[llvm] add power function to APInt (PR #122788)

[Tommy Chiang via llvm-commits]

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@@ -2263,6 +2263,9 @@ APInt mulhs(const APInt &C1, const APInt &C2);
 /// Returns the high N bits of the multiplication result.
 APInt mulhu(const APInt &C1, const APInt &C2);
 
+/// Compute X^N for N>=0.
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oToToT wrote:

If 0^0 is supported, it would be nice to be documented here.

https://github.com/llvm/llvm-project/pull/122788