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diff --git a/gnu/llvm/lib/Transforms/Scalar/LoopDeletion.cpp b/gnu/llvm/lib/Transforms/Scalar/LoopDeletion.cpp
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-//===- LoopDeletion.cpp - Dead Loop Deletion Pass ---------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements the Dead Loop Deletion Pass. This pass is responsible
-// for eliminating loops with non-infinite computable trip counts that have no
-// side effects or volatile instructions, and do not contribute to the
-// computation of the function's return value.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Transforms/Scalar/LoopDeletion.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/GlobalsModRef.h"
-#include "llvm/Analysis/LoopPass.h"
-#include "llvm/IR/Dominators.h"
-#include "llvm/IR/PatternMatch.h"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Scalar/LoopPassManager.h"
-#include "llvm/Transforms/Utils/LoopUtils.h"
-using namespace llvm;
-
-#define DEBUG_TYPE "loop-delete"
-
-STATISTIC(NumDeleted, "Number of loops deleted");
-
-enum class LoopDeletionResult {
- Unmodified,
- Modified,
- Deleted,
-};
-
-/// Determines if a loop is dead.
-///
-/// This assumes that we've already checked for unique exit and exiting blocks,
-/// and that the code is in LCSSA form.
-static bool isLoopDead(Loop *L, ScalarEvolution &SE,
- SmallVectorImpl<BasicBlock *> &ExitingBlocks,
- BasicBlock *ExitBlock, bool &Changed,
- BasicBlock *Preheader) {
- // Make sure that all PHI entries coming from the loop are loop invariant.
- // Because the code is in LCSSA form, any values used outside of the loop
- // must pass through a PHI in the exit block, meaning that this check is
- // sufficient to guarantee that no loop-variant values are used outside
- // of the loop.
- bool AllEntriesInvariant = true;
- bool AllOutgoingValuesSame = true;
- for (PHINode &P : ExitBlock->phis()) {
- Value *incoming = P.getIncomingValueForBlock(ExitingBlocks[0]);
-
- // Make sure all exiting blocks produce the same incoming value for the exit
- // block. If there are different incoming values for different exiting
- // blocks, then it is impossible to statically determine which value should
- // be used.
- AllOutgoingValuesSame =
- all_of(makeArrayRef(ExitingBlocks).slice(1), [&](BasicBlock *BB) {
- return incoming == P.getIncomingValueForBlock(BB);
- });
-
- if (!AllOutgoingValuesSame)
- break;
-
- if (Instruction *I = dyn_cast<Instruction>(incoming))
- if (!L->makeLoopInvariant(I, Changed, Preheader->getTerminator())) {
- AllEntriesInvariant = false;
- break;
- }
- }
-
- if (Changed)
- SE.forgetLoopDispositions(L);
-
- if (!AllEntriesInvariant || !AllOutgoingValuesSame)
- return false;
-
- // Make sure that no instructions in the block have potential side-effects.
- // This includes instructions that could write to memory, and loads that are
- // marked volatile.
- for (auto &I : L->blocks())
- if (any_of(*I, [](Instruction &I) { return I.mayHaveSideEffects(); }))
- return false;
- return true;
-}
-
-/// This function returns true if there is no viable path from the
-/// entry block to the header of \p L. Right now, it only does
-/// a local search to save compile time.
-static bool isLoopNeverExecuted(Loop *L) {
- using namespace PatternMatch;
-
- auto *Preheader = L->getLoopPreheader();
- // TODO: We can relax this constraint, since we just need a loop
- // predecessor.
- assert(Preheader && "Needs preheader!");
-
- if (Preheader == &Preheader->getParent()->getEntryBlock())
- return false;
- // All predecessors of the preheader should have a constant conditional
- // branch, with the loop's preheader as not-taken.
- for (auto *Pred: predecessors(Preheader)) {
- BasicBlock *Taken, *NotTaken;
- ConstantInt *Cond;
- if (!match(Pred->getTerminator(),
- m_Br(m_ConstantInt(Cond), Taken, NotTaken)))
- return false;
- if (!Cond->getZExtValue())
- std::swap(Taken, NotTaken);
- if (Taken == Preheader)
- return false;
- }
- assert(!pred_empty(Preheader) &&
- "Preheader should have predecessors at this point!");
- // All the predecessors have the loop preheader as not-taken target.
- return true;
-}
-
-/// Remove a loop if it is dead.
-///
-/// A loop is considered dead if it does not impact the observable behavior of
-/// the program other than finite running time. This never removes a loop that
-/// might be infinite (unless it is never executed), as doing so could change
-/// the halting/non-halting nature of a program.
-///
-/// This entire process relies pretty heavily on LoopSimplify form and LCSSA in
-/// order to make various safety checks work.
-///
-/// \returns true if any changes were made. This may mutate the loop even if it
-/// is unable to delete it due to hoisting trivially loop invariant
-/// instructions out of the loop.
-static LoopDeletionResult deleteLoopIfDead(Loop *L, DominatorTree &DT,
- ScalarEvolution &SE, LoopInfo &LI) {
- assert(L->isLCSSAForm(DT) && "Expected LCSSA!");
-
- // We can only remove the loop if there is a preheader that we can branch from
- // after removing it. Also, if LoopSimplify form is not available, stay out
- // of trouble.
