This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
Re: PATCH:[darwin] fix load of a misaligned double word
David Edelsohn <dje@watson.ibm.com> writes:
> >>>>> Geoff Keating writes:
>
> Geoff> Why would we want to discourage DFmode move operations that use GPRs?
>
> 1) Because an FP value is not very useful in a GPR
> 2) Symmetric with discouraging int in FPRs
> 3) Because of more limited addressing available
>
> What is the benefit of DFmode in GPRs other than conversion
> routines?
1. If the FP value is not useful, that's register allocation's job to
find this out by looking at the operations the value will be used
for.
2. Symmetric with discouraging int in FPRs: encourage float in GPRs.
3. It's reload's job to notice that there is more limited addressing,
and this is interfering with it.
4. It's faster to copy a value using GPRs than FPRs in many cases.
5. Better for values that change mode.
--
- Geoffrey Keating <geoffk@geoffk.org>