[llvm-branch-commits] [llvm] ValueTracking: Improve handling of fadd in computeKnownFPClass. (PR #174123)

[Yingwei Zheng via llvm-branch-commits]

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@@ -5619,14 +5619,22 @@ void computeKnownFPClass(const Value *V, const APInt &DemandedElts,
     computeKnownFPClass(Op->getOperand(1), DemandedElts, InterestedSrcs,
                         KnownRHS, Q, Depth + 1);
 
+    // Special case fadd x, x, which is the canonical form of fmul x, 2.
+    bool SameOperands = Op->getOperand(0) == Op->getOperand(1);
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dtcxzyw wrote:

Should check that x is not an undef.
Reference: https://github.com/llvm/llvm-project/blob/0b24580a26644c8a44abc6fba97609552ba41d42/llvm/lib/Analysis/ValueTracking.cpp#L550-L553

https://github.com/llvm/llvm-project/pull/174123