On Wed, Sep 22, 2021 at 12:46 PM Christoph Müllner <cmuell...@gcc.gnu.org> wrote:
> Would it make sense to extend this proposal to include __strcmpeq() > and __strncmpeq()? > > Both are already available internally in GCC in form of > BUILT_IN_STRCMP_EQ and BUILT_IN_STRNCMP_EQ > (tree-ssa-strlen.c detects them in handle_builtin_string_cmp() and > builtins.c tries to inline them in expand_builtin_memcmp()). > However, they are currently restricted to cases where the length of > the string or the size of the array (of both arguments) is known. > > A use case for strcmpeq() would be the comparison of std::type_info > objects (equality and inequality operator) in libstdc++. > > I agree and am happy to implement them along side __memcmpeq() if the proposal is accepted. Do they need a seperate writeup with full specifications? > On Tue, Sep 21, 2021 at 9:54 PM Noah Goldstein via Gcc <gcc@gcc.gnu.org> > wrote: > > > > On Fri, Sep 17, 2021 at 9:27 AM Florian Weimer via Libc-alpha < > > libc-al...@sourceware.org> wrote: > > > > > * Joseph Myers: > > > > > > > I was supposing a build-time decision (using > > > GCC_GLIBC_VERSION_GTE_IFELSE > > > > to know if the glibc version on the target definitely has this > > > function). > > > > But if we add a header declaration, you could check for __memcmpeq > being > > > > declared (and so cover arbitrary C libraries, not just glibc, and > avoid > > > > issues of needing to disable this logic for freestanding > compilations, > > > > which would otherwise be an issue if a glibc-target toolchain is used > > > for > > > > a freestanding kernel compilation). The case of people calling > > > > __builtin_memcmp (or declaring memcmp themselves) without string.h > > > > included probably isn't one it's important to optimize. > > > > > > The header-less case looks relevant to C++ and other language front > > > ends, though. So a GCC_GLIBC_VERSION_GTE_IFELSE check could still make > > > sense for them. > > > > > > (Dropping libc-coord.) > > > > > > Thanks, > > > Florian > > > > > > > > What are we going with? > > > > Should I go forward with the proposal in GLIBC? > > > > If I should go forward with it should I include a def in string.h? >
