[llvm] [InstCombine] Fold npos select around umin (PR #202748)

[Nikita Popov via llvm-commits]

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@@ -4526,6 +4526,29 @@ static Value *simplifyWithOpsReplaced(Value *V,
 
         return ConstantInt::get(I->getType(), 0);
       }
+
+      // umin(-1, x) -> x
+      // umin(x, -1) -> x
+      if (auto *MMI = dyn_cast<MinMaxIntrinsic>(II)) {
+        if (MMI->getIntrinsicID() == Intrinsic::umin) {
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nikic wrote:

This generalizes to other min/max intrinsics. Can you please add an API similar to MinMaxIntrinsic::getSaturationPoint() for this? E.g. MinMaxIntrinsic::getIdentity(). I'm kind of surprised it doesn't exist yet.

https://github.com/llvm/llvm-project/pull/202748