Hello, Everyone.
Please find patches for LLVM & llvm-gcc4 which enables external weak
linkage. This is just first "draft".
Know issues:
1. There is some "FIXME" in the llvm-backend.cpp connected with external
weak linkage. It seems to be somehow "old". Don't know, what should be
done with it.
2. FIXME's in backend code: Darwin & Mingw32 codegens should be
implemented
3. Linker & ExecutionEngine wasn't touched. TBD later.
4. Fixed somehow ELFWriter.cpp. It should be finished. The same applies
to MachOWriter.cpp. Unfortunately, I don't know this code well to finish
it.
--
With best regards, Anton Korobeynikov.
Faculty of Mathematics & Mechanics, Saint Petersburg State University.
diff -r 86069e5e6d4a lib/AsmParser/llvmAsmParser.y
--- a/lib/AsmParser/llvmAsmParser.y Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/AsmParser/llvmAsmParser.y Sat Nov 25 23:54:26 2006 +0300
@@ -2159,7 +2159,7 @@ 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 -r 86069e5e6d4a lib/CodeGen/ELFWriter.cpp
--- a/lib/CodeGen/ELFWriter.cpp Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/CodeGen/ELFWriter.cpp Sun Nov 26 00:27:24 2006 +0300
@@ -134,6 +134,7 @@ bool ELFCodeEmitter::finishFunction(Mach
break;
case GlobalValue::LinkOnceLinkage:
case GlobalValue::WeakLinkage:
+ case GlobalValue::ExternalWeakLinkage:
FnSym.SetBind(ELFWriter::ELFSym::STB_WEAK);
break;
case GlobalValue::InternalLinkage:
diff -r 86069e5e6d4a lib/Target/CBackend/Writer.cpp
--- a/lib/Target/CBackend/Writer.cpp Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/Target/CBackend/Writer.cpp Sun Nov 26 00:19:50 2006 +0300
@@ -1031,8 +1031,6 @@ static void generateCompilerSpecificCode
<< "#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"
@@ -1041,7 +1039,6 @@ static void generateCompilerSpecificCode
<< "#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"
@@ -1231,7 +1228,11 @@ 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";
+ }
}
}
@@ -1244,9 +1245,13 @@ 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))
@@ -1279,6 +1284,8 @@ 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 -r 86069e5e6d4a lib/Target/X86/X86ATTAsmPrinter.cpp
--- a/lib/Target/X86/X86ATTAsmPrinter.cpp Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/Target/X86/X86ATTAsmPrinter.cpp Sun Nov 26 03:36:43 2006 +0300
@@ -255,6 +255,10 @@ void X86ATTAsmPrinter::printOperand(cons
}
O << Name;
}
+
+ if (GV->hasExternalWeakLinkage()) {
+ ExtWeakSymbols.insert(Name);
+ }
int Offset = MO.getOffset();
if (Offset > 0)
diff -r 86069e5e6d4a lib/Target/X86/X86AsmPrinter.cpp
--- a/lib/Target/X86/X86AsmPrinter.cpp Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/Target/X86/X86AsmPrinter.cpp Sun Nov 26 03:32:49 2006 +0300
@@ -128,10 +128,11 @@ bool X86SharedAsmPrinter::doFinalization
// 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 +177,15 @@ bool X86SharedAsmPrinter::doFinalization
O << "\t\t" << TAI->getCommentString() << " " << I->getName() << "\n";
} else {
switch (I->getLinkage()) {
+ case GlobalValue::ExternalWeakLinkage:
+ if (Subtarget->isTargetDarwin()) {
+ assert(0 && "FIXME");
+ } else if (Subtarget->isTargetCygwin()) {
+ assert(0 && "FIXME");
+ } else {
+ O << "\t.weak " << name << "\n";
+ break;
+ }
case GlobalValue::LinkOnceLinkage:
case GlobalValue::WeakLinkage:
if (Subtarget->isTargetDarwin()) {
@@ -270,6 +280,22 @@ bool X86SharedAsmPrinter::doFinalization
i != e; ++i) {
O << "\t.ascii \" -export:" << *i << "\"\n";
}
+ if (ExtWeakSymbols.begin() != ExtWeakSymbols.end())
+ SwitchToDataSection("");
+
+ for (std::set<std::string>::iterator i = ExtWeakSymbols.begin(),
+ e = ExtWeakSymbols.end();
+ i != e; ++i) {
+
+ if (Subtarget->isTargetDarwin()) {
+ assert(0 && "FIXME");
+ } else if (Subtarget->isTargetCygwin()) {
+ assert(0 && "FIXME");
+ } else {
+ O << "\t.weak " << *i << "\n";
+ }
+ }
+
if (Subtarget->isTargetDarwin()) {
SwitchToDataSection("");
diff -r 86069e5e6d4a lib/Target/X86/X86AsmPrinter.h
--- a/lib/Target/X86/X86AsmPrinter.h Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/Target/X86/X86AsmPrinter.h Sun Nov 26 03:16:12 2006 +0300
@@ -84,6 +84,9 @@ struct VISIBILITY_HIDDEN X86SharedAsmPri
// 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 -r 86069e5e6d4a lib/VMCore/ConstantFolding.cpp
--- a/lib/VMCore/ConstantFolding.cpp Sat Nov 25 08:38:44 2006 +0000
+++ b/lib/VMCore/ConstantFolding.cpp Sun Nov 26 00:49:21 2006 +0300
@@ -810,12 +810,10 @@ Constant *llvm::ConstantFoldCastInstruct
const Type *DestTy) {
if (V->getType() == DestTy) return (Constant*)V;
- // 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.
