[llvm] [LV] Account for vp_merge in out of loop EVL reductions in legacy cost model (PR #115903)

[Florian Hahn via llvm-commits]

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@@ -0,0 +1,34 @@
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize \
+; RUN: -force-tail-folding-style=data-with-evl \
+; RUN: -prefer-predicate-over-epilogue=predicate-dont-vectorize \
+; RUN: -mtriple=riscv64 -mattr=+v -S < %s 2>&1 | FileCheck %s \
+; RUN: --check-prefix=EVL
+
+; RUN: opt -passes=loop-vectorize -debug-only=loop-vectorize \
+; RUN: -prefer-predicate-over-epilogue=predicate-dont-vectorize \
+; RUN: -mtriple=riscv64 -mattr=+v -S < %s 2>&1 | FileCheck %s \
+; RUN: --check-prefix=NO-EVL
+
+; EVL: Cost of 2 for VF vscale x 4: WIDEN-INTRINSIC vp<%{{.+}}> = call llvm.vp.merge(ir<true>, ir<%add>, ir<%rdx>, vp<%{{.+}}>)
+; EVL: LV: Found an estimated cost of 2 for VF vscale x 4 For instruction:   %rdx = phi i32 [ %start, %entry ], [ %add, %for.body ]
+
+; NO-EVL: Cost of 0 for VF vscale x 4: EMIT vp<%{{.+}}> = select vp<%active.lane.mask>, ir<%add>, ir<%rdx>
+; NO-EVL: LV: Found an estimated cost of 0 for VF vscale x 4 For instruction:   %rdx = phi i32 [ %start, %entry ], [ %add, %for.body ]
+
+define i32 @add(ptr %a, i64 %n, i32 %start) {
+entry:
+  br label %for.body
+
+for.body:
+  %iv = phi i64 [ 0, %entry ], [ %iv.next, %for.body ]
+  %rdx = phi i32 [ %start, %entry ], [ %add, %for.body ]
+  %arrayidx = getelementptr inbounds i32, ptr %a, i64 %iv
+  %0 = load i32, ptr %arrayidx, align 4
+  %add = add nsw i32 %0, %rdx
+  %iv.next = add nuw nsw i64 %iv, 1
+  %exitcond.not = icmp eq i64 %iv.next, %n
+  br i1 %exitcond.not, label %for.end, label %for.body
+
+for.end:
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fhahn wrote:

```suggestion
exit:
```

slightly shorter name

https://github.com/llvm/llvm-project/pull/115903