Distinguish `__block` variables that are captured by escaping blocks
from those that aren't.
This patch changes the way __block variables that aren't captured by
escaping blocks are handled:
- Since non-escaping blocks on the stack never get copied to the heap
(see https://reviews.llvm.org/D49303), Sema shouldn't error out when
the type of a non-escaping __block variable doesn't have an accessible
copy constructor.
- IRGen doesn't have to use the specialized byref structure (see
https://clang.llvm.org/docs/Block-ABI-Apple.html#id8) for a
non-escaping __block variable anymore. Instead IRGen can emit the
variable as a normal variable and copy the reference to the block
literal. Byref copy/dispose helpers aren't needed either.
This reapplies r343518 after fixing a use-after-free bug in function
Sema::ActOnBlockStmtExpr where the BlockScopeInfo was dereferenced after
it was popped and deleted.
rdar://problem/39352313
Differential Revision: https://reviews.llvm.org/D51564
llvm-svn: 343542
diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index dae148c..7230e4e 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -493,7 +493,11 @@
return CGF.BlockInfo->getCapture(VD).fieldType();
if (auto *FD = CGF.LambdaCaptureFields.lookup(VD))
return FD->getType();
- return VD->getType();
+ // If the captured variable is a non-escaping __block variable, the field
+ // type is the reference type. If the variable is a __block variable that
+ // already has a reference type, the field type is the variable's type.
+ return VD->isNonEscapingByref() ?
+ CGF.getContext().getLValueReferenceType(VD->getType()) : VD->getType();
}
/// Compute the layout of the given block. Attempts to lay the block
@@ -549,7 +553,7 @@
for (const auto &CI : block->captures()) {
const VarDecl *variable = CI.getVariable();
- if (CI.isByRef()) {
+ if (CI.isEscapingByref()) {
// We have to copy/dispose of the __block reference.
info.NeedsCopyDispose = true;
@@ -1032,7 +1036,7 @@
// The lambda capture in a lambda's conversion-to-block-pointer is
// special; we'll simply emit it directly.
src = Address::invalid();
- } else if (CI.isByRef()) {
+ } else if (CI.isEscapingByref()) {
if (BlockInfo && CI.isNested()) {
// We need to use the capture from the enclosing block.
const CGBlockInfo::Capture &enclosingCapture =
@@ -1060,7 +1064,7 @@
// the block field. There's no need to chase the forwarding
// pointer at this point, since we're building something that will
// live a shorter life than the stack byref anyway.
- if (CI.isByRef()) {
+ if (CI.isEscapingByref()) {
// Get a void* that points to the byref struct.
llvm::Value *byrefPointer;
if (CI.isNested())
@@ -1279,8 +1283,7 @@
return EmitCall(FnInfo, Callee, ReturnValue, Args);
}
-Address CodeGenFunction::GetAddrOfBlockDecl(const VarDecl *variable,
- bool isByRef) {
+Address CodeGenFunction::GetAddrOfBlockDecl(const VarDecl *variable) {
assert(BlockInfo && "evaluating block ref without block information?");
const CGBlockInfo::Capture &capture = BlockInfo->getCapture(variable);
@@ -1291,7 +1294,7 @@
Builder.CreateStructGEP(LoadBlockStruct(), capture.getIndex(),
capture.getOffset(), "block.capture.addr");
- if (isByRef) {
+ if (variable->isEscapingByref()) {
// addr should be a void** right now. Load, then cast the result
// to byref*.
@@ -1305,6 +1308,10 @@
variable->getName());
}
+ assert((!variable->isNonEscapingByref() ||
+ capture.fieldType()->isReferenceType()) &&
+ "the capture field of a non-escaping variable should have a "
+ "reference type");
if (capture.fieldType()->isReferenceType())
addr = EmitLoadOfReference(MakeAddrLValue(addr, capture.fieldType()));
@@ -1656,7 +1663,7 @@
return std::make_pair(BlockCaptureEntityKind::CXXRecord, BlockFieldFlags());
}
BlockFieldFlags Flags;
- if (CI.isByRef()) {
+ if (CI.isEscapingByref()) {
Flags = BLOCK_FIELD_IS_BYREF;
if (T.isObjCGCWeak())
Flags |= BLOCK_FIELD_IS_WEAK;
@@ -2102,7 +2109,7 @@
static std::pair<BlockCaptureEntityKind, BlockFieldFlags>
computeDestroyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
const LangOptions &LangOpts) {
- if (CI.isByRef()) {
+ if (CI.isEscapingByref()) {
BlockFieldFlags Flags = BLOCK_FIELD_IS_BYREF;
if (T.isObjCGCWeak())
Flags |= BLOCK_FIELD_IS_WEAK;
@@ -2564,6 +2571,9 @@
CodeGenFunction::buildByrefHelpers(llvm::StructType &byrefType,
const AutoVarEmission &emission) {
const VarDecl &var = *emission.Variable;
+ assert(var.isEscapingByref() &&
+ "only escaping __block variables need byref helpers");
+
QualType type = var.getType();
auto &byrefInfo = getBlockByrefInfo(&var);