[llvm] [GISEL] Fix bugs in G_EXTRACT_SUBVECTOR definition (PR #108848)

[Michael Maitland via llvm-commits]

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@@ -1788,7 +1788,7 @@ void MachineVerifier::verifyPreISelGenericInstruction(const MachineInstr *MI) {
     }
 
     uint64_t SrcMinLen = SrcTy.getElementCount().getKnownMinValue();
-    if (SrcTy.isScalable() && DstTy.isScalable() &&
+    if (SrcTy.isScalable() == DstTy.isScalable() &&
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michaelmaitland wrote:

Why? We haven’t specified the behavior for this case have we? I was thinking to have a follow up pr that synced the mixed case with the lang ref. 

https://github.com/llvm/llvm-project/pull/108848