[llvm] [RISCV] Vectorize phi for loop carried @llvm.vp.reduce.* (PR #131974)

[Luke Lau via llvm-commits]

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@@ -42,3 +42,459 @@ vector.body:
 exit:
   ret float %acc
 }
+
+define i32 @vp_reduce_add(ptr %a) {
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lukel97 wrote:

Can you add these tests in a separate commit in this PR so we can see the diff before and after?

https://github.com/llvm/llvm-project/pull/131974