[llvm] [PowerPC] Add a set of extended mnemonics that are missing from Power 10. (PR #73003)

[Lei Huang via llvm-commits]

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@@ -820,6 +820,27 @@ void PPCAsmParser::ProcessInstruction(MCInst &Inst,
                                       const OperandVector &Operands) {
   int Opcode = Inst.getOpcode();
   switch (Opcode) {
+  case PPC::PLA8:
+  case PPC::PLA: {
+    MCInst TmpInst;
+    TmpInst.setOpcode(PPC::PADDI);
+    TmpInst.setOpcode(Opcode == PPC::PLA ? PPC::PADDI : PPC::PADDI8);
+    TmpInst.addOperand(Inst.getOperand(0));
+    TmpInst.addOperand(Inst.getOperand(1));
+    TmpInst.addOperand(Inst.getOperand(2));
+    Inst = TmpInst;
+    break;
+  }
+  case PPC::PLA8pc:
+  case PPC::PLApc: {
+    MCInst TmpInst;
+    TmpInst.setOpcode(Opcode == PPC::PLApc ? PPC::PADDIpc : PPC::PADDI8pc);
+    TmpInst.addOperand(Inst.getOperand(0));
+    TmpInst.addOperand(MCOperand::createImm(0));
+    TmpInst.addOperand(Inst.getOperand(1));
+    Inst = TmpInst;
+    break;
+  }
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lei137 wrote:

nit: would it make sense to move these lower to where we handle `PPC:LA`?

https://github.com/llvm/llvm-project/pull/73003