Introducing external weak linkage. Darwin codegen should be added later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@32052 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/AsmParser/llvmAsmParser.y b/lib/AsmParser/llvmAsmParser.y
index a6f6c2e19b1063f1d622657214b3f1ca104056dc..1d1558eb6befbe39dada83a64483ef52d532f24d 100644 (file)
--- a/lib/AsmParser/llvmAsmParser.y
+++ b/lib/AsmParser/llvmAsmParser.y
@@ -2201,7 +2201,7 @@ Function : BasicBlockList END {
 
 FnDeclareLinkage: /*default*/ |
                   DLLIMPORT   { CurFun.Linkage = GlobalValue::DLLImportLinkage; } |
-                  EXTERN_WEAK { CurFun.Linkage = GlobalValue::DLLImportLinkage; };
+                  EXTERN_WEAK { CurFun.Linkage = GlobalValue::ExternalWeakLinkage; };
   
 FunctionProto : DECLARE { CurFun.isDeclare = true; } FnDeclareLinkage FunctionHeaderH {
     $$ = CurFun.CurrentFunction;

diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
index 683b4c75176583ddc491c9ec1ee278d0a60c6132..8447acf0e530dda0a308c3932a18447fd24f640e 100644 (file)
--- a/lib/ExecutionEngine/ExecutionEngine.cpp
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -681,7 +681,7 @@ void ExecutionEngine::emitGlobals() {
         
         // Otherwise, we know it's linkonce/weak, replace it if this is a strong
         // symbol.
-        if (GV->hasExternalLinkage())
+        if (GV->hasExternalLinkage() || GVEntry->hasExternalWeakLinkage())
           GVEntry = GV;
       }
     }

diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index 46f74359874eecdcadb941a2948e2edd6c8fa1b2..b09fd656f2ed83ad332b4b52df2f01e28dd4572f 100644 (file)
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -360,6 +360,7 @@ static bool GetLinkageResult(GlobalValue *Dest, GlobalValue *Src,
     // If Src is external or if both Src & Drc are external..  Just link the
     // external globals, we aren't adding anything.
     if (Src->hasDLLImportLinkage()) {
+      // If one of GVs has DLLImport linkage, result should be dllimport'ed.
       if (Dest->isExternal()) {
         LinkFromSrc = true;
         LT = Src->getLinkage();
@@ -379,8 +380,9 @@ static bool GetLinkageResult(GlobalValue *Dest, GlobalValue *Src,
     LinkFromSrc = true; // Special cased.
     LT = Src->getLinkage();
   } else if (Src->hasWeakLinkage() || Src->hasLinkOnceLinkage()) {
-    // At this point we know that Dest has LinkOnce, External, Weak, DLL* linkage.
-    if (Dest->hasLinkOnceLinkage() && Src->hasWeakLinkage()) {
+    // At this point we know that Dest has LinkOnce, External*, Weak, DLL* linkage.
+    if ((Dest->hasLinkOnceLinkage() && Src->hasWeakLinkage()) ||
+        Dest->hasExternalWeakLinkage()) {
       LinkFromSrc = true;
       LT = Src->getLinkage();
     } else {
@@ -388,16 +390,23 @@ static bool GetLinkageResult(GlobalValue *Dest, GlobalValue *Src,
       LT = Dest->getLinkage();
     }
   } else if (Dest->hasWeakLinkage() || Dest->hasLinkOnceLinkage()) {
-    // At this point we know that Src has External or DLL* linkage.
-    LinkFromSrc = true;
-    LT = GlobalValue::ExternalLinkage;
+    // At this point we know that Src has External* or DLL* linkage.
+    if (Src->hasExternalWeakLinkage()) {
+      LinkFromSrc = false;
+      LT = Dest->getLinkage();
+    } else {
+      LinkFromSrc = true;
+      LT = GlobalValue::ExternalLinkage;
+    }
   } else {
     assert((Dest->hasExternalLinkage() ||
             Dest->hasDLLImportLinkage() ||
-            Dest->hasDLLExportLinkage()) &&
+            Dest->hasDLLExportLinkage() ||
+            Dest->hasExternalWeakLinkage()) &&
            (Src->hasExternalLinkage() ||
             Src->hasDLLImportLinkage() ||
-            Src->hasDLLExportLinkage()) &&
+            Src->hasDLLExportLinkage() ||
+            Src->hasExternalWeakLinkage()) &&
            "Unexpected linkage type!");
     return Error(Err, "Linking globals named '" + Src->getName() +
                  "': symbol multiply defined!");
@@ -631,19 +640,22 @@ static bool LinkFunctionProtos(Module *Dest, const Module *Src,
       ValueMap.insert(std::make_pair(SF, DF));
       DF->setLinkage(SF->getLinkage());
     } else if (SF->hasWeakLinkage() || SF->hasLinkOnceLinkage()) {
-      // At this point we know that DF has LinkOnce, Weak, or External linkage.
+      // At this point we know that DF has LinkOnce, Weak, or External* linkage.
       ValueMap.insert(std::make_pair(SF, DF));
 
