[llvm] [ConstraintElim] Drop invalid rows instead of failing the elimination (PR #76299)

[Florian Hahn via llvm-commits]

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@@ -95,17 +95,19 @@ bool ConstraintSystem::eliminateUsingFM() {
           IdxUpper++;
         }
 
-        if (MulOverflow(UpperV, ((-1) * LowerLast), M1))
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fhahn wrote:

I think it might be possible to construct a case where it overflows. Ideally we would construct such a case, add a test and check for overflow. 

https://github.com/llvm/llvm-project/pull/76299