forked from OSchip/llvm-project
rewrite a big chunk of how DSE does recursive dead operand
elimination to use more modern infrastructure. Also do a bunch of small cleanups. llvm-svn: 60201
This commit is contained in:
Chris Lattner
parent
7283d44569
commit
1adb6759ef
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@ -22,7 +22,6 @@
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#include "llvm/Instructions.h"
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#include "llvm/IntrinsicInst.h"
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#include "llvm/Pass.h"
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#include "llvm/ADT/SetVector.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/AliasAnalysis.h"
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@ -49,16 +48,13 @@ namespace {
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}
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bool runOnBasicBlock(BasicBlock &BB);
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bool handleFreeWithNonTrivialDependency(FreeInst* F,
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Instruction* dependency,
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SetVector<Instruction*>& possiblyDead);
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bool handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead);
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bool handleFreeWithNonTrivialDependency(FreeInst *F, Instruction *Dep);
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bool handleEndBlock(BasicBlock &BB);
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bool RemoveUndeadPointers(Value* pointer, uint64_t killPointerSize,
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BasicBlock::iterator& BBI,
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SmallPtrSet<Value*, 64>& deadPointers,
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SetVector<Instruction*>& possiblyDead);
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void DeleteDeadInstructionChains(Instruction *I,
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SetVector<Instruction*> &DeadInsts);
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SmallPtrSet<Value*, 64>& deadPointers);
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void DeleteDeadInstruction(Instruction *I,
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SmallPtrSet<Value*, 64> *deadPointers = 0);
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// getAnalysisUsage - We require post dominance frontiers (aka Control
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@ -87,8 +83,6 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
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// Record the last-seen store to this pointer
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DenseMap<Value*, StoreInst*> lastStore;
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// Record instructions possibly made dead by deleting a store
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SetVector<Instruction*> possiblyDead;
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bool MadeChange = false;
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@ -127,20 +121,11 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
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continue;
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}
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// Remove it!
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MD.removeInstruction(last);
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// DCE instructions only used to calculate that store
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if (Instruction* D = dyn_cast<Instruction>(last->getOperand(0)))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(last->getOperand(1)))
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possiblyDead.insert(D);
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last->eraseFromParent();
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// Delete the store and now-dead instructions that feed it.
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DeleteDeadInstruction(last);
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NumFastStores++;
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deletedStore = true;
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MadeChange = true;
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break;
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}
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}
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@ -148,9 +133,8 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
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// Handle frees whose dependencies are non-trivial.
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if (FreeInst* F = dyn_cast<FreeInst>(BBI)) {
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if (!deletedStore)
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MadeChange |= handleFreeWithNonTrivialDependency(F,
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MD.getDependency(F),
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possiblyDead);
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MadeChange |= handleFreeWithNonTrivialDependency(F,MD.getDependency(F));
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// No known stores after the free
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last = 0;
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} else {
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@ -164,19 +148,13 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
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if (!S->isVolatile() && S->getParent() == L->getParent() &&
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S->getPointerOperand() == L->getPointerOperand() &&
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( dep == MemoryDependenceAnalysis::None ||
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dep == MemoryDependenceAnalysis::NonLocal ||
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DT.dominates(dep, L))) {
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(0)))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(1)))
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possiblyDead.insert(D);
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(dep == MemoryDependenceAnalysis::None ||
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dep == MemoryDependenceAnalysis::NonLocal ||
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DT.dominates(dep, L))) {
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// Avoid iterator invalidation.
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BBI--;
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MD.removeInstruction(S);
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S->eraseFromParent();
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BBI++;
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DeleteDeadInstruction(S);
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NumFastStores++;
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MadeChange = true;
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} else
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@ -191,25 +169,16 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
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// If this block ends in a return, unwind, unreachable, and eventually
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// tailcall, then all allocas are dead at its end.
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if (BB.getTerminator()->getNumSuccessors() == 0)
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MadeChange |= handleEndBlock(BB, possiblyDead);
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// Do a trivial DCE
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while (!possiblyDead.empty()) {
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Instruction *I = possiblyDead.back();
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possiblyDead.pop_back();
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DeleteDeadInstructionChains(I, possiblyDead);
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}
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MadeChange |= handleEndBlock(BB);
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return MadeChange;
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}
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/// handleFreeWithNonTrivialDependency - Handle frees of entire structures whose
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/// dependency is a store to a field of that structure
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bool DSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep,
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SetVector<Instruction*>& possiblyDead) {
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/// dependency is a store to a field of that structure.
