[llvm] [APFloat] add power (PR #122889)

[Iman Hosseini via llvm-commits]

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@@ -1536,6 +1536,26 @@ inline APFloat abs(APFloat X) {
   return X;
 }
 
+/// Returns X^N for N >= 0.
+inline APFloat powi(const APFloat &X, int64_t N) {
+  assert(N >= 0 && "negative exponents not supported.");
+  APFloat Acc = APFloat::getOne(X.getSemantics());
+  if (N == 0) {
+    return Acc;
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ImanHosseini wrote:

For N==0? Can you explain?

https://github.com/llvm/llvm-project/pull/122889