[TableGen] Store flat source operand number in OperandMap in PseudoLoweringEmitter. NFC

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 MIOperandNo and adding the sub index into
loop that updates OperandMap and the emitting loop just prints the index.

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: