[PATCH] D43841: Add an option to disable tail-call optimization for escaping blocks

[Akira Hatanaka via Phabricator via cfe-commits]

ahatanak created this revision.
ahatanak added a reviewer: rjmccall.

This patch adds a command line option (-fdisable-tail-calls-esca
ping-blocks) that annotates escaping block invoke functions with attribute "disable-tail-calls". This is an option that helps users in debugging their code who spend a lot of time trying to figure out where a block came from.

The user who is asking for this command line option does not want to disable tail-call optimization for non-escaping blocks. For example, in the following code, we should not disable tail-call optimization for the block that is directly passed to function "noescapefunc":

  void foo3(void);
  
  void foo1() {
    noescapefunc(^{ foo3(); }); // do not disable tail-call.
    BlockTy b = ^{ foo3(); }; // disable tail-call.
    noescapefunc(b);
  }

Ideally, I think we want to avoid disabling tail-call optimization for block "b" too, as it doesn't escape. However, this patch doesn't do anything to avoid disabling tail-call optimization for the block, since that would require a more complex analysis.

rdar://problem/35758207


https://reviews.llvm.org/D43841

Files:
  include/clang/AST/DeclObjC.h
  include/clang/AST/Type.h
  include/clang/Driver/Options.td
  include/clang/Frontend/CodeGenOptions.def
  lib/AST/DeclObjC.cpp
  lib/AST/Type.cpp
  lib/CodeGen/CGCall.cpp
  lib/CodeGen/CodeGenFunction.h
  lib/CodeGen/CodeGenModule.h
  lib/Driver/ToolChains/Clang.cpp
  lib/Frontend/CompilerInvocation.cpp
  test/CodeGenObjC/disable-tail-call-escaping-block.m
  test/Driver/fdisable-tail-calls-escaping-blocks.c

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