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CheckTailCallReturnConstraints is missing a check on the

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incomming chain of the RETURN node. The incomming chain must
be the outgoing chain of the CALL node. This causes the
backend to identify tail calls that are not tail calls. This
patch fixes this.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@73387 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Arnold Schwaighofer 2009-06-15 14:43:36 +00:00
parent c457b65087
commit 5d2c01e48a
2 changed files with 19 additions and 1 deletions
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6
lib/CodeGen/SelectionDAG/TargetLowering.cpp
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@ -2584,8 +2584,12 @@ bool TargetLowering::CheckTailCallReturnConstraints(CallSDNode *TheCall,
// Check that operand of the RET node sources from the CALL node. The RET node
// has at least two operands. Operand 0 holds the chain. Operand 1 holds the
// value.
// Also we need to check that there is no code in between the call and the
// return. Hence we also check that the incomming chain to the return sources
// from the outgoing chain of the call.
if (NumOps > 1 &&
IgnoreHarmlessInstructions(Ret.getOperand(1)) == SDValue(TheCall,0))
IgnoreHarmlessInstructions(Ret.getOperand(1)) == SDValue(TheCall,0) &&
Ret.getOperand(0) == SDValue(TheCall, TheCall->getNumValues()-1))
return true;
// void return: The RET node has the chain result value of the CALL node as
// input.

14
test/CodeGen/X86/2009-06-15-not-a-tail-call.ll Normal file
View File

@ -0,0 +1,14 @@
; RUN: llvm-as < %s | llc -march=x86 -tailcallopt | not grep TAILCALL
; Bug 4396. This tail call can NOT be optimized.
declare fastcc i8* @_D3gcx2GC12mallocNoSyncMFmkZPv() nounwind
define fastcc i8* @_D3gcx2GC12callocNoSyncMFmkZPv() nounwind {
entry:
%tmp6 = tail call fastcc i8* @_D3gcx2GC12mallocNoSyncMFmkZPv() ; <i8*> [#uses=2]
%tmp9 = tail call i8* @memset(i8* %tmp6, i32 0, i64 2) ; <i8*> [#uses=0]
ret i8* %tmp6
}
declare i8* @memset(i8*, i32, i64)