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InstCombine: Don't combine constants on unsigned icmps
Fixes a miscompile introduced in r204912. It would miscompile code like (unsigned)(a + -49) <= 5U. The transform would turn this into (unsigned)a < 55U, which would return true for values in [0, 49], when it should not. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204948 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -3010,7 +3010,8 @@ Instruction *InstCombiner::visitICmpInst(ICmpInst &I) {
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return FoldICmpAddOpCst(I, X, Cst, I.getSwappedPredicate());
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ConstantInt *Cst2;
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if (match(Op1, m_ConstantInt(Cst)) &&
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if (I.isSigned() &&
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match(Op1, m_ConstantInt(Cst)) &&
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match(Op0, m_Add(m_Value(X), m_ConstantInt(Cst2))) &&
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cast<BinaryOperator>(Op0)->hasNoSignedWrap()) {
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// icmp X+Cst2, Cst --> icmp X, Cst-Cst2
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@ -1409,3 +1409,13 @@ entry:
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%conv = zext i1 %cmp to i32
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ret i32 %conv
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}
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; CHECK-LABEL: icmp_add_const_ult
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; CHECK: %cmp = icmp ult i32 %add, 6
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define i32 @icmp_add_const_ult(i32 %a) #0 {
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entry:
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%add = add nsw i32 %a, -49
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%cmp = icmp ult i32 %add, 6
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%conv = zext i1 %cmp to i32
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ret i32 %conv
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}
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