Add support for ELF PLT references for ARM MC asm printing. Adding a

new VariantKind to the MCSymbolExpr seems like overkill, but I'm not sure
there's a more straightforward way to get the printing difference captured.
(i.e., x86 uses @PLT, ARM uses (PLT)).

llvm-svn: 114613

llvm/include/llvm/MC/MCExpr.h

@@ -137,6 +137,7 @@ public:
     VK_TPOFF,
     VK_ARM_HI16, // The R_ARM_MOVT_ABS relocation (:upper16: in the asm file)
     VK_ARM_LO16, // The R_ARM_MOVW_ABS_NC relocation (:lower16: in the asm file)
+    VK_ARM_PLT,  // ARM-style PLT symbol references. i.e., (PLT) instead of @PLT
     VK_TLVP // Mach-O thread local variable relocation
   };
 

llvm/lib/MC/MCExpr.cpp

@@ -50,9 +50,11 @@ void MCExpr::print(raw_ostream &OS) const {
     else
       OS << Sym;
 
-    if (SRE.getKind() != MCSymbolRefExpr::VK_None &&
-        SRE.getKind() != MCSymbolRefExpr::VK_ARM_HI16 &&
-        SRE.getKind() != MCSymbolRefExpr::VK_ARM_LO16)
+    if (SRE.getKind() == MCSymbolRefExpr::VK_ARM_PLT)
+      OS << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
+    else if (SRE.getKind() != MCSymbolRefExpr::VK_None &&
+             SRE.getKind() != MCSymbolRefExpr::VK_ARM_HI16 &&
+             SRE.getKind() != MCSymbolRefExpr::VK_ARM_LO16)
       OS << '@' << MCSymbolRefExpr::getVariantKindName(SRE.getKind());
 
     return;
@@ -177,6 +179,7 @@ StringRef MCSymbolRefExpr::getVariantKindName(VariantKind Kind) {
   case VK_TPOFF: return "TPOFF";
   case VK_ARM_HI16: return ":upper16:";
   case VK_ARM_LO16: return ":lower16:";
+  case VK_ARM_PLT: return "(PLT)";
   case VK_TLVP: return "TLVP";
   }
 }

llvm/lib/Target/ARM/ARMBaseInfo.h

@@ -181,7 +181,11 @@ namespace ARMII {
 
     /// MO_HI16 - On a symbol operand, this represents a relocation containing
     /// higher 16 bit of the address. Used only via movt instruction.
-    MO_HI16
+    MO_HI16,
+
+    /// MO_PLT - On a symbol operand, this represents an ELF PLT reference on a
+    /// call operand.
+    MO_PLT
   };
 } // end namespace ARMII
 

llvm/lib/Target/ARM/ARMISelLowering.cpp

@@ -1195,8 +1195,14 @@ ARMTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
       SDValue PICLabel = DAG.getConstant(ARMPCLabelIndex, MVT::i32);
       Callee = DAG.getNode(ARMISD::PIC_ADD, dl,
                            getPointerTy(), Callee, PICLabel);
-    } else
-      Callee = DAG.getTargetGlobalAddress(GV, dl, getPointerTy());
+    } else {
+      // On ELF targets for PIC code, direct calls should go through the PLT
+      unsigned OpFlags = 0;
+      if (Subtarget->isTargetELF() &&
+                  getTargetMachine().getRelocationModel() == Reloc::PIC_)
+        OpFlags = ARMII::MO_PLT;
+      Callee = DAG.getTargetGlobalAddress(GV, dl, getPointerTy(), 0, OpFlags);
+    }
   } else if (ExternalSymbolSDNode *S = dyn_cast<ExternalSymbolSDNode>(Callee)) {
     isDirect = true;
     bool isStub = Subtarget->isTargetDarwin() &&
@@ -1217,8 +1223,14 @@ ARMTargetLowering::LowerCall(SDValue Chain, SDValue Callee,
       SDValue PICLabel = DAG.getConstant(ARMPCLabelIndex, MVT::i32);
       Callee = DAG.getNode(ARMISD::PIC_ADD, dl,
                            getPointerTy(), Callee, PICLabel);
-    } else
-      Callee = DAG.getTargetExternalSymbol(Sym, getPointerTy());
+    } else {
+      unsigned OpFlags = 0;
+      // On ELF targets for PIC code, direct calls should go through the PLT
+      if (Subtarget->isTargetELF() &&
+                  getTargetMachine().getRelocationModel() == Reloc::PIC_)
+        OpFlags = ARMII::MO_PLT;
+      Callee = DAG.getTargetExternalSymbol(Sym, getPointerTy(), OpFlags);
+    }
   }
 
