[llvm] [RISCV] Support postRA vsetvl insertion pass (PR #70549)

[Philip Reames via llvm-commits]

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@@ -140,8 +140,9 @@ define <4 x i1> @buildvec_mask_v4i1() {
 define <4 x i1> @buildvec_mask_nonconst_v4i1(i1 %x, i1 %y) {
 ; CHECK-LABEL: buildvec_mask_nonconst_v4i1:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    vsetivli zero, 4, e8, mf4, ta, ma
+; CHECK-NEXT:    vsetivli zero, 1, e8, mf8, ta, ma
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preames wrote:

This is an interesting missed optimization.  This looks like an actual regression from this patch.  

https://github.com/llvm/llvm-project/pull/70549