[llvm] [RISCV] Simplify mask operand check in VLOptimizer. NFC (PR #150373)

[Luke Lau via llvm-commits]

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@@ -24,6 +24,7 @@ body:     |
     %0:vr = COPY $v8
     %1:vr = COPY $v9
     %2:gprnox0 = COPY $x10
-    renamable $v8 = PseudoVAADD_VV_MF8 undef $noreg, %0, %1, 0, %2, 3 /* e8 */, 0
+    %3:vr = PseudoVAADD_VV_MF8 undef $noreg, %0, %1, 0, %2, 3 /* e8 */, 0
+    $v8 = COPY %3
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lukel97 wrote:

I guess this test is supposed to be written the way it immediately comes out of SelectionDAG, but here the def was to a physical register. In reality it's always a virtual register so I've tweaked it to be more representative, and it allows us to tighten the assert in isCandidate to always check for virtual registers, not physical ones

https://github.com/llvm/llvm-project/pull/150373