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Don't let a noalias difference disrupt the tailcall optimization.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@88672 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-11-13 18:49:38 +00:00
parent 0d1680a7d8
commit 01205a80f5
2 changed files with 19 additions and 4 deletions
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7
lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
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@ -4349,7 +4349,7 @@ SelectionDAGLowering::visitIntrinsicCall(CallInst &I, unsigned Intrinsic) {
/// TargetLowering::IsEligibleForTailCallOptimization.
///
static bool
isInTailCallPosition(const Instruction *I, Attributes RetAttr,
isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
const TargetLowering &TLI) {
const BasicBlock *ExitBB = I->getParent();
const TerminatorInst *Term = ExitBB->getTerminator();
@ -4377,8 +4377,9 @@ isInTailCallPosition(const Instruction *I, Attributes RetAttr,
if (!Ret || Ret->getNumOperands() == 0) return true;
// Conservatively require the attributes of the call to match those of
// the return.
if (F->getAttributes().getRetAttributes() != RetAttr)
// the return. Ignore noalias because it doesn't affect the call sequence.
unsigned CallerRetAttr = F->getAttributes().getRetAttributes();
if ((CalleeRetAttr ^ CallerRetAttr) & ~Attribute::NoAlias)
return false;
// Otherwise, make sure the unmodified return value of I is the return value.

16
test/CodeGen/X86/tailcall1.ll
View File

@ -1,4 +1,4 @@
; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL
; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 3
define fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4) {
entry:
ret i32 %a3
@ -9,3 +9,17 @@ entry:
%tmp11 = tail call fastcc i32 @tailcallee( i32 %in1, i32 %in2, i32 %in1, i32 %in2 ) ; <i32> [#uses=1]
ret i32 %tmp11
}
declare fastcc i8* @alias_callee()
define fastcc noalias i8* @noalias_caller() nounwind {
%p = tail call fastcc i8* @alias_callee()
ret i8* %p
}
declare fastcc noalias i8* @noalias_callee()
define fastcc i8* @alias_caller() nounwind {
%p = tail call fastcc noalias i8* @noalias_callee()
ret i8* %p
}