[PATCH] D26410: [CodeGen] Don't emit the same global block multiple times.

[George Burgess IV via cfe-commits]

george.burgess.iv created this revision.
george.burgess.iv added a reviewer: rjmccall.
george.burgess.iv added a subscriber: cfe-commits.

https://reviews.llvm.org/D14274 makes our constexpr evaluator more aggressive with some variables marked `const`. This changes how we behave on code like the following:

  void foo() {
    void (^const block_A)(void) = ^{ return; };
    get_kernel_work_group_size(block_A);
    get_kernel_work_group_size(block_A);
  }

The constexpr evaluator will now give us `^{ return; }` three times (one for each use of `block_A`) instead of once (in `block_A`'s assignment). CodeGen emits a block every time it gets handed a `BlockExpr`, so we end up emitting the code for `^{ return; }` three times in total. We can fix this by tracking which global `BlockExpr`s we've already generated code for.

This seems to not happen for local `BlockExpr`s, since the constexpr fails for `BlockExpr`s with captures (see `PointerExprEvaluator::VisitBlockExpr` in lib/AST/ExprConstant.cpp). That said, I'm happy to add this uniquing code for `BlockExpr`s with captures if anyone wants me to.


https://reviews.llvm.org/D26410

Files:
  lib/CodeGen/CGBlocks.cpp
  lib/CodeGen/CodeGenFunction.h
  lib/CodeGen/CodeGenModule.h
  test/CodeGenCXX/block-in-ctor-dtor.cpp
  test/CodeGenOpenCL/cl20-device-side-enqueue.cl

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