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bool DSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep) {
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TargetData &TD = getAnalysis<TargetData>();
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AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
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MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
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if (dep == MemoryDependenceAnalysis::None ||
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dep == MemoryDependenceAnalysis::NonLocal)
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@ -229,22 +198,13 @@ bool DSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep,
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AliasAnalysis::AliasResult A = AA.alias(F->getPointerOperand(), ~0U,
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depPointer, depPointerSize);
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if (A == AliasAnalysis::MustAlias) {
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// Remove it!
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MD.removeInstruction(dependency);
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if (A != AliasAnalysis::MustAlias)
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return false;
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// DCE instructions only used to calculate that store
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if (Instruction* D = dyn_cast<Instruction>(dependency->getOperand(0)))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(dependency->getOperand(1)))
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possiblyDead.insert(D);
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dependency->eraseFromParent();
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NumFastStores++;
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return true;
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}
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return false;
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// DCE instructions only used to calculate that store
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DeleteDeadInstruction(dependency);
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NumFastStores++;
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return true;
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}
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/// handleEndBlock - Remove dead stores to stack-allocated locations in the
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@ -253,22 +213,23 @@ bool DSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep,
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/// ...
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/// store i32 1, i32* %A
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/// ret void
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bool DSE::handleEndBlock(BasicBlock& BB,
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SetVector<Instruction*>& possiblyDead) {
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bool DSE::handleEndBlock(BasicBlock &BB) {
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TargetData &TD = getAnalysis<TargetData>();
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AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
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MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
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bool MadeChange = false;
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// Pointers alloca'd in this function are dead in the end block
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SmallPtrSet<Value*, 64> deadPointers;
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// Find all of the alloca'd pointers in the entry block
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// Find all of the alloca'd pointers in the entry block.
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BasicBlock *Entry = BB.getParent()->begin();
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for (BasicBlock::iterator I = Entry->begin(), E = Entry->end(); I != E; ++I)
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if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
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deadPointers.insert(AI);
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// Treat byval arguments the same, stores to them are dead at the end of the
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// function.
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for (Function::arg_iterator AI = BB.getParent()->arg_begin(),
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AE = BB.getParent()->arg_end(); AI != AE; ++AI)
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if (AI->hasByValAttr())
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@ -278,7 +239,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
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--BBI;
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// If we find a store whose pointer is dead...
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// If we find a store whose pointer is dead.
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if (StoreInst* S = dyn_cast<StoreInst>(BBI)) {
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if (!S->isVolatile()) {
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// See through pointer-to-pointer bitcasts
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@ -287,71 +248,45 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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// Alloca'd pointers or byval arguments (which are functionally like
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// alloca's) are valid candidates for removal.
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if (deadPointers.count(pointerOperand)) {
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// Remove it!
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MD.removeInstruction(S);
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// DCE instructions only used to calculate that store
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(0)))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(1)))
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possiblyDead.insert(D);
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// DCE instructions only used to calculate that store.
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BBI++;
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MD.removeInstruction(S);
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S->eraseFromParent();
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DeleteDeadInstruction(S, &deadPointers);
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NumFastStores++;
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MadeChange = true;
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}
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}
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continue;
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}
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// We can also remove memcpy's to local variables at the end of a function
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} else if (MemCpyInst* M = dyn_cast<MemCpyInst>(BBI)) {
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Value* dest = M->getDest()->getUnderlyingObject();
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// We can also remove memcpy's to local variables at the end of a function.
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if (MemCpyInst *M = dyn_cast<MemCpyInst>(BBI)) {
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Value *dest = M->getDest()->getUnderlyingObject();
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if (deadPointers.count(dest)) {
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MD.removeInstruction(M);
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// DCE instructions only used to calculate that memcpy
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if (Instruction* D = dyn_cast<Instruction>(M->getRawSource()))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(M->getLength()))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(M->getRawDest()))
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possiblyDead.insert(D);
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BBI++;
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M->eraseFromParent();
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DeleteDeadInstruction(M, &deadPointers);
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NumFastOther++;
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MadeChange = true;
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continue;
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}
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// Because a memcpy is also a load, we can't skip it if we didn't remove it
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// Because a memcpy is also a load, we can't skip it if we didn't remove
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// it.
