https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98060
--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Uros Bizjak <u...@gcc.gnu.org>: https://gcc.gnu.org/g:c111f6066043d3b7bc4141ca0411eae9294aa6c5 commit r12-311-gc111f6066043d3b7bc4141ca0411eae9294aa6c5 Author: Uros Bizjak <ubiz...@gmail.com> Date: Fri Apr 30 10:15:26 2021 +0200 i386: Introduce reversed ADC and SBB patterns [PR98060] The compiler is able to merge LTU comparisons with PLUS or MINUS pattern to form addition with carry (ADC) and subtraction with borrow (SBB) instructions: op = op + carry [ADC $0, op] op = op - carry [SBB $0, op] The patch introduces reversed ADC and SBB insn patterns: op = op + !carry [SBB $-1, op] op = op - !carry [ADC $-1, op] allowing the compiler to also merge GEU comparisons. 2021-04-30 Uroš Bizjak <ubiz...@gmail.com> gcc/ PR target/98060 * config/i386/i386.md (*add<mode>3_carry_0r): New insn pattern. (*addsi3_carry_zext_0r): Ditto. (*sub<mode>3_carry_0): Ditto. (*subsi3_carry_zext_0r): Ditto. * config/i386/predicates.md (ix86_carry_flag_unset_operator): New predicate. * config/i386/i386.c (ix86_rtx_costs) <case PLUS, case MINUS>: Also consider ix86_carry_flag_unset_operator to calculate the cost of adc/sbb insn. gcc/testsuite/ PR target/98060 * gcc.target/i386/pr98060.c: New test.
