[llvm] [mlir] [ADT] Add implementations for mulhs and mulhu to APInt (PR #84609)

[Jakub Kuderski via llvm-commits]

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@@ -2193,6 +2193,16 @@ inline const APInt absdiff(const APInt &A, const APInt &B) {
   return A.uge(B) ? (A - B) : (B - A);
 }
 
+/// Compute the higher order bits of unsigned multiplication of two APInts
+/// Mathematically, this computes the value: (C1 * C2) >> C2.getBitWidth()
+/// where (C1 * C2) has double the bit width of the original values.
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kuhar wrote:

uber nit:
```suggestion
/// Compute the higher order bits of unsigned multiplication of two APInts
/// Mathematically, this computes the value: `(C1 * C2) >> C2.getBitWidth()`
/// where `(C1 * C2)` has double the bit width of the original values.
```

https://github.com/llvm/llvm-project/pull/84609