https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79173
--- Comment #22 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:2b4e0415ad664cdb3ce87d1f7eee5ca26911a05b commit r14-1896-g2b4e0415ad664cdb3ce87d1f7eee5ca26911a05b Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Jun 16 19:47:28 2023 +0200 uiltins: Add support for clang compatible __builtin_{add,sub}c{,l,ll} [PR79173] While the design of these builtins in clang is questionable, rather than being say unsigned __builtin_addc (unsigned, unsigned, bool, bool *) so that it is clear they add two [0, 0xffffffff] range numbers plus one [0, 1] range carry in and give [0, 0xffffffff] range return plus [0, 1] range carry out, they actually instead add 3 [0, 0xffffffff] values together but the carry out isn't then the expected [0, 2] value because 0xffffffffULL + 0xffffffff + 0xffffffff is 0x2fffffffd, but just [0, 1] whether there was any overflow at all. It is something used in the wild and shorter to write than the corresponding #define __builtin_addc(a,b,carry_in,carry_out) \ ({ unsigned _s; \ unsigned _c1 = __builtin_uadd_overflow (a, b, &_s); \ unsigned _c2 = __builtin_uadd_overflow (_s, carry_in, &_s); \ *(carry_out) = (_c1 | _c2); \ _s; }) and so a canned builtin for something people could often use. It isn't that hard to maintain on the GCC side, as we just lower it to two .ADD_OVERFLOW calls early, and the already committed pottern recognization code can then make .UADDC/.USUBC calls out of that if the carry in is in [0, 1] range and the corresponding optab is supported by the target. 2023-06-16 Jakub Jelinek <ja...@redhat.com> PR middle-end/79173 * builtin-types.def (BT_FN_UINT_UINT_UINT_UINT_UINTPTR, BT_FN_ULONG_ULONG_ULONG_ULONG_ULONGPTR, BT_FN_ULONGLONG_ULONGLONG_ULONGLONG_ULONGLONG_ULONGLONGPTR): New types. * builtins.def (BUILT_IN_ADDC, BUILT_IN_ADDCL, BUILT_IN_ADDCLL, BUILT_IN_SUBC, BUILT_IN_SUBCL, BUILT_IN_SUBCLL): New builtins. * builtins.cc (fold_builtin_addc_subc): New function. (fold_builtin_varargs): Handle BUILT_IN_{ADD,SUB}C{,L,LL}. * doc/extend.texi (__builtin_addc, __builtin_subc): Document. * gcc.target/i386/pr79173-11.c: New test. * gcc.dg/builtin-addc-1.c: New test.
