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.

rdar://problem/39352313

Differential Revision: https://reviews.llvm.org/D51564

llvm-svn: 341754

1 files changed, 3 insertions, 0 deletions

diff --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 8eb6c61525d..97303da9a16 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -936,6 +936,7 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
       Record.push_back(static_cast<unsigned>(IPD->getParameterKind()));
     else
       Record.push_back(0);
+    Record.push_back(D->isEscapingByref());
   }
   Record.push_back(D->getLinkageInternal());
 
@@ -1006,6 +1007,7 @@ void ASTDeclWriter::VisitVarDecl(VarDecl *D) {
       !D->isInitCapture() &&
       !D->isPreviousDeclInSameBlockScope() &&
       !(D->hasAttr<BlocksAttr>() && D->getType()->getAsCXXRecordDecl()) &&
+      !D->isEscapingByref() &&
       D->getStorageDuration() != SD_Static &&
       !D->getMemberSpecializationInfo())
     AbbrevToUse = Writer.getDeclVarAbbrev();
@@ -2057,6 +2059,7 @@ void ASTWriter::WriteDeclAbbrevs() {
   Abv->Add(BitCodeAbbrevOp(0));                         // isInitCapture
   Abv->Add(BitCodeAbbrevOp(0));                         // isPrevDeclInSameScope
   Abv->Add(BitCodeAbbrevOp(0));                         // ImplicitParamKind
+  Abv->Add(BitCodeAbbrevOp(0));                         // EscapingByref
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 3)); // Linkage
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // IsInitICE (local)
   Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // VarKind (local enum)