+ // Cast of a global address to boolean is always true, when symbol doesn't
+ // have external weak linkage.
+ if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
+ if (DestTy == Type::BoolTy && !GV->hasExternalWeakLinkage())
return ConstantBool::getTrue();
} else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
if (CE->getOpcode() == Instruction::Cast) {
diff -r da2c731b5893 gcc/crtstuff.c
--- a/gcc/crtstuff.c Tue Nov 21 18:34:05 2006 +0000
+++ b/gcc/crtstuff.c Sun Nov 26 03:58:43 2006 +0300
@@ -65,13 +65,6 @@ 02111-1307, USA. */
#include "coretypes.h"
#include "tm.h"
#include "unwind-dw2-fde.h"
-
-/* APPLE LOCAL begin LLVM */
-#ifdef __llvm__
- /* FIXME: Remove when external weak linkage will be alive. */
- #undef JCR_SECTION_NAME
-#endif
-/* APPLE LOCAL end LLVM */
#ifndef FORCE_CODE_SECTION_ALIGN
# define FORCE_CODE_SECTION_ALIGN
diff -r da2c731b5893 gcc/llvm-backend.cpp
--- a/gcc/llvm-backend.cpp Tue Nov 21 18:34:05 2006 +0000
+++ b/gcc/llvm-backend.cpp Sun Nov 26 02:32:04 2006 +0300
@@ -673,6 +675,11 @@ void make_decl_llvm(tree decl) {
FnEntry = new Function(Ty, Function::ExternalLinkage, Name, TheModule);
FnEntry->setCallingConv(CC);
+ // Check for external weak linkage
+ if (DECL_EXTERNAL(decl) && DECL_WEAK(decl)) {
+ FnEntry->setLinkage(Function::ExternalWeakLinkage);
+ }
+
#ifdef TARGET_ADJUST_LLVM_LINKAGE
TARGET_ADJUST_LLVM_LINKAGE(FnEntry,decl);
#endif /* TARGET_ADJUST_LLVM_LINKAGE */
@@ -692,6 +699,11 @@ void make_decl_llvm(tree decl) {
if (Name[0] == 0) { // Global has no name.
GV = new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage, 0,
Name, TheModule);
+
+ // Check for external weak linkage
+ if (DECL_EXTERNAL(decl) && DECL_WEAK(decl)) {
+ GV->setLinkage(GlobalValue::ExternalWeakLinkage);
+ }
#ifdef TARGET_ADJUST_LLVM_LINKAGE
TARGET_ADJUST_LLVM_LINKAGE(GV,decl);
@@ -704,6 +716,11 @@ void make_decl_llvm(tree decl) {
if (GVE == 0) {
GVE = GV = new GlobalVariable(Ty, false, GlobalValue::ExternalLinkage,0,
Name, TheModule);
+
+ // Check for external weak linkage
+ if (DECL_EXTERNAL(decl) && DECL_WEAK(decl)) {
+ GV->setLinkage(GlobalValue::ExternalWeakLinkage);
+ }
#ifdef TARGET_ADJUST_LLVM_LINKAGE
TARGET_ADJUST_LLVM_LINKAGE(GV,decl);
@@ -752,17 +769,21 @@ const char *llvm_get_decl_name(void *LLV
}
// llvm_mark_decl_weak - Used by varasm.c, called when a decl is found to be
-// weak, but it already had an llvm object created for it. This marks the LLVM
+// weak, but it already had an llvm object created for it. This marks the LLVM
// object weak as well.
void llvm_mark_decl_weak(tree decl) {
assert(DECL_LLVM_SET_P(decl) && DECL_WEAK(decl) &&
isa<GlobalValue>(DECL_LLVM(decl)) && "Decl isn't marked weak!");
GlobalValue *GV = cast<GlobalValue>(DECL_LLVM(decl));
- if (!GV->isExternal() && // FIXME: Support external weak globals!
- // Do not mark something that is already known to be linkonce or internal.
- GV->getLinkage() == GlobalValue::ExternalLinkage)
- GV->setLinkage(GlobalValue::WeakLinkage);
+ // Do not mark something that is already known to be linkonce or internal.
+ if (GV->getLinkage() == GlobalValue::ExternalLinkage) {
+ if (GV->isExternal()) {
+ GV->setLinkage(GlobalValue::ExternalWeakLinkage);
+ } else {
+ GV->setLinkage(GlobalValue::WeakLinkage);
+ }
+ }
}
// llvm_emit_ctor_dtor - Called to emit static ctors/dtors to LLVM code. fndecl
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