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isAllocLikeFn is allowed to return true for functions which read memory; make

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sure we account for that correctly in DeadStoreElimination.  Fixes a regression
from r158919.  PR13547.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161468 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Eli Friedman 2012-08-08 02:17:32 +00:00
parent 913ff09a9a
commit 1b88fc0122
2 changed files with 24 additions and 2 deletions
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11
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -740,12 +740,19 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
continue;
}
if (isa<AllocaInst>(BBI) || isAllocLikeFn(BBI)) {
if (isa<AllocaInst>(BBI)) {
// Remove allocas from the list of dead stack objects; there can't be
// any references before the definition.
DeadStackObjects.remove(BBI);
continue;
}
if (CallSite CS = cast<Value>(BBI)) {
// Remove allocation function calls from the list of dead stack objects;
// there can't be any references before the definition.
if (isAllocLikeFn(BBI))
DeadStackObjects.remove(BBI);
// If this call does not access memory, it can't be loading any of our
// pointers.
if (AA->doesNotAccessMemory(CS))
@ -771,7 +778,7 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
// If all of the allocas were clobbered by the call then we're not going
// to find anything else to process.
if (DeadStackObjects.empty())
return MadeChange;
break;
continue;
}

15
test/Transforms/DeadStoreElimination/simple.ll
View File

@ -276,3 +276,18 @@ define void @test22(i1 %i, i32 %k, i32 %m) nounwind {
; CHECK-NEXT: ret void
ret void
}
; PR13547
; CHECK: @test23
; CHECK: store i8 97
; CHECK: store i8 0
declare noalias i8* @strdup(i8* nocapture) nounwind
define noalias i8* @test23() nounwind uwtable ssp {
%x = alloca [2 x i8], align 1
%arrayidx = getelementptr inbounds [2 x i8]* %x, i64 0, i64 0
store i8 97, i8* %arrayidx, align 1
%arrayidx1 = getelementptr inbounds [2 x i8]* %x, i64 0, i64 1
store i8 0, i8* %arrayidx1, align 1
%call = call i8* @strdup(i8* %arrayidx) nounwind
ret i8* %call
}