Avoid a Symbol -> Name -> Symbol conversion.

Before this we were producing a TargetExternalSymbol from a MCSymbol.
That meant extracting the symbol name and fetching the symbol again
down the pipeline.

This patch adds a DAG.getMCSymbol that lets the MCSymbol pass unchanged on the
DAG.

Doing so removes the need for MO_NOPREFIX and fixes the root cause of pr23900,
allowing r240130 to be committed again.

llvm-svn: 240300

6 files changed, 24 insertions, 6 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp b/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
index 7abc0c4e791..42595cb010c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/InstrEmitter.cpp
@@ -422,6 +422,8 @@ void InstrEmitter::AddOperand(MachineInstrBuilder &MIB,
     MIB.addConstantPoolIndex(Idx, Offset, CP->getTargetFlags());
   } else if (ExternalSymbolSDNode *ES = dyn_cast<ExternalSymbolSDNode>(Op)) {
     MIB.addExternalSymbol(ES->getSymbol(), ES->getTargetFlags());
+  } else if (auto *SymNode = dyn_cast<MCSymbolSDNode>(Op)) {
+    MIB.addSym(SymNode->getMCSymbol());
   } else if (BlockAddressSDNode *BA = dyn_cast<BlockAddressSDNode>(Op)) {
     MIB.addBlockAddress(BA->getBlockAddress(),
                         BA->getOffset(),
diff --git a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
index 4c74182014a..5403baef034 100644
--- a/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
+++ b/llvm/lib/CodeGen/SelectionDAG/ScheduleDAGSDNodes.h
@@ -64,6 +64,7 @@ namespace llvm {
       if (isa<TargetIndexSDNode>(Node))    return true;
       if (isa<JumpTableSDNode>(Node))      return true;
       if (isa<ExternalSymbolSDNode>(Node)) return true;
+      if (isa<MCSymbolSDNode>(Node))       return true;
       if (isa<BlockAddressSDNode>(Node))   return true;
       if (Node->getOpcode() == ISD::EntryToken ||
           isa<MDNodeSDNode>(Node)) return true;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 0eff930cedd..5e4459bba63 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -427,12 +427,12 @@ static void AddNodeIDNode(FoldingSetNodeID &ID, unsigned short OpC,
   AddNodeIDOperands(ID, OpList);
 }
 
-/// AddNodeIDCustom - If this is an SDNode with special info, add this info to
-/// the NodeID data.
+/// If this is an SDNode with special info, add this info to the NodeID data.
 static void AddNodeIDCustom(FoldingSetNodeID &ID, const SDNode *N) {
   switch (N->getOpcode()) {
   case ISD::TargetExternalSymbol:
   case ISD::ExternalSymbol:
+  case ISD::MCSymbol:
     llvm_unreachable("Should only be used on nodes with operands");
   default: break;  // Normal nodes don't need extra info.
   case ISD::TargetConstant:
@@ -797,6 +797,11 @@ bool SelectionDAG::RemoveNodeFromCSEMaps(SDNode *N) {
                                                     ESN->getTargetFlags()));
     break;
   }
+  case ISD::MCSymbol: {
+    auto *MCSN = cast<MCSymbolSDNode>(N);
+    Erased = MCSymbols.erase(MCSN->getMCSymbol());
+    break;
+  }
   case ISD::VALUETYPE: {
     EVT VT = cast<VTSDNode>(N)->getVT();
     if (VT.isExtended()) {
@@ -1014,6 +1019,7 @@ void SelectionDAG::clear() {
   ExtendedValueTypeNodes.clear();
   ExternalSymbols.clear();
   TargetExternalSymbols.clear();
+  MCSymbols.clear();
   std::fill(CondCodeNodes.begin(), CondCodeNodes.end(),
             static_cast<CondCodeSDNode*>(nullptr));
   std::fill(ValueTypeNodes.begin(), ValueTypeNodes.end(),
@@ -1469,6 +1475,15 @@ SDValue SelectionDAG::getExternalSymbol(const char *Sym, EVT VT) {
   return SDValue(N, 0);
 }
 
+SDValue SelectionDAG::getMCSymbol(MCSymbol *Sym, EVT VT) {
+  SDNode *&N = MCSymbols[Sym];
+  if (N)
+    return SDValue(N, 0);
+  N = new (NodeAllocator) MCSymbolSDNode(Sym, VT);
+  InsertNode(N);
+  return SDValue(N, 0);
+}
+
 SDValue SelectionDAG::getTargetExternalSymbol(const char *Sym, EVT VT,
                                               unsigned char TargetFlags) {
   SDNode *&N =
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 8313a48c346..43c6e0d96e8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -4976,11 +4976,9 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
         MF.getMMI().getContext().getOrCreateFrameAllocSymbol(
             GlobalValue::getRealLinkageName(Fn->getName()), IdxVal);
 
-    // Create a TargetExternalSymbol for the label to avoid any target lowering
+    // Create a MCSymbol for the label to avoid any target lowering
     // that would make this PC relative.
-    StringRef Name = FrameAllocSym->getName();
-    assert(Name.data()[Name.size()] == '\0' && "not null terminated");
-    SDValue OffsetSym = DAG.getTargetExternalSymbol(Name.data(), PtrVT);
+    SDValue OffsetSym = DAG.getMCSymbol(FrameAllocSym, PtrVT);
     SDValue OffsetVal =
         DAG.getNode(ISD::FRAME_ALLOC_RECOVER, sdl, PtrVT, OffsetSym);
 
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
index 96ee8991407..6951910d147 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
@@ -130,6 +130,7 @@ std::string SDNode::getOperationName(const SelectionDAG *G) const {
   case ISD::TargetJumpTable:            return "TargetJumpTable";
   case ISD::TargetConstantPool:         return "TargetConstantPool";
   case ISD::TargetExternalSymbol:       return "TargetExternalSymbol";
+  case ISD::MCSymbol:                   return "MCSymbol";
   case ISD::TargetBlockAddress:         return "TargetBlockAddress";
 
   case ISD::CopyToReg:                  return "CopyToReg";
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index c5562cd3106..7c4b97040f9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -2562,6 +2562,7 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
   case ISD::TargetConstantPool:
   case ISD::TargetFrameIndex:
   case ISD::TargetExternalSymbol:
+  case ISD::MCSymbol:
   case ISD::TargetBlockAddress:
   case ISD::TargetJumpTable:
   case ISD::TargetGlobalTLSAddress: