[llvm] [ConstantFold] Fold `erf` and `erff` when the input parameter is a constant value. (PR #113079)

[via llvm-commits]

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@@ -3624,6 +3628,10 @@ bool llvm::isMathLibCallNoop(const CallBase *Call,
       case LibFunc_sqrtf:
         return Op.isNaN() || Op.isZero() || !Op.isNegative();
 
+      case LibFunc_erf:
+      case LibFunc_erff:
+        return true;
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c8ef wrote:

Actually, I previously tried using erf, but I still couldn't achieve folding because it returns false in `isMathLibCallNoop`. Therefore, it's at least safe. Perhaps we should calculate the underflow boundary and add it into `isMathLibCallNoop` to enable constant folding.

https://github.com/llvm/llvm-project/pull/113079