   // FIXME: handle tail calls differently.

llvm/lib/Target/ARM/ARMMCInstLower.cpp

@@ -33,7 +33,6 @@ MCSymbol *ARMMCInstLower::GetGlobalAddressSymbol(const GlobalValue *GV) const {
 const MCSymbolRefExpr *ARMMCInstLower::
 GetSymbolRef(const MachineOperand &MO) const {
   assert(MO.isGlobal() && "Isn't a global address reference?");
-  // FIXME: HANDLE PLT references how??
 
   const MCSymbolRefExpr *SymRef;
   const MCSymbol *Symbol = GetGlobalAddressSymbol(MO.getGlobal());
@@ -49,22 +48,36 @@ GetSymbolRef(const MachineOperand &MO) const {
   case ARMII::MO_HI16:
     SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_ARM_HI16, Ctx);
     break;
+  case ARMII::MO_PLT:
+    SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_ARM_PLT, Ctx);
+    break;
   }
 
   return SymRef;
 }
 
-MCSymbol *ARMMCInstLower::
+const MCSymbolRefExpr *ARMMCInstLower::
 GetExternalSymbolSymbol(const MachineOperand &MO) const {
-  // FIXME: HANDLE PLT references how??
-  // FIXME: This probably needs to be merged with the above SymbolRef stuff
-  // to handle :lower16: and :upper16: (?)
+  const MCSymbolRefExpr *SymRef;
+  const MCSymbol *Symbol = Printer.GetExternalSymbolSymbol(MO.getSymbolName());
+
   switch (MO.getTargetFlags()) {
-  default: assert(0 && "Unknown target flag on GV operand");
-  case 0: break;
+  default: assert(0 && "Unknown target flag on external symbol operand");
+  case 0:
+    SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_None, Ctx);
+    break;
+  case ARMII::MO_LO16:
+    SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_ARM_LO16, Ctx);
+    break;
+  case ARMII::MO_HI16:
+    SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_ARM_HI16, Ctx);
+    break;
+  case ARMII::MO_PLT:
+    SymRef = MCSymbolRefExpr::Create(Symbol, MCSymbolRefExpr::VK_ARM_PLT, Ctx);
+    break;
   }
 
-  return Printer.GetExternalSymbolSymbol(MO.getSymbolName());
+  return SymRef;
 }
 
 
@@ -157,7 +170,7 @@ void ARMMCInstLower::Lower(const MachineInstr *MI, MCInst &OutMI) const {
       MCOp = LowerSymbolRefOperand(MO, GetSymbolRef(MO));
       break;
     case MachineOperand::MO_ExternalSymbol:
-      MCOp = LowerSymbolOperand(MO, GetExternalSymbolSymbol(MO));
+      MCOp = LowerSymbolRefOperand(MO, GetExternalSymbolSymbol(MO));
       break;
     case MachineOperand::MO_JumpTableIndex:
       MCOp = LowerSymbolOperand(MO, GetJumpTableSymbol(MO));

llvm/lib/Target/ARM/ARMMCInstLower.h

@@ -43,7 +43,8 @@ public:
   //MCSymbol *GetPICBaseSymbol() const;
   MCSymbol *GetGlobalAddressSymbol(const GlobalValue *GV) const;
   const MCSymbolRefExpr *GetSymbolRef(const MachineOperand &MO) const;
-  MCSymbol *GetExternalSymbolSymbol(const MachineOperand &MO) const;
+  const MCSymbolRefExpr *GetExternalSymbolSymbol(const MachineOperand &MO)
+    const;
   MCSymbol *GetJumpTableSymbol(const MachineOperand &MO) const;
   MCSymbol *GetConstantPoolIndexSymbol(const MachineOperand &MO) const;
   MCOperand LowerSymbolRefOperand(const MachineOperand &MO,