[PATCH, rs6000] power8 patches, patch #4 (revised), new power8 builtins
Segher Boessenkool
segher@kernel.crashing.org
Wed Jun 5 20:06:00 GMT 2013
> I also wonder whether it would be useful to have 32-bit do the
> vector logical
> ops in gprs as well. At the moment, the patches don't allow it
> (vector types
> must be done in the altivec/vsx registers, an TImode is done by
> splitting the
> operation into 4 separate categories). On the 64-bit side, having
> __int128_t
> passed in GPRs, means you want to avoid ping-ponging between the
> GPRs and VSX
> registers. In addition, the atomic quad word support (patch #7)
> has to run in
> GPRs, so we need add/subtract/logical to have versions that run in
> GPRs.
It might work better if you added a mode V1TI for TI in vector
regs, and then used plain TI only for GPRs. It certainly will
make things a lot more regular; whether it actually works better,
I have no idea.
The way you have things now, only after reload the vector patterns
are split to GPR patterns; much too late to do most optimisations
on it. On the other hand, deciding early what register set some
op should go to isn't too pleasant either; is it always the best
choice to use the vector regs when possible?
Segher
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