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diff --git a/gnu/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp b/gnu/llvm/lib/Transforms/Scalar/SimplifyCFGPass.cpp
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-//===- SimplifyCFGPass.cpp - CFG Simplification 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 dead code elimination and basic block merging, along
-// with a collection of other peephole control flow optimizations. For example:
-//
-// * Removes basic blocks with no predecessors.
-// * Merges a basic block into its predecessor if there is only one and the
-// predecessor only has one successor.
-// * Eliminates PHI nodes for basic blocks with a single predecessor.
-// * Eliminates a basic block that only contains an unconditional branch.
-// * Changes invoke instructions to nounwind functions to be calls.
-// * Change things like "if (x) if (y)" into "if (x&y)".
-// * etc..
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/AssumptionCache.h"
-#include "llvm/Analysis/CFG.h"
-#include "llvm/Analysis/GlobalsModRef.h"
-#include "llvm/Analysis/TargetTransformInfo.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/IR/Attributes.h"
-#include "llvm/IR/CFG.h"
-#include "llvm/IR/Constants.h"
-#include "llvm/IR/DataLayout.h"
-#include "llvm/IR/Instructions.h"
-#include "llvm/IR/IntrinsicInst.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Transforms/Scalar/SimplifyCFG.h"
-#include <utility>
-using namespace llvm;
-
-#define DEBUG_TYPE "simplifycfg"
-
-static cl::opt<unsigned> UserBonusInstThreshold(
- "bonus-inst-threshold", cl::Hidden, cl::init(1),
- cl::desc("Control the number of bonus instructions (default = 1)"));
-
-static cl::opt<bool> UserKeepLoops(
- "keep-loops", cl::Hidden, cl::init(true),
- cl::desc("Preserve canonical loop structure (default = true)"));
-
-static cl::opt<bool> UserSwitchToLookup(
- "switch-to-lookup", cl::Hidden, cl::init(false),
- cl::desc("Convert switches to lookup tables (default = false)"));
-
-static cl::opt<bool> UserForwardSwitchCond(
- "forward-switch-cond", cl::Hidden, cl::init(false),
- cl::desc("Forward switch condition to phi ops (default = false)"));
-
-static cl::opt<bool> UserSinkCommonInsts(
- "sink-common-insts", cl::Hidden, cl::init(false),
- cl::desc("Sink common instructions (default = false)"));
-
-
-STATISTIC(NumSimpl, "Number of blocks simplified");
-
-/// If we have more than one empty (other than phi node) return blocks,
-/// merge them together to promote recursive block merging.
-static bool mergeEmptyReturnBlocks(Function &F) {
- bool Changed = false;
-
- BasicBlock *RetBlock = nullptr;
-
- // Scan all the blocks in the function, looking for empty return blocks.
- for (Function::iterator BBI = F.begin(), E = F.end(); BBI != E; ) {
- BasicBlock &BB = *BBI++;
-
- // Only look at return blocks.
- ReturnInst *Ret = dyn_cast<ReturnInst>(BB.getTerminator());
- if (!Ret) continue;
-
- // Only look at the block if it is empty or the only other thing in it is a
- // single PHI node that is the operand to the return.
- if (Ret != &BB.front()) {
- // Check for something else in the block.
- BasicBlock::iterator I(Ret);
- --I;
- // Skip over debug info.
- while (isa<DbgInfoIntrinsic>(I) && I != BB.begin())
- --I;
- if (!isa<DbgInfoIntrinsic>(I) &&
- (!isa<PHINode>(I) || I != BB.begin() || Ret->getNumOperands() == 0 ||
- Ret->getOperand(0) != &*I))
- continue;
- }
-
- // If this is the first returning block, remember it and keep going.
- if (!RetBlock) {
- RetBlock = &BB;
- continue;
- }
-
- // Otherwise, we found a duplicate return block. Merge the two.
- Changed = true;
-
- // Case when there is no input to the return or when the returned values
- // agree is trivial. Note that they can't agree if there are phis in the
- // blocks.
