[llvm] [RISCV] Add 2^N + 2^M expanding pattern for mul (PR #137954)

[Philip Reames via llvm-commits]

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@@ -494,6 +494,36 @@ define i32 @muli32_p14(i32 %a) nounwind {
   ret i32 %1
 }
 
+define i32 @muli32_p18(i32 %a) nounwind {
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preames wrote:

I'd prefer the pre-commit given the accumulated changes on the branch.  Do I have your permission to precommit them on your behalf?

https://github.com/llvm/llvm-project/pull/137954