[llvm] InstSimplify: teach simplifyICmpWithConstant about samesign (PR #125899)

[Yingwei Zheng via llvm-commits]

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@@ -3012,7 +3012,7 @@ static Value *simplifyICmpWithConstant(CmpPredicate Pred, Value *LHS,
   }
 
   // Rule out tautological comparisons (eg., ult 0 or uge 0).
-  ConstantRange RHS_CR = ConstantRange::makeExactICmpRegion(Pred, *C);
+  ConstantRange RHS_CR = ConstantRange::makeAllowedICmpRegion(Pred, *C);
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dtcxzyw wrote:

While it doesn't change the outcome, it changes the semantics. We expect `makeExactICmpRegion` to return an exact result instead of a superset.

Can we change `makeExactICmpRegion` to support `samesign`?



https://github.com/llvm/llvm-project/pull/125899