Re: [Gc] libatomic-ops nios2

On 2016/1/28 12:28 PM, Marek Vasut wrote:
>> You may want to go the direct kuser route. A little bit of inline asm
>> > should get you more performance compared to calling into libgcc, and
>> > nios2 softcores can really use that bit of optimization. That's also
>> > what I did in glibc.
> Aren't those gcc builtins expanded in place anyway ? Or do you see some
> real performance drop if you don't use the kuser helper directly ?

No, the GCC builtins are not expanded inline, the __sync_* routines are implemented in libgcc.

I have no evidence of significant performance gaps, though at least under PIC,
the nios2 function call overhead is a bit costly. However, my concerns may be unfounded.

> btw. I tried making two patches, one for libatomic-ops and one for bdwgc,
> find them below, but I have no clue if they are correct:

I'm not familiar with this code to review, but if there is a generic implementation
ready to use, then it should work for nios2. You can just start there.

Chung-Lin