llvm-mirror/test/Transforms/InstSimplify/2011-11-23-MaskedBitsCrash.ll
Duncan Sands 3c1878ef53 Fix a crash in which a multiplication was being reported as being both negative
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).

llvm-svn: 145104
2011-11-23 16:26:47 +00:00

18 lines
605 B
LLVM

; RUN: opt < %s -instsimplify
; The mul can be proved to always overflow (turning a negative value
; into a positive one) and thus results in undefined behaviour. At
; the same time we were deducing from the nsw flag that that mul could
; be assumed to have a negative value (since if not it has an undefined
; value, which can be taken to be negative). We were reporting the mul
; as being both positive and negative, firing an assertion!
define i1 @test1(i32 %a) {
entry:
%0 = or i32 %a, 1
%1 = shl i32 %0, 31
%2 = mul nsw i32 %1, 4
%3 = and i32 %2, -4
%4 = icmp ne i32 %3, 0
ret i1 %4
}