocSize(Ty)) { - FirstIdx = Offset/TySize; - Offset -= FirstIdx*TySize; - - // Handle hosts where % returns negative instead of values [0..TySize). - if (Offset < 0) { - --FirstIdx; - Offset += TySize; - assert(Offset >= 0); - } - assert((uint64_t)Offset < (uint64_t)TySize && "Out of range offset"); - } - - NewIndices.push_back(ConstantInt::get(IndexTy, FirstIdx)); - - // Index into the types. If we fail, set OrigBase to null. - while (Offset) { - // Indexing into tail padding between struct/array elements. - if (uint64_t(Offset * 8) >= DL.getTypeSizeInBits(Ty)) - return nullptr; - - if (StructType *STy = dyn_cast<StructType>(Ty)) { - const StructLayout *SL = DL.getStructLayout(STy); - assert(Offset < (int64_t)SL->getSizeInBytes() && - "Offset must stay within the indexed type"); - - unsigned Elt = SL->getElementContainingOffset(Offset); - NewIndices.push_back(ConstantInt::get(Type::getInt32Ty(Ty->getContext()), - Elt)); - - Offset -= SL->getElementOffset(Elt); - Ty = STy->getElementType(Elt); - } else if (ArrayType *AT = dyn_cast<ArrayType>(Ty)) { - uint64_t EltSize = DL.getTypeAllocSize(AT->getElementType()); - assert(EltSize && "Cannot index into a zero-sized array"); - NewIndices.push_back(ConstantInt::get(IndexTy,Offset/EltSize)); - Offset %= EltSize; - Ty = AT->getElementType(); - } else { - // Otherwise, we can't index into the middle of this atomic type, bail. - return nullptr; - } - } - - return Ty; -} - -static bool shouldMergeGEPs(GEPOperator &GEP, GEPOperator &Src) { - // If this GEP has only 0 indices, it is the same pointer as - // Src. If Src is not a trivial GEP too, don't combine - // the indices. - if (GEP.hasAllZeroIndices() && !Src.hasAllZeroIndices() && - !Src.hasOneUse()) - return false; - return true; -} - -/// Return a value X such that Val = X * Scale, or null if none. -/// If the multiplication is known not to overflow, then NoSignedWrap is set. -Value *InstCombiner::Descale(Value *Val, APInt Scale, bool &NoSignedWrap) { - assert(isa<IntegerType>(Val->getType()) && "Can only descale integers!"); - assert(cast<IntegerType>(Val->getType())->getBitWidth() == - Scale.getBitWidth() && "Scale not compatible with value!"); - - // If Val is zero or Scale is one then Val = Val * Scale. - if (match(Val, m_Zero()) || Scale == 1) { - NoSignedWrap = true; - return Val; - } - - // If Scale is zero then it does not divide Val. - if (Scale.isMinValue()) - return nullptr; - - // Look through chains of multiplications, searching for a constant that is - // divisible by Scale. For example, descaling X*(Y*(Z*4)) by a factor of 4 - // will find the constant factor 4 and produce X*(Y*Z). Descaling X*(Y*8) by - // a factor of 4 will produce X*(Y*2). The principle of operation is to bore - // down from Val: - // - // Val = M1 * X || Analysis starts here and works down - // M1 = M2 * Y || Doesn't descend into terms with more - // M2 = Z * 4 \/ than one use - // - // Then to modify a term at the bottom: - // - // Val = M1 * X - // M1 = Z * Y || Replaced M2 with Z - // - // Then to work back up correcting nsw flags. - - // Op - the term we are currently analyzing. Starts at Val then drills down. - // Replaced with its descaled value before exiting from the drill down loop. - Value *Op = Val; - - // Parent - initially null, but after drilling down notes where Op came from. - // In the example above, Parent is (Val, 0) when Op is M1, because M1 is the - // 0'th operand of Val. - std::pair<Instruction *, unsigned> Parent; - - // Set if the transform requires a descaling at deeper levels that doesn't - // overflow. - bool RequireNoSignedWrap = false; - - // Log base 2 of the scale. Negative if not a power of 2. - int32_t logScale = Scale.exactLogBase2(); - - for (;; Op = Parent.first->getOperand(Parent.second)) { // Drill down - if (ConstantInt *CI = dyn_cast<ConstantInt>(Op)) { - // If Op is a constant divisible by Scale then descale to the quotient. - APInt Quotient(Scale), Remainder(Scale); // Init ensures right bitwidth. - APInt::sdivrem(CI->getValue(), Scale, Quotient, Remainder); - if (!Remainder.isMinValue()) - // Not divisible by Scale. - return nullptr; - // Replace with the quotient in the parent. - Op = ConstantInt::get(CI->getType(), Quotient); - NoSignedWrap = true; - break; - } - - if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Op)) { - if (BO->getOpcode() == Instruction::Mul) { - // Multiplication. - NoSignedWrap = BO->hasNoSignedWrap(); - if (RequireNoSignedWrap && !NoSignedWrap) - return nullptr; - - // There are three cases for multiplication: multiplication by exactly - // the scale, multiplication by a constant different to the scale, and - // multiplication by something else. - Value *LHS = BO->getOperand(0); - Value *RHS = BO->getOperand(1); - - if (ConstantInt *CI = dyn_cast<ConstantInt>(RHS)) { - // Multiplication by a constant. - if (CI->getValue() == Scale) { - // Multiplication by exactly the scale, replace the multiplication - // by its left-hand side in the parent. - Op = LHS; - break; - } - - // Otherwise drill down into the constant. - if (!Op->hasOneUse()) - return nullptr; - - Parent = std::make_pair(BO, 1); - continue; - } - - // Multiplication by something else. Drill down into the left-hand side - // since that's where the reassociate pass puts the good stuff. - if (!Op->hasOneUse()) - return nullptr; - - Parent = std::make_pair(BO, 0); - continue; - } - - if (logScale > 0 && BO->getOpcode() == Instruction::Shl && - isa<ConstantInt>(BO->getOperand(1))) { - // Multiplication by a power of 2. - NoSignedWrap = BO->hasNoSignedWrap(); - if (RequireNoSignedWrap && !NoSignedWrap) - return nullptr; - - Value *LHS = BO->getOperand(0); - int32_t Amt = cast<ConstantInt>(BO->getOperand(1))-> - getLimitedValue(Scale.getBitWidth()); - // Op = LHS << Amt. - - if (Amt == logScale) { - // Multiplication by exactly the scale, replace the multiplication - // by its left-hand side in the parent. - Op = LHS; - break; - } - if (Amt < logScale || !Op->hasOneUse()) - return nullptr; - - // Multiplication by more than the scale. Reduce the multiplying amount - // by the scale in the parent. - Parent = std::make_pair(BO, 1); - Op = ConstantInt::get(BO->getType(), Amt - logScale); - break; - } - } - - if (!Op->hasOneUse()) - return nullptr; - - if (CastInst *Cast = dyn_cast<CastInst>(Op)) { - if (Cast->getOpcode() == Instruction::SExt) { - // Op is sign-extended from a smaller type, descale in the smaller type. - unsigned SmallSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); - APInt SmallScale = Scale.trunc(SmallSize); - // Suppose Op = sext X, and we descale X as Y * SmallScale. We want to - // descale Op as (sext Y) * Scale. In order to have - // sext (Y * SmallScale) = (sext Y) * Scale - // some conditions need to hold however: SmallScale must sign-extend to - // Scale and the multiplication Y * SmallScale should not overflow. - if (SmallScale.sext(Scale.getBitWidth()) != Scale) - // SmallScale does not sign-extend to Scale. - return nullptr; - assert(SmallScale.exactLogBase2() == logScale); - // Require that Y * SmallScale must not overflow. - RequireNoSignedWrap = true; - - // Drill down through the cast. - Parent = std::make_pair(Cast, 0); - Scale = SmallScale; - continue; - } - - if (Cast->getOpcode() == Instruction::Trunc) { - // Op is truncated from a larger type, descale in the larger type. - // Suppose Op = trunc X, and we descale X as Y * sext Scale. Then - // trunc (Y * sext Scale) = (trunc Y) * Scale - // always holds. However (trunc Y) * Scale may overflow even if - // trunc (Y * sext Scale) does not, so nsw flags need to be cleared - // from this point up in the expression (see later). - if (RequireNoSignedWrap) - return nullptr; - - // Drill down through the cast. - unsigned LargeSize = Cast->getSrcTy()->getPrimitiveSizeInBits(); - Parent = std::make_pair(Cast, 0); - Scale = Scale.sext(LargeSize); - if (logScale + 1 == (int32_t)Cast->getType()->getPrimitiveSizeInBits()) - logScale = -1; - assert(Scale.exactLogBase2() == logScale); - continue; - } - } - - // Unsupported expression, bail out. - return nullptr; - } - - // If Op is zero then Val = Op * Scale. - if (match(Op, m_Zero())) { - NoSignedWrap = true; - return Op; - } - - // We know that we can successfully descale, so from here on we can safely - // modify the IR. Op holds the descaled version of the deepest term in the - // expression. NoSignedWrap is 'true' if multiplying Op by Scale is known - // not to overflow. - - if (!Parent.first) - // The expression only had one term. - return Op; - - // Rewrite the parent using the descaled version of its operand. - assert(Parent.first->hasOneUse() && "Drilled down when more than one use!"); - assert(Op != Parent.first->getOperand(Parent.second) && - "Descaling was a no-op?"); - Parent.first->setOperand(Parent.second, Op); - Worklist.Add(Parent.first); - - // Now work back up the expression correcting nsw flags. The logic is based - // on the following observation: if X * Y is known not to overflow as a signed - // multiplication, and Y is replaced by a value Z with smaller absolute value, - // then X * Z will not overflow as a signed multiplication either. As we work - // our way up, having NoSignedWrap 'true' means that the descaled value at the - // current level has strictly smaller absolute value than the original. - Instruction *Ancestor = Parent.first; - do { - if (BinaryOperator *BO = dyn_cast<BinaryOperator>(Ancestor)) { - // If the multiplication wasn't nsw then we can't say anything about the - // value of the descaled multiplication, and we have to clear nsw flags - // from this point on up. - bool OpNoSignedWrap = BO->hasNoSignedWrap(); - NoSignedWrap &= OpNoSignedWrap; - if (NoSignedWrap != OpNoSignedWrap) { - BO->setHasNoSignedWrap(NoSignedWrap); - Worklist.Add(Ancestor); - } - } else if (Ancestor->getOpcode() == Instruction::Trunc) { - // The fact that the descaled input to the trunc has smaller absolute - // value than the original input doesn't tell us anything useful about - // the absolute values of the truncations. - NoSignedWrap = false; - } - assert((Ancestor->getOpcode() != Instruction::SExt || NoSignedWrap) && - "Failed to keep proper track of nsw flags while drilling down?"); - - if (Ancestor == Val) - // Got to the top, all done! - return Val; - - // Move up one level in the expression. - assert(Ancestor->hasOneUse() && "Drilled down when more than one use!"); - Ancestor = Ancestor->user_back(); - } while (true); -} - -Instruction *InstCombiner::foldVectorBinop(BinaryOperator &Inst) { - if (!Inst.getType()->isVectorTy()) return nullptr; - - BinaryOperator::BinaryOps Opcode = Inst.getOpcode(); - unsigned NumElts = cast<VectorType>(Inst.getType())->getNumElements(); - Value *LHS = Inst.getOperand(0), *RHS = Inst.getOperand(1); - assert(cast<VectorType>(LHS->getType())->getNumElements() == NumElts); - assert(cast<VectorType>(RHS->getType())->getNumElements() == NumElts); - - // If both operands of the binop are vector concatenations, then perform the - // narrow binop on each pair of the source operands followed by concatenation - // of the results. - Value *L0, *L1, *R0, *R1; - Constant *Mask; - if (match(LHS, m_ShuffleVector(m_Value(L0), m_Value(L1), m_Constant(Mask))) && - match(RHS, m_ShuffleVector(m_Value(R0), m_Value(R1), m_Specific(Mask))) && - LHS->hasOneUse() && RHS->hasOneUse() && - cast<ShuffleVectorInst>(LHS)->isConcat() && - cast<ShuffleVectorInst>(RHS)->isConcat()) { - // This