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Enable the tail call optimization when the caller returns undef.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@88737 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman 2009-11-14 02:06:30 +00:00
parent 0cd22dd738
commit ed9bab3b4d
2 changed files with 12 additions and 1 deletions
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4
lib/CodeGen/SelectionDAG/SelectionDAGBuild.cpp
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@ -4376,6 +4376,10 @@ isInTailCallPosition(const Instruction *I, Attributes CalleeRetAttr,
// what the call's return type is.
if (!Ret || Ret->getNumOperands() == 0) return true;
// If the return value is undef, it doesn't matter what the call's
// return type is.
if (isa<UndefValue>(Ret->getOperand(0))) return true;
// Conservatively require the attributes of the call to match those of
// the return. Ignore noalias because it doesn't affect the call sequence.
unsigned CallerRetAttr = F->getAttributes().getRetAttributes();

9
test/CodeGen/X86/tailcall1.ll
View File

@ -1,4 +1,4 @@
; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 3
; RUN: llc < %s -march=x86 -tailcallopt | grep TAILCALL | count 4
define fastcc i32 @tailcallee(i32 %a1, i32 %a2, i32 %a3, i32 %a4) {
entry:
ret i32 %a3
@ -23,3 +23,10 @@ define fastcc i8* @alias_caller() nounwind {
%p = tail call fastcc noalias i8* @noalias_callee()
ret i8* %p
}
declare fastcc i32 @i32_callee()
define fastcc i32 @ret_undef() nounwind {
%p = tail call fastcc i32 @i32_callee()
ret i32 undef
}