       // Linkonce+Weak = Weak
-      if (DF->hasLinkOnceLinkage() && SF->hasWeakLinkage())
+      // *+External Weak = *
+      if ((DF->hasLinkOnceLinkage() && SF->hasWeakLinkage()) ||
+          DF->hasExternalWeakLinkage())
         DF->setLinkage(SF->getLinkage());
 
+
     } else if (DF->hasWeakLinkage() || DF->hasLinkOnceLinkage()) {
-      // At this point we know that SF has LinkOnce or External linkage.
+      // At this point we know that SF has LinkOnce or External* linkage.
       ValueMap.insert(std::make_pair(SF, DF));
-      if (!SF->hasLinkOnceLinkage())   // Don't inherit linkonce linkage
+      if (!SF->hasLinkOnceLinkage() && !SF->hasExternalWeakLinkage())
+        // Don't inherit linkonce & external weak linkage
         DF->setLinkage(SF->getLinkage());
-
     } else if (SF->getLinkage() != DF->getLinkage()) {
       return Error(Err, "Functions named '" + SF->getName() +
                    "' have different linkage specifiers!");

diff --git a/lib/Target/CBackend/CBackend.cpp b/lib/Target/CBackend/CBackend.cpp
index fa869db6aa34cfe16a3585a561519aa01cbe84e9..6d83aeb85db6e27fcef350b37cd9155e877e1c76 100644 (file)
--- a/lib/Target/CBackend/CBackend.cpp
+++ b/lib/Target/CBackend/CBackend.cpp
@@ -1157,8 +1157,6 @@ static void generateCompilerSpecificCode(std::ostream& Out) {
       << "#define __attribute__(X)\n"
       << "#endif\n\n";
 
-#if 0
-  // At some point, we should support "external weak" vs. "weak" linkages.
   // On Mac OS X, "external weak" is spelled "__attribute__((weak_import))".
   Out << "#if defined(__GNUC__) && defined(__APPLE_CC__)\n"
       << "#define __EXTERNAL_WEAK__ __attribute__((weak_import))\n"
@@ -1167,7 +1165,6 @@ static void generateCompilerSpecificCode(std::ostream& Out) {
       << "#else\n"
       << "#define __EXTERNAL_WEAK__\n"
       << "#endif\n\n";
-#endif
 
   // For now, turn off the weak linkage attribute on Mac OS X. (See above.)
   Out << "#if defined(__GNUC__) && defined(__APPLE_CC__)\n"
@@ -1357,7 +1354,11 @@ bool CWriter::doInitialization(Module &M) {
         Out << "__declspec(dllimport) ";
         printType(Out, I->getType()->getElementType(), Mang->getValueName(I));
         Out << ";\n";        
-      }      
+      } else if (I->hasExternalWeakLinkage()) {
+        Out << "extern ";
+        printType(Out, I->getType()->getElementType(), Mang->getValueName(I));
+        Out << " __EXTERNAL_WEAK__ ;\n";
+      }
     }
   }
 
@@ -1370,9 +1371,13 @@ bool CWriter::doInitialization(Module &M) {
     // Don't print declarations for intrinsic functions.
     if (!I->getIntrinsicID() && I->getName() != "setjmp" && 
         I->getName() != "longjmp" && I->getName() != "_setjmp") {
+      if (I->hasExternalWeakLinkage())
+        Out << "extern ";
       printFunctionSignature(I, true);
       if (I->hasWeakLinkage() || I->hasLinkOnceLinkage()) 
         Out << " __ATTRIBUTE_WEAK__";
+      if (I->hasExternalWeakLinkage())
+        Out << " __EXTERNAL_WEAK__";
       if (StaticCtors.count(I))
         Out << " __ATTRIBUTE_CTOR__";
       if (StaticDtors.count(I))
@@ -1405,6 +1410,8 @@ bool CWriter::doInitialization(Module &M) {
           Out << " __attribute__((common))";
         else if (I->hasWeakLinkage())
           Out << " __ATTRIBUTE_WEAK__";
+        else if (I->hasExternalWeakLinkage())
+          Out << " __EXTERNAL_WEAK__";
         Out << ";\n";
       }
   }

