[llvm-branch-commits] [llvm] ValueTracking: Handle amdgcn.rsq intrinsic in computeKnownFPClass (PR #171837)

[Yingwei Zheng via llvm-branch-commits]

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@@ -5553,6 +5553,37 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
 
       // TODO: Copy inf handling from instructions
       break;
+    case Intrinsic::amdgcn_rsq: {
+      KnownFPClass KnownSrc;
+      // The only negative value that can be returned is -0 for -0 inputs.
+      Known.knownNot(fcNegInf | fcNegSubnormal | fcNegNormal);
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dtcxzyw wrote:

`rsq(-0.0) = -inf`.

https://github.com/llvm/llvm-project/pull/171837