transform does not have the speculative execution constraint as - // below because the shuffle is a concatenation. The new binops are - // operating on exactly the same elements as the existing binop. - // TODO: We could ease the mask requirement to allow different undef lanes, - // but that requires an analysis of the binop-with-undef output value. - Value *NewBO0 = Builder.CreateBinOp(Opcode, L0, R0); - if (auto *BO = dyn_cast<BinaryOperator>(NewBO0)) - BO->copyIRFlags(&Inst); - Value *NewBO1 = Builder.CreateBinOp(Opcode, L1, R1); - if (auto *BO = dyn_cast<BinaryOperator>(NewBO1)) - BO->copyIRFlags(&Inst); - return new ShuffleVectorInst(NewBO0, NewBO1, Mask); - } - - // It may not be safe to reorder shuffles and things like div, urem, etc. - // because we may trap when executing those ops on unknown vector elements. - // See PR20059. - if (!isSafeToSpeculativelyExecute(&Inst)) - return nullptr; - - auto createBinOpShuffle = [&](Value *X, Value *Y, Constant *M) { - Value *XY = Builder.CreateBinOp(Opcode, X, Y); - if (auto *BO = dyn_cast<BinaryOperator>(XY)) - BO->copyIRFlags(&Inst); - return new ShuffleVectorInst(XY, UndefValue::get(XY->getType()), M); - }; - - // If both arguments of the binary operation are shuffles that use the same - // mask and shuffle within a single vector, move the shuffle after the binop. - Value *V1, *V2; - if (match(LHS, m_ShuffleVector(m_Value(V1), m_Undef(), m_Constant(Mask))) && - match(RHS, m_ShuffleVector(m_Value(V2), m_Undef(), m_Specific(Mask))) && - V1->getType() == V2->getType() && - (LHS->hasOneUse() || RHS->hasOneUse() || LHS == RHS)) { - // Op(shuffle(V1, Mask), shuffle(V2, Mask)) -> shuffle(Op(V1, V2), Mask) - return createBinOpShuffle(V1, V2, Mask); - } - - // If one argument is a shuffle within one vector and the other is a constant, - // try moving the shuffle after the binary operation. This canonicalization - // intends to move shuffles closer to other shuffles and binops closer to - // other binops, so they can be folded. It may also enable demanded elements - // transforms. - Constant *C; - if (match(&Inst, m_c_BinOp( - m_OneUse(m_ShuffleVector(m_Value(V1), m_Undef(), m_Constant(Mask))), - m_Constant(C))) && - V1->getType()->getVectorNumElements() <= NumElts) { - assert(Inst.getType()->getScalarType() == V1->getType()->getScalarType() && - "Shuffle should not change scalar type"); - - // Find constant NewC that has property: - // shuffle(NewC, ShMask) = C - // If such constant does not exist (example: ShMask=<0,0> and C=<1,2>) - // reorder is not possible. A 1-to-1 mapping is not required. Example: - // ShMask = <1,1,2,2> and C = <5,5,6,6> --> NewC = <undef,5,6,undef> - bool ConstOp1 = isa<Constant>(RHS); - SmallVector<int, 16> ShMask; - ShuffleVectorInst::getShuffleMask(Mask, ShMask); - unsigned SrcVecNumElts = V1->getType()->getVectorNumElements(); - UndefValue *UndefScalar = UndefValue::get(C->getType()->getScalarType()); - SmallVector<Constant *, 16> NewVecC(SrcVecNumElts, UndefScalar); - bool MayChange = true; - for (unsigned I = 0; I < NumElts; ++I) { - Constant *CElt = C->getAggregateElement(I); - if (ShMask[I] >= 0) { - assert(ShMask[I] < (int)NumElts && "Not expecting narrowing shuffle"); - Constant *NewCElt = NewVecC[ShMask[I]]; - // Bail out if: - // 1. The constant vector contains a constant expression. - // 2. The shuffle needs an element of the constant vector that can't - // be mapped to a new constant vector. - // 3. This is a widening shuffle that copies elements of V1 into the - // extended elements (extending with undef is allowed). - if (!CElt || (!isa<UndefValue>(NewCElt) && NewCElt != CElt) || - I >= SrcVecNumElts) { - MayChange = false; - break; - } - NewVecC[ShMask[I]] = CElt; - } - // If this is a widening shuffle, we must be able to extend with undef - // elements. If the original binop does not produce an undef in the high - // lanes, then this transform is not safe. - // TODO: We could shuffle those non-undef constant values into the - // result by using a constant vector (rather than an undef vector) - // as operand 1 of the new binop, but that might be too aggressive - // for target-independent shuffle creation. - if (I >= SrcVecNumElts) { - Constant *MaybeUndef = - ConstOp1 ? ConstantExpr::get(Opcode, UndefScalar, CElt) - : ConstantExpr::get(Opcode, CElt, UndefScalar); - if (!isa<UndefValue>(MaybeUndef)) { - MayChange = false; - break; - } - } - } - if (MayChange) { - Constant *NewC = ConstantVector::get(NewVecC); - // It may not be safe to execute a binop on a vector with undef elements - // because the entire instruction can be folded to undef or create poison - // that did not exist in the original code. - if (Inst.isIntDivRem() || (Inst.isShift() && ConstOp1)) - NewC = getSafeVectorConstantForBinop(Opcode, NewC, ConstOp1); - - // Op(shuffle(V1, Mask), C) -> shuffle(Op(V1, NewC), Mask) - // Op(C, shuffle(V1, Mask)) -> shuffle(Op(NewC, V1), Mask) - Value *NewLHS = ConstOp1 ? V1 : NewC; - Value *NewRHS = ConstOp1 ? NewC : V1; - return createBinOpShuffle(NewLHS, NewRHS, Mask); - } - } - - return nullptr; -} - -/// Try to narrow the width of a binop if at least 1 operand is an extend of -/// of a value. This requires a potentially expensive known bits check to make -/// sure the narrow op does not overflow. -Instruction *InstCombiner::narrowMathIfNoOverflow(BinaryOperator &BO) { - // We need at least one extended operand. - Value *Op0 = BO.getOperand(0), *Op1 = BO.getOperand(1); - - // If this is a sub, we swap the operands since we always want an extension - // on the RHS. The LHS can be an extension or a constant. - if (BO.getOpcode() == Instruction::Sub) - std::swap(Op0, Op1); - - Value *X; - bool IsSext = match(Op0, m_SExt(m_Value(X))); - if (!IsSext && !match(Op0, m_ZExt(m_Value(X)))) - return nullptr; - - // If both operands are the same extension from the same source type and we - // can eliminate at least one (hasOneUse), this might work. - CastInst::CastOps CastOpc = IsSext ? Instruction::SExt : Instruction::ZExt; - Value *Y; - if (!(match(Op1, m_ZExtOrSExt(m_Value(Y))) && X->getType() == Y->getType() && - cast<Operator>(Op1)->getOpcode() == CastOpc && - (Op0->hasOneUse() || Op1->hasOneUse()))) { - // If that did not match, see if we have a suitable constant operand. - // Truncating and extending must produce the same constant. - Constant *WideC; - if (!Op0->hasOneUse() || !match(Op1, m_Constant(WideC))) - return nullptr; - Constant *NarrowC = ConstantExpr::getTrunc(WideC, X->getType()); - if (ConstantExpr::getCast(CastOpc, NarrowC, BO.getType()) != WideC) - return nullptr; - Y = NarrowC; - } - - // Swap back now that we found our operands. - if (BO.getOpcode() == Instruction::Sub) - std::swap(X, Y); - - // Both operands have narrow versions. Last step: the math must not overflow - // in the narrow width. - if (!willNotOverflow(BO.getOpcode(), X, Y, BO, IsSext)) - return nullptr; - - // bo (ext X), (ext Y) --> ext (bo X, Y) - // bo (ext X), C --> ext (bo X, C') - Value *NarrowBO = Builder.CreateBinOp(BO.getOpcode(), X, Y, "narrow"); - if (auto *NewBinOp = dyn_cast<BinaryOperator>(NarrowBO)) { - if (IsSext) - NewBinOp->setHasNoSignedWrap(); - else - NewBinOp->setHasNoUnsignedWrap(); - } - return CastInst::Create(CastOpc, NarrowBO, BO.getType()); -} - -Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) { - SmallVector<Value*, 8> Ops(GEP.op_begin(), GEP.op_end()); - Type *GEPType = GEP.getType(); - Type *GEPEltType = GEP.getSourceElementType(); - if (Value *V = SimplifyGEPInst(GEPEltType, Ops, SQ.getWithInstruction(&GEP))) - return replaceInstUsesWith(GEP, V); - - Value *PtrOp = GEP.getOperand(0); - - // Eliminate unneeded casts for indices, and replace indices which displace - // by multiples of a zero size type with zero. - bool MadeChange = false; - - // Index width may not be the same width as pointer width. - // Data layout chooses the right type based on supported integer types. - Type *NewScalarIndexTy = - DL.getIndexType(GEP.getPointerOperandType()->getScalarType()); - - gep_type_iterator GTI = gep_type_begin(GEP); - for (User::op_iterator I = GEP.op_begin() + 1, E = GEP.op_end(); I != E; - ++I, ++GTI) { - // Skip indices into struct types. - if (GTI.isStruct()) - continue; - - Type *IndexTy = (*I)->getType(); - Type *NewIndexType = - IndexTy->isVectorTy() - ? VectorType::get(NewScalarIndexTy, IndexTy->getVectorNumElements()) - : NewScalarIndexTy; - - // If the element type has zero size then any index over it is equivalent - // to an index of zero, so replace it with zero if it is not zero already. - Type *EltTy = GTI.getIndexedType(); - if (EltTy->isSized() && DL.getTypeAllocSize(EltTy) == 0) - if (!isa<Constant>(*I) || !cast<Constant>(*I)->isNullValue()) { - *I = Constant::getNullValue(NewIndexType); - MadeChange = true; - } - - if (IndexTy != NewIndexType) { - // If we are using a wider index than needed for this platform, shrink - // it to what we need. If narrower, sign-extend it to what we need. - // This explicit cast can make subsequent optimizations more obvious. - *I = Builder.CreateIntCast(*I, NewIndexType, true); - MadeChange = true; - } - } - if (MadeChange) - return &GEP; - - // Check to see if the inputs to the PHI node are getelementptr instructions. - if (auto *PN = dyn_cast<PHINode>(PtrOp)) { - auto *Op1 = dyn_cast<GetElementPtrInst>(PN->getOperand(0)); - if (!Op1) - return nullptr; - - // Don't fold a GEP into itself through a PHI node. This can only happen - // through the back-edge of a loop. Folding a GEP into itself means that - // the value of the previous iteration needs to be stored in the meantime, - // thus requiring an additional register variable to be live, but not - // actually achieving anything (the GEP still needs to be executed once per - // loop iteration). - if (Op1 == &GEP) - return nullptr; - - int DI = -1; - - for (auto I = PN->op_begin()+1, E = PN->op_end(); I !