[SelectionDAG] Prevent converting a virtual register to an MCRegister.

[topperc]

I believe the goal is that MCRegister is only for physical registers.

[llvmbot]

@llvm/pr-subscribers-llvm-selectiondag

Author: Craig Topper (topperc)

Changes

I believe the goal is that MCRegister is only for physical registers.

---

Full diff: https://github.com/llvm/llvm-project/pull/122857.diff

1 Files Affected:

• (modified) llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp (+50-46)

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index d64a90bcaae7da..c918ca3df7cd21 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -705,53 +705,57 @@ bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
     if (InstrRef)
       continue;
 
-    // If Reg is live-in then update debug info to track its copy in a vreg.
-    DenseMap<MCRegister, Register>::iterator LDI = LiveInMap.find(Reg);
-    if (LDI != LiveInMap.end()) {
-      assert(!hasFI && "There's no handling of frame pointer updating here yet "
-                       "- add if needed");
-      MachineInstr *Def = RegInfo->getVRegDef(LDI->second);
-      MachineBasicBlock::iterator InsertPos = Def;
-      const MDNode *Variable = MI->getDebugVariable();
-      const MDNode *Expr = MI->getDebugExpression();
-      DebugLoc DL = MI->getDebugLoc();
-      bool IsIndirect = MI->isIndirectDebugValue();
-      if (IsIndirect)
-        assert(MI->getDebugOffset().getImm() == 0 &&
-               "DBG_VALUE with nonzero offset");
-      assert(cast<DILocalVariable>(Variable)->isValidLocationForIntrinsic(DL) &&
-             "Expected inlined-at fields to agree");
-      assert(MI->getOpcode() != TargetOpcode::DBG_VALUE_LIST &&
-             "Didn't expect to see a DBG_VALUE_LIST here");
-      // Def is never a terminator here, so it is ok to increment InsertPos.
-      BuildMI(*EntryMBB, ++InsertPos, DL, TII->get(TargetOpcode::DBG_VALUE),
-              IsIndirect, LDI->second, Variable, Expr);
-
-      // If this vreg is directly copied into an exported register then
-      // that COPY instructions also need DBG_VALUE, if it is the only
-      // user of LDI->second.
-      MachineInstr *CopyUseMI = nullptr;
-      for (MachineInstr &UseMI : RegInfo->use_instructions(LDI->second)) {
-        if (UseMI.isDebugValue())
-          continue;
-        if (UseMI.isCopy() && !CopyUseMI && UseMI.getParent() == EntryMBB) {
-          CopyUseMI = &UseMI;
-          continue;
+    if (Reg.isPhysical()) {
+      // If Reg is live-in then update debug info to track its copy in a vreg.
+      DenseMap<MCRegister, Register>::iterator LDI = LiveInMap.find(Reg);
+      if (LDI != LiveInMap.end()) {
+        assert(!hasFI &&
+               "There's no handling of frame pointer updating here yet "
+               "- add if needed");
+        MachineInstr *Def = RegInfo->getVRegDef(LDI->second);
+        MachineBasicBlock::iterator InsertPos = Def;
+        const MDNode *Variable = MI->getDebugVariable();
+        const MDNode *Expr = MI->getDebugExpression();
+        DebugLoc DL = MI->getDebugLoc();
+        bool IsIndirect = MI->isIndirectDebugValue();
+        if (IsIndirect)
+          assert(MI->getDebugOffset().getImm() == 0 &&
+                 "DBG_VALUE with nonzero offset");
+        assert(
+            cast<DILocalVariable>(Variable)->isValidLocationForIntrinsic(DL) &&
+            "Expected inlined-at fields to agree");
+        assert(MI->getOpcode() != TargetOpcode::DBG_VALUE_LIST &&
+               "Didn't expect to see a DBG_VALUE_LIST here");
+        // Def is never a terminator here, so it is ok to increment InsertPos.
+        BuildMI(*EntryMBB, ++InsertPos, DL, TII->get(TargetOpcode::DBG_VALUE),
+                IsIndirect, LDI->second, Variable, Expr);
+
+        // If this vreg is directly copied into an exported register then
+        // that COPY instructions also need DBG_VALUE, if it is the only
+        // user of LDI->second.
+        MachineInstr *CopyUseMI = nullptr;
+        for (MachineInstr &UseMI : RegInfo->use_instructions(LDI->second)) {
+          if (UseMI.isDebugValue())
+            continue;
+          if (UseMI.isCopy() && !CopyUseMI && UseMI.getParent() == EntryMBB) {
+            CopyUseMI = &UseMI;
+            continue;
+          }
+          // Otherwise this is another use or second copy use.
+          CopyUseMI = nullptr;
+          break;
+        }
+        if (CopyUseMI &&
+            TRI.getRegSizeInBits(LDI->second, MRI) ==
+                TRI.getRegSizeInBits(CopyUseMI->getOperand(0).getReg(), MRI)) {
+          // Use MI's debug location, which describes where Variable was
+          // declared, rather than whatever is attached to CopyUseMI.
+          MachineInstr *NewMI =
+              BuildMI(*MF, DL, TII->get(TargetOpcode::DBG_VALUE), IsIndirect,
+                      CopyUseMI->getOperand(0).getReg(), Variable, Expr);
+          MachineBasicBlock::iterator Pos = CopyUseMI;
+          EntryMBB->insertAfter(Pos, NewMI);
         }
-        // Otherwise this is another use or second copy use.
-        CopyUseMI = nullptr;
-        break;
-      }
-      if (CopyUseMI &&
-          TRI.getRegSizeInBits(LDI->second, MRI) ==
-              TRI.getRegSizeInBits(CopyUseMI->getOperand(0).getReg(), MRI)) {
-        // Use MI's debug location, which describes where Variable was
-        // declared, rather than whatever is attached to CopyUseMI.
-        MachineInstr *NewMI =
-            BuildMI(*MF, DL, TII->get(TargetOpcode::DBG_VALUE), IsIndirect,
-                    CopyUseMI->getOperand(0).getReg(), Variable, Expr);
-        MachineBasicBlock::iterator Pos = CopyUseMI;
-        EntryMBB->insertAfter(Pos, NewMI);
       }
     }
   }

[arsenm]

Probably should extract into its own function at this point