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remove the (x-y) < 0 comparison xform, it miscompiles

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things that are not equality comparisons, for example:
   (2147479553+4096)-2147479553 < 0    !=   (2147479553+4096) < 2147479553


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45612 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-01-05 01:18:20 +00:00
parent a393cd3306
commit b656601943
1 changed files with 5 additions and 11 deletions
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16
lib/Transforms/Scalar/InstructionCombining.cpp
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@ -4835,17 +4835,11 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) {
Value *A, *B;
// (icmp cond (sub A B) 0) -> ...
if (CI->isNullValue() && match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
// (icmp cond A B) if cond is signed or equality
if (CmpInst::isSigned(I.getPredicate()) || I.isEquality())
return new ICmpInst(I.getPredicate(), A, B);
// (icmp ne A B) if cond is ugt
else if (I.getPredicate() == ICmpInst::ICMP_UGT)
return new ICmpInst(ICmpInst::ICMP_NE, A, B);
// (icmp eq A B) if cond is ule
else if (I.getPredicate() == ICmpInst::ICMP_ULE)
return new ICmpInst(ICmpInst::ICMP_EQ, A, B);
// (icmp ne/eq (sub A B) 0) -> (icmp ne/eq A, B)
if (I.isEquality() && CI->isNullValue() &&
match(Op0, m_Sub(m_Value(A), m_Value(B)))) {
// (icmp cond A B) if cond is equality
return new ICmpInst(I.getPredicate(), A, B);
}
switch (I.getPredicate()) {