Re: Add post_expand_call_insn hook

[Richard Henderson <rth at redhat dot com>]

On 04/29/2014 01:59 AM, Tom de Vries wrote:
> On 24-04-14 17:13, Eric Botcazou wrote:
>>> The hook is called right after expansion of calls, and allows a target to do
>>> additional processing, such as f.i. adding clobbers to
>>> CALL_INSN_FUNCTION_USAGE.
>>>
>>> Instead of using the hook, we could add code to the preparation statements
>>> operand of the different call expands, but that requires those expands not
>>> to use the rtl template, and generate all the rtl through c code. Which
>>> requires a rewrite of the call expands in case of Aarch64.
>>
>> If Aarch64 is the only problematic back-end, then it should be changed to do
>> what the other back-ends already do to use use_reg.  IMO adding such a bogus
>> hook should be the very last resort solution.
>>
> 
> Eric,
> 
> I've written this concept patch, which tries to address the same problem, but
> in a different (and I hope more generic) way.
> 
> It adds a post-emission C-code operand to define_expand.
> 
> As an example of how this could be useful, for the define_expand of call and
> call_value in the arm target, I'm using the new operand to do the post-emit
> call processing done currently in arm_emit_call_insn. This allows us to
> eliminate the call_internal and call_value_internal define_expands, and
> simplifies the call and call_value define_expands.


Is this patch really any better?  I can't see that it is myself.  It seems to
me that the existing mechanism to emit the call, then append to FUNCTION_USAGE
is perfectly clear.  This new argument to define_expand seems less clear.

What are you trying to fix, anyway?


r~