Automatic Reference Counting.
Language-design credit goes to a lot of people, but I particularly want
to single out Blaine Garst and Patrick Beard for their contributions.
Compiler implementation credit goes to Argyrios, Doug, Fariborz, and myself,
in no particular order.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133103 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGBlocks.cpp b/lib/CodeGen/CGBlocks.cpp
index e5da703..ac47034 100644
--- a/lib/CodeGen/CGBlocks.cpp
+++ b/lib/CodeGen/CGBlocks.cpp
@@ -347,13 +347,23 @@
continue;
}
- // Block pointers require copy/dispose.
- if (variable->getType()->isBlockPointerType()) {
- info.NeedsCopyDispose = true;
+ // If we have a lifetime qualifier, honor it for capture purposes.
+ // That includes *not* copying it if it's __unsafe_unretained.
+ if (Qualifiers::ObjCLifetime lifetime
+ = variable->getType().getObjCLifetime()) {
+ switch (lifetime) {
+ case Qualifiers::OCL_None: llvm_unreachable("impossible");
+ case Qualifiers::OCL_ExplicitNone:
+ case Qualifiers::OCL_Autoreleasing:
+ break;
- // So do Objective-C pointers.
- } else if (variable->getType()->isObjCObjectPointerType() ||
- C.isObjCNSObjectType(variable->getType())) {
+ case Qualifiers::OCL_Strong:
+ case Qualifiers::OCL_Weak:
+ info.NeedsCopyDispose = true;
+ }
+
+ // Block pointers require copy/dispose. So do Objective-C pointers.
+ } else if (variable->getType()->isObjCRetainableType()) {
info.NeedsCopyDispose = true;
// So do types that require non-trivial copy construction.
@@ -591,6 +601,11 @@
// Otherwise, fake up a POD copy into the block field.
} else {
+ // Fake up a new variable so that EmitScalarInit doesn't think
+ // we're referring to the variable in its own initializer.
+ ImplicitParamDecl blockFieldPseudoVar(/*DC*/ 0, SourceLocation(),
+ /*name*/ 0, type);
+
// We use one of these or the other depending on whether the
// reference is nested.
DeclRefExpr notNested(const_cast<VarDecl*>(variable), type, VK_LValue,
@@ -603,15 +618,29 @@
ImplicitCastExpr l2r(ImplicitCastExpr::OnStack, type, CK_LValueToRValue,
declRef, VK_RValue);
- EmitExprAsInit(&l2r, variable, blockField,
+ EmitExprAsInit(&l2r, &blockFieldPseudoVar, blockField,
getContext().getDeclAlign(variable),
/*captured by init*/ false);
}
// Push a destructor if necessary. The semantics for when this
// actually gets run are really obscure.
- if (!ci->isByRef() && CGM.getLangOptions().CPlusPlus)
- PushDestructorCleanup(type, blockField);
+ if (!ci->isByRef()) {
+ switch (type.isDestructedType()) {
+ case QualType::DK_none:
+ break;
+ case QualType::DK_cxx_destructor:
+ PushDestructorCleanup(type, blockField);
+ break;
+ case QualType::DK_objc_strong_lifetime:
+ PushARCReleaseCleanup(getARCCleanupKind(), type, blockField, false);
+ break;
+ case QualType::DK_objc_weak_lifetime:
+ // __weak objects on the stack always get EH cleanups.
+ PushARCWeakReleaseCleanup(NormalAndEHCleanup, type, blockField);
+ break;
+ }
+ }
}
// Cast to the converted block-pointer type, which happens (somewhat
@@ -1023,8 +1052,6 @@
-
-
llvm::Constant *
CodeGenFunction::GenerateCopyHelperFunction(const CGBlockInfo &blockInfo) {
ASTContext &C = getContext();
@@ -1084,21 +1111,40 @@
if (capture.isConstant()) continue;
const Expr *copyExpr = ci->getCopyExpr();
- unsigned flags = 0;
+ BlockFieldFlags flags;
+
+ bool isARCWeakCapture = false;
if (copyExpr) {
assert(!ci->isByRef());
// don't bother computing flags
+
} else if (ci->isByRef()) {
flags = BLOCK_FIELD_IS_BYREF;
- if (type.isObjCGCWeak()) flags |= BLOCK_FIELD_IS_WEAK;
- } else if (type->isBlockPointerType()) {
- flags = BLOCK_FIELD_IS_BLOCK;
- } else if (type->isObjCObjectPointerType() || C.isObjCNSObjectType(type)) {
- flags = BLOCK_FIELD_IS_OBJECT;
- }
+ if (type.isObjCGCWeak())
+ flags |= BLOCK_FIELD_IS_WEAK;
- if (!copyExpr && !flags) continue;
+ } else if (type->isObjCRetainableType()) {
+ flags = BLOCK_FIELD_IS_OBJECT;
+ if (type->isBlockPointerType())
+ flags = BLOCK_FIELD_IS_BLOCK;
+
+ // Special rules for ARC captures:
+ if (getLangOptions().ObjCAutoRefCount) {
+ Qualifiers qs = type.getQualifiers();
+
+ // Don't generate special copy logic for a captured object
+ // unless it's __strong or __weak.