=E; ++I) { - auto *Op2 = dyn_cast<GetElementPtrInst>(*I); - if (!Op2 || Op1->getNumOperands() != Op2->getNumOperands()) - return nullptr; - - // As for Op1 above, don't try to fold a GEP into itself. - if (Op2 == &GEP) - return nullptr; - - // Keep track of the type as we walk the GEP. - Type *CurTy = nullptr; - - for (unsigned J = 0, F = Op1->getNumOperands(); J != F; ++J) { - if (Op1->getOperand(J)->getType() != Op2->getOperand(J)->getType()) - return nullptr; - - if (Op1->getOperand(J) != Op2->getOperand(J)) { - if (DI == -1) { - // We have not seen any differences yet in the GEPs feeding the - // PHI yet, so we record this one if it is allowed to be a - // variable. - - // The first two arguments can vary for any GEP, the rest have to be - // static for struct slots - if (J > 1 && CurTy->isStructTy()) - return nullptr; - - DI = J; - } else { - // The GEP is different by more than one input. While this could be - // extended to support GEPs that vary by more than one variable it - // doesn't make sense since it greatly increases the complexity and - // would result in an R+R+R addressing mode which no backend - // directly supports and would need to be broken into several - // simpler instructions anyway. - return nullptr; - } - } - - // Sink down a layer of the type for the next iteration. - if (J > 0) { - if (J == 1) { - CurTy = Op1->getSourceElementType(); - } else if (auto *CT = dyn_cast<CompositeType>(CurTy)) { - CurTy = CT->getTypeAtIndex(Op1->getOperand(J)); - } else { - CurTy = nullptr; - } - } - } - } - - // If not all GEPs are identical we'll have to create a new PHI node. - // Check that the old PHI node has only one use so that it will get - // removed. - if (DI != -1 && !PN->hasOneUse()) - return nullptr; - - auto *NewGEP = cast<GetElementPtrInst>(Op1->clone()); - if (DI == -1) { - // All the GEPs feeding the PHI are identical. Clone one down into our - // BB so that it can be merged with the current GEP. - GEP.getParent()->getInstList().insert( - GEP.getParent()->getFirstInsertionPt(), NewGEP); - } else { - // All the GEPs feeding the PHI differ at a single offset. Clone a GEP - // into the current block so it can be merged, and create a new PHI to - // set that index. - PHINode *NewPN; - { - IRBuilderBase::InsertPointGuard Guard(Builder); - Builder.SetInsertPoint(PN); - NewPN = Builder.CreatePHI(Op1->getOperand(DI)->getType(), - PN->getNumOperands()); - } - - for (auto &I : PN->operands()) - NewPN->addIncoming(cast<GEPOperator>(I)->getOperand(DI), - PN->getIncomingBlock(I)); - - NewGEP->setOperand(DI, NewPN); - GEP.getParent()->getInstList().insert( - GEP.getParent()->getFirstInsertionPt(), NewGEP); - NewGEP->setOperand(DI, NewPN); - } - - GEP.setOperand(0, NewGEP); - PtrOp = NewGEP; - } - - // Combine Indices - If the source pointer to this getelementptr instruction - // is a getelementptr instruction, combine the indices of the two - // getelementptr instructions into a single instruction. - if (auto *Src = dyn_cast<GEPOperator>(PtrOp)) { - if (!shouldMergeGEPs(*cast<GEPOperator>(&GEP), *Src)) - return nullptr; - - // Try to reassociate loop invariant GEP chains to enable LICM. - if (LI && Src->getNumOperands() == 2 && GEP.getNumOperands() == 2 && - Src->hasOneUse()) { - if (Loop *L = LI->getLoopFor(GEP.getParent())) { - Value *GO1 = GEP.getOperand(1); - Value *SO1 = Src->getOperand(1); - // Reassociate the two GEPs if SO1 is variant in the loop and GO1 is - // invariant: this breaks the dependence between GEPs and allows LICM - // to hoist the invariant part out of the loop. - if (L->isLoopInvariant(GO1) && !L->isLoopInvariant(SO1)) { - // We have to be careful here. - // We have something like: - // %src = getelementptr <ty>, <ty>* %base, <ty> %idx - // %gep = getelementptr <ty>, <ty>* %src, <ty> %idx2 - // If we just swap idx & idx2 then we could inadvertantly - // change %src from a vector to a scalar, or vice versa. - // Cases: - // 1) %base a scalar & idx a scalar & idx2 a vector - // => Swapping idx & idx2 turns %src into a vector type. - // 2) %base a scalar & idx a vector & idx2 a scalar - // => Swapping idx & idx2 turns %src in a scalar type - // 3) %base, %idx, and %idx2 are scalars - // => %src & %gep are scalars - // => swapping idx & idx2 is safe - // 4) %base a vector - // => %src is a vector - // => swapping idx & idx2 is safe. - auto *SO0 = Src->getOperand(0); - auto *SO0Ty = SO0->getType(); - if (!isa<VectorType>(GEPType) || // case 3 - isa<VectorType>(SO0Ty)) { // case 4 - Src->setOperand(1, GO1); - GEP.setOperand(1, SO1); - return &GEP; - } else { - // Case 1 or 2 - // -- have to recreate %src & %gep - // put NewSrc at same location as %src - Builder.SetInsertPoint(cast<Instruction>(PtrOp)); - auto *NewSrc = cast<GetElementPtrInst>( - Builder.CreateGEP(SO0, GO1, Src->getName())); - NewSrc->setIsInBounds(Src->isInBounds()); - auto *NewGEP = GetElementPtrInst::Create(nullptr, NewSrc, {SO1}); - NewGEP->setIsInBounds(GEP.isInBounds()); - return NewGEP; - } - } - } - } - - // Note that if our source is a gep chain itself then we wait for that - // chain to be resolved before we perform this transformation. This - // avoids us creating a TON of code in some cases. - if (auto *SrcGEP = dyn_cast<GEPOperator>(Src->getOperand(0))) - if (SrcGEP->getNumOperands() == 2 && shouldMergeGEPs(*Src, *SrcGEP)) - return nullptr; // Wait until our source is folded to completion. - - SmallVector<Value*, 8> Indices; - - // Find out whether the last index in the source GEP is a sequential idx. - bool EndsWithSequential = false; - for (gep_type_iterator I = gep_type_begin(*Src), E = gep_type_end(*Src); - I != E; ++I) - EndsWithSequential = I.isSequential(); - - // Can we combine the two pointer arithmetics offsets? - if (EndsWithSequential) { - // Replace: gep (gep %P, long B), long A, ... - // With: T = long A+B; gep %P, T, ... - Value *SO1 = Src->getOperand(Src->getNumOperands()-1); - Value *GO1 = GEP.getOperand(1); - - // If they aren't the same type, then the input hasn't been processed - // by the loop above yet (which canonicalizes sequential index types to - // intptr_t). Just avoid transforming this until the input has been - // normalized. - if (SO1->getType() != GO1->getType()) - return nullptr; - - Value *Sum = - SimplifyAddInst(GO1, SO1, false, false, SQ.getWithInstruction(&GEP)); - // Only do the combine when we are sure the cost after the - // merge is never more than that before the merge. - if (Sum == nullptr) - return nullptr; - - // Update the GEP in place if possible. - if (Src->getNumOperands() == 2) { - GEP.setOperand(0, Src->getOperand(0)); - GEP.setOperand(1, Sum); - return &GEP; - } - Indices.append(Src->op_begin()+1, Src->op_end()-1); - Indices.push_back(Sum); - Indices.append(GEP.op_begin()+2, GEP.op_end()); - } else if (isa<Constant>(*GEP.idx_begin()) && - cast<Constant>(*GEP.idx_begin())->isNullValue() && - Src->getNumOperands() != 1) { - // Otherwise we can do the fold if the first index of the GEP is a zero - Indices.append(Src->op_begin()+1, Src->op_end()); - Indices.append(GEP.idx_begin()+1, GEP.idx_end()); - } - - if (!Indices.empty()) - return GEP.isInBounds() && Src->isInBounds() - ? GetElementPtrInst::CreateInBounds( - Src->getSourceElementType(), Src->getOperand(0), Indices, - GEP.getName()) - : GetElementPtrInst::Create(Src->getSourceElementType(), - Src->getOperand(0), Indices, - GEP.getName()); - } - - if (GEP.getNumIndices() == 1) { - unsigned AS = GEP.getPointerAddressSpace(); - if (GEP.getOperand(1)->getType()->getScalarSizeInBits() == - DL.getIndexSizeInBits(AS)) { - uint64_t TyAllocSize = DL.getTypeAllocSize(GEPEltType); - - bool Matched = false; - uint64_t C; - Value *V = nullptr; - if (TyAllocSize == 1) { - V = GEP.getOperand(1); - Matched = true; - } else if (match(GEP.getOperand(1), - m_AShr(m_Value(V), m_ConstantInt(C)))) { - if (TyAllocSize == 1ULL << C) - Matched = true; - } else if (match(GEP.getOperand(1), - m_SDiv(m_Value(V), m_ConstantInt(C)))) { - if (TyAllocSize == C) - Matched = true; - } - - if (Matched) { - // Canonicalize (gep i8* X, -(ptrtoint Y)) - // to (inttoptr (sub (ptrtoint X), (ptrtoint Y))) - // The GEP pattern is emitted by the SCEV expander for certain kinds of - // pointer arithmetic. - if (match(V, m_Neg(m_PtrToInt(m_Value())))) { - Operator *Index = cast<Operator>(V); - Value *PtrToInt = Builder.CreatePtrToInt(PtrOp, Index->getType()); - Value *NewSub = Builder.CreateSub(PtrToInt, Index->getOperand(1)); - return CastInst::Create(Instruction::IntToPtr, NewSub, GEPType); - } - // Canonicalize (gep i8* X, (ptrtoint Y)-(ptrtoint X)) - // to (bitcast Y) - Value *Y; - if (match(V, m_Sub(m_PtrToInt(m_Value(Y)), - m_PtrToInt(m_Specific(GEP.getOperand(0)))))) - return CastInst::CreatePointerBitCastOrAddrSpaceCast(Y, GEPType); - } - } - } - - // We do not handle pointer-vector geps here. - if (GEPType->isVectorTy()) - return nullptr; - - // Handle gep(bitcast x) and gep(gep x, 0, 0, 0). - Value *StrippedPtr = PtrOp->stripPointerCasts(); - PointerType *StrippedPtrTy = cast<PointerType>(StrippedPtr->getType()); - - if (StrippedPtr != PtrOp) { - bool HasZeroPointerIndex = false; - if (auto *C = dyn_cast<ConstantInt>(GEP.getOperand(1))) - HasZeroPointerIndex = C->isZero(); - - // Transform: GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... - // into : GEP [10 x i8]* X, i32 0, ... - // - // Likewise, transform: GEP (bitcast i8* X to [0 x i8]*), i32 0, ... - // into : GEP i8* X, ... - // - // This occurs when the program declares an array extern like "int X[];" - if (HasZeroPointerIndex) { - if (auto *CATy = dyn_cast<ArrayType>(GEPEltType)) { - // GEP (bitcast i8* X to [0 x i8]*), i32 0, ... ? - if (CATy->getElementType() == StrippedPtrTy->getElementType()) { - // -> GEP i8* X, ... - SmallVector<Value*, 8> Idx(GEP.idx_begin()+1, GEP.idx_end()); - GetElementPtrInst *Res = GetElementPtrInst::Create( - StrippedPtrTy->getElementType(), StrippedPtr, Idx, GEP.getName()); - Res->setIsInBounds(GEP.isInBounds()); - if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) - return Res; - // Insert Res, and create an addrspacecast. - // e.g., - // GEP (addrspacecast i8 addrspace(1)* X to [0 x i8]*), i32 0, ... - // -> - // %0 = GEP i8 addrspace(1)* X, ... - // addrspacecast i8 addrspace(1)* %0 to i8* - return new AddrSpaceCastInst(Builder.Insert(Res), GEPType); - } - - if (auto *XATy = dyn_cast<ArrayType>(StrippedPtrTy->getElementType())) { - // GEP (bitcast [10 x i8]* X to [0 x i8]*), i32 0, ... ? - if (CATy->getElementType() == XATy->getElementType()) { - // -> GEP [10 x i8]* X, i32 0, ... - // At this point, we know that the cast source type is a pointer - // to an array of the same type as the destination pointer - // array. Because the array type is never stepped over (there - // is a leading zero) we can fold the cast into this GEP. - if (StrippedPtrTy->getAddressSpace() == GEP.getAddressSpace()) { - GEP.setOperand(0, StrippedPtr); - GEP.setSourceElementType(XATy); - return &GEP; - } - // Cannot replace the base pointer directly because StrippedPtr's - // address space is different. Instead, create a new GEP followed by - // an addrspacecast. - // e.g., - // GEP (addrspacecast [10 x i8] addrspace(1)* X to [0 x i8]*), - // i32 0, ... - // -> - // %0 = GEP [10 x i8] addrspace(1)* X, ... - // addrspacecast i8 addrspace(1)* %0 to i8* - SmallVector<Value*, 8> Idx(GEP.idx_begin(), GEP.idx_end()); - Value *NewGEP = GEP.isInBounds() - ? Builder.CreateInBoundsGEP( - nullptr, StrippedPtr, Idx, GEP.getName()) - : Builder.CreateGEP(nullptr, StrippedPtr, Idx, - GEP.getName()); - return new AddrSpaceCastInst(NewGEP, GEPType); - } - } - } - } else if (GEP.getNumOperands() == 2) { - // Transform things like: - // %t = getelementptr i32* bitcast ([2 x i32]* %str to i32*), i32 %V - // into: %t1 = getelementptr [2 x i32]* %str, i32 0, i32 %V; bitcast - Type *SrcEltTy = StrippedPtrTy->getElementType(); - if (SrcEltTy->isArrayTy() && - DL.getTypeAllocSize(SrcEltTy->getArrayElementType()) == - DL.getTypeAllocSize(GEPEltType)) { - Type *IdxType = DL.getIndexType(GEPType); - Value *Idx[2] = { Constant::getNullValue(IdxType), GEP.getOperand(1) }; - Value *NewGEP = - GEP.isInBounds() - ? Builder.CreateInBoundsGEP(nullptr, StrippedPtr, Idx, - GEP.getName()) - : Builder.CreateGEP(nullptr, StrippedPtr, Idx, GEP.getName()); - - // V and GEP are both pointer types --> BitCast - return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, GEPType); - } - - // Transform things like: - // %V = mul i64 %N, 4 - // %t = getelementptr i8* bitcast (i32* %arr to i8*), i32 %V - // into: %t1 = getelementptr i32* %arr, i32 %N; bitcast - if (GEPEltType->isSized() && SrcEltTy->isSized()) { - // Check that changing the type amounts to dividing the index by a scale - // factor. - uint64_t ResSize = DL.getTypeAllocSize(GEPEltType); - uint64_t SrcSize = DL.getTypeAllocSize(SrcEltTy); - if (ResSize && SrcSize % ResSize == 0) { - Value *Idx = GEP.getOperand(1); - unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); - uint64_t Scale = SrcSize / ResSize; - - // Earlier transforms ensure that the index has the right type - // according to Data Layout, which considerably simplifies the - // logic by eliminating implicit casts. - assert(Idx->getType() == DL.getIndexType(GEPType) && - "Index type does not match the Data Layout preferences"); - - bool NSW; - if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { - // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. - // If the multiplication NewIdx * Scale may overflow then the new - // GEP may not be "inbounds". - Value *NewGEP = - GEP.isInBounds() && NSW - ? Builder.CreateInBoundsGEP(nullptr, StrippedPtr, NewIdx, - GEP.getName()) - : Builder.CreateGEP(nullptr, StrippedPtr, NewIdx, - GEP.getName()); - - // The NewGEP must be pointer typed, so must the old one -> BitCast - return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, - GEPType); - } - } - } - - // Similarly, transform things like: - // getelementptr i8* bitcast ([100 x double]* X to i8*), i32 %tmp - // (where tmp = 8*tmp2) into: - // getelementptr [100 x double]* %arr, i32 0, i32 %tmp2; bitcast - if (GEPEltType->isSized() && SrcEltTy->isSized() && - SrcEltTy->isArrayTy()) { - // Check that changing to the array element type amounts to dividing the - // index by a scale factor. - uint64_t ResSize = DL.getTypeAllocSize(GEPEltType); - uint64_t ArrayEltSize = - DL.getTypeAllocSize(SrcEltTy->getArrayElementType()); - if (ResSize && ArrayEltSize % ResSize == 0) { - Value *Idx = GEP.getOperand(1); - unsigned BitWidth = Idx->getType()->getPrimitiveSizeInBits(); - uint64_t Scale = ArrayEltSize / ResSize; - - // Earlier transforms ensure that the index has the right type - // according to the Data Layout, which considerably simplifies - // the logic by eliminating implicit casts. - assert(Idx->getType() == DL.getIndexType(GEPType) && - "Index type does not match the Data Layout preferences"); - - bool NSW; - if (Value *NewIdx = Descale(Idx, APInt(BitWidth, Scale), NSW)) { - // Successfully decomposed Idx as NewIdx * Scale, form a new GEP. - // If the multiplication NewIdx * Scale may overflow then the new - // GEP may not be "inbounds". - Type *IndTy = DL.getIndexType(GEPType); - Value *Off[2] = {Constant::getNullValue(IndTy), NewIdx}; - - Value *NewGEP = GEP.isInBounds() && NSW - ? Builder.CreateInBoundsGEP( - SrcEltTy, StrippedPtr, Off, GEP.getName()) - : Builder.CreateGEP(SrcEltTy, StrippedPtr, Off, - GEP.getName()); - // The NewGEP must be pointer typed, so must the old one -> BitCast - return CastInst::CreatePointerBitCastOrAddrSpaceCast(NewGEP, - GEPType); - } - } - } - } - } - - // addrspacecast between types is canonicalized as a bitcast, then an - // addrspacecast. To take advantage of the below bitcast + struct GEP, look - // through the addrspacecast. - Value *ASCStrippedPtrOp = PtrOp; - if (auto *ASC = dyn_cast<AddrSpaceCastInst>(PtrOp)) { - // X = bitcast A addrspace(1)* to B addrspace(1)* - // Y = addrspacecast A addrspace(1)* to B addrspace(2)* - // Z = gep Y, <...constant indices...> - // Into an addrspacecasted GEP of the struct. - if (auto *BC = dyn_cast<BitCastInst>(ASC->getOperand(0))) - ASCStrippedPtrOp = BC; - } - - if (auto *BCI = dyn_cast<BitCastInst>(ASCStrippedPtrOp)) { - Value *SrcOp = BCI->getOperand(0); - PointerType *SrcType = cast<PointerType>(BCI->getSrcTy()); - Type *SrcEltType = SrcType->getElementType(); - - // GEP directly using the source operand if this GEP is accessing an element - // of a bitcasted pointer to vector or array of the same dimensions: - // gep (bitcast <c x ty>* X to [c x ty]*), Y, Z --> gep X, Y, Z - // gep (bitcast [c x ty]* X to <c x ty>*), Y, Z --> gep X, Y, Z - auto areMatchingArrayAndVecTypes = [](Type *ArrTy, Type *VecTy) { - return ArrTy->getArrayElementType() == VecTy->getVectorElementType() && - ArrTy->getArrayNumElements() == VecTy->getVectorNumElements(); - }; - if (GEP.getNumOperands() == 3 && - ((GEPEltType->isArrayTy() && SrcEltType->isVectorTy() && - areMatchingArrayAndVecTypes(GEPEltType, SrcEltType)) || - (GEPEltType->isVectorTy() && SrcEltType->isArrayTy() && - areMatchingArrayAndVecTypes(SrcEltType, GEPEltType)))) { - - // Create a new GEP here, as using `setOperand()` followed by - // `setSourceElementType()` won't actually update the type of the - // existing GEP Value. Causing issues if this Value is accessed when - // constructing an AddrSpaceCastInst - Value *NGEP = - GEP.isInBounds() - ? Builder.CreateInBoundsGEP(nullptr, SrcOp, {Ops[1], Ops[2]}) - : Builder.CreateGEP(nullptr, SrcOp, {Ops[1], Ops[2]}); - NGEP->takeName(&GEP); - - // Preserve GEP address space to satisfy users - if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace()) - return new AddrSpaceCastInst(NGEP, GEPType); - - return replaceInstUsesWith(GEP, NGEP); - } - - // See if we can simplify: - // X = bitcast A* to B* - // Y = gep X, <...constant indices...> - // into a gep of the original struct. This is important for SROA and alias - // analysis of unions. If "A" is also a bitcast, wait for A/X to be merged. - unsigned OffsetBits = DL.getIndexTypeSizeInBits(GEPType); - APInt Offset(OffsetBits, 0); - if (!isa<BitCastInst>(SrcOp) && GEP.accumulateConstantOffset(DL, Offset)) { - // If this GEP instruction doesn't move the pointer, just replace the GEP - // with a bitcast of the real input to the dest type. - if (!Offset) { - // If the bitcast is of an allocation, and the allocation will be - // converted to match the type of the cast, don't touch this. - if (isa<AllocaInst>(SrcOp) || isAllocationFn(SrcOp, &TLI)) { - // See if the bitcast simplifies, if so, don't nuke this GEP yet. - if (Instruction *I = visitBitCast(*BCI)) { - if (I != BCI) { - I->takeName(BCI); - BCI->getParent()->getInstList().insert(BCI->getIterator(), I); - replaceInstUsesWith(*BCI, I); - } - return &GEP; - } - } - - if (SrcType->getPointerAddressSpace() != GEP.getAddressSpace()) - return new AddrSpaceCastInst(SrcOp, GEPType); - return new BitCastInst(SrcOp, GEPType); - } - - // Otherwise, if the offset is non-zero, we need to find out if there is a - // field at Offset in 'A's type. If so, we can pull the cast through the - // GEP. - SmallVector<Value*, 8> NewIndices; - if (FindElementAtOffset(SrcType, Offset.getSExtValue(), NewIndices)) { - Value *NGEP = - GEP.isInBounds() - ? Builder.CreateInBoundsGEP(nullptr, SrcOp, NewIndices) - : Builder.CreateGEP(nullptr, SrcOp, NewIndices); - - if (NGEP->getType() == GEPType) - return replaceInstUsesWith(GEP, NGEP); - NGEP->takeName(&GEP); - - if (NGEP->getType()->getPointerAddressSpace() != GEP.getAddressSpace()) - return new AddrSpaceCastInst(NGEP, GEPType); - return new BitCastInst(NGEP, GEPType); - } - } - } - - if (!GEP.isInBounds()) { - unsigned IdxWidth = - DL.getIndexSizeInBits(PtrOp->getType()->getPointerAddressSpace()); - APInt BasePtrOffset(IdxWidth, 0); - Value *UnderlyingPtrOp = - PtrOp->stripAndAccumulateInBoundsConstantOffsets(DL, - BasePtrOffset); - if (auto *AI = dyn_cast<AllocaInst>(UnderlyingPtrOp)) { - if (GEP.accumulateConstantOffset(DL, BasePtrOffset) && - BasePtrOffset.isNonNegative()) { - APInt AllocSize(IdxWidth, DL.getTypeAllocSize(AI->getAllocatedType())); - if (BasePtrOffset.ule(AllocSize)) { - return GetElementPtrInst::CreateInBounds( - PtrOp, makeArrayRef(Ops).slice(1), GEP.getName()); - } - } - } - } - - return nullptr; -} - -static bool isNeverEqualToUnescapedAlloc(Value *V, const TargetLibraryInfo *TLI, - Instruction *AI) { - if (isa<ConstantPointerNull>(V)) - return true; - if (auto *LI = dyn_cast<LoadInst>(V)) - return isa<GlobalVariable>(LI->getPointerOperand()); - // Two distinct allocations will never be equal. - // We rely on LookThroughBitCast in isAllocLikeFn being false, since looking - // through bitcasts of V can cause - // the result statement below to be true, even when AI and V (ex: - // i8* ->i32* ->i8* of AI) are the same allocations. - return isAllocLikeFn(V, TLI) && V != AI; -} - -static bool isAllocSiteRemovable(Instruction *AI, - SmallVectorImpl<WeakTrackingVH> &Users, - const TargetLibraryInfo *TLI) { - SmallVector<Instruction*, 4> Worklist; - Worklist.push_back(AI); - - do { - Instruction *PI = Worklist.pop_back_val(); - for (User *U : PI->users()) { - Instruction *I = cast<Instruction>(U); - switch (I->getOpcode()) { - default: - // Give up the moment we see something we can't handle. - return false; - - case Instruction::AddrSpaceCast: - case Instruction::BitCast: - case Instruction::GetElementPtr: - Users.emplace_back(I); - Worklist.push_back(I); - continue; - - case Instruction::ICmp: { - ICmpInst *ICI = cast<ICmpInst>(I); - // We can fold eq/ne comparisons with null to false/true, respectively. - // We also fold comparisons in some conditions provided the alloc has - // not escaped (see isNeverEqualToUnescapedAlloc). - if (!ICI->isEquality()) - return false; - unsigned OtherIndex = (ICI->getOperand(0) == PI) ? 1 : 0; - if (!isNeverEqualToUnescapedAlloc(ICI->getOperand(OtherIndex), TLI, AI)) - return false; - Users.emplace_back(I); - continue; - } - - case Instruction::Call: - // Ignore no-op and store intrinsics. - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { - switch (II->getIntrinsicID()) { - default: - return false; - - case Intrinsic::memmove: - case Intrinsic::memcpy: - case Intrinsic::memset: { - MemIntrinsic *MI = cast<MemIntrinsic>(II); - if (MI->isVolatile() || MI->getRawDest() != PI) - return false; - LLVM_FALLTHROUGH; - } - case Intrinsic::invariant_start: - case Intrinsic::invariant_end: - case Intrinsic::lifetime_start: - case Intrinsic::lifetime_end: - case Intrinsic::objectsize: - Users.emplace_back(I); - continue; - } - } - - if (isFreeCall(I, TLI)) { - Users.emplace_back(I); - continue; - } - return false; - - case Instruction::Store: { - StoreInst *SI = cast<StoreInst>(I); - if (SI->isVolatile() || SI->getPointerOperand() != PI) - return false; - Users.emplace_back(I); - continue; - } - } - llvm_unreachable("missing a return?"); - } - } while (!Worklist.empty()); - return true; -} - -Instruction *InstCombiner::visitAllocSite(Instruction &MI) { - // If we have a malloc call which is only used in any amount of comparisons to - // null and free calls, delete the calls and replace the comparisons with true - // or false as appropriate. - - // This is based on the principle that we can substitute our own allocation - // function (which will never return null) rather than knowledge of the - // specific function being called. In some sense this can change the permitted - // outputs of a program (when we convert a malloc to an alloca, the fact that - // the allocation is now on the stack is potentially visible, for example), - // but we believe in a permissible manner. - SmallVector<WeakTrackingVH, 64> Users; - - // If we are removing an alloca with a dbg.declare, insert dbg.value calls - // before each store. - TinyPtrVector<DbgVariableIntrinsic *> DIIs; - std::unique_ptr<DIBuilder> DIB; - if (isa<AllocaInst>(MI)) { - DIIs = FindDbgAddrUses(&MI); - DIB.reset(new DIBuilder(*MI.getModule(), /*AllowUnresolved=*/false)); - } - - if (isAllocSiteRemovable(&MI, Users, &TLI)) { - for (unsigned i = 0, e = Users.size(); i != e; ++i) { - // Lowering all @llvm.objectsize calls first because they may - // use a bitcast/GEP of the alloca we are removing. - if (!Users[i]) - continue; - - Instruction *I = cast<Instruction>(&*Users[i]); - - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) { - if (II->getIntrinsicID() == Intrinsic::objectsize) { - ConstantInt *Result = lowerObjectSizeCall(II, DL, &TLI, - /*MustSucceed=*/true); - replaceInstUsesWith(*I, Result); - eraseInstFromFunction(*I); - Users[i] = nullptr; // Skip examining in the next loop. - } - } - } - for (unsigned i = 0, e = Users.size(); i != e; ++i) { - if (!Users[i]) - continue; - - Instruction *I = cast<Instruction>(&*Users[i]); - - if (ICmpInst *C = dyn_cast<ICmpInst>(I)) { - replaceInstUsesWith(*C, - ConstantInt::get(Type::getInt1Ty(C->getContext()), - C->isFalseWhenEqual())); - } else if (isa<BitCastInst>(I) || isa<GetElementPtrInst>(I) || - isa<AddrSpaceCastInst>(I)) { - replaceInstUsesWith(*I, UndefValue::get(I->getType())); - } else if (auto *SI = dyn_cast<StoreInst>(I)) { - for (auto *DII : DIIs) - ConvertDebugDeclareToDebugValue(DII, SI, *DIB); - } - eraseInstFromFunction(*I); - } - - if (InvokeInst *II = dyn_cast<InvokeInst>(&MI)) { - // Replace invoke with a NOP intrinsic to maintain the original CFG - Module *M = II->getModule(); - Function *F = Intrinsic::getDeclaration(M, Intrinsic::donothing); - InvokeInst::Create(F, II->getNormalDest(), II->getUnwindDest(), - None, "", II->getParent()); - } - - for (auto *DII : DIIs) - eraseInstFromFunction(*DII); - - return eraseInstFromFunction(MI); - } - return nullptr; -} - -/// Move the call to free before a NULL test. -/// -/// Check if this free is accessed after its argument has been test -/// against NULL (property 0). -/// If yes, it is legal to move this call in its predecessor block. -/// -/// The move is performed only if the block containing the call to free -/// will be removed, i.e.: -/// 1. it has only one predecessor P, and P has two successors -/// 2. it contains the call, noops, and an unconditional branch -/// 3. its successor is the same as its predecessor's successor -/// -/// The profitability is out-of concern here and this function should -/// be called only if the caller knows this transformation would be -/// profitable (e.g., for code size). -static Instruction *tryToMoveFreeBeforeNullTest(CallInst &FI, - const DataLayout &DL) { - Value *Op = FI.getArgOperand(0); - BasicBlock *FreeInstrBB = FI.getParent(); - BasicBlock *PredBB = FreeInstrBB->getSinglePredecessor(); - - // Validate part of constraint #1: Only one predecessor - // FIXME: We can extend the number of predecessor, but in that case, we - // would duplicate the call to free in each predecessor and it may - // not be profitable even for code size. - if (!PredBB) - return nullptr; - - // Validate constraint #2: Does this block contains only the call to - // free, noops, and an unconditional branch? - BasicBlock *SuccBB; - Instruction *FreeInstrBBTerminator = FreeInstrBB->getTerminator(); - if (!match(FreeInstrBBTerminator, m_UnconditionalBr(SuccBB))) - return nullptr; - - // If there are only 2 instructions in the block, at this point, - // this is the call to free and unconditional. - // If there are more than 2 instructions, check that they are noops - // i.e., they won't hurt the performance of the generated code. - if (FreeInstrBB->size() != 2) { - for (const Instruction &Inst : *FreeInstrBB) { - if (&Inst == &FI || &Inst == FreeInstrBBTerminator) - continue; - auto *Cast = dyn_cast<CastInst>(&Inst); - if (!Cast || !Cast->isNoopCast(DL)) - return nullptr; - } - } - // Validate the rest of constraint #1 by matching on the pred branch. - Instruction *TI = PredBB->getTerminator(); - BasicBlock *TrueBB, *FalseBB; - ICmpInst::Predicate Pred; - if (!match(TI, m_Br(m_ICmp(Pred, - m_CombineOr(m_Specific(Op), - m_Specific(Op->stripPointerCasts())), - m_Zero()), - TrueBB, FalseBB))) - return nullptr; - if (Pred != ICmpInst::ICMP_EQ && Pred != ICmpInst::ICMP_NE) - return nullptr; - - // Validate constraint #3: Ensure the null case just falls through. - if (SuccBB != (Pred == ICmpInst::ICMP_EQ ? TrueBB : FalseBB)) - return nullptr; - assert(FreeInstrBB == (Pred == ICmpInst::ICMP_EQ ? FalseBB : TrueBB) && - "Broken CFG: missing edge from predecessor to successor"); - - // At this point, we know that everything in FreeInstrBB can be moved - // before TI. - for (BasicBlock::iterator It = FreeInstrBB->begin(), End = FreeInstrBB->end(); - It != End;) { - Instruction &Instr = *It++; - if (&Instr == FreeInstrBBTerminator) - break; - Instr.moveBefore(TI); - } - assert(FreeInstrBB->size() == 1 && - "Only the branch instruction should remain"); - return &FI; -} - -Instruction *InstCombiner::visitFree(CallInst &FI) { - Value *Op = FI.getArgOperand(0); - - // free undef -> unreachable. - if (isa<UndefValue>(Op)) { - // Insert a new store to null because we cannot modify the CFG here. - Builder.CreateStore(ConstantInt::getTrue(FI.getContext()), - UndefValue::get(Type::getInt1PtrTy(FI.getContext()))); - return eraseInstFromFunction(FI); - } - - // If we have 'free null' delete the instruction. This can happen in stl code - // when lots of inlining happens. - if (isa<ConstantPointerNull>(Op)) - return eraseInstFromFunction(FI); - - // If we optimize for code size, try to move the call to free before the null - // test so that simplify cfg can remove the empty block and dead code - // elimination the branch. I.e., helps to turn something like: - // if (foo) free(foo); - // into - // free(foo); - if (MinimizeSize) - if (Instruction *I = tryToMoveFreeBeforeNullTest(FI, DL)) - return I; - - return nullptr; -} - -Instruction *InstCombiner::visitReturnInst(ReturnInst &RI) { - if (RI.getNumOperands() == 0) // ret void - return nullptr; - - Value *ResultOp = RI.getOperand(0); - Type *VTy = ResultOp->getType(); - if (!VTy->isIntegerTy()) - return nullptr; - - // There might be assume intrinsics dominating this return that completely - // determine the value. If so, constant fold it. - KnownBits Known = computeKnownBits(ResultOp, 0, &RI); - if (Known.isConstant()) - RI.setOperand(0, Constant::getIntegerValue(VTy, Known.getConstant())); - - return nullptr; -} - -Instruction *InstCombiner::visitBranchInst(BranchInst &BI) { - // Change br (not X), label True, label False to: br X, label False, True - Value *X = nullptr; - BasicBlock *TrueDest; - BasicBlock *FalseDest; - if (match(&BI, m_Br(m_Not(m_Value(X)), TrueDest, FalseDest)) && - !isa<Constant>(X)) { - // Swap Destinations and condition... - BI.setCondition(X); - BI.swapSuccessors(); - return &BI; - } - - // If the condition is irrelevant, remove the use so that other - // transforms on the condition become more effective. - if (BI.isConditional() && !isa<ConstantInt>(BI.getCondition()) && - BI.getSuccessor(0) == BI.getSuccessor(1)) { - BI.setCondition(ConstantInt::getFalse(BI.getCondition()->getType())); - return &BI; - } - - // Canonicalize, for example, icmp_ne -> icmp_eq or fcmp_one -> fcmp_oeq. - CmpInst::Predicate Pred; - if (match(&BI, m_Br(m_OneUse(m_Cmp(Pred, m_Value(), m_Value())), TrueDest, - FalseDest)) && - !isCanonicalPredicate(Pred)) { - // Swap destinations and condition. - CmpInst *Cond = cast<CmpInst>(BI.getCondition()); - Cond->setPredicate(CmpInst::getInversePredicate(Pred)); - BI.swapSuccessors(); - Worklist.Add(Cond); - return &BI; - } - - return nullptr; -} - -Instruction *InstCombiner::visitSwitchInst(SwitchInst &SI) { - Value *Cond = SI.getCondition(); - Value *Op0; - ConstantInt *AddRHS; - if (match(Cond, m_Add(m_Value(Op0), m_ConstantInt(AddRHS)))) { - // Change 'switch (X+4) case 1:' into 'switch (X) case -3'. - for (auto Case : SI.cases()) { - Constant *NewCase = ConstantExpr::getSub(Case.getCaseValue(), AddRHS); - assert(isa<ConstantInt>(NewCase) && - "Result of expression should be constant"); - Case.setValue(cast<ConstantInt>(NewCase)); - } - SI.setCondition(Op0); - return &SI; - } - - KnownBits Known = computeKnownBits(Cond, 0, &SI); - unsigned LeadingKnownZeros = Known.countMinLeadingZeros(); - unsigned LeadingKnownOnes = Known.countMinLeadingOnes(); - - // Compute the number of leading bits we can ignore. - // TODO: A better way to determine this would use ComputeNumSignBits(). - for (auto &C : SI.cases()) { - LeadingKnownZeros = std::min( - LeadingKnownZeros, C.getCaseValue()->getValue().countLeadingZeros()); - LeadingKnownOnes = std::min( - LeadingKnownOnes, C.getCaseValue()->getValue().countLeadingOnes()); - } - - unsigned NewWidth = Known.getBitWidth() - std::max(LeadingKnownZeros, LeadingKnownOnes); - - // Shrink the condition operand if the new type is smaller than the old type. - // But do not shrink to a non-standard type, because backend can't generate - // good code for that yet. - // TODO: We can make it aggressive again after fixing PR39569. - if (NewWidth > 0 && NewWidth < Known.getBitWidth() && - shouldChangeType(Known.getBitWidth(), NewWidth)) { - IntegerType *Ty = IntegerType::get(SI.getContext(), NewWidth); - Builder.SetInsertPoint(&SI); - Value *NewCond = Builder.CreateTrunc(Cond, Ty, "trunc"); - SI.setCondition(NewCond); - - for (auto Case : SI.cases()) { - APInt TruncatedCase = Case.getCaseValue()->getValue().trunc(NewWidth); - Case.setValue(ConstantInt::get(SI.getContext(), TruncatedCase)); - } - return &SI; - } - - return nullptr; -} - -Instruction *InstCombiner::visitExtractValueInst(ExtractValueInst &EV) { - Value *Agg = EV.getAggregateOperand(); - - if (!EV.hasIndices()) - return replaceInstUsesWith(EV, Agg); - - if (Value *V = SimplifyExtractValueInst(Agg, EV.getIndices(), - SQ.getWithInstruction(&EV))) - return replaceInstUsesWith(EV, V); - - if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) { - // We're extracting from an insertvalue instruction, compare the indices - const unsigned *exti, *exte, *insi, *inse; - for (exti = EV.idx_begin(), insi = IV->idx_begin(), - exte = EV.idx_end(), inse = IV->idx_end(); - exti != exte && insi != inse; - ++exti, ++insi) { - if (*insi != *exti) - // The insert and extract both reference distinctly different elements. - // This means the extract is not influenced by the insert, and we can - // replace the aggregate operand of the extract with the aggregate - // operand of the insert. i.e., replace - // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 - // %E = extractvalue { i32, { i32 } } %I, 0 - // with - // %E = extractvalue { i32, { i32 } } %A, 0 - return ExtractValueInst::Create(IV->getAggregateOperand(), - EV.getIndices()); - } - if (exti == exte && insi == inse) - // Both iterators are at the end: Index lists are identical. Replace - // %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 - // %C = extractvalue { i32, { i32 } } %B, 1, 0 - // with "i32 42" - return replaceInstUsesWith(EV, IV->getInsertedValueOperand()); - if (exti == exte) { - // The extract list is a prefix of the insert list. i.e. replace - // %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0 - // %E = extractvalue { i32, { i32 } } %I, 1 - // with - // %X = extractvalue { i32, { i32 } } %A, 1 - // %E = insertvalue { i32 } %X, i32 42, 0 - // by switching the order of the insert and extract (though the - // insertvalue should be left in, since it may have other uses). - Value *NewEV = Builder.CreateExtractValue(IV->getAggregateOperand(), - EV.getIndices()); - return InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(), - makeArrayRef(insi, inse)); - } - if (insi == inse) - // The insert list is a prefix of the extract list - // We can simply remove the common indices from the extract and make it - // operate on the inserted value instead of the insertvalue result. - // i.e., replace - // %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1 - // %E = extractvalue { i32, { i32 } } %I, 1, 0 - // with - // %E extractvalue { i32 } { i32 42 }, 0 - return ExtractValueInst::Create(IV->getInsertedValueOperand(), - makeArrayRef(exti, exte)); - } - if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Agg)) { - // We're extracting from an intrinsic, see if we're the only user, which - // allows us to simplify multiple result intrinsics to simpler things that - // just get one value. - if (II->hasOneUse()) { - // Check if we're grabbing the overflow bit or the result of a 'with - // overflow' intrinsic. If it's the latter we can remove the intrinsic - // and replace it with a traditional binary instruction. - switch (II->getIntrinsicID()) { - case Intrinsic::uadd_with_overflow: - case Intrinsic::sadd_with_overflow: - if (*EV.idx_begin() == 0) { // Normal result. - Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); - replaceInstUsesWith(*II, UndefValue::get(II->getType())); - eraseInstFromFunction(*II); - return BinaryOperator::CreateAdd(LHS, RHS); - } - - // If the normal result of the add is dead, and the RHS is a constant, - // we can transform this into a range comparison. - // overflow = uadd a, -4 --> overflow = icmp ugt a, 3 - if (II->getIntrinsicID() == Intrinsic::uadd_with_overflow) - if (ConstantInt *CI = dyn_cast<ConstantInt>(II->getArgOperand(1))) - return new ICmpInst(ICmpInst::ICMP_UGT, II->getArgOperand(0), - ConstantExpr::getNot(CI)); - break; - case Intrinsic::usub_with_overflow: - case Intrinsic::ssub_with_overflow: - if (*EV.idx_begin() == 0) { // Normal result. - Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); - replaceInstUsesWith(*II, UndefValue::get(II->getType())); - eraseInstFromFunction(*II); - return BinaryOperator::CreateSub(LHS, RHS); - } - break; - case Intrinsic::umul_with_overflow: - case Intrinsic::smul_with_overflow: - if (*EV.idx_begin() == 0) { // Normal result. - Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1); - replaceInstUsesWith(*II, UndefValue::get(II->getType())); - eraseInstFromFunction(*II); - return BinaryOperator::CreateMul(LHS, RHS); - } - break; - default: - break; - } - } - } - if (LoadInst *L = dyn_cast<LoadInst>(Agg)) - // If the (non-volatile) load only has one use, we can rewrite this to a - // load from a GEP. This reduces the size of the load. If a load is used - // only by extractvalue instructions then this either must have been - // optimized before, or it is a struct with padding, in which case we - // don't want to do the transformation as it loses padding knowledge. - if (L->isSimple() && L->hasOneUse()) { - // extractvalue has integer indices, getelementptr has Value*s. Convert. - SmallVector<Value*, 4> Indices; - // Prefix an i32 0 since we need the first element. - Indices.push_back(Builder.getInt32(0)); - for (ExtractValueInst::idx_iterator I = EV.idx_begin(), E = EV.idx_end(); - I != E; ++I) - Indices.push_back(Builder.getInt32(*I)); - - // We need to insert these at the location of the old load, not at that of - // the extractvalue. - Builder.SetInsertPoint(L); - Value *GEP = Builder.CreateInBoundsGEP(L->getType(), - L->getPointerOperand(), Indices); - Instruction *NL = Builder.CreateLoad(GEP); - // Whatever aliasing information we had for the orignal load must also - // hold for the smaller load, so propagate the annotations. - AAMDNodes Nodes; - L->getAAMetadata(Nodes); - NL->setAAMetadata(Nodes); - // Returning the load directly will cause the main loop to insert it in - // the wrong spot, so use replaceInstUsesWith(). - return replaceInstUsesWith(EV, NL); - } - // We could simplify extracts from other values. Note that nested extracts may - // already be simplified implicitly by the above: extract (extract (insert) ) - // will be translated into extract ( insert ( extract ) ) first and then just - // the value inserted, if appropriate. Similarly for extracts from single-use - // loads: extract (extract (load)) will be translated to extract (load (gep)) - // and if again single-use then via load (gep (gep)) to load (gep). - // However, double extracts from e.g. function arguments or return values - // aren't handled yet. - return nullptr; -} - -/// Return 'true' if the given typeinfo will match anything. -static bool isCatchAll(EHPersonality Personality, Constant *TypeInfo) { - switch (Personality) { - case EHPersonality::GNU_C: - case EHPersonality::GNU_C_SjLj: - case EHPersonality::Rust: - // The GCC C EH and Rust personality only exists to support cleanups, so - // it's not clear what the semantics of catch clauses are. - return false; - case EHPersonality::Unknown: - return false; - case EHPersonality::GNU_Ada: - // While __gnat_all_others_value will match any Ada exception, it doesn't - // match foreign exceptions (or didn't, before gcc-4.7). - return false; - case EHPersonality::GNU_CXX: - case EHPersonality::GNU_CXX_SjLj: - case EHPersonality::GNU_ObjC: - case EHPersonality::MSVC_X86SEH: - case EHPersonality::MSVC_Win64SEH: - case EHPersonality::MSVC_CXX: - case EHPersonality::CoreCLR: - case EHPersonality::Wasm_CXX: - return TypeInfo->isNullValue(); - } - llvm_unreachable("invalid enum"); -} - -static bool shorter_filter(const Value *LHS, const Value *RHS) { - return - cast<ArrayType>(LHS->getType())->getNumElements() - < - cast<ArrayType>(RHS->getType())->getNumElements(); -} - -Instruction *InstCombiner::visitLandingPadInst(LandingPadInst &LI) { - // The logic here should be correct for any real-world personality function. - // However if that turns out not to be true, the offending logic can always - // be conditioned on the personality function, like the catch-all logic is. - EHPersonality Personality = - classifyEHPersonality(LI.getParent()->getParent()->getPersonalityFn()); - - // Simplify the list of clauses, eg by removing repeated catch clauses - // (these are often created by inlining). - bool MakeNewInstruction = false; // If true, recreate using the following: - SmallVector<Constant *, 16> NewClauses; // - Clauses for the new instruction; - bool CleanupFlag = LI.isCleanup(); // - The new instruction is a cleanup. - - SmallPtrSet<Value *, 16> AlreadyCaught; // Typeinfos known caught already. - for (unsigned i = 0, e = LI.getNumClauses(); i != e; ++i) { - bool isLastClause = i + 1 == e; - if (LI.isCatch(i)) { - // A catch clause. - Constant *CatchClause = LI.getClause(i); - Constant *TypeInfo = CatchClause->stripPointerCasts(); - - // If we already saw this clause, there is no point in having a second - // copy of it. - if (AlreadyCaught.insert(TypeInfo).second) { - // This catch clause was not already seen. - NewClauses.push_back(CatchClause); - } else { - // Repeated catch clause - drop the redundant copy. - MakeNewInstruction = true; - } - - // If this is a catch-all then there is no point in keeping any following - // clauses or marking the landingpad as having a cleanup. - if (isCatchAll(Personality, TypeInfo)) { - if (!isLastClause) - MakeNewInstruction = true; - CleanupFlag = false; - break; - } - } else { - // A filter clause. If any of the filter elements were already caught - // then they can be dropped from the filter. It is tempting to try to - // exploit the filter further by saying that any typeinfo that does not - // occur in the filter can't be caught later (and thus can be dropped). - // However this would be wrong, since typeinfos can match without being - // equal (for example if one represents a C++ class, and the other some - // class derived from it). - assert(LI.isFilter(i) && "Unsupported landingpad clause!"); - Constant *FilterClause = LI.getClause(i); - ArrayType *FilterType = cast<ArrayType>(FilterClause->getType()); - unsigned NumTypeInfos = FilterType->getNumElements(); - - // An empty filter catches everything, so there is no point in keeping any - // following clauses or marking the landingpad as having a cleanup. By - // dealing with this case here the following code is made a bit simpler. - if (!NumTypeInfos) { - NewClauses.push_back(FilterClause); - if (!isLastClause) - MakeNewInstruction = true; - CleanupFlag = false; - break; - } - - bool MakeNewFilter = false; // If true, make a new filter. - SmallVector<Constant *, 16> NewFilterElts; // New elements. - if (isa<ConstantAggregateZero>(FilterClause)) { - // Not an empty filter - it contains at least one null typeinfo. - assert(NumTypeInfos > 0 && "Should have handled empty filter already!"); - Constant *TypeInfo = - Constant::getNullValue(FilterType->getElementType()); - // If this typeinfo is a catch-all then the filter can never match. - if (isCatchAll(Personality, TypeInfo)) { - // Throw the filter away. - MakeNewInstruction = true; - continue; - } - - // There is no point in having multiple copies of this typeinfo, so - // discard all but the first copy if there is more than one. - NewFilterElts.push_back(TypeInfo); - if (NumTypeInfos > 1) - MakeNewFilter = true; - } else { - ConstantArray *Filter = cast<ConstantArray>(FilterClause); - SmallPtrSet<Value *, 16> SeenInFilter; // For uniquing the elements. - NewFilterElts.reserve(NumTypeInfos); - - // Remove any filter elements that were already caught or that already - // occurred in the filter. While there, see if any of the elements are - // catch-alls. If so, the filter can be discarded. - bool SawCatchAll = false; - for (unsigned j = 0; j != NumTypeInfos; ++j) { - Constant *Elt = Filter->getOperand(j); - Constant *TypeInfo = Elt->stripPointerCasts(); - if (isCatchAll(Personality, TypeInfo)) { - // This element is a catch-all. Bail out, noting this fact. - SawCatchAll = true; - break; - } - - // Even if we've seen a type in a catch clause, we don't want to - // remove it from the filter. An unexpected type handler may be - // set up for a call site which throws an exception of the same - // type caught. In order for the exception thrown by the unexpected - // handler to propagate correctly, the filter must be correctly - // described for the call site. - // - // Example: - // - // void unexpected() { throw 1;} - // void foo() throw (int) { - // std::set_unexpected(unexpected); - // try { - // throw 2.0; - // } catch (int i) {} - // } - - // There is no point in having multiple copies of the same typeinfo in - // a filter, so only add it if we didn't already. - if (SeenInFilter.insert(TypeInfo).second) - NewFilterElts.push_back(cast<Constant>(Elt)); - } - // A filter containing a catch-all cannot match anything by definition. - if (SawCatchAll) { - // Throw the filter away. - MakeNewInstruction = true; - continue; - } - - // If we dropped something from the filter, make a new one. - if (NewFilterElts.size() < NumTypeInfos) - MakeNewFilter = true; - } - if (MakeNewFilter) { - FilterType = ArrayType::get(FilterType->getElementType(), - NewFilterElts.size()); - FilterClause = ConstantArray::get(FilterType, NewFilterElts); - MakeNewInstruction = true; - } - - NewClauses.push_back(FilterClause); - - // If the new filter is empty then it will catch everything so there is - // no point in