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Re: Register allocation issues
On 9/6/07, David Edelsohn <dje@watson.ibm.com> wrote:
> >>>>> Matt Lee writes:
>
> Matt> The problem is, that though the loads can be optimized by pipelining
> Matt> them. The register allocator has created a dependency by using only r3
> Matt> and r4, instead of using the other volatiles.
>
> GCC's register allocator currently is designed to minimize the
> number of hard registers. As Ian mentioned, -frename-registers tries to
> perform register renaming with available registers after register
> allocation. As they say, "Your Mileage May Vary".
>
There is no point trying to minimize usage of volatile hard registers,
is there? They are precisely there to be used up as much as needed.
The function is a leaf procedure as well, so there are no other
considerations. Lastly, architectures like PPC do make use of more
registers (without -frename-registers), so there has to be something
in the PPC back-end that allows for the liberal use or in mine that
prevents such.
--
thanks,
Matt