[llvm] [InitUndef] Don't use largest super class (PR #107885)

[Nikita Popov via llvm-commits]

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@@ -14,9 +14,9 @@ body:             |
     ; CHECK-NEXT: [[INSERT_SUBREG:%[0-9]+]]:vrm4 = INSERT_SUBREG [[DEF]], [[PseudoVLE32_V_M1_]], %subreg.sub_vrm1_0
     ; CHECK-NEXT: dead $x0 = PseudoVSETIVLI 0, 210 /* e32, m4, ta, ma */, implicit-def $vl, implicit-def $vtype
     ; CHECK-NEXT: %pt2:vrm4 = IMPLICIT_DEF
-    ; CHECK-NEXT: [[INIT_UNDEF:%[0-9]+]]:vrm2 = INIT_UNDEF
+    ; CHECK-NEXT: [[INIT_UNDEF:%[0-9]+]]:vrm2nov0 = INIT_UNDEF
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nikic wrote:

I found this weird as well, but I think the reason is that if we're allocating consecutive registers, then only the bottom one can be v0, so the rest end up with a nov0 regclass.

https://github.com/llvm/llvm-project/pull/107885