keeping any following clauses or marking the landingpad - // as having a cleanup. The case of the original filter being empty was - // already handled above. - if (MakeNewFilter && !NewFilterElts.size()) { - assert(MakeNewInstruction && "New filter but not a new instruction!"); - CleanupFlag = false; - break; - } - } - } - - // If several filters occur in a row then reorder them so that the shortest - // filters come first (those with the smallest number of elements). This is - // advantageous because shorter filters are more likely to match, speeding up - // unwinding, but mostly because it increases the effectiveness of the other - // filter optimizations below. - for (unsigned i = 0, e = NewClauses.size(); i + 1 < e; ) { - unsigned j; - // Find the maximal 'j' s.t. the range [i, j) consists entirely of filters. - for (j = i; j != e; ++j) - if (!isa<ArrayType>(NewClauses[j]->getType())) - break; - - // Check whether the filters are already sorted by length. We need to know - // if sorting them is actually going to do anything so that we only make a - // new landingpad instruction if it does. - for (unsigned k = i; k + 1 < j; ++k) - if (shorter_filter(NewClauses[k+1], NewClauses[k])) { - // Not sorted, so sort the filters now. Doing an unstable sort would be - // correct too but reordering filters pointlessly might confuse users. - std::stable_sort(NewClauses.begin() + i, NewClauses.begin() + j, - shorter_filter); - MakeNewInstruction = true; - break; - } - - // Look for the next batch of filters. - i = j + 1; - } - - // If typeinfos matched if and only if equal, then the elements of a filter L - // that occurs later than a filter F could be replaced by the intersection of - // the elements of F and L. In reality two typeinfos can match without being - // equal (for example if one represents a C++ class, and the other some class - // derived from it) so it would be wrong to perform this transform in general. - // However the transform is correct and useful if F is a subset of L. In that - // case L can be replaced by F, and thus removed altogether since repeating a - // filter is pointless. So here we look at all pairs of filters F and L where - // L follows F in the list of clauses, and remove L if every element of F is - // an element of L. This can occur when inlining C++ functions with exception - // specifications. - for (unsigned i = 0; i + 1 < NewClauses.size(); ++i) { - // Examine each filter in turn. - Value *Filter = NewClauses[i]; - ArrayType *FTy = dyn_cast<ArrayType>(Filter->getType()); - if (!FTy) - // Not a filter - skip it. - continue; - unsigned FElts = FTy->getNumElements(); - // Examine each filter following this one. Doing this backwards means that - // we don't have to worry about filters disappearing under us when removed. - for (unsigned j = NewClauses.size() - 1; j != i; --j) { - Value *LFilter = NewClauses[j]; - ArrayType *LTy = dyn_cast<ArrayType>(LFilter->getType()); - if (!LTy) - // Not a filter - skip it. - continue; - // If Filter is a subset of LFilter, i.e. every element of Filter is also - // an element of LFilter, then discard LFilter. - SmallVectorImpl<Constant *>::iterator J = NewClauses.begin() + j; - // If Filter is empty then it is a subset of LFilter. - if (!FElts) { - // Discard LFilter. - NewClauses.erase(J); - MakeNewInstruction = true; - // Move on to the next filter. - continue; - } - unsigned LElts = LTy->getNumElements(); - // If Filter is longer than LFilter then it cannot be a subset of it. - if (FElts > LElts) - // Move on to the next filter. - continue; - // At this point we know that LFilter has at least one element. - if (isa<ConstantAggregateZero>(LFilter)) { // LFilter only contains zeros. - // Filter is a subset of LFilter iff Filter contains only zeros (as we - // already know that Filter is not longer than LFilter). - if (isa<ConstantAggregateZero>(Filter)) { - assert(FElts <= LElts && "Should have handled this case earlier!"); - // Discard LFilter. - NewClauses.erase(J); - MakeNewInstruction = true; - } - // Move on to the next filter. - continue; - } - ConstantArray *LArray = cast<ConstantArray>(LFilter); - if (isa<ConstantAggregateZero>(Filter)) { // Filter only contains zeros. - // Since Filter is non-empty and contains only zeros, it is a subset of - // LFilter iff LFilter contains a zero. - assert(FElts > 0 && "Should have eliminated the empty filter earlier!"); - for (unsigned l = 0; l != LElts; ++l) - if (LArray->getOperand(l)->isNullValue()) { - // LFilter contains a zero - discard it. - NewClauses.erase(J); - MakeNewInstruction = true; - break; - } - // Move on to the next filter. - continue; - } - // At this point we know that both filters are ConstantArrays. Loop over - // operands to see whether every element of Filter is also an element of - // LFilter. Since filters tend to be short this is probably faster than - // using a method that scales nicely. - ConstantArray *FArray = cast<ConstantArray>(Filter); - bool AllFound = true; - for (unsigned f = 0; f != FElts; ++f) { - Value *FTypeInfo = FArray->getOperand(f)->stripPointerCasts(); - AllFound = false; - for (unsigned l = 0; l != LElts; ++l) { - Value *LTypeInfo = LArray->getOperand(l)->stripPointerCasts(); - if (LTypeInfo == FTypeInfo) { - AllFound = true; - break; - } - } - if (!AllFound) - break; - } - if (AllFound) { - // Discard LFilter. - NewClauses.erase(J); - MakeNewInstruction = true; - } - // Move on to the next filter. - } - } - - // If we changed any of the clauses, replace the old landingpad instruction - // with a new one. - if (MakeNewInstruction) { - LandingPadInst *NLI = LandingPadInst::Create(LI.getType(), - NewClauses.size()); - for (unsigned i = 0, e = NewClauses.size(); i != e; ++i) - NLI->addClause(NewClauses[i]); - // A landing pad with no clauses must have the cleanup flag set. It is - // theoretically possible, though highly unlikely, that we eliminated all - // clauses. If so, force the cleanup flag to true. - if (NewClauses.empty()) - CleanupFlag = true; - NLI->setCleanup(CleanupFlag); - return NLI; - } - - // Even if none of the clauses changed, we may nonetheless have understood - // that the cleanup flag is pointless. Clear it if so. - if (LI.isCleanup() != CleanupFlag) { - assert(!CleanupFlag && "Adding a cleanup, not removing one?!"); - LI.setCleanup(CleanupFlag); - return &LI; - } - - return nullptr; -} - -/// Try to move the specified instruction from its current block into the -/// beginning of DestBlock, which can only happen if it's safe to move the -/// instruction past all of the instructions between it and the end of its -/// block. -static bool TryToSinkInstruction(Instruction *I, BasicBlock *DestBlock) { - assert(I->hasOneUse() && "Invariants didn't hold!"); - BasicBlock *SrcBlock = I->getParent(); - - // Cannot move control-flow-involving, volatile loads, vaarg, etc. - if (isa<PHINode>(I) || I->isEHPad() || I->mayHaveSideEffects() || - I->isTerminator()) - return false; - - // Do not sink static or dynamic alloca instructions. Static allocas must - // remain in the entry block, and dynamic allocas must not be sunk in between - // a stacksave / stackrestore pair, which would incorrectly shorten its - // lifetime. - if (isa<AllocaInst>(I)) - return false; - - // Do not sink into catchswitch blocks. - if (isa<CatchSwitchInst>(DestBlock->getTerminator())) - return false; - - // Do not sink convergent call instructions. - if (auto *CI = dyn_cast<CallInst>(I)) { - if (CI->isConvergent()) - return false; - } - // We can only sink load instructions if there is nothing between the load and - // the end of block that could change the value. - if (I->mayReadFromMemory()) { - for (BasicBlock::iterator Scan = I->getIterator(), - E = I->getParent()->end(); - Scan != E; ++Scan) - if (Scan->mayWriteToMemory()) - return false; - } - BasicBlock::iterator InsertPos = DestBlock->getFirstInsertionPt(); - I->moveBefore(&*InsertPos); - ++NumSunkInst; - - // Also sink all related debug uses from the source basic block. Otherwise we - // get debug use before the def. - SmallVector<DbgVariableIntrinsic *, 1> DbgUsers; - findDbgUsers(DbgUsers, I); - for (auto *DII : DbgUsers) { - if (DII->getParent() == SrcBlock) { - DII->moveBefore(&*InsertPos); - LLVM_DEBUG(dbgs() << "SINK: " << *DII << '\n'); - } - } - return true; -} - -bool InstCombiner::run() { - while (!Worklist.isEmpty()) { - Instruction *I = Worklist.RemoveOne(); - if (I == nullptr) continue; // skip null values. - - // Check to see if we can DCE the instruction. - if (isInstructionTriviallyDead(I, &TLI)) { - LLVM_DEBUG(dbgs() << "IC: DCE: " << *I << '\n'); - eraseInstFromFunction(*I); - ++NumDeadInst; - MadeIRChange = true; - continue; - } - - if (!DebugCounter::shouldExecute(VisitCounter)) - continue; - - // Instruction isn't dead, see if we can constant propagate it. - if (!I->use_empty() && - (I->getNumOperands() == 0 || isa<Constant>(I->getOperand(0)))) { - if (Constant *C = ConstantFoldInstruction(I, DL, &TLI)) { - LLVM_DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << *I - << '\n'); - - // Add operands to the worklist. - replaceInstUsesWith(*I, C); - ++NumConstProp; - if (isInstructionTriviallyDead(I, &TLI)) - eraseInstFromFunction(*I); - MadeIRChange = true; - continue; - } - } - - // In general, it is possible for computeKnownBits to determine all bits in - // a value even when the operands are not all constants. - Type *Ty = I->getType(); - if (ExpensiveCombines && !I->use_empty() && Ty->isIntOrIntVectorTy()) { - KnownBits Known = computeKnownBits(I, /*Depth*/0, I); - if (Known.isConstant()) { - Constant *C = ConstantInt::get(Ty, Known.getConstant()); - LLVM_DEBUG(dbgs() << "IC: ConstFold (all bits known) to: " << *C - << " from: " << *I << '\n'); - - // Add operands to the worklist. - replaceInstUsesWith(*I, C); - ++NumConstProp; - if (isInstructionTriviallyDead(I, &TLI)) - eraseInstFromFunction(*I); - MadeIRChange = true; - continue; - } - } - - // See if we can trivially sink this instruction to a successor basic block. - if (EnableCodeSinking && I->hasOneUse()) { - BasicBlock *BB = I->getParent(); - Instruction *UserInst = cast<Instruction>(*I->user_begin()); - BasicBlock *UserParent; - - // Get the block the use occurs in. - if (PHINode *PN = dyn_cast<PHINode>(UserInst)) - UserParent = PN->getIncomingBlock(*I->use_begin()); - else - UserParent = UserInst->getParent(); - - if (UserParent != BB) { - bool UserIsSuccessor = false; - // See if the user is one of our successors. - for (succ_iterator SI = succ_begin(BB), E = succ_end(BB); SI != E; ++SI) - if (*SI == UserParent) { - UserIsSuccessor = true; - break; - } - - // If the user is one of our immediate successors, and if that successor - // only has us as a predecessors (we'd have to split the critical edge - // otherwise), we can keep going. - if (UserIsSuccessor && UserParent->getUniquePredecessor()) { - // Okay, the CFG is simple enough, try to sink this instruction. - if (TryToSinkInstruction(I, UserParent)) { - LLVM_DEBUG(dbgs() << "IC: Sink: " << *I << '\n'); - MadeIRChange = true; - // We'll add uses of the sunk instruction below, but since sinking - // can expose opportunities for it's *operands* add them to the - // worklist - for (Use &U : I->operands()) - if (Instruction *OpI = dyn_cast<Instruction>(U.get())) - Worklist.Add(OpI); - } - } - } - } - - // Now that we have an