[clang] [llvm] [RISCV] Added the MIPS prefetch extensions for MIPS RV64 P8700. (PR #145647)

[Craig Topper via cfe-commits]

================
@@ -103,9 +109,41 @@ class SWPFormat<dag outs, dag ins, string opcodestr, string argstr>
   let Inst{6-0} = OPC_CUSTOM_0.Value;
 }
 
+// Prefetch format.
+let hasSideEffects = 0, mayLoad = 1,mayStore = 1 in
+class Mips_prefetch_ri<dag outs, dag ins, string opcodestr, string argstr>
+    : RVInst<outs, ins, opcodestr, argstr, [], InstFormatI> {
+  bits<9> imm9;
+  bits<5> rs1;
+  bits<5> hint;
+
+  let Inst{31 - 29} = 0b000;
+  let Inst{28 - 20} = imm9{8 - 0};
+  let Inst{19 - 15} = rs1;
+  let Inst{14 - 12} = 0b000;
+  let Inst{11 - 7} = hint;
+  let Inst{6 - 0} = OPC_CUSTOM_0.Value;
+}
+
 //===----------------------------------------------------------------------===//
 // MIPS extensions
 //===----------------------------------------------------------------------===//
+let Predicates = [HasVendorXMIPSCBOP] ,DecoderNamespace = "Xmipscbop" in {
+  def MIPSPREFETCH : Mips_prefetch_ri<(outs),(ins GPR:$rs1, uimm9:$imm9, uimm5:$hint),
----------------
topperc wrote:

```suggestion
  def MIPSPREFETCH : Mips_prefetch_ri<(outs), (ins GPR:$rs1, uimm9:$imm9, uimm5:$hint),
```

https://github.com/llvm/llvm-project/pull/145647