[llvm] [RISCV] Add `2^N + 2^M` expanding pattern for mul (PR #137195)

[Max Graey via llvm-commits]

================
@@ -672,6 +748,34 @@ define i32 @muli32_p65(i32 %a) nounwind {
   ret i32 %1
 }
 
+define i32 @muli32_p66(i32 %a) nounwind {
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MaxGraey wrote:

```suggestion
define i32 @muli32_p65(i32 %a) nounwind {
```

https://github.com/llvm/llvm-project/pull/137195