[Patch,AVR]: PR49687 (better widening 32-bit mul)

Georg-Johann Lay avr@gjlay.de
Thu Jul 28 09:40:00 GMT 2011


Weddington, Eric wrote:
>> Subject: Re: [Patch,AVR]: PR49687 (better widening 32-bit mul)
>>
>>> I didn't review the asm code, but the rest of the patch look ok to me.
>>>
>>> r~
>> Thanks, Eric will review the asm part  :-)
> 
> LOL
> I trust you on the asm stuff. Ok by me.

Ok, I installed it.  Don't forget to rebuild *all* your libraries
including avr-libc after upgrading!

> However, how is our test coverage in this area?
> 
> Eric

As I wrote in the initial mail

http://gcc.gnu.org/ml/gcc-patches/2011-07/msg02113.html

> The patch passes without regressions, of course.
> 
> Moreover, I drove individual tests of the routines against the old implementation
> before integrating them into libgcc to run regression tests.

so I think there is reasonable test coverage.

libgcc.S already contained routines for widening multiply for the case when no
multiplier is available; these parts are dead code up to now; IMHO small devices
would benefit from supporting them in the compiler; in particular the two
16 = 8 * 8 cases.

I did not yet try to run the testsuite for a target without MUL, i.e. compile
for a target without MUL but simulate on ATmega128.

Did you ever run testsuite for a target without MUL?

Johann



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