[llvm] [RISCV] Add P-ext MC support for pli.dh, pli.db, and plui.dh. (PR #153972)

[Craig Topper via llvm-commits]

================
@@ -161,14 +171,33 @@ class RVPBinary_rr<bits<4> f, bits<2> w, bits<3> funct3, string opcodestr>
 let hasSideEffects = 0, mayLoad = 0, mayStore = 0 in
 class RVPTernary_rrr<bits<4> f, bits<2> w, bits<3> funct3, string opcodestr>
     : RVInstRBase<funct3, OPC_OP_32, (outs GPR:$rd_wb),
-                  (ins GPR:$rd, GPR:$rs1, GPR:$rs2), opcodestr, "$rd, $rs1, $rs2"> {
+                  (ins GPR:$rd, GPR:$rs1, GPR:$rs2), opcodestr,
+                  "$rd, $rs1, $rs2"> {
   let Inst{31} = 0b1;
   let Inst{30-27} = f;
   let Inst{26-25} = w;
 
   let Constraints = "$rd = $rd_wb";
 }
 
+// Common base for pli.b/h/w and plui.h/w
----------------
topperc wrote:

```suggestion
// Common base for pli.db/h/w and plui.dh/w
```

https://github.com/llvm/llvm-project/pull/153972