Re: fuse-caller-save - hook format

[Tom de Vries <Tom_deVries at mentor dot com>]

On 22-04-14 17:27, Richard Sandiford wrote:
> Tom de Vries <Tom_deVries@mentor.com> writes:
> > 2. post_expand_call_insn.
> > A utility hook to facilitate adding the clobbers to CALL_INSN_FUNCTION_USAGE.
>
> Why is this needed though?  Like I say, I think targets should update
> CALL_INSN_FUNCTION_USAGE when emitting calls as part of the call expander.
> Splitting the functionality of the call expanders across the define_expand
> and a new hook just makes things unnecessarily complicated IMO.

Richard,

It is not needed, but it is convenient.

There are targets where the define_expands for calls use the rtl template. 
Having to add clobbers to the CALL_INSN_FUNCTION_USAGE for such a target means 
you cannot use the rtl template any more and instead need to generate all needed 
RTL insns in C code.

This hook means that you can keep using the rtl template, which is less 
intrusive for those targets.

Thanks,
- Tom

> Thanks,
> Richard