- if (Ret->getNumOperands() == 0 ||
- Ret->getOperand(0) ==
- cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0)) {
- BB.replaceAllUsesWith(RetBlock);
- BB.eraseFromParent();
- continue;
- }
-
- // If the canonical return block has no PHI node, create one now.
- PHINode *RetBlockPHI = dyn_cast<PHINode>(RetBlock->begin());
- if (!RetBlockPHI) {
- Value *InVal = cast<ReturnInst>(RetBlock->getTerminator())->getOperand(0);
- pred_iterator PB = pred_begin(RetBlock), PE = pred_end(RetBlock);
- RetBlockPHI = PHINode::Create(Ret->getOperand(0)->getType(),
- std::distance(PB, PE), "merge",
- &RetBlock->front());
-
- for (pred_iterator PI = PB; PI != PE; ++PI)
- RetBlockPHI->addIncoming(InVal, *PI);
- RetBlock->getTerminator()->setOperand(0, RetBlockPHI);
- }
-
- // Turn BB into a block that just unconditionally branches to the return
- // block. This handles the case when the two return blocks have a common
- // predecessor but that return different things.
- RetBlockPHI->addIncoming(Ret->getOperand(0), &BB);
- BB.getTerminator()->eraseFromParent();
- BranchInst::Create(RetBlock, &BB);
- }
-
- return Changed;
-}
-
-/// Call SimplifyCFG on all the blocks in the function,
-/// iterating until no more changes are made.
-static bool iterativelySimplifyCFG(Function &F, const TargetTransformInfo &TTI,
- const SimplifyCFGOptions &Options) {
- bool Changed = false;
- bool LocalChange = true;
-
- SmallVector<std::pair<const BasicBlock *, const BasicBlock *>, 32> Edges;
- FindFunctionBackedges(F, Edges);
- SmallPtrSet<BasicBlock *, 16> LoopHeaders;
- for (unsigned i = 0, e = Edges.size(); i != e; ++i)
- LoopHeaders.insert(const_cast<BasicBlock *>(Edges[i].second));
-
- while (LocalChange) {
- LocalChange = false;
-
- // Loop over all of the basic blocks and remove them if they are unneeded.
- for (Function::iterator BBIt = F.begin(); BBIt != F.end(); ) {
- if (simplifyCFG(&*BBIt++, TTI, Options, &LoopHeaders)) {
- LocalChange = true;
- ++NumSimpl;
- }
- }
- Changed |= LocalChange;
- }
- return Changed;
-}
-
-static bool simplifyFunctionCFG(Function &F, const TargetTransformInfo &TTI,
- const SimplifyCFGOptions &Options) {
- bool EverChanged = removeUnreachableBlocks(F);
- EverChanged |= mergeEmptyReturnBlocks(F);
- EverChanged |= iterativelySimplifyCFG(F, TTI, Options);
-
- // If neither pass changed anything, we're done.
- if (!EverChanged) return false;
-
- // iterativelySimplifyCFG can (rarely) make some loops dead. If this happens,
- // removeUnreachableBlocks is needed to nuke them, which means we should
- // iterate between the two optimizations. We structure the code like this to
- // avoid rerunning iterativelySimplifyCFG if the second pass of
- // removeUnreachableBlocks doesn't do anything.
- if (!removeUnreachableBlocks(F))
- return true;
-
- do {
- EverChanged = iterativelySimplifyCFG(F, TTI, Options);
- EverChanged |= removeUnreachableBlocks(F);
- } while (EverChanged);
-
- return true;
-}
-
-// Command-line settings override compile-time settings.
