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

[Jakub Kuderski via llvm-commits]

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@@ -2263,6 +2263,10 @@ 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.
+/// 0^0 would return 1.
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kuhar wrote:

ubernit: maybe something more descriptive like:
```suggestion
/// 0^0 is supported and returns 1.
```

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