[llvm] [RISCV][VLOPT] Add support for checkUsers when UserMI is a Single-Width Integer Reduction (PR #120345)

[Philip Reames via llvm-commits]

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@@ -149,8 +152,11 @@ define i32 @mul_i32(<4 x i32> %a, <4 x i32> %b) {
 ; RV64-NEXT:    vslidedown.vi v10, v9, 2
 ; RV64-NEXT:    vmul.vv v9, v9, v10
 ; RV64-NEXT:    vrgather.vi v10, v8, 1
+; RV64-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
 ; RV64-NEXT:    vmul.vv v8, v8, v10
+; RV64-NEXT:    vsetivli zero, 4, e32, m1, ta, ma
 ; RV64-NEXT:    vrgather.vi v10, v9, 1
+; RV64-NEXT:    vsetivli zero, 1, e32, m1, ta, ma
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preames wrote:

I looked at these regressions earlier.  If you note, most of them are from product reduction expansion cases.  I don't think these regressions are particularly representative of real world code.  I think we can safely ignore the apparent increase in toggles in these cases.

https://github.com/llvm/llvm-project/pull/120345