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disable this instcombine xform, it miscompiles:

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define i32 @main() {
entry:
	%z = alloca i32		; <i32*> [#uses=2]
	store i32 0, i32* %z
	%tmp = load i32* %z		; <i32> [#uses=1]
	%sub = sub i32 %tmp, 1		; <i32> [#uses=1]
	%cmp = icmp ult i32 %sub, 0		; <i1> [#uses=1]
	%retval = select i1 %cmp, i32 1, i32 0		; <i32> [#uses=1]
	ret i32 %retval
}

into ret 1, instead of ret 0.

Christopher, please investigate.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45383 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2007-12-28 06:24:31 +00:00
parent 166a268656
commit c48b138869
1 changed files with 2 additions and 0 deletions
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2
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4835,9 +4835,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A, *B;
#if 0
// (icmp cond (sub A B) 0) -> (icmp cond A B)
if (CI->isNullValue() && match(Op0, m_Sub(m_Value(A), m_Value(B))))
return new ICmpInst(I.getPredicate(), A, B);
#endif
switch (I.getPredicate()) {
default: break;