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

[Matt Arsenault 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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arsenm wrote:

I'm unclear on if and when errno is written. The linux man page says this. The C standard seems to suggest it raises a range error, which depending on platform configuration may be errno and/or fp exception 

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