[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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@@ -12,9 +12,11 @@ define i16 @ctz_v4i32(<4 x i32> %a) {
 ; RV32-NEXT:    vsetvli zero, zero, e8, mf4, ta, ma
 ; RV32-NEXT:    vmv.v.i v8, 0
 ; RV32-NEXT:    vmerge.vim v8, v8, -1, v0
+; RV32-NEXT:    vsetivli zero, 1, e8, mf4, ta, ma
 ; RV32-NEXT:    vid.v v9
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preames wrote:

Given this is coming from the expansion of the cttz.elts intrinsic, this is probably (maybe?) a missing combine on STEP_VECTOR when VL=1.  

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