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By querying previously-defined file-identifier macros, `host-config.h' is able to get information about its environment and, based on this information, select more appropriate function-specific ifunc selectors. This reduces the number of unnecessary feature tests that need to be carried out in order to find the best atomic implementation for a function at run-time. An immediate benefit of this is that we can further fine-tune the architectural requirements for each atomic function without risk of incurring the maintenance and runtime-performance penalties of having to maintain an ifunc selector with a huge number of alternatives, most of which are irrelevant for any particular function. Consequently, for AArch64 targets, we relax the architectural requirements of `compare_exchange_16', which now requires only LSE as opposed to the newer LSE2. The new flexibility provided by this approach also means that certain functions can now be called directly, doing away with ifunc selectors altogether when only a single implementation is available for it on a given target. As per the macro expansion framework laid out in `libatomic_i.h', such functions should have their names prefixed with `__atomic_' as opposed to `libat_'. This is the same prefix applied to function names when Libatomic is configured with `--disable-gnu-indirect-function'. To achieve this, these functions unconditionally apply the aliasing rule that at present is conditionally applied only when libatomic is built without ifunc support, which ensures that the default `libat_##NAME' is accessible via the equivalent `__atomic_##NAME' too. This is ensured by using the new `ENTRY_ALIASED' macro. Finally, this means we are able to do away with a whole set of function aliases that were needed until now, thus considerably cleaning up the implementation. libatomic/ChangeLog: * config/linux/aarch64/atomic_16.S: Remove unnecessary aliasing. (LSE): New. (ENTRY_ALIASED): Likewise. * config/linux/aarch64/host-config.h (LSE_ATOP): New. (LSE2_ATOP): Likewise. (LSE128_ATOP): Likewise. (IFUNC_COND_1): Make its definition conditional on above 3 macros. (IFUNC_NCOND): Likewise.
This directory contains the GNU Compiler Collection (GCC). The GNU Compiler Collection is free software. See the files whose names start with COPYING for copying permission. The manuals, and some of the runtime libraries, are under different terms; see the individual source files for details. The directory INSTALL contains copies of the installation information as HTML and plain text. The source of this information is gcc/doc/install.texi. The installation information includes details of what is included in the GCC sources and what files GCC installs. See the file gcc/doc/gcc.texi (together with other files that it includes) for usage and porting information. An online readable version of the manual is in the files gcc/doc/gcc.info*. See http://gcc.gnu.org/bugs/ for how to report bugs usefully. Copyright years on GCC source files may be listed using range notation, e.g., 1987-2012, indicating that every year in the range, inclusive, is a copyrightable year that could otherwise be listed individually.