[llvm] [DAG] Fix a miscompile in insert_subvector undef (insert_subvector undef, ..), idx combine (PR #73587)

[Craig Topper via llvm-commits]

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@@ -512,9 +512,7 @@ define <vscale x 2 x i64> @insert_nxv2i64_nxv3i64(<3 x i64> %sv) #0 {
 define <vscale x 8 x i32> @insert_insert_combine(<2 x i32> %subvec) {
 ; CHECK-LABEL: insert_insert_combine:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    vsetivli zero, 6, e32, m4, ta, ma
-; CHECK-NEXT:    vslideup.vi v12, v8, 4
-; CHECK-NEXT:    vmv.v.v v8, v12
+; CHECK-NEXT:    vmv1r.v v10, v8
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topperc wrote:

Drop the FIXME in the commit that fixes it

https://github.com/llvm/llvm-project/pull/73587