Re: [PING^2][PATCH] -fuse-caller-save - Implement TARGET_FN_OTHER_HARD_REG_USAGE hook for MIPS

[Richard Sandiford <rdsandiford@googlemail.com>]

Tom de Vries <Tom_deVries@mentor.com> writes:
> On 25/12/13 14:02, Tom de Vries wrote:
>> On 07-12-13 16:07, Tom de Vries wrote:
>>> Richard,
>>>
>>> This patch implements the target hook TARGET_FN_OTHER_HARD_REG_USAGE (posted
>>> here: http://gcc.gnu.org/ml/gcc-patches/2013-03/msg01318.html) for MIPS, to
>>> address the issue that $6 is sometimes used in split calls.
>>>
>>> Build and reg-tested on MIPS.
>>>
>>> OK for stage1?
>>>
>> 
>
> Richard,
>
> Ping.
>
> This patch is the only part of -fuse-caller-save that still needs approval.

Hmm, where were parts 4 and 6 approved?  Was looking for the discussion
in the hope that it would answer the question I don't really understand,
which is: this hook is only used during final, is that right?  And the
clobber that you're adding is exposed at the rtl level.  So why do we
need the hook at all?  Why not just collect the usage information at
the end of final rather than at the beginning, so that all splits during
final have been done?  For other cases (where the usage isn't explicit
at the rtl level), why not record the usage in CALL_INSN_FUNCTION_USAGE
instead?

Thanks,
Richard