+ if (!qs.hasStrongOrWeakObjCLifetime())
+ continue;
+
+ // Support __weak direct captures.
+ if (qs.getObjCLifetime() == Qualifiers::OCL_Weak)
+ isARCWeakCapture = true;
+ }
+ } else {
+ continue;
+ }
unsigned index = capture.getIndex();
llvm::Value *srcField = Builder.CreateStructGEP(src, index);
@@ -1107,12 +1153,14 @@
// If there's an explicit copy expression, we do that.
if (copyExpr) {
EmitSynthesizedCXXCopyCtor(dstField, srcField, copyExpr);
+ } else if (isARCWeakCapture) {
+ EmitARCCopyWeak(dstField, srcField);
} else {
llvm::Value *srcValue = Builder.CreateLoad(srcField, "blockcopy.src");
srcValue = Builder.CreateBitCast(srcValue, VoidPtrTy);
llvm::Value *dstAddr = Builder.CreateBitCast(dstField, VoidPtrTy);
Builder.CreateCall3(CGM.getBlockObjectAssign(), dstAddr, srcValue,
- llvm::ConstantInt::get(Int32Ty, flags));
+ llvm::ConstantInt::get(Int32Ty, flags.getBitMask()));
}
}
@@ -1176,20 +1224,37 @@
BlockFieldFlags flags;
const CXXDestructorDecl *dtor = 0;
+ bool isARCWeakCapture = false;
+
if (ci->isByRef()) {
flags = BLOCK_FIELD_IS_BYREF;
- if (type.isObjCGCWeak()) flags |= BLOCK_FIELD_IS_WEAK;
- } else if (type->isBlockPointerType()) {
- flags = BLOCK_FIELD_IS_BLOCK;
- } else if (type->isObjCObjectPointerType() || C.isObjCNSObjectType(type)) {
+ if (type.isObjCGCWeak())
+ flags |= BLOCK_FIELD_IS_WEAK;
+ } else if (const CXXRecordDecl *record = type->getAsCXXRecordDecl()) {
+ if (record->hasTrivialDestructor())
+ continue;
+ dtor = record->getDestructor();
+ } else if (type->isObjCRetainableType()) {
flags = BLOCK_FIELD_IS_OBJECT;
- } else if (C.getLangOptions().CPlusPlus) {
- if (const CXXRecordDecl *record = type->getAsCXXRecordDecl())
- if (!record->hasTrivialDestructor())
- dtor = record->getDestructor();
- }
+ if (type->isBlockPointerType())
+ flags = BLOCK_FIELD_IS_BLOCK;
- if (!dtor && flags.empty()) continue;
+ // Special rules for ARC captures.
+ if (getLangOptions().ObjCAutoRefCount) {
+ Qualifiers qs = type.getQualifiers();
+
+ // Don't generate special dispose logic for a captured object
+ // unless it's __strong or __weak.
+ if (!qs.hasStrongOrWeakObjCLifetime())
+ continue;
+
+ // Support __weak direct captures.
+ if (qs.getObjCLifetime() == Qualifiers::OCL_Weak)
+ isARCWeakCapture = true;
+ }
+ } else {
+ continue;
+ }
unsigned index = capture.getIndex();
llvm::Value *srcField = Builder.CreateStructGEP(src, index);
@@ -1198,6 +1263,10 @@
if (dtor) {
PushDestructorCleanup(dtor, srcField);
+ // If this is a __weak capture, emit the release directly.
+ } else if (isARCWeakCapture) {
+ EmitARCDestroyWeak(srcField);
+
// Otherwise we call _Block_object_dispose. It wouldn't be too
// hard to just emit this as a cleanup if we wanted to make sure
// that things were done in reverse.
@@ -1251,6 +1320,55 @@
}
};
+/// Emits the copy/dispose helpers for an ARC __block __weak variable.
