Fix PR6473.
Clang's support for weakref is now better than llvm-gcc's :-)
We don't introduce a new symbol and we correctly mark undefined references weak only if there is no
definition or regular undefined references in the same file.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@97733 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 030d2c9..dc9ecd6 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1062,6 +1062,16 @@
LValue CodeGenFunction::EmitDeclRefLValue(const DeclRefExpr *E) {
const NamedDecl *ND = E->getDecl();
+ if (ND->hasAttr<WeakRefAttr>()) {
+ const ValueDecl* VD = cast<ValueDecl>(ND);
+ llvm::Constant *Aliasee = CGM.GetWeakRefReference(VD);
+
+ Qualifiers Quals = MakeQualifiers(E->getType());
+ LValue LV = LValue::MakeAddr(Aliasee, Quals);
+
+ return LV;
+ }
+
if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
// Check if this is a global variable.
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index bc2bd6c..e6e9b1a 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -619,9 +619,41 @@
return false;
}
+llvm::Constant *CodeGenModule::GetWeakRefReference(const ValueDecl *VD) {
+ const AliasAttr *AA = VD->getAttr<AliasAttr>();
+ assert(AA && "No alias?");
+
+ const llvm::Type *DeclTy = getTypes().ConvertTypeForMem(VD->getType());
+
+ // Unique the name through the identifier table.
+ const char *AliaseeName =
+ getContext().Idents.get(AA->getAliasee()).getNameStart();
+
+ // See if there is already something with the target's name in the module.
+ llvm::GlobalValue *Entry = GlobalDeclMap[AliaseeName];
+
+ llvm::Constant *Aliasee;
+ if (isa<llvm::FunctionType>(DeclTy))
+ Aliasee = GetOrCreateLLVMFunction(AliaseeName, DeclTy, GlobalDecl());
+ else
+ Aliasee = GetOrCreateLLVMGlobal(AliaseeName,
+ llvm::PointerType::getUnqual(DeclTy), 0);
+ if (!Entry) {
+ llvm::GlobalValue* F = cast<llvm::GlobalValue>(Aliasee);
+ F->setLinkage(llvm::Function::ExternalWeakLinkage);
+ WeakRefReferences.insert(F);
+ }
+
+ return Aliasee;
+}
+
void CodeGenModule::EmitGlobal(GlobalDecl GD) {
const ValueDecl *Global = cast<ValueDecl>(GD.getDecl());
+ // Weak references don't produce any output by themselves.
+ if (Global->hasAttr<WeakRefAttr>())
+ return;
+
// If this is an alias definition (which otherwise looks like a declaration)
// emit it now.
if (Global->hasAttr<AliasAttr>())
@@ -708,6 +740,14 @@
// Lookup the entry, lazily creating it if necessary.
llvm::GlobalValue *&Entry = GlobalDeclMap[MangledName];
if (Entry) {
+ if (WeakRefReferences.count(Entry)) {
+ const FunctionDecl *FD = cast_or_null<FunctionDecl>(D.getDecl());
+ if (FD && !FD->hasAttr<WeakAttr>())
+ Entry->setLinkage(llvm::Function::ExternalLinkage);
+
+ WeakRefReferences.erase(Entry);
+ }
+
if (Entry->getType()->getElementType() == Ty)
return Entry;
@@ -817,6 +857,13 @@
// Lookup the entry, lazily creating it if necessary.
llvm::GlobalValue *&Entry = GlobalDeclMap[MangledName];
if (Entry) {
+ if (WeakRefReferences.count(Entry)) {
+ if (D && !D->hasAttr<WeakAttr>())
+ Entry->setLinkage(llvm::Function::ExternalLinkage);
+
+ WeakRefReferences.erase(Entry);
+ }
+
if (Entry->getType() == Ty)
return Entry;
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index ac83326..c839b42 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -29,6 +29,7 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/StringMap.h"
#include "llvm/ADT/StringSet.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Support/ValueHandle.h"
#include <list>
@@ -117,6 +118,11 @@
/// pointer lookups instead of full string lookups.
llvm::DenseMap<const char*, llvm::GlobalValue*> GlobalDeclMap;
+ // WeakRefReferences - A set of references that have only been seen via
+ // a weakref so far. This is used to remove the weak of the reference if we ever
+ // see a direct reference or a definition.
+ llvm::SmallPtrSet<llvm::GlobalValue*, 10> WeakRefReferences;
+
/// \brief Contains the strings used for mangled names.
///
/// FIXME: Eventually, this should map from the semantic/canonical
@@ -243,6 +249,9 @@
void BuildThunksForVirtual(GlobalDecl GD);
void BuildThunksForVirtualRecursive(GlobalDecl GD, GlobalDecl BaseOGD);
+ /// GetWeakRefReference - Get a reference to the target of VD.
+ llvm::Constant *GetWeakRefReference(const ValueDecl *VD);
+
/// BuildThunk - Build a thunk for the given method.
llvm::Constant *BuildThunk(GlobalDecl GD, bool Extern,
const ThunkAdjustment &ThisAdjustment);