-SimplifyCFGPass::SimplifyCFGPass(const SimplifyCFGOptions &Opts) {
- Options.BonusInstThreshold = UserBonusInstThreshold.getNumOccurrences()
- ? UserBonusInstThreshold
- : Opts.BonusInstThreshold;
- Options.ForwardSwitchCondToPhi = UserForwardSwitchCond.getNumOccurrences()
- ? UserForwardSwitchCond
- : Opts.ForwardSwitchCondToPhi;
- Options.ConvertSwitchToLookupTable = UserSwitchToLookup.getNumOccurrences()
- ? UserSwitchToLookup
- : Opts.ConvertSwitchToLookupTable;
- Options.NeedCanonicalLoop = UserKeepLoops.getNumOccurrences()
- ? UserKeepLoops
- : Opts.NeedCanonicalLoop;
- Options.SinkCommonInsts = UserSinkCommonInsts.getNumOccurrences()
- ? UserSinkCommonInsts
- : Opts.SinkCommonInsts;
-}
-
-PreservedAnalyses SimplifyCFGPass::run(Function &F,
- FunctionAnalysisManager &AM) {
- auto &TTI = AM.getResult<TargetIRAnalysis>(F);
- Options.AC = &AM.getResult<AssumptionAnalysis>(F);
- if (!simplifyFunctionCFG(F, TTI, Options))
- return PreservedAnalyses::all();
- PreservedAnalyses PA;
- PA.preserve<GlobalsAA>();
- return PA;
-}
-
-namespace {
-struct CFGSimplifyPass : public FunctionPass {
- static char ID;
- SimplifyCFGOptions Options;
- std::function<bool(const Function &)> PredicateFtor;
-
- CFGSimplifyPass(unsigned Threshold = 1, bool ForwardSwitchCond = false,
- bool ConvertSwitch = false, bool KeepLoops = true,
- bool SinkCommon = false,
- std::function<bool(const Function &)> Ftor = nullptr)
- : FunctionPass(ID), PredicateFtor(std::move(Ftor)) {
-
- initializeCFGSimplifyPassPass(*PassRegistry::getPassRegistry());
-
- // Check for command-line overrides of options for debug/customization.
- Options.BonusInstThreshold = UserBonusInstThreshold.getNumOccurrences()
- ? UserBonusInstThreshold
- : Threshold;
-
- Options.ForwardSwitchCondToPhi = UserForwardSwitchCond.getNumOccurrences()
- ? UserForwardSwitchCond
- : ForwardSwitchCond;
-
- Options.ConvertSwitchToLookupTable = UserSwitchToLookup.getNumOccurrences()
- ? UserSwitchToLookup
- : ConvertSwitch;
-
- Options.NeedCanonicalLoop =
- UserKeepLoops.getNumOccurrences() ? UserKeepLoops : KeepLoops;
-
- Options.SinkCommonInsts = UserSinkCommonInsts.getNumOccurrences()
- ? UserSinkCommonInsts
- : SinkCommon;
- }
-
- bool runOnFunction(Function &F) override {
- if (skipFunction(F) || (PredicateFtor && !PredicateFtor(F)))
- return false;
-
- Options.AC = &getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
- auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
- return simplifyFunctionCFG(F, TTI, Options);
- }
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.addRequired<AssumptionCacheTracker>();
- AU.addRequired<TargetTransformInfoWrapperPass>();
- AU.addPreserved<GlobalsAAWrapperPass>();
- }
-};
-}
-
-char CFGSimplifyPass::ID = 0;
-INITIALIZE_PASS_BEGIN(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
- false)
-INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
-INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
-INITIALIZE_PASS_END(CFGSimplifyPass, "simplifycfg", "Simplify the CFG", false,
- false)
-
-// Public interface to the CFGSimplification pass
-FunctionPass *
-llvm::createCFGSimplificationPass(unsigned Threshold, bool ForwardSwitchCond,
- bool ConvertSwitch, bool KeepLoops,
- bool SinkCommon,
- std::function<bool(const Function &)> Ftor) {
- return new CFGSimplifyPass(Threshold, ForwardSwitchCond, ConvertSwitch,
- KeepLoops, SinkCommon, std::move(Ftor));
-}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.