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and positive: positive, because it could be directly computed to be positive; negative, because the nsw flags means it is either negative or undefined (the multiplication always overflowed). git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145104 91177308-0d34-0410-b5e6-96231b3b80d8
18 lines
605 B
LLVM
18 lines
605 B
LLVM
; RUN: opt < %s -instsimplify
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; The mul can be proved to always overflow (turning a negative value
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; into a positive one) and thus results in undefined behaviour. At
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; the same time we were deducing from the nsw flag that that mul could
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; be assumed to have a negative value (since if not it has an undefined
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; value, which can be taken to be negative). We were reporting the mul
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; as being both positive and negative, firing an assertion!
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define i1 @test1(i32 %a) {
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entry:
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%0 = or i32 %a, 1
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%1 = shl i32 %0, 31
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%2 = mul nsw i32 %1, 4
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%3 = and i32 %2, -4
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%4 = icmp ne i32 %3, 0
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ret i1 %4
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}
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