[llvm] [TableGen] Combine the two separate OperandMapping loops in PseudoLoweringEmitter. (PR #136007)

[Sergei Barannikov via llvm-commits]

================
@@ -180,37 +176,43 @@ void PseudoLoweringEmitter::evaluateExpansion(const Record *Rec) {
   for (const auto &[Idx, SrcOp] : enumerate(SourceInsn.Operands))
     SourceOperands[SrcOp.Name] = Idx;
 
-  LLVM_DEBUG(dbgs() << "  Operand mapping:\n");
-  for (const auto &[Idx, Opnd] : enumerate(Insn.Operands)) {
-    // We've already handled constant values. Just map instruction operands
-    // here.
-    if (OperandMap[Opnd.MIOperandNo].Kind != OpData::Operand)
-      continue;
-    StringMap<unsigned>::iterator SourceOp =
-        SourceOperands.find(Dag->getArgNameStr(Idx));
-    if (SourceOp == SourceOperands.end())
-      PrintFatalError(Rec, "In pseudo instruction '" + Rec->getName() +
-                               "', 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() + "'");
+  unsigned NumMIOperands = 0;
+  for (const auto &Op : Insn.Operands)
+    NumMIOperands += Op.MINumOperands;
+  IndexedMap<OpData> OperandMap;
+  OperandMap.grow(NumMIOperands);
 
-    // Map the source operand to the destination operand index for each
-    // MachineInstr operand.
-    for (unsigned I = 0, E = Opnd.MINumOperands; I != E; ++I)
-      OperandMap[Opnd.MIOperandNo + I].Data.Operand = SrcOpnd.MIOperandNo + I;
+  // FIXME: This pass currently can only expand a pseudo to a single
+  // instruction. The pseudo expansion really should take a list of dags, not
+  // just a single dag, so we can do fancier things.
+  LLVM_DEBUG(dbgs() << "  Operand mapping:\n");
+  for (const auto &[Idx, DstOp] : enumerate(Insn.Operands)) {
+    unsigned MIOpNo = DstOp.MIOperandNo;
 
-    LLVM_DEBUG(dbgs() << "    " << SourceOp->getValue() << " ==> " << Idx
-                      << "\n");
+    if (const auto *SubDag = dyn_cast<DagInit>(Dag->getArg(Idx))) {
+      if (DstOp.MIOperandInfo->getNumArgs() == 0)
----------------
s-barannikov wrote:

It is awkward, but not all operands derive from Operand, e.g., RegisterOperand.

> I think we need both.

Kind of redundant with the next check, but SG.


https://github.com/llvm/llvm-project/pull/136007