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Re: [patch,avr] make progmem work on AVR_TINY, use TARGET_ADDR_SPACE_DIAGNOSE_USAGE


2016-07-15 18:26 GMT+03:00 Georg-Johann Lay <avr@gjlay.de>:
> This patch needs new hook TARGET_ADDR_SPACE_DIAGNOSE_USAGE:
> https://gcc.gnu.org/ml/gcc-patches/2016-07/msg00839.html
>
> This patch turns attribute progmem into a working feature for AVR_TINY
> cores.
>
> It boils down to adding 0x4000 to all symbols with progmem:  Flash memory
> can be seen in the RAM address space starting at 0x4000, i.e. data in flash
> can be read by means of LD instruction if we add offsets of 0x4000.  There
> is no need for special access macros like pgm_read_* or special address
> spaces as there is nothing like a LPM instruction.
>
> This is simply achieved by setting a respective symbol_ref_flag, and when
> such a symbol has to be printed, then plus_constant with 0x4000 is used.
>
> Diagnosing of unsupported address spaces is now performed by
> TARGET_ADDR_SPACE_DIAGNOSE_USAGE which has exact location information.
> Hence there is no need to scan all decls for invalid address spaces.
>
> For AVR_TINY, alls address spaces have been disabled.  They are of no use.
> Supporting __flash would just make the backend more complicated without any
> gains.
>
>
> Ok for trunk?
>
> Johann
>
>
> gcc/
>         * doc/extend.texi (AVR Variable Attributes) [progmem]: Add
>         documentation how it works on reduced Tiny cores.
>         (AVR Named Address Spaces): No support for reduced Tiny.
>         * avr-protos.h (avr_addr_space_supported_p): New prototype.
>         * avr.c (AVR_SYMBOL_FLAG_TINY_PM): New macro.
>         (avr_address_tiny_pm_p): New static function.
>         (avr_print_operand_address) [AVR_TINY]: Add AVR_TINY_PM_OFFSET
>         if the address is in progmem.
>         (avr_assemble_integer): Same.
>         (avr_encode_section_info) [AVR_TINY]: Set AVR_SYMBOL_FLAG_TINY_PM
>         for symbol_ref in progmem.
>         (TARGET_ADDR_SPACE_DIAGNOSE_USAGE): New hook define...
>         (avr_addr_space_diagnose_usage): ...and implementation.
>         (avr_addr_space_supported_p): New function.
>         (avr_nonconst_pointer_addrspace, avr_pgm_check_var_decl): Only
>         report bad address space usage if that space is supported.
>         (avr_insert_attributes): Same.  No more complain about unsupported
>         address spaces.
>         * avr.h (AVR_TINY_PM_OFFSET): New macro.
>         * avr-c.c (tm_p.h): Include it.
>         (avr_cpu_cpp_builtins) [__AVR_TINY_PM_BASE_ADDRESS__]: Use
>         AVR_TINY_PM_OFFSET instead of magic 0x4000 when built-in def'ing.
>         Only define addr-space related built-in macro if
>         avr_addr_space_supported_p.
> gcc/testsuite/
>         * gcc.target/avr/torture/tiny-progmem.c: New test.
>

Approved.


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