instruction, try combining it to simplify it. - Builder.SetInsertPoint(I); - Builder.SetCurrentDebugLocation(I->getDebugLoc()); - -#ifndef NDEBUG - std::string OrigI; -#endif - LLVM_DEBUG(raw_string_ostream SS(OrigI); I->print(SS); OrigI = SS.str();); - LLVM_DEBUG(dbgs() << "IC: Visiting: " << OrigI << '\n'); - - if (Instruction *Result = visit(*I)) { - ++NumCombined; - // Should we replace the old instruction with a new one? - if (Result != I) { - LLVM_DEBUG(dbgs() << "IC: Old = " << *I << '\n' - << " New = " << *Result << '\n'); - - if (I->getDebugLoc()) - Result->setDebugLoc(I->getDebugLoc()); - // Everything uses the new instruction now. - I->replaceAllUsesWith(Result); - - // Move the name to the new instruction first. - Result->takeName(I); - - // Push the new instruction and any users onto the worklist. - Worklist.AddUsersToWorkList(*Result); - Worklist.Add(Result); - - // Insert the new instruction into the basic block... - BasicBlock *InstParent = I->getParent(); - BasicBlock::iterator InsertPos = I->getIterator(); - - // If we replace a PHI with something that isn't a PHI, fix up the - // insertion point. - if (!isa<PHINode>(Result) && isa<PHINode>(InsertPos)) - InsertPos = InstParent->getFirstInsertionPt(); - - InstParent->getInstList().insert(InsertPos, Result); - - eraseInstFromFunction(*I); - } else { - LLVM_DEBUG(dbgs() << "IC: Mod = " << OrigI << '\n' - << " New = " << *I << '\n'); - - // If the instruction was modified, it's possible that it is now dead. - // if so, remove it. - if (isInstructionTriviallyDead(I, &TLI)) { - eraseInstFromFunction(*I); - } else { - Worklist.AddUsersToWorkList(*I); - Worklist.Add(I); - } - } - MadeIRChange = true; - } - } - - Worklist.Zap(); - return MadeIRChange; -} - -/// Walk the function in depth-first order, adding all reachable code to the -/// worklist. -/// -/// This has a couple of tricks to make the code faster and more powerful. In -/// particular, we constant fold and DCE instructions as we go, to avoid adding -/// them to the worklist (this significantly speeds up instcombine on code where -/// many instructions are dead or constant). Additionally, if we find a branch -/// whose condition is a known constant, we only visit the reachable successors. -static bool AddReachableCodeToWorklist(BasicBlock *BB, const DataLayout &DL, - SmallPtrSetImpl<BasicBlock *> &Visited, - InstCombineWorklist &ICWorklist, - const TargetLibraryInfo *TLI) { - bool MadeIRChange = false; - SmallVector<BasicBlock*, 256> Worklist; - Worklist.push_back(BB); - - SmallVector<Instruction*, 128> InstrsForInstCombineWorklist; - DenseMap<Constant *, Constant *> FoldedConstants; - - do { - BB = Worklist.pop_back_val(); - - // We have now visited this block! If we've already been here, ignore it. - if (!Visited.insert(BB).second) - continue; - - for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E; ) { - Instruction *Inst = &*BBI++; - - // DCE instruction if trivially dead. - if (isInstructionTriviallyDead(Inst, TLI)) { - ++NumDeadInst; - LLVM_DEBUG(dbgs() << "IC: DCE: " << *Inst << '\n'); - salvageDebugInfo(*Inst); - Inst->eraseFromParent(); - MadeIRChange = true; - continue; - } - - // ConstantProp instruction if trivially constant. - if (!Inst->use_empty() && - (Inst->getNumOperands() == 0 || isa<Constant>(Inst->getOperand(0)))) - if (Constant *C = ConstantFoldInstruction(Inst, DL, TLI)) { - LLVM_DEBUG(dbgs() << "IC: ConstFold to: " << *C << " from: " << *Inst - << '\n'); - Inst->replaceAllUsesWith(C); - ++NumConstProp; - if (isInstructionTriviallyDead(Inst, TLI)) - Inst->eraseFromParent(); - MadeIRChange = true; - continue; - } - - // See if we can constant fold its operands. - for (Use &U : Inst->operands()) { - if (!isa<ConstantVector>(U) && !isa<ConstantExpr>(U)) - continue; - - auto *C = cast<Constant>(U); - Constant *&FoldRes = FoldedConstants[C]; - if (!FoldRes) - FoldRes = ConstantFoldConstant(C, DL, TLI); - if (!FoldRes) - FoldRes = C; - - if (FoldRes != C) { - LLVM_DEBUG(dbgs() << "IC: ConstFold operand of: " << *Inst - << "\n Old = " << *C - << "\n New = " << *FoldRes << '\n'); - U = FoldRes; - MadeIRChange = true; - } - } - - // Skip processing debug intrinsics in InstCombine. Processing these call instructions - // consumes non-trivial amount of time and provides no value for the optimization. - if (!isa<DbgInfoIntrinsic>(Inst)) - InstrsForInstCombineWorklist.push_back(Inst); - } - - // Recursively visit successors. If this is a branch or switch on a - // constant, only visit the reachable successor. - Instruction *TI = BB->getTerminator(); - if (BranchInst *BI = dyn_cast<BranchInst>(TI)) { - if (BI->isConditional() && isa<ConstantInt>(BI->getCondition())) { - bool CondVal = cast<ConstantInt>(BI->getCondition())->getZExtValue(); - BasicBlock *ReachableBB = BI->getSuccessor(!CondVal); - Worklist.push_back(ReachableBB); - continue; - } - } else if (SwitchInst *SI = dyn_cast<SwitchInst>(TI)) { - if (ConstantInt *Cond = dyn_cast<ConstantInt>(SI->getCondition())) { - Worklist.push_back(SI->findCaseValue(Cond)->getCaseSuccessor()); - continue; - } - } - - for (BasicBlock *SuccBB : successors(TI)) - Worklist.push_back(SuccBB); - } while (!Worklist.empty()); - - // Once we've found all of the instructions to add to instcombine's worklist, - // add them in reverse order. This way instcombine will visit from the top - // of the function down. This jives well with the way that it adds all uses - // of instructions to the worklist after doing a transformation, thus avoiding - // some N^2 behavior in pathological cases. - ICWorklist.AddInitialGroup(InstrsForInstCombineWorklist); - - return MadeIRChange; -} - -/// Populate the IC worklist from a function, and prune any dead basic -/// blocks discovered in the process. -/// -/// This also does basic constant propagation and other forward fixing to make -/// the combiner itself run much faster. -static bool prepareICWorklistFromFunction(Function &F, const DataLayout &DL, - TargetLibraryInfo *TLI, - InstCombineWorklist &ICWorklist) { - bool MadeIRChange = false; - - // Do a depth-first traversal of the function, populate the worklist with - // the reachable instructions. Ignore blocks that are not reachable. Keep - // track of which blocks we visit. - SmallPtrSet<BasicBlock *, 32> Visited; - MadeIRChange |= - AddReachableCodeToWorklist(&F.front(), DL, Visited, ICWorklist, TLI); - - // Do a quick scan over the function. If we find any blocks that are - // unreachable, remove any instructions inside of them. This prevents - // the instcombine code from having to deal with some bad special cases. - for (BasicBlock &BB : F) { - if (Visited.count(&BB)) - continue; - - unsigned NumDeadInstInBB = removeAllNonTerminatorAndEHPadInstructions(&BB); - MadeIRChange |= NumDeadInstInBB > 0; - NumDeadInst += NumDeadInstInBB; - } - - return MadeIRChange; -} - -static bool combineInstructionsOverFunction( - Function &F, InstCombineWorklist &Worklist, AliasAnalysis *AA, - AssumptionCache &AC, TargetLibraryInfo &TLI, DominatorTree &DT, - OptimizationRemarkEmitter &ORE, bool ExpensiveCombines = true, - LoopInfo *LI = nullptr) { - auto &DL = F.getParent()->getDataLayout(); - ExpensiveCombines |= EnableExpensiveCombines; - - /// Builder - This is an IRBuilder that automatically inserts new - /// instructions into the worklist when they are created. - IRBuilder<TargetFolder, IRBuilderCallbackInserter> Builder( - F.getContext(), TargetFolder(DL), - IRBuilderCallbackInserter([&Worklist, &AC](Instruction *I) { - Worklist.Add(I); - if (match(I, m_Intrinsic<Intrinsic::assume>())) - AC.registerAssumption(cast<CallInst>(I)); - })); - - // Lower dbg.declare intrinsics otherwise their value may be clobbered - // by instcombiner. - bool MadeIRChange = false; - if (ShouldLowerDbgDeclare) - MadeIRChange = LowerDbgDeclare(F); - - // Iterate while there is work to do. - int Iteration = 0; - while (true) { - ++Iteration; - LLVM_DEBUG(dbgs() << "\n\nINSTCOMBINE ITERATION #" << Iteration << " on " - << F.getName() << "\n"); - - MadeIRChange |= prepareICWorklistFromFunction(F, DL, &TLI, Worklist); - - InstCombiner IC(Worklist, Builder, F.optForMinSize(), ExpensiveCombines, AA, - AC, TLI, DT, ORE, DL, LI); - IC.MaxArraySizeForCombine = MaxArraySize; - - if (!IC.run()) - break; - } - - return MadeIRChange || Iteration > 1; -} - -PreservedAnalyses InstCombinePass::run(Function &F, - FunctionAnalysisManager &AM) { - auto &AC = AM.getResult<AssumptionAnalysis>(F); - auto &DT = AM.getResult<DominatorTreeAnalysis>(F); - auto &TLI = AM.getResult<TargetLibraryAnalysis>(F); - auto &ORE = AM.getResult<OptimizationRemarkEmitterAnalysis>(F); - - auto *LI = AM.getCachedResult<LoopAnalysis>(F); - - auto *AA = &AM.getResult<AAManager>(F); - if (!combineInstructionsOverFunction(F, Worklist, AA, AC, TLI, DT, ORE, - ExpensiveCombines, LI)) - // No changes, all analyses are preserved. - return PreservedAnalyses::all(); - - // Mark all the analyses that instcombine updates as preserved. - PreservedAnalyses PA; - PA.preserveSet<CFGAnalyses>(); - PA.preserve<AAManager>(); - PA.preserve<BasicAA>(); - PA.preserve<GlobalsAA>(); - return PA; -} - -void InstructionCombiningPass::getAnalysisUsage(AnalysisUsage &AU) const { - AU.setPreservesCFG(); - AU.addRequired<AAResultsWrapperPass>(); - AU.addRequired<AssumptionCacheTracker>(); - AU.addRequired<TargetLibraryInfoWrapperPass>(); - AU.addRequired<DominatorTreeWrapperPass>(); - AU.addRequired<OptimizationRemarkEmitterWrapperPass>(); - AU.addPreserved<DominatorTreeWrapperPass>(); - AU.addPreserved<AAResultsWrapperPass>(); - AU.addPreserved<BasicAAWrapperPass>(); - AU.addPreserved<GlobalsAAWrapperPass>(); -} - -bool InstructionCombiningPass::runOnFunction(Function &F) { - if (skipFunction(F)) - return false; - - // Required analyses. - auto AA = &getAnalysis<AAResultsWrapperPass>().getAAResults(); - auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F); - auto &TLI = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); - auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); - auto &ORE = getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE(); - - // Optional analyses. - auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>(); - auto *LI = LIWP ? &LIWP->getLoopInfo() : nullptr; - - return combineInstructionsOverFunction(F, Worklist, AA, AC, TLI, DT, ORE, - ExpensiveCombines, LI); -} - -char InstructionCombiningPass::ID = 0; - -INITIALIZE_PASS_BEGIN(InstructionCombiningPass, "instcombine", - "Combine redundant instructions", false, false) -INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker) -INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass) -INITIALIZE_PASS_DEPENDENCY(GlobalsAAWrapperPass) -INITIALIZE_PASS_DEPENDENCY(OptimizationRemarkEmitterWrapperPass) -INITIALIZE_PASS_END(InstructionCombiningPass, "instcombine", - "Combine redundant instructions", false, false) - -// Initialization Routines -void llvm::initializeInstCombine(PassRegistry &Registry) { - initializeInstructionCombiningPassPass(Registry); -} - -void LLVMInitializeInstCombine(LLVMPassRegistryRef R) { - initializeInstructionCombiningPassPass(*unwrap(R)); -} - -FunctionPass *llvm::createInstructionCombiningPass(bool ExpensiveCombines) { - return new InstructionCombiningPass(ExpensiveCombines); -} - -void LLVMAddInstructionCombiningPass(LLVMPassManagerRef PM) { - unwrap(PM)->add(createInstructionCombiningPass()); -} |