[llvm] [RISCV] Remove vmv.s.x and vmv.x.s lmul pseudo variants (PR #71501)

[Luke Lau via llvm-commits]

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@@ -3362,7 +3362,9 @@ static bool usesAllOnesMask(SDNode *N, unsigned MaskOpIdx) {
 
 static bool isImplicitDef(SDValue V) {
   return V.isMachineOpcode() &&
-         V.getMachineOpcode() == TargetOpcode::IMPLICIT_DEF;
+         (V.getMachineOpcode() == TargetOpcode::IMPLICIT_DEF ||
+          (V.getMachineOpcode() == TargetOpcode::EXTRACT_SUBREG &&
+           isImplicitDef(V.getOperand(0))));
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lukel97 wrote:

This is needed for the implicit_def -> noregister peephole: Without it we lose some CSE when we have (vmv_s_x IMPLICIT_DEF, ...) and (vmv_s_x (extract_subreg IMPLICIT_DEF, ...), ...)

https://github.com/llvm/llvm-project/pull/71501