https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78904
--- Comment #18 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Roger Sayle <sa...@gcc.gnu.org>: https://gcc.gnu.org/g:8f6c747c8638d4c3c47ba2d4c8be86909e183132 commit r14-2065-g8f6c747c8638d4c3c47ba2d4c8be86909e183132 Author: Roger Sayle <ro...@nextmovesoftware.com> Date: Sat Jun 24 23:05:25 2023 +0100 i386: Add alternate representation for {and,or,xor}b %ah,%dh. A patch that I'm working on to improve RTL simplifications in the middle-end results in the regression of pr78904-1b.c, due to changes in the canonical representation of high-byte (%ah, %bh, %ch, %dh) logic. See also PR target/78904. This patch avoids/prevents those failures by adding support for the alternate representation, duplicating the existing *<code>qi_ext<mode>_2 as *<code>qi_ext<mode>_3 (the new version also replacing any_or with any_logic to provide *andqi_ext<mode>_3 in the same pattern). Removing the original pattern isn't trivial, as it's generated by define_split, but this can be investigated after the other pieces are approved. The current representation of this instruction is: (set (zero_extract:DI (reg/v:DI 87 [ aD.2763 ]) (const_int 8 [0x8]) (const_int 8 [0x8])) (subreg:DI (xor:QI (subreg:QI (zero_extract:DI (reg:DI 94) (const_int 8 [0x8]) (const_int 8 [0x8])) 0) (subreg:QI (zero_extract:DI (reg/v:DI 87 [ aD.2763 ]) (const_int 8 [0x8]) (const_int 8 [0x8])) 0)) 0)) after my proposed middle-end improvement, we attempt to recognize: (set (zero_extract:DI (reg/v:DI 87 [ aD.2763 ]) (const_int 8 [0x8]) (const_int 8 [0x8])) (zero_extract:DI (xor:DI (reg:DI 94) (reg/v:DI 87 [ aD.2763 ])) (const_int 8 [0x8]) (const_int 8 [0x8]))) 2023-06-24 Roger Sayle <ro...@nextmovesoftware.com> gcc/ChangeLog * config/i386/i386.md (*<code>qi_ext<mode>_3): New define_insn.