diff --git a/lib/Target/CBackend/Writer.cpp b/lib/Target/CBackend/Writer.cpp
index fa869db6aa34cfe16a3585a561519aa01cbe84e9..6d83aeb85db6e27fcef350b37cd9155e877e1c76 100644 (file)
--- a/lib/Target/CBackend/Writer.cpp
+++ b/lib/Target/CBackend/Writer.cpp
@@ -1157,8 +1157,6 @@ static void generateCompilerSpecificCode(std::ostream& Out) {
       << "#define __attribute__(X)\n"
       << "#endif\n\n";
 
-#if 0
-  // At some point, we should support "external weak" vs. "weak" linkages.
   // On Mac OS X, "external weak" is spelled "__attribute__((weak_import))".
   Out << "#if defined(__GNUC__) && defined(__APPLE_CC__)\n"
       << "#define __EXTERNAL_WEAK__ __attribute__((weak_import))\n"
@@ -1167,7 +1165,6 @@ static void generateCompilerSpecificCode(std::ostream& Out) {
       << "#else\n"
       << "#define __EXTERNAL_WEAK__\n"
       << "#endif\n\n";
-#endif
 
   // For now, turn off the weak linkage attribute on Mac OS X. (See above.)
   Out << "#if defined(__GNUC__) && defined(__APPLE_CC__)\n"
@@ -1357,7 +1354,11 @@ bool CWriter::doInitialization(Module &M) {
         Out << "__declspec(dllimport) ";
         printType(Out, I->getType()->getElementType(), Mang->getValueName(I));
         Out << ";\n";        
-      }      
+      } else if (I->hasExternalWeakLinkage()) {
+        Out << "extern ";
+        printType(Out, I->getType()->getElementType(), Mang->getValueName(I));
+        Out << " __EXTERNAL_WEAK__ ;\n";
+      }
     }
   }
 
@@ -1370,9 +1371,13 @@ bool CWriter::doInitialization(Module &M) {
     // Don't print declarations for intrinsic functions.
     if (!I->getIntrinsicID() && I->getName() != "setjmp" && 
         I->getName() != "longjmp" && I->getName() != "_setjmp") {
+      if (I->hasExternalWeakLinkage())
+        Out << "extern ";
       printFunctionSignature(I, true);
       if (I->hasWeakLinkage() || I->hasLinkOnceLinkage()) 
         Out << " __ATTRIBUTE_WEAK__";
+      if (I->hasExternalWeakLinkage())
+        Out << " __EXTERNAL_WEAK__";
       if (StaticCtors.count(I))
         Out << " __ATTRIBUTE_CTOR__";
       if (StaticDtors.count(I))
@@ -1405,6 +1410,8 @@ bool CWriter::doInitialization(Module &M) {
           Out << " __attribute__((common))";
         else if (I->hasWeakLinkage())
           Out << " __ATTRIBUTE_WEAK__";
+        else if (I->hasExternalWeakLinkage())
+          Out << " __EXTERNAL_WEAK__";
         Out << ";\n";
       }
   }

diff --git a/lib/Target/X86/X86ATTAsmPrinter.cpp b/lib/Target/X86/X86ATTAsmPrinter.cpp
index 7784f621ae8feb10fd5de7a018cf3f12cc44031e..88d0c7c16fe04e48a4fa85107a35029bf772de55 100755 (executable)
--- a/lib/Target/X86/X86ATTAsmPrinter.cpp
+++ b/lib/Target/X86/X86ATTAsmPrinter.cpp
@@ -255,6 +255,10 @@ void X86ATTAsmPrinter::printOperand(const MachineInstr *MI, unsigned OpNo,
       }       
       O << Name;
     }
+
+    if (GV->hasExternalWeakLinkage()) {
+      ExtWeakSymbols.insert(Name);
+    }
     
     int Offset = MO.getOffset();
     if (Offset > 0)

diff --git a/lib/Target/X86/X86AsmPrinter.cpp b/lib/Target/X86/X86AsmPrinter.cpp
index 2c53b72bd2a44f0e8c1ac20337289491455a9b2c..cb792ad1ce0be0bbbe8814893546b51a0a7ffff8 100644 (file)
--- a/lib/Target/X86/X86AsmPrinter.cpp
+++ b/lib/Target/X86/X86AsmPrinter.cpp
@@ -128,11 +128,12 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
   // from how MASM does things.  When making changes here don't forget to look
   // at X86IntelAsmPrinter::doFinalization().
   const TargetData *TD = TM.getTargetData();
-
+  
   // Print out module-level global variables here.
   for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
        I != E; ++I) {
-    if (!I->hasInitializer()) continue;   // External global require no code
+    if (!I->hasInitializer() && !I->hasExternalWeakLinkage())
+      continue;   // External global require no code
     
