Am 03/03/2015 um 02:21 PM schrieb Senthil Kumar Selvaraj:
> On Mon, Mar 02, 2015 at 08:40:17PM +0100, Georg-Johann Lay wrote:
>> The new specs file generation introduces several problems.  This patch
>>
>> - Fix build warnings
>>
>> - Clean up unused code and the old, now dead specs definitions.
>>
>> - Removes unused files and adjust build scripts / rules.
>>
>> - Issues with avr-libc awareness:
>>
>> -- Makes specs-generation aware of avr-libc (include tm.h in build script
>> and depend on WITH_AVRLIBC).
>>
>> -- avr-libc implements functions in libm.a which usually live in libgcc,
>> hence add -lm to libgcc_spec, cf. PR54461.
>>
>> -- The new libdev.a is a feature of avr-libc and not available with, e.g.,
>> newlib.  Hence remove it from lib_spec if the compiler is not configured for
>> avr-libc (--with-avrlibc=no).
>>
>> - Many minor issues with option propagation.
>>
>> - -march had been added to multilib generation some time ago, but
>> driver_self_spec was not aware of that option.
>>
>>
>> Ok for trunk?
>>
>>
>> BTW, anyone knows what -march= is good for?  It allows all kinds of silly
>> option combinations like "-march=avrtiny -mmcu=atmega8" without any
>> complaints.
>
> IIRC, -march was added because replacing -mmcu=<device> to
> -mmcu=<arch> in the driver's self specs broke multilib selection - the
> driver always acted as if no -mmcu was specified. Adding

For me both multilib selection and multilib generation are working as expected 
with -mmcu= and without that -march=.

Attached is a 2nd part of improvements for the specs file generation:

- Remove -arch= and use -mmcu= again.

- Wrap specs file selection into a new specs function so that a comprehensible 
error message can be issued if no specs file is found.  It also informs about a 
link to spec file documentation of gcc inline docs.

- Remove genopt.sh and avr-tables.opt.  These files are no more used because 
-mmcu= is a vanilla string option now.  Using Enum option for -mmcu= does not 
allow to specify unknown devices, and target_handle_option cannot letgigimize 
unknown strings of Enum options.

- Resurrect driver-avr.c but with new content: The new specs function.

- New file specs.h with specs known to gcc and which can be overridden by 
avrlibc.h, rtems.h, etc.

- New device-specs files mostly repeat spec definitions, e.g.

     fprintf (f, "*startfile:\n\t%s\n\n", STARTFILE_SPEC);
     fprintf (f, "*endfile:\n\t%s\n\n", ENDFILE_SPEC);

- Device feature are expressed as subspecs now, e.g. avrlibc_startfile spec.

- Clean up code from "current device" stuff, adjust diagnostics, avr-arch.h, etc.

- Use INSTALL_DATA to install spec files, not INSTALL_PROGRAM.



Ok to install this, too?


Johann

	PR target/65296
	* config.gcc (extra_options) [avr]: Remove.
	(extra_gcc_objs) [avr]: Use driver-avr.o, avr-devices.o.
	(tm_file) [avr]: Add avr/specs.h after avr/avr.h.
	(tm_defines) [avr, rtems]: Add WITH_RTEMS.

	* config/avr/genmultilib.awk: Use -mmcu= instead of -march=.
	* config/avr/t-multilib: Regenerate.
	* config/avr/specs.h: New file.
	* config/avr/driver-avr.c: New file.
	* config/avr/genopt.sh: Remove file.
	* config/avr/avr-tables.opt: Remove file.
	* config/avr/predicates.md (avr_current_arch): Rename to avr_arch.
	* config/avr/avr-c.c: Same.
	* avr-arch.h: Same.
	(avr_current_device): Remove proto.
	* config/avr/avr.c (avr_current_arch): Rename to avr_arch.
	(avr_current_device): Remove definition and usage.
	(avr_set_core_architecture): New static function.
	(avr_option_override): Use it.
	* config/avr/avr.h (avr_current_arch): Rename to avr_arch.
	(AVR_HAVE_8BIT_SP): Don't depend on avr_current_device.
	(EXTRA_SPEC_FUNCTIONS): Define.
	(avr_devicespecs_file): New specs function proto.
	(DRIVER_SELF_SPECS): Use device-specs-file spec function.
	* config/avr/avr-devices.c (diagnostic.h, avr-arch.h): Include them.
	(mcu_name): New static array.
	(comparator, avr_archs_str, avr_mcus_str): New static functions.
	(avr_inform_devices, avr_inform_core_architectures): New functions.
	* config/avr/gen-avr-mmcu-specs.c (avr-arch.h, specs.h): Include.
	(avrlibc.h) [WITH_AVRLIBC]: Include.
	(../rtems.h, rtems.h) [WITH_RTEMS]: Include.
	(print_mcu): Rewrite from scratch.
	* config/avr/avrlibc.h (LIB_SPEC, LIBGCC_SPEC, STARTFILE_SPEC):
	Forward to avr-specific specs defined in device-specs file.
	* config/avr/avr.opt (config/avr/avr-arch.h): Remove include.
	(-mmcu=): Add Var and MissingArgError properties.
	(-march=): Remove.
	* config/avr/t-avr (driver-avr.o): New rule.
	(avr-devices.o): Depend on avr-arch.h.
	(avr-mcus): No more depend on avr-tables.opt.
	(avr-tables.opt): Remove rule.
	(install-device-specs): Use INSTALL_DATA, not INSTALL_PROGRAM.


> a new option (-march), translating mmcu=<device> to march=<arch> and then
> basing t-multilib on that worked ok.
>
>>
>> What's wrong with -mmcu=avr* ? All architecture names start with "avr", and
>> /no/ device name starts /with/ "avr", hence -mmcu= should be fine and work
>> as smooth as in the last 10 years.
>>
>> Why that -march= option?  If there is not a good reason for -march=, I'd
>> propose to clean it up and use -mmcu=avr* instead.
>>
>>
>> Johann