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}
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Value* killPointer = 0;
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uint64_t killPointerSize = ~0UL;
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// If we encounter a use of the pointer, it is no longer considered dead
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if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
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if (LoadInst *L = dyn_cast<LoadInst>(BBI)) {
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// However, if this load is unused and not volatile, we can go ahead and
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// remove it, and not have to worry about it making our pointer undead!
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if (L->use_empty() && !L->isVolatile()) {
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MD.removeInstruction(L);
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// DCE instructions only used to calculate that load
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if (Instruction* D = dyn_cast<Instruction>(L->getPointerOperand()))
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possiblyDead.insert(D);
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BBI++;
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L->eraseFromParent();
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DeleteDeadInstruction(L, &deadPointers);
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NumFastOther++;
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MadeChange = true;
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possiblyDead.remove(L);
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continue;
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}
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@ -368,17 +303,10 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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// Dead alloca's can be DCE'd when we reach them
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if (A->use_empty()) {
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MD.removeInstruction(A);
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// DCE instructions only used to calculate that load
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if (Instruction* D = dyn_cast<Instruction>(A->getArraySize()))
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possiblyDead.insert(D);
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BBI++;
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A->eraseFromParent();
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DeleteDeadInstruction(A, &deadPointers);
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NumFastOther++;
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MadeChange = true;
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possiblyDead.remove(A);
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}
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continue;
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@ -434,25 +362,14 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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deadPointers.erase(*I);
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continue;
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} else {
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} else if (isInstructionTriviallyDead(BBI)) {
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// For any non-memory-affecting non-terminators, DCE them as we reach them
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Instruction *CI = BBI;
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if (!CI->isTerminator() && CI->use_empty() && !isa<FreeInst>(CI)) {
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// DCE instructions only used to calculate that load
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for (Instruction::op_iterator OI = CI->op_begin(), OE = CI->op_end();
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OI != OE; ++OI)
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if (Instruction* D = dyn_cast<Instruction>(OI))
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possiblyDead.insert(D);
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BBI++;
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CI->eraseFromParent();
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NumFastOther++;
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MadeChange = true;
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possiblyDead.remove(CI);
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continue;
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}
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Instruction *Inst = BBI;
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BBI++;
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DeleteDeadInstruction(Inst, &deadPointers);
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NumFastOther++;
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MadeChange = true;
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continue;
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}
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if (!killPointer)
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@ -462,7 +379,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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// Deal with undead pointers
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MadeChange |= RemoveUndeadPointers(killPointer, killPointerSize, BBI,
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deadPointers, possiblyDead);
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deadPointers);
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}
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return MadeChange;
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@ -471,38 +388,36 @@ bool DSE::handleEndBlock(BasicBlock& BB,
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/// RemoveUndeadPointers - check for uses of a pointer that make it
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/// undead when scanning for dead stores to alloca's.
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bool DSE::RemoveUndeadPointers(Value* killPointer, uint64_t killPointerSize,
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BasicBlock::iterator& BBI,
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SmallPtrSet<Value*, 64>& deadPointers,
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SetVector<Instruction*>& possiblyDead) {
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BasicBlock::iterator &BBI,
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SmallPtrSet<Value*, 64>& deadPointers) {
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TargetData &TD = getAnalysis<TargetData>();
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AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
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MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
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// If the kill pointer can be easily reduced to an alloca,
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// don't bother doing extraneous AA queries
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// don't bother doing extraneous AA queries.
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if (deadPointers.count(killPointer)) {
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deadPointers.erase(killPointer);
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return false;
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} else if (isa<GlobalValue>(killPointer)) {
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// A global can't be in the dead pointer set
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return false;
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}
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// A global can't be in the dead pointer set.
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if (isa<GlobalValue>(killPointer))
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return false;
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bool MadeChange = false;
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std::vector<Value*> undead;
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SmallVector<Value*, 16> undead;
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for (SmallPtrSet<Value*, 64>::iterator I = deadPointers.begin(),
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E = deadPointers.end(); I != E; ++I) {
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// Get size information for the alloca
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// Get size information for the alloca.
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unsigned pointerSize = ~0U;
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if (AllocaInst* A = dyn_cast<AllocaInst>(*I)) {
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if (ConstantInt* C = dyn_cast<ConstantInt>(A->getArraySize()))
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pointerSize = C->getZExtValue() * \
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pointerSize = C->getZExtValue() *
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TD.getABITypeSize(A->getAllocatedType());
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} else {
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const PointerType* PT = cast<PointerType>(
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cast<Argument>(*I)->getType());
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const PointerType* PT = cast<PointerType>(cast<Argument>(*I)->getType());
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pointerSize = TD.getABITypeSize(PT->getElementType());
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}
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@ -515,56 +430,65 @@ bool DSE::RemoveUndeadPointers(Value* killPointer, uint64_t killPointerSize,
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StoreInst* S = cast<StoreInst>(BBI);
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// Remove it!