+class ARCWeakByrefHelpers : public CodeGenModule::ByrefHelpers {
+public:
+ ARCWeakByrefHelpers(CharUnits alignment) : ByrefHelpers(alignment) {}
+
+ void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+ llvm::Value *srcField) {
+ CGF.EmitARCMoveWeak(destField, srcField);
+ }
+
+ void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+ CGF.EmitARCDestroyWeak(field);
+ }
+
+ void profileImpl(llvm::FoldingSetNodeID &id) const {
+ // 0 is distinguishable from all pointers and byref flags
+ id.AddInteger(0);
+ }
+};
+
+/// Emits the copy/dispose helpers for an ARC __block __strong variable
+/// that's not of block-pointer type.
+class ARCStrongByrefHelpers : public CodeGenModule::ByrefHelpers {
+public:
+ ARCStrongByrefHelpers(CharUnits alignment) : ByrefHelpers(alignment) {}
+
+ void emitCopy(CodeGenFunction &CGF, llvm::Value *destField,
+ llvm::Value *srcField) {
+ // Do a "move" by copying the value and then zeroing out the old
+ // variable.
+
+ llvm::Value *value = CGF.Builder.CreateLoad(srcField);
+ llvm::Value *null =
+ llvm::ConstantPointerNull::get(cast<llvm::PointerType>(value->getType()));
+ CGF.Builder.CreateStore(value, destField);
+ CGF.Builder.CreateStore(null, srcField);
+ }
+
+ void emitDispose(CodeGenFunction &CGF, llvm::Value *field) {
+ llvm::Value *value = CGF.Builder.CreateLoad(field);
+ CGF.EmitARCRelease(value, /*precise*/ false);
+ }
+
+ void profileImpl(llvm::FoldingSetNodeID &id) const {
+ // 1 is distinguishable from all pointers and byref flags
+ id.AddInteger(1);
+ }
+};
+
/// Emits the copy/dispose helpers for a __block variable with a
/// nontrivial copy constructor or destructor.
class CXXByrefHelpers : public CodeGenModule::ByrefHelpers {
@@ -1318,6 +1436,7 @@
SC_Static,
SC_None,
false, true);
+
CGF.StartFunction(FD, R, Fn, FI, args, SourceLocation());
if (byrefInfo.needsCopy()) {
@@ -1449,6 +1568,52 @@
return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
}
+ // Otherwise, if we don't have a retainable type, there's nothing to do.
+ // that the runtime does extra copies.
+ if (!type->isObjCRetainableType()) return 0;
+
+ Qualifiers qs = type.getQualifiers();
+
+ // If we have lifetime, that dominates.
+ if (Qualifiers::ObjCLifetime lifetime = qs.getObjCLifetime()) {
+ assert(getLangOptions().ObjCAutoRefCount);
+
+ switch (lifetime) {
+ case Qualifiers::OCL_None: llvm_unreachable("impossible");
+
+ // These are just bits as far as the runtime is concerned.
+ case Qualifiers::OCL_ExplicitNone:
+ case Qualifiers::OCL_Autoreleasing:
+ return 0;
+
+ // Tell the runtime that this is ARC __weak, called by the
+ // byref routines.
+ case Qualifiers::OCL_Weak: {
+ ARCWeakByrefHelpers byrefInfo(emission.Alignment);
+ return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+ }
+
+ // ARC __strong __block variables need to be retained.
+ case Qualifiers::OCL_Strong:
+ // Block-pointers need to be _Block_copy'ed, so we let the
+ // runtime be in charge. But we can't use the code below
+ // because we don't want to set BYREF_CALLER, which will
+ // just make the runtime ignore us.
+ if (type->isBlockPointerType()) {
+ BlockFieldFlags flags = BLOCK_FIELD_IS_BLOCK;
+ ObjectByrefHelpers byrefInfo(emission.Alignment, flags);
+ return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+
+ // Otherwise, we transfer ownership of the retain from the stack
+ // to the heap.
+ } else {
+ ARCStrongByrefHelpers byrefInfo(emission.Alignment);
+ return ::buildByrefHelpers(CGM, byrefType, byrefInfo);
+ }
+ }
+ llvm_unreachable("fell out of lifetime switch!");
+ }
+
BlockFieldFlags flags;
if (type->isBlockPointerType()) {
flags |= BLOCK_FIELD_IS_BLOCK;
@@ -1639,6 +1804,7 @@
CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {}
void Emit(CodeGenFunction &CGF, bool IsForEH) {
+ // Should we be passing FIELD_IS_WEAK here?
CGF.BuildBlockRelease(Addr, BLOCK_FIELD_IS_BYREF);
}
};