Re: [patch 2/2,avr] PR49847: Add hook to place read-only lookup-tables in named address-space

[Denis Chertykov <chertykov at gmail dot com>]

2017-07-27 16:50 GMT+04:00 Georg-Johann Lay <avr@gjlay.de>:
> On 27.07.2017 14:29, Georg-Johann Lay wrote:
>>
>> For some targets, the best place to put read-only lookup tables as
>> generated by -ftree-switch-conversion is not the generic address space
>> but some target specific address space.
>>
>> This is the case for AVR, where for most devices .rodata must be
>> located in RAM.
>>
>> Part #1 adds a new, optional target hook that queries the back-end
>> about the desired address space.  There is currently only one user:
>> tree-switch-conversion.c::build_one_array() which re-builds value_type
>> and array_type if the address space returned by the backend is not
>> the generic one.
>>
>> Part #2 is the AVR part that implements the new hook and adds some
>> sugar around it.
>
>
> This is the AVR part.
>
> It implements the new hook which returns a convenient flash address
> space for devices where .rodata is located in RAM:  The 16-bit __flash
> for devices with <= 64 KiB flash and 24-bit __memx for > 64 KiB flash.
>
> It adds a new option -madd-space-for-lookup= which allows to pick a
> specific address space.
>
> Some new insns and combine-split suport best code generation by the
> knowledge that the 24-bit addresses will never point to RAM so that
> the expensive decision-at-runtime whether LD or LPM has to be used
> can be avoided.
>
> Passed without new regressions on atmega128.
>
> Ok for trunk provided the gcc part 1/2 is approved?

It's cool. Thank you.
Please apply.


>
> Johann
>
>
>         Implement TARGET_ADDR_SPACE_FOR_ARTIFICIAL_RODATA.
>
>         PR target/49857
>         * config/avr/avr-opts.h: New file.
>         * config/avr/avr.opt: Include it.
>         (-maddr-space-for-lookup=): New option and...
>         (avr_opt_addr_space_for_lookup): ...associated Var.
>         (avr_aspace_for_lookup): New option enums used by above.
>         * config/avr/avr-protos.h (avr_out_load_flashx): New proto.
>         * config/avr/avr.c (avr_out_load_flashx): New function.
>         * avr_adjust_insn_length [ADJUST_LEN_LOAD_FLASHX]: Handle it.
>         * avr_rtx_costs_1 [ZERO_EXTEND, SIGN_EXTEND]: Handle
>         shift-and-extend-by-1 of HI -> PSI.
>         [ASHIFT,PSImode]: Describe cost of extend-and-shift-by-1.
>         (TARGET_ADDR_SPACE_FOR_ARTIFICIAL_RODATA): Define to...
>         (avr_addr_space_for_artificial_rodata): ...this new static function.
>         * config/avr/avr.md (unspec): Add UNSPEC_LOAD_FLASHX.
>         (adjust_len): Add load_flashx.
>         (*ashiftpsi.1_sign_extend.hi, *ashiftpsi.1_zero_extend.hi)
>         (*extendpsi.ashift.1.uqi, *load<mode>-flashx): New insns.
>         (*split_xload<mode>-cswtch): New insn-and-split.
>         * doc/invoke.texi (AVR Options) <-maddr-space-for-lookup=>:
> Document.
>