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  <roger@nextmovesoftware.com>

gcc/ChangeLog
	* config/i386/i386.md (*<code>qi_ext<mode>_3): New define_insn.

0 files changed, 0 insertions, 0 deletions