[llvm] [InstCombine] Simplify fractions when there is no overflow (PR #92949)

[via llvm-commits]

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@@ -1176,6 +1176,45 @@ Instruction *InstCombinerImpl::commonIDivTransforms(BinaryOperator &I) {
         Mul->setHasNoSignedWrap(OBO->hasNoSignedWrap());
         return Mul;
       }
+
+      // We can reduce expressions of things like * 150 / 100 to * 3 / 2
+      if (Op0->hasOneUse() && !C2->isZero() &&
+          !(IsSigned && C1->isMinSignedValue() && C2->isAllOnes())) {
+        assert(!C2->isMinSignedValue() &&
+               "This should have been folded away by InstSimplify");
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goldsteinn wrote:

Not InstSimplify, InstCombine. It will get folded, but this shouldn't be an assert as we sometimes move around folds. Just check it in the above if statement.

https://github.com/llvm/llvm-project/pull/92949