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Treat lifetime begin/end markers as allocations/frees respectively for the

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purposes for GVN/DSE.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85383 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2009-10-28 07:05:35 +00:00
parent 40cc524ede
commit b62f792e78
5 changed files with 94 additions and 3 deletions
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18
lib/Analysis/MemoryDependenceAnalysis.cpp
View File

@ -185,10 +185,9 @@ getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
if (invariantTag == Inst) {
invariantTag = 0;
continue;
// If we pass an invariant-end marker, then we've just entered an invariant
// region and can start ignoring dependencies.
} else if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(Inst)) {
// If we pass an invariant-end marker, then we've just entered an
// invariant region and can start ignoring dependencies.
if (II->getIntrinsicID() == Intrinsic::invariant_end) {
uint64_t invariantSize = ~0ULL;
if (ConstantInt* CI = dyn_cast<ConstantInt>(II->getOperand(2)))
@ -200,6 +199,19 @@ getPointerDependencyFrom(Value *MemPtr, uint64_t MemSize, bool isLoad,
invariantTag = II->getOperand(1);
continue;
}
// If we reach a lifetime begin or end marker, then the query ends here
// because the value is undefined.
} else if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end) {
uint64_t invariantSize = ~0ULL;
if (ConstantInt* CI = dyn_cast<ConstantInt>(II->getOperand(1)))
invariantSize = CI->getZExtValue();
AliasAnalysis::AliasResult R =
AA->alias(II->getOperand(2), invariantSize, MemPtr, MemSize);
if (R == AliasAnalysis::MustAlias)
return MemDepResult::getDef(II);
}
}

20
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -154,6 +154,26 @@ bool DSE::runOnBasicBlock(BasicBlock &BB) {
continue;
}
}
// If this is a lifetime end marker, we can throw away the store.
if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(InstDep.getInst())) {
if (II->getIntrinsicID() == Intrinsic::lifetime_end) {
// Delete the store and now-dead instructions that feed it.
// DeleteDeadInstruction can delete the current instruction. Save BBI
// in case we need it.
WeakVH NextInst(BBI);
DeleteDeadInstruction(SI);
if (NextInst == 0) // Next instruction deleted.
BBI = BB.begin();
else if (BBI != BB.begin()) // Revisit this instruction if possible.
--BBI;
NumFastStores++;
MadeChange = true;
continue;
}
}
}
// If this block ends in a return, unwind, or unreachable, all allocas are

21
lib/Transforms/Scalar/GVN.cpp
View File

@ -1248,6 +1248,15 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
UndefValue::get(LI->getType())));
continue;
}
// Loading immediately after lifetime begin or end -> undef.
if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(DepInst)) {
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end) {
ValuesPerBlock.push_back(AvailableValueInBlock::get(DepBB,
UndefValue::get(LI->getType())));
}
}
if (StoreInst *S = dyn_cast<StoreInst>(DepInst)) {
// Reject loads and stores that are to the same address but are of
@ -1591,6 +1600,18 @@ bool GVN::processLoad(LoadInst *L, SmallVectorImpl<Instruction*> &toErase) {
NumGVNLoad++;
return true;
}
// If this load occurs either right after a lifetime begin or a lifetime end,
// then the loaded value is undefined.
if (IntrinsicInst* II = dyn_cast<IntrinsicInst>(DepInst)) {
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end) {
L->replaceAllUsesWith(UndefValue::get(L->getType()));
toErase.push_back(L);
NumGVNLoad++;
return true;
}
}
return false;
}

18
test/Transforms/DeadStoreElimination/lifetime-simple.ll Normal file
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@ -0,0 +1,18 @@
; RUN: opt < %s -dse -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin7"
define i8 @test2(i8* %P) nounwind {
; CHECK: @test2
; CHECK-NOT: store i8 1
; CHECK: ret i8 0
entry:
call void @llvm.lifetime.start(i64 32, i8* %P)
call void @llvm.lifetime.end(i64 32, i8* %P)
store i8 1, i8* %P
ret i8 0
}
declare {}* @llvm.lifetime.start(i64 %S, i8* nocapture %P) readonly
declare void @llvm.lifetime.end(i64 %S, i8* nocapture %P)

20
test/Transforms/GVN/lifetime-simple.ll Normal file
View File

@ -0,0 +1,20 @@
; RUN: opt < %s -gvn -S | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
target triple = "i386-apple-darwin7"
define i8 @test(i8* %P) nounwind {
; CHECK: @test
; CHECK-NOT: load
; CHECK: ret i8 undef
entry:
call void @llvm.lifetime.start(i64 32, i8* %P)
%0 = load i8* %P
store i8 1, i8* %P
call void @llvm.lifetime.end(i64 32, i8* %P)
%1 = load i8* %P
ret i8 %1
}
declare {}* @llvm.lifetime.start(i64 %S, i8* nocapture %P) readonly
declare void @llvm.lifetime.end(i64 %S, i8* nocapture %P)