- BasicBlock *Preheader = L->getLoopPreheader();
- if (!Preheader || !L->hasDedicatedExits()) {
- LLVM_DEBUG(
- dbgs()
- << "Deletion requires Loop with preheader and dedicated exits.\n");
- return LoopDeletionResult::Unmodified;
- }
- // We can't remove loops that contain subloops. If the subloops were dead,
- // they would already have been removed in earlier executions of this pass.
- if (L->begin() != L->end()) {
- LLVM_DEBUG(dbgs() << "Loop contains subloops.\n");
- return LoopDeletionResult::Unmodified;
- }
-
-
- BasicBlock *ExitBlock = L->getUniqueExitBlock();
-
- if (ExitBlock && isLoopNeverExecuted(L)) {
- LLVM_DEBUG(dbgs() << "Loop is proven to never execute, delete it!");
- // Set incoming value to undef for phi nodes in the exit block.
- for (PHINode &P : ExitBlock->phis()) {
- std::fill(P.incoming_values().begin(), P.incoming_values().end(),
- UndefValue::get(P.getType()));
- }
- deleteDeadLoop(L, &DT, &SE, &LI);
- ++NumDeleted;
- return LoopDeletionResult::Deleted;
- }
-
- // The remaining checks below are for a loop being dead because all statements
- // in the loop are invariant.
- SmallVector<BasicBlock *, 4> ExitingBlocks;
- L->getExitingBlocks(ExitingBlocks);
-
- // We require that the loop only have a single exit block. Otherwise, we'd
- // be in the situation of needing to be able to solve statically which exit
- // block will be branched to, or trying to preserve the branching logic in
- // a loop invariant manner.
- if (!ExitBlock) {
- LLVM_DEBUG(dbgs() << "Deletion requires single exit block\n");
- return LoopDeletionResult::Unmodified;
- }
- // Finally, we have to check that the loop really is dead.
- bool Changed = false;
- if (!isLoopDead(L, SE, ExitingBlocks, ExitBlock, Changed, Preheader)) {
- LLVM_DEBUG(dbgs() << "Loop is not invariant, cannot delete.\n");
- return Changed ? LoopDeletionResult::Modified
- : LoopDeletionResult::Unmodified;
- }
-
- // Don't remove loops for which we can't solve the trip count.
- // They could be infinite, in which case we'd be changing program behavior.
- const SCEV *S = SE.getMaxBackedgeTakenCount(L);
- if (isa<SCEVCouldNotCompute>(S)) {
- LLVM_DEBUG(dbgs() << "Could not compute SCEV MaxBackedgeTakenCount.\n");
- return Changed ? LoopDeletionResult::Modified
- : LoopDeletionResult::Unmodified;
- }
-
- LLVM_DEBUG(dbgs() << "Loop is invariant, delete it!");
- deleteDeadLoop(L, &DT, &SE, &LI);
- ++NumDeleted;
-
- return LoopDeletionResult::Deleted;
-}
-
-PreservedAnalyses LoopDeletionPass::run(Loop &L, LoopAnalysisManager &AM,
- LoopStandardAnalysisResults &AR,
- LPMUpdater &Updater) {
-
- LLVM_DEBUG(dbgs() << "Analyzing Loop for deletion: ");
- LLVM_DEBUG(L.dump());
- std::string LoopName = L.getName();
- auto Result = deleteLoopIfDead(&L, AR.DT, AR.SE, AR.LI);
- if (Result == LoopDeletionResult::Unmodified)
- return PreservedAnalyses::all();
-
- if (Result == LoopDeletionResult::Deleted)
- Updater.markLoopAsDeleted(L, LoopName);
-
- return getLoopPassPreservedAnalyses();
-}
-
-namespace {
-class LoopDeletionLegacyPass : public LoopPass {
-public:
- static char ID; // Pass ID, replacement for typeid
- LoopDeletionLegacyPass() : LoopPass(ID) {
- initializeLoopDeletionLegacyPassPass(*PassRegistry::getPassRegistry());
- }
-
- // Possibly eliminate loop L if it is dead.
- bool runOnLoop(Loop *L, LPPassManager &) override;
-
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- getLoopAnalysisUsage(AU);
- }
-};
-}
-
-char LoopDeletionLegacyPass::ID = 0;
-INITIALIZE_PASS_BEGIN(LoopDeletionLegacyPass, "loop-deletion",
- "Delete dead loops", false, false)
-INITIALIZE_PASS_DEPENDENCY(LoopPass)
-INITIALIZE_PASS_END(LoopDeletionLegacyPass, "loop-deletion",
- "Delete dead loops", false, false)
-
-Pass *llvm::createLoopDeletionPass() { return new LoopDeletionLegacyPass(); }
-
-bool LoopDeletionLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) {
- if (skipLoop(L))
- return false;
- DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
- ScalarEvolution &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
- LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
-
- LLVM_DEBUG(dbgs() << "Analyzing Loop for deletion: ");
- LLVM_DEBUG(L->dump());
-
- LoopDeletionResult Result = deleteLoopIfDead(L, DT, SE, LI);
-
- if (Result == LoopDeletionResult::Deleted)
- LPM.markLoopAsDeleted(*L);
-
- return Result != LoopDeletionResult::Unmodified;
-}
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