     // Check to see if this is a special global used by LLVM, if so, emit it.
     if (EmitSpecialLLVMGlobal(I))
@@ -176,6 +177,17 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
       O << "\t\t" << TAI->getCommentString() << " " << I->getName() << "\n";
     } else {
       switch (I->getLinkage()) {
+      case GlobalValue::ExternalWeakLinkage:
+       if (Subtarget->isTargetDarwin()) {
+         assert(0 && "External weak linkage for Darwin not implemented yet");
+       } else if (Subtarget->isTargetCygwin()) {
+         // There is no external weak linkage on Mingw32 platform.
+         // Defaulting just to external
+         O << "\t.globl " << name << "\n";
+       } else {
+         O << "\t.weak " << name << "\n";
+         break;
+       }
       case GlobalValue::LinkOnceLinkage:
       case GlobalValue::WeakLinkage:
         if (Subtarget->isTargetDarwin()) {
@@ -270,7 +282,24 @@ bool X86SharedAsmPrinter::doFinalization(Module &M) {
          i != e; ++i) {
     O << "\t.ascii \" -export:" << *i << "\"\n";
   }    
- 
+
+  if (Subtarget->isTargetDarwin()) {
+    if (ExtWeakSymbols.begin() != ExtWeakSymbols.end())
+      assert(0 && "External weak linkage for Darwin not implemented yet");
+  } else if (Subtarget->isTargetCygwin()) {
+    // There is no external weak linkage on Mingw32 platform.
+    // Defaulting to external
+  } else {
+    if (ExtWeakSymbols.begin() != ExtWeakSymbols.end())
+      SwitchToDataSection("");
+
+    for (std::set<std::string>::iterator i = ExtWeakSymbols.begin(),
+         e = ExtWeakSymbols.end();
+         i != e; ++i) {
+      O << "\t.weak " << *i << "\n";
+    }
+  }
+  
   if (Subtarget->isTargetDarwin()) {
     SwitchToDataSection("");
 

diff --git a/lib/Target/X86/X86AsmPrinter.h b/lib/Target/X86/X86AsmPrinter.h
index 3503e37c0bc709e82a4f893d4c09200e37ee1c74..8dad733bb288288ff45cb106684e63ebdcaa5fb6 100755 (executable)
--- a/lib/Target/X86/X86AsmPrinter.h
+++ b/lib/Target/X86/X86AsmPrinter.h
@@ -84,6 +84,9 @@ struct VISIBILITY_HIDDEN X86SharedAsmPrinter : public AsmPrinter {
 
   // Necessary for dllexport support
   std::set<std::string> DLLExportedFns, DLLExportedGVs;
+
+  // Necessary for external weak linkage support
+  std::set<std::string> ExtWeakSymbols;
   
   inline static bool isScale(const MachineOperand &MO) {
     return MO.isImmediate() &&

diff --git a/lib/VMCore/ConstantFold.cpp b/lib/VMCore/ConstantFold.cpp
index 9974071385b71a460c5b56643fc6df4d30492dea..fd6ad108a9cb88de908295a2cbbd1029766f3365 100644 (file)
--- a/lib/VMCore/ConstantFold.cpp
+++ b/lib/VMCore/ConstantFold.cpp
@@ -894,11 +894,8 @@ Constant *llvm::ConstantFoldCastInstruction(unsigned opc, const Constant *V,
 
   case Instruction::PtrToInt:
     // Cast of a global address to boolean is always true.
-    if (isa<GlobalValue>(V)) {
-      if (DestTy == Type::BoolTy)
-        // FIXME: When we support 'external weak' references, we have to 
-        // prevent this transformation from happening.  This code will need 
-        // to be updated to ignore external weak symbols when we support it.
+    if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
+      if (DestTy == Type::BoolTy && !GV->hasExternalWeakLinkage())
         return ConstantBool::getTrue();
     }
     break;