[llvm] [RISCV] Add codegen support for ri.vinsert.v.x and ri.vextract.x.v (PR #136708)

[Luke Lau via llvm-commits]

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@@ -538,6 +542,12 @@ DemandedFields getDemanded(const MachineInstr &MI, const RISCVSubtarget *ST) {
     Res.MaskPolicy = false;
   }
 
+  if (isVExtractInstr(MI)) {
+    assert(!RISCVII::hasVLOp(TSFlags));
+    // TODO: LMUL can be any larger value (without cost)
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lukel97 wrote:

This would be an interesting optimisation. I could imagine us having more demanded LMUL types e.g.  `Res.LMUL = Res.LMULGreaterThanOrEqualToMX`

https://github.com/llvm/llvm-project/pull/136708