fix a fixme in TargetLoweringObjectFile::getExprForDwarfReference

where we used ot create an MCSymbol for ".".  Now emit an assembler
temporary label and reference it instead of "." textually.

rdar://7739457


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98292 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Target/Mangler.h

@@ -51,6 +51,12 @@ public:
   // symbols.
   Mangler(const MCAsmInfo &mai) : MAI(mai), NextAnonGlobalID(1) {}
 
+  /// getUniqueID() - Allocate and return a unique ID.
+  /// FIXME: Remove this.
+  unsigned getUniqueID() {
+    return NextAnonGlobalID++;
+  }
+  
   /// getNameWithPrefix - Fill OutName with the name of the appropriate prefix
   /// and the specified global variable's name.  If the global variable doesn't
   /// have a name, this fills in a unique name for the global.

include/llvm/Target/TargetLoweringObjectFile.h

@@ -208,8 +208,8 @@ public:
 
   /// 
   const MCExpr *
-  getExprForDwarfReference(const MCSymbol *Sym, MachineModuleInfo *MMI,
-                           unsigned Encoding,
+  getExprForDwarfReference(const MCSymbol *Sym, Mangler *Mang,
+                           MachineModuleInfo *MMI, unsigned Encoding,
                            MCStreamer &Streamer) const;
   
   virtual unsigned getPersonalityEncoding() const;

lib/CodeGen/AsmPrinter/DwarfPrinter.cpp

@@ -189,7 +189,8 @@ void DwarfPrinter::EmitULEB128(unsigned Value, const char *Desc,
 void DwarfPrinter::EmitReference(const MCSymbol *Sym, unsigned Encoding) const {
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
 
-  const MCExpr *Exp = TLOF.getExprForDwarfReference(Sym, Asm->MMI, Encoding,
+  const MCExpr *Exp = TLOF.getExprForDwarfReference(Sym, Asm->Mang,
+                                                    Asm->MMI, Encoding,
                                                     Asm->OutStreamer);
   Asm->OutStreamer.EmitValue(Exp, SizeOfEncodedValue(Encoding), /*addrspace*/0);
 }

lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -421,7 +421,7 @@ getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
     }
 
     return TargetLoweringObjectFile::
-      getExprForDwarfReference(Sym, MMI,
+      getExprForDwarfReference(Sym, Mang, MMI,
                                Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
   }
 
@@ -784,8 +784,8 @@ getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
     }
 
     return TargetLoweringObjectFile::
-      getExprForDwarfReference(Sym, MMI, Encoding & ~dwarf::DW_EH_PE_indirect,
-                               Streamer);
+      getExprForDwarfReference(Sym, Mang, MMI,
+                               Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
   }
 
   return TargetLoweringObjectFile::

lib/Target/TargetLoweringObjectFile.cpp

@@ -19,6 +19,7 @@
 #include "llvm/GlobalVariable.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Target/Mangler.h"
 #include "llvm/Target/TargetData.h"
@@ -307,29 +308,34 @@ getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
   else
     Sym = getContext().GetOrCreateSymbol(Name.str());
 
-  return getExprForDwarfReference(Sym, MMI, Encoding, Streamer);
+  return getExprForDwarfReference(Sym, Mang, MMI, Encoding, Streamer);
 }
 
 const MCExpr *TargetLoweringObjectFile::
-getExprForDwarfReference(const MCSymbol *Sym, MachineModuleInfo *MMI,
-                         unsigned Encoding, MCStreamer &Streamer) const {
+getExprForDwarfReference(const MCSymbol *Sym, Mangler *Mang,
+                         MachineModuleInfo *MMI, unsigned Encoding,
+                         MCStreamer &Streamer) const {
   const MCExpr *Res = MCSymbolRefExpr::Create(Sym, getContext());
 
   switch (Encoding & 0xF0) {
   default:
     llvm_report_error("We do not support this DWARF encoding yet!");
-    break;
   case dwarf::DW_EH_PE_absptr:
     // Do nothing special
-    break;
-  case dwarf::DW_EH_PE_pcrel:
-    // FIXME: PCSymbol
-    const MCExpr *PC = MCSymbolRefExpr::Create(".", getContext());
-    Res = MCBinaryExpr::CreateSub(Res, PC, getContext());
-    break;
-  }
+    return Res;
+  case dwarf::DW_EH_PE_pcrel: {
+    // Emit a label to the streamer for the current position.  This gives us
+    // .-foo addressing.
+    SmallString<128> Name;
+    Mang->getNameWithPrefix(Name, Twine("PCtemp") + Twine(Mang->getUniqueID()),
+                            Mangler::Private);
 
-  return Res;
+    MCSymbol *PCSym = getContext().GetOrCreateTemporarySymbol(Name.str());
+    Streamer.EmitLabel(PCSym);
+    const MCExpr *PC = MCSymbolRefExpr::Create(PCSym, getContext());
+    return MCBinaryExpr::CreateSub(Res, PC, getContext());
+  }
+  }
 }
 
 unsigned TargetLoweringObjectFile::getPersonalityEncoding() const {