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

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@343542 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1 insertions, 0 deletions

diff --git a/test/CodeGen/exceptions.c b/test/CodeGen/exceptions.c
index 039ec84d2e..57b869196b 100644
--- a/test/CodeGen/exceptions.c
+++ b/test/CodeGen/exceptions.c
@@ -23,6 +23,7 @@ void test1() {
 void test2_helper();
 void test2() {
   __block int x = 10;
+  ^{ (void)x; };
   test2_helper(5, 6, 7);
 }
 void test2_helper(int x, int y) {