Did this functionality land before the 6.0 branch, that is, should we copy the release notes to the branch?
Thanks Hans On Tue, Jan 9, 2018 at 12:37 AM, Erich Keane via Phabricator <revi...@reviews.llvm.org> wrote: > This revision was automatically updated to reflect the committed changes. > Closed by commit rC322043: Document attribute target multiversioning. > (authored by erichkeane, committed by ). > > Changed prior to commit: > https://reviews.llvm.org/D41837?vs=128982&id=128995#toc > > Repository: > rC Clang > > https://reviews.llvm.org/D41837 > > Files: > docs/ReleaseNotes.rst > include/clang/Basic/AttrDocs.td > > > Index: docs/ReleaseNotes.rst > =================================================================== > --- docs/ReleaseNotes.rst > +++ docs/ReleaseNotes.rst > @@ -80,6 +80,12 @@ > Attribute Changes in Clang > -------------------------- > > +- Clang now supports function multiversioning with attribute 'target' on ELF > + based x86/x86-64 environments by using indirect functions. This > implementation > + has a few minor limitations over the GCC implementation for the sake of AST > + sanity, however it is otherwise compatible with existing code using this > + feature for GCC. Consult the documentation for the target attribute for > more > + information. > - ... > > Windows Support > Index: include/clang/Basic/AttrDocs.td > =================================================================== > --- include/clang/Basic/AttrDocs.td > +++ include/clang/Basic/AttrDocs.td > @@ -1474,6 +1474,24 @@ > Example "subtarget features" from the x86 backend include: "mmx", "sse", > "sse4.2", > "avx", "xop" and largely correspond to the machine specific options handled > by > the front end. > + > +Additionally, this attribute supports function multiversioning for ELF based > +x86/x86-64 targets, which can be used to create multiple implementations of > the > +same function that will be resolved at runtime based on the priority of their > +``target`` attribute strings. A function is considered a multiversioned > function > +if either two declarations of the function have different ``target`` > attribute > + strings, or if it has a ``target`` attribute string of ``default``. For > + example: > + > + .. code-block:: c++ > + __attribute__((target("arch=atom"))) > + void foo() {} // will be called on 'atom' processors. > + __attribute__((target("default"))) > + void foo() {} // will be called on any other processors. > + > +All multiversioned functions must contain a ``default`` (fallback) > +implementation, otherwise usages of the function are considered invalid. > +Additionally, a function may not become multiversioned after its first use. > }]; > } > > > _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
