llvm-project/clang
Reid Kleckner 092d065265 Don't assume cleanup emission preserves dominance in expr evaluation
Summary:
Because of the existence branches out of GNU statement expressions, it
is possible that emitting cleanups for a full expression may cause the
new insertion point to not be dominated by the result of the inner
expression. Consider this example:

  struct Foo { Foo(); ~Foo(); int x; };
  int g(Foo, int);
  int f(bool cond) {
    int n = g(Foo(), ({ if (cond) return 0; 42; }));
    return n;
  }

Before this change, result of the call to 'g' did not dominate its use
in the store to 'n'. The early return exit from the statement expression
branches to a shared cleanup block, which ends in a switch between the
fallthrough destination (the assignment to 'n') or the function exit
block.

This change solves the problem by spilling and reloading expression
evaluation results when any of the active cleanups have branches.

I audited the other call sites of enterFullExpression, and they don't
appear to keep and Values live across the site of the cleanup, except in
ARC code. I wasn't able to create a test case for ARC that exhibits this
problem, though.

Reviewers: rjmccall, rsmith

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D30590

llvm-svn: 297084
2017-03-06 22:18:34 +00:00
..
INPUTS
bindings [libclang] [OpenCL] Expose half type. 2017-02-10 15:51:11 +00:00
cmake [CMake] Add Fuchsia toolchain CMake cache files 2017-02-17 19:28:54 +00:00
docs Add examples to clang-format configuration 2017-03-06 16:35:28 +00:00
examples Add LLVMOption to clang-interpreter, corresponding to r291938. 2017-01-14 08:54:05 +00:00
include [MS] Add support for __ud2 and __int2c MSVC intrinsics 2017-03-06 19:43:16 +00:00
lib Don't assume cleanup emission preserves dominance in expr evaluation 2017-03-06 22:18:34 +00:00
runtime [sanitizer] Passthrough CMAKE_OSX_DEPLOYMENT_TARGET and CMAKE_OSX_SYSROOT when building compiler-rt from clang/runtime/CMakeLists.txt 2016-12-15 23:20:54 +00:00
test Don't assume cleanup emission preserves dominance in expr evaluation 2017-03-06 22:18:34 +00:00
tools [scan-build-py] create decorator for compiler wrapper methods 2017-03-04 01:08:05 +00:00
unittests [clang-format] Add tests for ambiguous namespaces to the comment fixer 2017-03-06 17:29:25 +00:00
utils Improve workaround for Sphinx's lack of support for command line options containing '+', '.' etc. to be more stable as the set of options changes. 2017-01-27 01:54:42 +00:00
www Update cxx_dr_status page. 2017-02-25 23:54:18 +00:00
.arcconfig Upgrade all the .arcconfigs to https. 2016-07-14 13:15:37 +00:00
.clang-format
.clang-tidy
.gitignore
CMakeLists.txt clang/CMakeLists.txt: Rework r294954 -- use file(TO_CMAKE_PATH). 2017-02-19 03:17:31 +00:00
CODE_OWNERS.TXT
INSTALL.txt
LICENSE.TXT
ModuleInfo.txt
NOTES.txt
README.txt

README.txt

//===----------------------------------------------------------------------===//
// C Language Family Front-end
//===----------------------------------------------------------------------===//

Welcome to Clang.  This is a compiler front-end for the C family of languages
(C, C++, Objective-C, and Objective-C++) which is built as part of the LLVM
compiler infrastructure project.

Unlike many other compiler frontends, Clang is useful for a number of things
beyond just compiling code: we intend for Clang to be host to a number of
different source-level tools.  One example of this is the Clang Static Analyzer.

If you're interested in more (including how to build Clang) it is best to read
the relevant web sites.  Here are some pointers:

Information on Clang:              http://clang.llvm.org/
Building and using Clang:          http://clang.llvm.org/get_started.html
Clang Static Analyzer:             http://clang-analyzer.llvm.org/
Information on the LLVM project:   http://llvm.org/

If you have questions or comments about Clang, a great place to discuss them is
on the Clang development mailing list:
  http://lists.llvm.org/mailman/listinfo/cfe-dev

If you find a bug in Clang, please file it in the LLVM bug tracker:
  http://llvm.org/bugs/