[llvm] [SelectionDAG] Calculate KnownBits for SMIN (PR #85584)

[Craig Topper via llvm-commits]

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@@ -4017,6 +4015,16 @@ KnownBits SelectionDAG::computeKnownBits(SDValue Op, const APInt &DemandedElts,
       }
     }
 
+    // For SMIN, if CstHigh is negative we know the result will be
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topperc wrote:

It's possible to know the LHS has some number of sign bits without knowing whether it is positive or negative. Here's the patch that added the SMAX code https://reviews.llvm.org/D126896

https://github.com/llvm/llvm-project/pull/85584