[PATCH] D32601: [CodeGen][ObjC] Don't retain/release capture objects at block creation that are const-qualified

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.

When a block captures an ObjC object pointer, clang emits a retain/release pair to prevent prematurely destroying the object the pointer points to before the block is called or copied.

When the captured object pointer is const-qualified, we can avoid emitting the retain/release pair since the pointer variable cannot be modified in the scope in which the block literal is introduced.

  void test(const id x) {
    callee(^{ (void)x; });
  }

This patch implements that optimization.

rdar://problem/28894510


https://reviews.llvm.org/D32601

Files:
  lib/CodeGen/CGBlocks.cpp
  lib/CodeGen/CGObjC.cpp
  lib/CodeGen/CodeGenFunction.h
  test/CodeGenObjC/arc-blocks.m
  test/CodeGenObjC/arc-foreach.m

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