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

1 files changed, 1 insertions, 0 deletions

diff --git a/clang/test/CodeGenObjC/arc-unoptimized-byref-var.m b/clang/test/CodeGenObjC/arc-unoptimized-byref-var.m
index 9d856d6..ffc73a4 100644
--- a/clang/test/CodeGenObjC/arc-unoptimized-byref-var.m
+++ b/clang/test/CodeGenObjC/arc-unoptimized-byref-var.m
@@ -3,6 +3,7 @@
 
 void test19() {
    __block id x;
+   ^{ (void)x; };
 // CHECK-UNOPT-LABEL: define internal void @__Block_byref_object_copy
 // CHECK-UNOPT: [[X:%.*]] = getelementptr inbounds [[BYREF_T:%.*]], [[BYREF_T:%.*]]* [[VAR:%.*]], i32 0, i32 6
 // CHECK-UNOPT: [[X2:%.*]] = getelementptr inbounds [[BYREF_T:%.*]], [[BYREF_T:%.*]]* [[VAR1:%.*]], i32 0, i32 6