[TableGen] Store flat source operand number in OperandMap in PseudoLoweringEmitter. NFC (llvm#135886)

Previously we stored the index into the source CodeGenInstruction's
operand list. Any operand with sub operands stored the same index into
all of the OperandMap entries for that operand. The emitting loop would
look up the MIOperandNo for the source and add the sub index.

This patch moves the logic into the loop that updates the OperandMap.
Now the emitting loop only needs to print the value.

While there, I've added a check that MIOperandNo is the same for source
and destination.

Author: topperc

llvm/utils/TableGen/PseudoLoweringEmitter.cpp

@@ -181,24 +181,32 @@ void PseudoLoweringEmitter::evaluateExpansion(const Record *Rec) {
     SourceOperands[SrcOp.Name] = Idx;
 
   LLVM_DEBUG(dbgs() << "  Operand mapping:\n");
-  for (unsigned i = 0, e = Insn.Operands.size(); i != e; ++i) {
+  for (const auto &[Idx, Opnd] : enumerate(Insn.Operands)) {
     // We've already handled constant values. Just map instruction operands
     // here.
-    if (OperandMap[Insn.Operands[i].MIOperandNo].Kind != OpData::Operand)
+    if (OperandMap[Opnd.MIOperandNo].Kind != OpData::Operand)
       continue;
     StringMap<unsigned>::iterator SourceOp =
-        SourceOperands.find(Dag->getArgNameStr(i));
+        SourceOperands.find(Dag->getArgNameStr(Idx));
     if (SourceOp == SourceOperands.end())
       PrintFatalError(Rec, "In pseudo instruction '" + Rec->getName() +
-                               "', output operand '" + Dag->getArgNameStr(i) +
+                               "', output operand '" + Dag->getArgNameStr(Idx) +
                                "' has no matching source operand");
+    const auto &SrcOpnd = SourceInsn.Operands[SourceOp->getValue()];
+    if (Opnd.MINumOperands != SrcOpnd.MINumOperands)
+      PrintFatalError(
+          Rec,
+          "In pseudo instruction '" + Rec->getName() + "', output operand '" +
+              Opnd.Rec->getName() +
+              "' has a different number of sub operands than source operand '" +
+              SrcOpnd.Rec->getName() + "'");
+
     // Map the source operand to the destination operand index for each
     // MachineInstr operand.
-    for (unsigned I = 0, E = Insn.Operands[i].MINumOperands; I != E; ++I)
-      OperandMap[Insn.Operands[i].MIOperandNo + I].Data.Operand =
-          SourceOp->getValue();
+    for (unsigned I = 0, E = Opnd.MINumOperands; I != E; ++I)
+      OperandMap[Opnd.MIOperandNo + I].Data.Operand = SrcOpnd.MIOperandNo + I;
 
-    LLVM_DEBUG(dbgs() << "    " << SourceOp->getValue() << " ==> " << i
+    LLVM_DEBUG(dbgs() << "    " << SourceOp->getValue() << " ==> " << Idx
                       << "\n");
   }
 
@@ -236,10 +244,7 @@ void PseudoLoweringEmitter::emitLoweringEmitter(raw_ostream &o) {
           switch (Expansion.OperandMap[MIOpNo + i].Kind) {
           case OpData::Operand:
             o << "    lowerOperand(MI->getOperand("
-              << Source.Operands[Expansion.OperandMap[MIOpNo].Data.Operand]
-                         .MIOperandNo +
-                     i
-              << "), MCOp);\n"
+              << Expansion.OperandMap[MIOpNo + i].Data.Operand << "), MCOp);\n"
               << "    Inst.addOperand(MCOp);\n";
             break;
           case OpData::Imm: