On Wed, Apr 14, 2021 at 01:47:04PM -0500, Segher Boessenkool wrote:
> A subreg:QI of the match_dup should match fine. You can use a subreg
> wherever GCC tries to match a reg.
>
> > match_dup means insn-recog.c calls rtx_equal_p and that returns false if the
> > mode is not the same.
>
> Yes, but they are the same :-)
In the end sure.
>
> (reg:SI whatever) and (subreg:QI (reg:SI whatever) 0)
The question is what to write in the splitter pattern so that
they would match.
[(set (match_operand:GPI 0 "register_operand")
(LOGICAL:GPI
(and:GPI (ashift:GPI (match_operator:GPI 4 "subreg_lowpart_operator"
[(match_operand 1 "register_operand")])
(match_operand:QI 2 "aarch64_shift_imm_<mode>"))
(match_operand:GPI 3 "const_int_operand"))
(zero_extend:GPI (match_dup 1))))]
provably doesn't (that is from the splitter I wrote for the non-hard regs),
nor
[(set (match_operand:GPI 0 "register_operand")
(LOGICAL:GPI
(and:GPI (ashift:GPI (match_operand:GPI 1 "register_operand")
(match_operand:QI 2 "aarch64_shift_imm_<mode>"))
(match_operand:GPI 3 "const_int_operand"))
(zero_extend:GPI (subreg (match_dup 1) 0))))]
works (and it is unclear how I'd find out the mode of the subreg even if it
worked).
Jakub
