https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117860
--- Comment #5 from GCC 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:b3cb0c3302a7c16e661a08c15c897c8f7bbb5d23 commit r15-5950-gb3cb0c3302a7c16e661a08c15c897c8f7bbb5d23 Author: Uros Bizjak <ubiz...@gmail.com> Date: Thu Dec 5 17:02:46 2024 +0100 i386: Fix addcarry/subborrow issues [PR117860] Fix several things to enable combine to handle addcarry/subborrow patterns: - Fix wrong canonical form of addcarry<mode> insn and friends. For commutative operand (PLUS RTX) binary operand (LTU) takes precedence before unary operand (ZERO_EXTEND). - Swap operands of GTU comparison to canonicalize addcarry/subborrow comparison. Again, the canonical form of the compare is PLUS RTX before ZERO_EXTEND RTX. GTU comparison is not a carry flag comparison, so we have to swap operands in x86_canonicalize_comparison to a non-canonical form to use LTU comparison. - Return correct compare mode (CCCmode) for addcarry/subborrow pattern from ix86_cc_mode, so combine is able to emit required compare mode for combined insn. - Add *subborrow<mode>_1 pattern having const_scalar_int_operand predicate. Here, canonicalization of SUB (op1, const) RTX to PLUS (op1, -const) requires negation of constant operand when ckecking operands. With the above changes, combine is able to create *addcarry_1/*subborrow_1 pattern with immediate operand for the testcase in the PR: SomeAddFunc: addq %rcx, %rsi # 10 [c=4 l=3] adddi3_cc_overflow_1/0 movq %rdi, %rax # 33 [c=4 l=3] *movdi_internal/3 adcq $5, %rdx # 19 [c=4 l=4] *addcarrydi_1/0 movq %rsi, (%rdi) # 23 [c=4 l=3] *movdi_internal/5 movq %rdx, 8(%rdi) # 24 [c=4 l=4] *movdi_internal/5 setc %dl # 39 [c=4 l=3] *setcc_qi movzbl %dl, %edx # 40 [c=4 l=3] zero_extendqidi2/0 movq %rdx, 16(%rdi) # 26 [c=4 l=4] *movdi_internal/5 ret # 43 [c=0 l=1] simple_return_internal SomeSubFunc: subq %rcx, %rsi # 10 [c=4 l=3] *subdi_3/0 movq %rdi, %rax # 42 [c=4 l=3] *movdi_internal/3 sbbq $17, %rdx # 19 [c=4 l=4] *subborrowdi_1/0 movq %rsi, (%rdi) # 33 [c=4 l=3] *movdi_internal/5 sbbq %rcx, %rcx # 29 [c=8 l=3] *x86_movdicc_0_m1_neg movq %rdx, 8(%rdi) # 34 [c=4 l=4] *movdi_internal/5 movq %rcx, 16(%rdi) # 35 [c=4 l=4] *movdi_internal/5 ret # 51 [c=0 l=1] simple_return_internal PR target/117860 gcc/ChangeLog: * config/i386/i386.cc (ix86_canonicalize_comparison): Swap operands of GTU comparison to canonicalize addcarry/subborrow comparison. (ix86_cc_mode): Return CCCmode for the comparison of addcarry/subborrow pattern. * config/i386/i386.md (addcarry<mode>): Swap operands of PLUS RTX to make it canonical. (*addcarry<mode>_1): Ditto. (addcarry peephole2s): Update RTXes for addcarry<mode>_1 change. (*add<dwi>3_doubleword_cc_overflow_1): Ditto. (*subborrow<mode>_1): New insn pattern. gcc/testsuite/ChangeLog: * gcc.target/i386/pr117860.c: New test.
