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bda134910a
While the term "Target" is in the name, it doesn't really have to do with the LLVM Target library -- this isn't an abstraction which LLVM targets generally need to implement or extend. It has much more to do with modeling the various runtime libraries on different OSes and with different runtime environments. The "target" in this sense is the more general sense of a target of cross compilation. This is in preparation for porting this analysis to the new pass manager. No functionality changed, and updates inbound for Clang and Polly. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@226078 91177308-0d34-0410-b5e6-96231b3b80d8
118 lines
4.8 KiB
C++
118 lines
4.8 KiB
C++
//===------ SimplifyInstructions.cpp - Remove redundant instructions ------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This is a utility pass used for testing the InstructionSimplify analysis.
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// The analysis is applied to every instruction, and if it simplifies then the
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// instruction is replaced by the simplification. If you are looking for a pass
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// that performs serious instruction folding, use the instcombine pass instead.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/DepthFirstIterator.h"
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#include "llvm/ADT/SmallPtrSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/AssumptionCache.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/Type.h"
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#include "llvm/Pass.h"
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#include "llvm/Analysis/TargetLibraryInfo.h"
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#include "llvm/Transforms/Utils/Local.h"
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using namespace llvm;
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#define DEBUG_TYPE "instsimplify"
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STATISTIC(NumSimplified, "Number of redundant instructions removed");
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namespace {
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struct InstSimplifier : public FunctionPass {
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static char ID; // Pass identification, replacement for typeid
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InstSimplifier() : FunctionPass(ID) {
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initializeInstSimplifierPass(*PassRegistry::getPassRegistry());
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}
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.setPreservesCFG();
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AU.addRequired<AssumptionCacheTracker>();
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AU.addRequired<TargetLibraryInfo>();
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}
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/// runOnFunction - Remove instructions that simplify.
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bool runOnFunction(Function &F) override {
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const DominatorTreeWrapperPass *DTWP =
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getAnalysisIfAvailable<DominatorTreeWrapperPass>();
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const DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
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DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
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const DataLayout *DL = DLP ? &DLP->getDataLayout() : nullptr;
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const TargetLibraryInfo *TLI = &getAnalysis<TargetLibraryInfo>();
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AssumptionCache *AC =
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&getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F);
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SmallPtrSet<const Instruction*, 8> S1, S2, *ToSimplify = &S1, *Next = &S2;
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bool Changed = false;
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do {
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for (BasicBlock *BB : depth_first(&F.getEntryBlock()))
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// Here be subtlety: the iterator must be incremented before the loop
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// body (not sure why), so a range-for loop won't work here.
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for (BasicBlock::iterator BI = BB->begin(), BE = BB->end(); BI != BE;) {
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Instruction *I = BI++;
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// The first time through the loop ToSimplify is empty and we try to
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// simplify all instructions. On later iterations ToSimplify is not
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// empty and we only bother simplifying instructions that are in it.
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if (!ToSimplify->empty() && !ToSimplify->count(I))
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continue;
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// Don't waste time simplifying unused instructions.
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if (!I->use_empty())
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if (Value *V = SimplifyInstruction(I, DL, TLI, DT, AC)) {
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// Mark all uses for resimplification next time round the loop.
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for (User *U : I->users())
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Next->insert(cast<Instruction>(U));
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I->replaceAllUsesWith(V);
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++NumSimplified;
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Changed = true;
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}
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bool res = RecursivelyDeleteTriviallyDeadInstructions(I, TLI);
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if (res) {
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// RecursivelyDeleteTriviallyDeadInstruction can remove
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// more than one instruction, so simply incrementing the
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// iterator does not work. When instructions get deleted
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// re-iterate instead.
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BI = BB->begin(); BE = BB->end();
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Changed |= res;
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}
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}
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// Place the list of instructions to simplify on the next loop iteration
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// into ToSimplify.
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std::swap(ToSimplify, Next);
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Next->clear();
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} while (!ToSimplify->empty());
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return Changed;
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}
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};
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}
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char InstSimplifier::ID = 0;
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INITIALIZE_PASS_BEGIN(InstSimplifier, "instsimplify",
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"Remove redundant instructions", false, false)
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INITIALIZE_PASS_DEPENDENCY(AssumptionCacheTracker)
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
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INITIALIZE_PASS_END(InstSimplifier, "instsimplify",
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"Remove redundant instructions", false, false)
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char &llvm::InstructionSimplifierID = InstSimplifier::ID;
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// Public interface to the simplify instructions pass.
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FunctionPass *llvm::createInstructionSimplifierPass() {
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return new InstSimplifier();
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}
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