On Thursday 03 November 2016 06:19 PM, Georg-Johann Lay wrote:
> On 03.11.2016 08:58, Pitchumani Sivanupandi wrote:
>> Most of the AVR's 8k memorydevices have only rjmp instruction, not 
>> jmp. So, it
>> is important to wrap around jump destination to check if it can reach 
>> backwards.
>>
>> Currently link specs passes --pmem-wrap-around=xxK when mrelax and
>> mpmem-wrap-around options are enabled. Attached patch changes the 
>> specs so that
>> option --pmem-wrap-around=8K is passed for 8k memory devices if
>> -mno-pmem-wrap-around is not enabled.
>>
>> If OK, could someone commit please?
>>
>> Note: Currently 8k devices are identified based on name prefix. We 
>> are working
>> on alternative method to incorporate flash memory size.
>
> Currently, "at90usb8" this the only prefix that results in wrap_k = 8, 
> so without adding knowledge about flash sizes to the compiler, the 
> change makes not much sense... (but does not do harm either).
There are ~40 devices with 8K flash. Current checks are out-dated.
>
> The right place for flash size info would be avr-mcus.def together 
> with a new command option to specify the flash size and draw 
> conclusions from it.  When I asked Atmel about a mapping of Device to 
> flash size, the support told me to check the data sheets -- not really 
> practical for ~300 devices in avr-mcus.def :-)  Atmel *must* have 
> information about this...

I have updated patch to include the flash size as well. Took that info 
from device headers (it was fed into crt's device information note 
section also).
>
> The new option would render -mn-flash superfluous, but we should keep 
> it for backward compatibility.
Ok.
> Shouldn't link_pmem_wrap then be removed from link_relax, i.e. from 
> LINK_RELAX_SPEC?  And what happens if relaxation is off?
Yes. Removed link_pmem_wrap from link_relax.
Disabling relaxation doesn't change -mpmem-wrap-around behavior.

Now, wrap around behavior is changed as follows:

For 8K flash devices:
Device specs adds --pmem-wrap-around=8k linker option if 
-mno-pmem-wrap-around is NOT enabled.
It makes the --pmem-wrap-around=8k linker option default for 8k flash 
devices.

For 16/32/64K flash devices:
Spec string 'link_pmem_wrap' added to all 16/32/64k flash devices specs.
Other wise no changes i.e. It adds --pmem-wrap-around=16/32/64k option 
if -mpmem-wrap-around option is enabled.

For other devices, no changes in device specs.

Reg tested with default and -mrelax options enabled. No issues.

If OK, could someone commit please?

Regards,
Pitchumani


gcc/ChangeLog

2016-11-08  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

     * config/avr/avr-arch.h (avr_mcu_t): Add flash_size member.
     * config/avr/avr-devices.c(avr_mcu_types): Add flash size info.
     * config/avr/avr-mcu.def: Likewise.
     * config/avr/gen-avr-mmcu-specs.c (print_mcu): Remove hard-coded prefix
     check to find wrap-around value, instead use MCU flash size. For 8k 
flash
     devices, update link_pmem_wrap spec string to add 
--pmem-wrap-around=8k.
     * config/avr/specs.h: Remove link_pmem_wrap from LINK_RELAX_SPEC and
     add to linker specs (LINK_SPEC) directly.