https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79173
--- Comment #20 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:43a3252c42af12ad90082e4088ea58eecd0bf582 commit r14-1837-g43a3252c42af12ad90082e4088ea58eecd0bf582 Author: Jakub Jelinek <ja...@redhat.com> Date: Thu Jun 15 09:12:40 2023 +0200 middle-end, i386: Pattern recognize add/subtract with carry [PR79173] The following patch introduces {add,sub}c5_optab and pattern recognizes various forms of add with carry and subtract with carry/borrow, see pr79173-{1,2,3,4,5,6}.c tests on what is matched. Primarily forms with 2 __builtin_add_overflow or __builtin_sub_overflow calls per limb (with just one for the least significant one), for add with carry even when it is hand written in C (for subtraction reassoc seems to change it too much so that the pattern recognition doesn't work). __builtin_{add,sub}_overflow are standardized in C23 under ckd_{add,sub} names, so it isn't any longer a GNU only extension. Note, clang has for these (IMHO badly designed) __builtin_{add,sub}c{b,s,,l,ll} builtins which don't add/subtract just a single bit of carry, but basically add 3 unsigned values or subtract 2 unsigned values from one, and result in carry out of 0, 1, or 2 because of that. If we wanted to introduce those for clang compatibility, we could and lower them early to just two __builtin_{add,sub}_overflow calls and let the pattern matching in this patch recognize it later. I've added expanders for this on ix86 and in addition to that added various peephole2s (in preparation patches for this patch) to make sure we get nice (and small) code for the common cases. I think there are other PRs which request that e.g. for the _{addcarry,subborrow}_u{32,64} intrinsics, which the patch also improves. Would be nice if support for these optabs was added to many other targets, arm/aarch64 and powerpc* certainly have such instructions, I'd expect in fact that most targets do. The _BitInt support I'm working on will also need this to emit reasonable code. 2023-06-15 Jakub Jelinek <ja...@redhat.com> PR middle-end/79173 * internal-fn.def (UADDC, USUBC): New internal functions. * internal-fn.cc (expand_UADDC, expand_USUBC): New functions. (commutative_ternary_fn_p): Return true also for IFN_UADDC. * optabs.def (uaddc5_optab, usubc5_optab): New optabs. * tree-ssa-math-opts.cc (uaddc_cast, uaddc_ne0, uaddc_is_cplxpart, match_uaddc_usubc): New functions. (math_opts_dom_walker::after_dom_children): Call match_uaddc_usubc for PLUS_EXPR, MINUS_EXPR, BIT_IOR_EXPR and BIT_XOR_EXPR unless other optimizations have been successful for those. * gimple-fold.cc (gimple_fold_call): Handle IFN_UADDC and IFN_USUBC. * fold-const-call.cc (fold_const_call): Likewise. * gimple-range-fold.cc (adjust_imagpart_expr): Likewise. * tree-ssa-dce.cc (eliminate_unnecessary_stmts): Likewise. * doc/md.texi (uaddc<mode>5, usubc<mode>5): Document new named patterns. * config/i386/i386.md (uaddc<mode>5, usubc<mode>5): New define_expand patterns. (*setcc_qi_addqi3_cconly_overflow_1_<mode>, *setccc): Split into NOTE_INSN_DELETED note rather than nop instruction. (*setcc_qi_negqi_ccc_1_<mode>, *setcc_qi_negqi_ccc_2_<mode>): Likewise. * gcc.target/i386/pr79173-1.c: New test. * gcc.target/i386/pr79173-2.c: New test. * gcc.target/i386/pr79173-3.c: New test. * gcc.target/i386/pr79173-4.c: New test. * gcc.target/i386/pr79173-5.c: New test. * gcc.target/i386/pr79173-6.c: New test. * gcc.target/i386/pr79173-7.c: New test. * gcc.target/i386/pr79173-8.c: New test. * gcc.target/i386/pr79173-9.c: New test. * gcc.target/i386/pr79173-10.c: New test.
