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Teach globalopt how memset/cpy/move affect memory, to allow better optimization. 

llvm-svn: 20352
This commit is contained in:
Chris Lattner 2005-02-27 18:58:52 +00:00
parent a1079acb0a
commit 7561ca1d15
1 changed files with 40 additions and 25 deletions
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65
llvm/lib/Transforms/IPO/GlobalOpt.cpp
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@ -18,6 +18,7 @@
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
@ -194,7 +195,7 @@ static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
} else {
GS.StoredType = GlobalStatus::isStored;
}
} else if (I->getOpcode() == Instruction::GetElementPtr) {
} else if (isa<GetElementPtrInst>(I)) {
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
// If the first two indices are constants, this can be SRA'd.
@ -212,7 +213,7 @@ static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
} else {
GS.isNotSuitableForSRA = true;
}
} else if (I->getOpcode() == Instruction::Select) {
} else if (isa<SelectInst>(I)) {
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
GS.isNotSuitableForSRA = true;
} else if (PHINode *PN = dyn_cast<PHINode>(I)) {
@ -223,6 +224,16 @@ static bool AnalyzeGlobal(Value *V, GlobalStatus &GS,
GS.isNotSuitableForSRA = true;
} else if (isa<SetCondInst>(I)) {
GS.isNotSuitableForSRA = true;
} else if (isa<MemCpyInst>(I) || isa<MemMoveInst>(I)) {
if (I->getOperand(1) == V)
GS.StoredType = GlobalStatus::isStored;
if (I->getOperand(2) == V)
GS.isLoaded = true;
GS.isNotSuitableForSRA = true;
} else if (isa<MemSetInst>(I)) {
assert(I->getOperand(1) == V && "Memset only takes one pointer!");
GS.StoredType = GlobalStatus::isStored;
GS.isNotSuitableForSRA = true;
} else {
return true; // Any other non-load instruction might take address!
}
@ -270,6 +281,7 @@ static Constant *getAggregateConstantElement(Constant *Agg, Constant *Idx) {
}
static Constant *TraverseGEPInitializer(User *GEP, Constant *Init) {
if (Init == 0) return 0;
if (GEP->getNumOperands() == 1 ||
!isa<Constant>(GEP->getOperand(1)) ||
!cast<Constant>(GEP->getOperand(1))->isNullValue())
@ -294,47 +306,50 @@ static bool CleanupConstantGlobalUsers(Value *V, Constant *Init) {
User *U = *UI++;
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
// Replace the load with the initializer.
LI->replaceAllUsesWith(Init);
LI->eraseFromParent();
Changed = true;
if (Init) {
// Replace the load with the initializer.
LI->replaceAllUsesWith(Init);
LI->eraseFromParent();
Changed = true;
}
} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// Store must be unreachable or storing Init into the global.
SI->eraseFromParent();
Changed = true;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
if (Constant *SubInit = TraverseGEPInitializer(CE, Init))
Changed |= CleanupConstantGlobalUsers(CE, SubInit);
if (CE->use_empty()) {
CE->destroyConstant();
Changed = true;
}
Constant *SubInit = TraverseGEPInitializer(CE, Init);
Changed |= CleanupConstantGlobalUsers(CE, SubInit);
} else if (CE->getOpcode() == Instruction::Cast &&
isa<PointerType>(CE->getType())) {
// Pointer cast, delete any stores and memsets to the global.
Changed |= CleanupConstantGlobalUsers(CE, 0);
}
if (CE->use_empty()) {
CE->destroyConstant();
Changed = true;
}
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
if (Constant *SubInit = TraverseGEPInitializer(GEP, Init))
Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
else {
// If this GEP has variable indexes, we should still be able to delete
// any stores through it.
for (Value::use_iterator GUI = GEP->use_begin(), E = GEP->use_end();
GUI != E;)
if (StoreInst *SI = dyn_cast<StoreInst>(*GUI++)) {
SI->eraseFromParent();
Changed = true;
}
}
Constant *SubInit = TraverseGEPInitializer(GEP, Init);
Changed |= CleanupConstantGlobalUsers(GEP, SubInit);
if (GEP->use_empty()) {
GEP->eraseFromParent();
Changed = true;
}
} else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
if (MI->getRawDest() == V) {
MI->eraseFromParent();
Changed = true;
}
} else if (Constant *C = dyn_cast<Constant>(U)) {
// If we have a chain of dead constantexprs or other things dangling from
// us, and if they are all dead, nuke them without remorse.
if (ConstantIsDead(C)) {
C->destroyConstant();
// This could have incalidated UI, start over from scratch.x
// This could have invalidated UI, start over from scratch.
CleanupConstantGlobalUsers(V, Init);
return true;
}