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MD.removeInstruction(S);
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// DCE instructions only used to calculate that store
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(0)))
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possiblyDead.insert(D);
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if (Instruction* D = dyn_cast<Instruction>(S->getOperand(1)))
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possiblyDead.insert(D);
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BBI++;
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S->eraseFromParent();
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DeleteDeadInstruction(S, &deadPointers);
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NumFastStores++;
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MadeChange = true;
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continue;
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// Otherwise, it is undead
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} else if (A != AliasAnalysis::NoAlias)
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undead.push_back(*I);
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} else if (A != AliasAnalysis::NoAlias)
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undead.push_back(*I);
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}
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for (std::vector<Value*>::iterator I = undead.begin(), E = undead.end();
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for (SmallVector<Value*, 16>::iterator I = undead.begin(), E = undead.end();
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I != E; ++I)
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deadPointers.erase(*I);
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return MadeChange;
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}
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/// DeleteDeadInstructionChains - takes an instruction and a setvector of
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/// dead instructions. If I is dead, it is erased, and its operands are
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/// checked for deadness. If they are dead, they are added to the dead
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/// setvector.
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void DSE::DeleteDeadInstructionChains(Instruction *I,
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SetVector<Instruction*> &DeadInsts) {
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// Instruction must be dead.
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if (!I->use_empty() || !isInstructionTriviallyDead(I)) return;
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/// DeleteDeadInstruction - Delete this instruction. Before we do, go through
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/// and zero out all the operands of this instruction. If any of them become
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/// dead, delete them and the computation tree that feeds them.
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///
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/// If ValueSet is non-null, remove any deleted instructions from it as well.
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///
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void DSE::DeleteDeadInstruction(Instruction *I,
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SmallPtrSet<Value*, 64> *ValueSet) {
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SmallVector<Instruction*, 32> NowDeadInsts;
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// Let the memory dependence know
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getAnalysis<MemoryDependenceAnalysis>().removeInstruction(I);
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NowDeadInsts.push_back(I);
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--NumFastOther;
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// See if this made any operands dead. We do it this way in case the
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// instruction uses the same operand twice. We don't want to delete a
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// value then reference it.
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for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
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if (I->getOperand(i)->hasOneUse())
|
||||
if (Instruction* Op = dyn_cast<Instruction>(I->getOperand(i)))
|
||||
DeadInsts.insert(Op); // Attempt to nuke it later.
|
||||
// Before we touch this instruction, remove it from memdep!
|
||||
MemoryDependenceAnalysis &MDA = getAnalysis<MemoryDependenceAnalysis>();
|
||||
while (!NowDeadInsts.empty()) {
|
||||
Instruction *DeadInst = NowDeadInsts.back();
|
||||
NowDeadInsts.pop_back();
|
||||
|
||||
I->setOperand(i, 0); // Drop from the operand list.
|
||||
++NumFastOther;
|
||||
|
||||
// This instruction is dead, zap it, in stages. Start by removing it from
|
||||
// MemDep, which needs to know the operands and needs it to be in the
|
||||
// function.
|
||||
MDA.removeInstruction(DeadInst);
|
||||
|
||||
for (unsigned op = 0, e = DeadInst->getNumOperands(); op != e; ++op) {
|
||||
Value *Op = DeadInst->getOperand(op);
|
||||
DeadInst->setOperand(op, 0);
|
||||
|
||||
// If this operand just became dead, add it to the NowDeadInsts list.
|
||||
if (!Op->use_empty()) continue;
|
||||
|
||||
if (Instruction *OpI = dyn_cast<Instruction>(Op))
|
||||
if (isInstructionTriviallyDead(OpI))
|
||||
NowDeadInsts.push_back(OpI);
|
||||
}
|
||||
|
||||
DeadInst->eraseFromParent();
|
||||
|
||||
if (ValueSet) ValueSet->erase(DeadInst);
|
||||
}
|
||||
|
||||
I->eraseFromParent();
|
||||
++NumFastOther;
|
||||
}
|
||||
|
|
|
|||
Loading…
Reference in New Issue