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Allow GVN to eliminate read-only function calls when it can detect that they are redundant.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44323 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson
2007-11-26 02:26:36 +00:00
parent fd94dd58ff
commit 00a6d1448d
3 changed files with 24 additions and 6 deletions
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9
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@@ -79,9 +79,6 @@ Instruction* MemoryDependenceAnalysis::getCallSiteDependency(CallSite C,
if (StoreInst* S = dyn_cast<StoreInst>(QI)) { if (StoreInst* S = dyn_cast<StoreInst>(QI)) {
pointer = S->getPointerOperand(); pointer = S->getPointerOperand();
pointerSize = TD.getTypeStoreSize(S->getOperand(0)->getType()); pointerSize = TD.getTypeStoreSize(S->getOperand(0)->getType());
} else if (LoadInst* L = dyn_cast<LoadInst>(QI)) {
pointer = L->getPointerOperand();
pointerSize = TD.getTypeStoreSize(L->getType());
} else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) { } else if (AllocationInst* AI = dyn_cast<AllocationInst>(QI)) {
pointer = AI; pointer = AI;
if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize())) if (ConstantInt* C = dyn_cast<ConstantInt>(AI->getArraySize()))
@@ -98,7 +95,11 @@ Instruction* MemoryDependenceAnalysis::getCallSiteDependency(CallSite C,
// FreeInsts erase the entire structure // FreeInsts erase the entire structure
pointerSize = ~0UL; pointerSize = ~0UL;
} else if (CallSite::get(QI).getInstruction() != 0) { } else if (CallSite::get(QI).getInstruction() != 0) {
if (AA.getModRefInfo(C, CallSite::get(QI)) != AliasAnalysis::NoModRef) { AliasAnalysis::ModRefBehavior result =
AA.getModRefBehavior(cast<CallInst>(QI)->getCalledFunction(),
CallSite::get(QI));
if (result != AliasAnalysis::DoesNotAccessMemory &&
result != AliasAnalysis::OnlyReadsMemory) {
if (!start && !block) { if (!start && !block) {
depGraphLocal.insert(std::make_pair(C.getInstruction(), depGraphLocal.insert(std::make_pair(C.getInstruction(),
std::make_pair(QI, true))); std::make_pair(QI, true)));

19
lib/Transforms/Scalar/GVN.cpp
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@@ -476,7 +476,8 @@ uint32_t ValueTable::lookup_or_add(Value* V) {
if (CallInst* C = dyn_cast<CallInst>(V)) { if (CallInst* C = dyn_cast<CallInst>(V)) {
if (C->getCalledFunction() && if (C->getCalledFunction() &&
AA->doesNotAccessMemory(C->getCalledFunction())) { (AA->doesNotAccessMemory(C->getCalledFunction()) ||
AA->onlyReadsMemory(C->getCalledFunction()))) {
Expression e = create_expression(C); Expression e = create_expression(C);
DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e); DenseMap<Expression, uint32_t>::iterator EI = expressionNumbering.find(e);
@@ -1038,6 +1039,22 @@ bool GVN::processInstruction(Instruction* I,
} else if (currAvail.test(num)) { } else if (currAvail.test(num)) {
Value* repl = find_leader(currAvail, num); Value* repl = find_leader(currAvail, num);
if (CallInst* CI = dyn_cast<CallInst>(I)) {
AliasAnalysis& AA = getAnalysis<AliasAnalysis>();
if (CI->getCalledFunction() &&
!AA.doesNotAccessMemory(CI->getCalledFunction())) {
MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
if (MD.getDependency(CI) != MD.getDependency(cast<CallInst>(repl))) {
// There must be an intervening may-alias store, so nothing from
// this point on will be able to be replaced with the preceding call
currAvail.erase(repl);
currAvail.insert(I);
return false;
}
}
}
VN.erase(I); VN.erase(I);
I->replaceAllUsesWith(repl); I->replaceAllUsesWith(repl);
toErase.push_back(I); toErase.push_back(I);

2
test/Analysis/BasicAA/pure-const-dce.ll
View File

@@ -1,5 +1,5 @@
; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestConst | count 2 ; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestConst | count 2
; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestPure | not count 2 ; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestPure | count 3
; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestNone | count 4 ; RUN: llvm-as < %s | opt -basicaa -gvn | llvm-dis | grep TestNone | count 4
@g = global i32 0 ; <i32*> [#uses=1] @g = global i32 0 ; <i32*> [#uses=1]