forked from OSchip/llvm-project
d889d1efef
Add support for continuously syncing profile counter updates to a file. The motivation for this is that programs do not always exit cleanly. On iOS, for example, programs are usually killed via a signal from the OS. Running atexit() handlers after catching a signal is unreliable, so some method for progressively writing out profile data is necessary. The approach taken here is to mmap() the `__llvm_prf_cnts` section onto a raw profile. To do this, the linker must page-align the counter and data sections, and the runtime must ensure that counters are mapped to a page-aligned offset within a raw profile. Continuous mode is (for the moment) incompatible with the online merging mode. This limitation is lifted in https://reviews.llvm.org/D69586. Continuous mode is also (for the moment) incompatible with value profiling, as I'm not sure whether there is interest in this and the implementation may be tricky. As I have not been able to test extensively on non-Darwin platforms, only Darwin support is included for the moment. However, continuous mode may "just work" without modification on Linux and some UNIX-likes. AIUI the default value for the GNU linker's `--section-alignment` flag is set to the page size on many systems. This appears to be true for LLD as well, as its `no_nmagic` option is on by default. Continuous mode will not "just work" on Fuchsia or Windows, as it's not possible to mmap() a section on these platforms. There is a proposal to add a layer of indirection to the profile instrumentation to support these platforms. rdar://54210980 Differential Revision: https://reviews.llvm.org/D68351 |
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| cmake | ||
| docs | ||
| include | ||
| lib | ||
| test | ||
| tools | ||
| unittests | ||
| utils | ||
| www | ||
| .arcconfig | ||
| .gitignore | ||
| CMakeLists.txt | ||
| CODE_OWNERS.TXT | ||
| CREDITS.TXT | ||
| LICENSE.TXT | ||
| README.txt | ||
README.txt
Compiler-RT ================================ This directory and its subdirectories contain source code for the compiler support routines. Compiler-RT is open source software. You may freely distribute it under the terms of the license agreement found in LICENSE.txt. ================================