RPCS3/llvm
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm.git synced 2025-02-23 20:22:09 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Add support for eliminating memcpy's at the end of functions. Also fix some errors I noticed in

Browse Source 
the handling of eliminating stores to byval arguments.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46494 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2008-01-29 06:18:36 +00:00
parent b7cbab8b28
commit a34d8a0d83
1 changed files with 63 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

89
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -20,6 +20,7 @@
#include "llvm/Constants.h"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Pass.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallPtrSet.h"
@ -53,7 +54,7 @@ namespace {
bool handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead);
bool RemoveUndeadPointers(Value* pointer,
BasicBlock::iterator& BBI,
SmallPtrSet<AllocaInst*, 64>& deadPointers,
SmallPtrSet<Value*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead);
void DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts);
@ -249,13 +250,17 @@ bool DSE::handleEndBlock(BasicBlock& BB,
bool MadeChange = false;
// Pointers alloca'd in this function are dead in the end block
SmallPtrSet<AllocaInst*, 64> deadPointers;
SmallPtrSet<Value*, 64> deadPointers;
// Find all of the alloca'd pointers in the entry block
BasicBlock *Entry = BB.getParent()->begin();
for (BasicBlock::iterator I = Entry->begin(), E = Entry->end(); I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
deadPointers.insert(AI);
for (Function::arg_iterator AI = BB.getParent()->arg_begin(),
AE = BB.getParent()->arg_end(); AI != AE; ++AI)
if (AI->hasByValAttr())
deadPointers.insert(AI);
// Scan the basic block backwards
for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
@ -270,10 +275,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
// Alloca'd pointers or byval arguments (which are functionally like
// alloca's) are valid candidates for removal.
if ( (isa<AllocaInst>(pointerOperand) &&
deadPointers.count(cast<AllocaInst>(pointerOperand))) ||
(isa<Argument>(pointerOperand) &&
cast<Argument>(pointerOperand)->hasByValAttr())) {
if (deadPointers.count(pointerOperand)) {
// Remove it!
MD.removeInstruction(S);
@ -291,6 +293,32 @@ bool DSE::handleEndBlock(BasicBlock& BB,
}
continue;
// We can also remove memcpy's to local variables at the end of a function
} else if (MemCpyInst* M = dyn_cast<MemCpyInst>(BBI)) {
Value* dest = M->getDest();
TranslatePointerBitCasts(dest);
if (deadPointers.count(dest)) {
MD.removeInstruction(M);
// DCE instructions only used to calculate that memcpy
if (Instruction* D = dyn_cast<Instruction>(M->getSource()))
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(M->getLength()))
possiblyDead.insert(D);
if (Instruction* D = dyn_cast<Instruction>(M->getRawDest()))
possiblyDead.insert(D);
BBI++;
M->eraseFromParent();
NumFastOther++;
MadeChange = true;
continue;
}
// Because a memcpy is also a load, we can't skip it if we didn't remove it
}
Value* killPointer = 0;
@ -314,8 +342,8 @@ bool DSE::handleEndBlock(BasicBlock& BB,
unsigned other = 0;
// Remove any pointers made undead by the call from the dead set
std::vector<Instruction*> dead;
for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
std::vector<Value*> dead;
for (SmallPtrSet<Value*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// HACK: if we detect that our AA is imprecise, it's not
// worth it to scan the rest of the deadPointers set. Just
@ -328,9 +356,15 @@ bool DSE::handleEndBlock(BasicBlock& BB,
// Get size information for the alloca
unsigned pointerSize = ~0U;
if (ConstantInt* C = dyn_cast<ConstantInt>((*I)->getArraySize()))
pointerSize = C->getZExtValue() * \
TD.getABITypeSize((*I)->getAllocatedType());
if (AllocaInst* A = dyn_cast<AllocaInst>(*I)) {
if (ConstantInt* C = dyn_cast<ConstantInt>(A->getArraySize()))
pointerSize = C->getZExtValue() * \
TD.getABITypeSize(A->getAllocatedType());
} else {
const PointerType* PT = cast<PointerType>(
cast<Argument>(*I)->getType());
pointerSize = TD.getABITypeSize(PT->getElementType());
}
// See if the call site touches it
AliasAnalysis::ModRefResult A = AA.getModRefInfo(CS, *I, pointerSize);
@ -344,10 +378,9 @@ bool DSE::handleEndBlock(BasicBlock& BB,
dead.push_back(*I);
}
for (std::vector<Instruction*>::iterator I = dead.begin(), E = dead.end();
for (std::vector<Value*>::iterator I = dead.begin(), E = dead.end();
I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(*I))
deadPointers.erase(AI);
deadPointers.erase(*I);
continue;
}
@ -369,7 +402,7 @@ bool DSE::handleEndBlock(BasicBlock& BB,
/// undead when scanning for dead stores to alloca's.
bool DSE::RemoveUndeadPointers(Value* killPointer,
BasicBlock::iterator& BBI,
SmallPtrSet<AllocaInst*, 64>& deadPointers,
SmallPtrSet<Value*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead) {
TargetData &TD = getAnalysis<TargetData>();
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
@ -377,9 +410,8 @@ bool DSE::RemoveUndeadPointers(Value* killPointer,
// If the kill pointer can be easily reduced to an alloca,
// don't bother doing extraneous AA queries
if (AllocaInst* A = dyn_cast<AllocaInst>(killPointer)) {
if (deadPointers.count(A))
deadPointers.erase(A);
if (deadPointers.count(killPointer)) {
deadPointers.erase(killPointer);
return false;
} else if (isa<GlobalValue>(killPointer)) {
// A global can't be in the dead pointer set
@ -388,15 +420,21 @@ bool DSE::RemoveUndeadPointers(Value* killPointer,
bool MadeChange = false;
std::vector<Instruction*> undead;
std::vector<Value*> undead;
for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
for (SmallPtrSet<Value*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// Get size information for the alloca
unsigned pointerSize = ~0U;
if (ConstantInt* C = dyn_cast<ConstantInt>((*I)->getArraySize()))
pointerSize = C->getZExtValue() * \
TD.getABITypeSize((*I)->getAllocatedType());
if (AllocaInst* A = dyn_cast<AllocaInst>(*I)) {
if (ConstantInt* C = dyn_cast<ConstantInt>(A->getArraySize()))
pointerSize = C->getZExtValue() * \
TD.getABITypeSize(A->getAllocatedType());
} else {
const PointerType* PT = cast<PointerType>(
cast<Argument>(*I)->getType());
pointerSize = TD.getABITypeSize(PT->getElementType());
}
// See if this pointer could alias it
AliasAnalysis::AliasResult A = AA.alias(*I, pointerSize,
@ -427,10 +465,9 @@ bool DSE::RemoveUndeadPointers(Value* killPointer,
undead.push_back(*I);
}
for (std::vector<Instruction*>::iterator I = undead.begin(), E = undead.end();
for (std::vector<Value*>::iterator I = undead.begin(), E = undead.end();
I != E; ++I)
if (AllocaInst *AI = dyn_cast<AllocaInst>(*I))
deadPointers.erase(AI);
deadPointers.erase(*I);
return MadeChange;
}