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Re: -fuse-caller-save - Enable for MIPS


Tom de Vries <Tom_deVries@mentor.com> writes:
> On 27-04-14 12:27, Richard Sandiford wrote:
>> Tom de Vries <Tom_deVries@mentor.com> writes:
>>>   mips_emit_call_insn (rtx pattern, rtx orig_addr, rtx addr, bool lazy_p)
>>>   {
>>>     rtx insn, reg;
>>>
>>> -  insn = emit_call_insn (pattern);
>>> +  emit_call_insn (pattern);
>>> +  insn = last_call_insn ();
>>>
>>>     if (TARGET_MIPS16 && mips_use_pic_fn_addr_reg_p (orig_addr))
>>>       {
>>
>> This change isn't necessary; emit_call_insn is defined to return a CALL_INSN.
>>
>
> I dropped this change, as well as the change in the untyped_call expand, I 
> realized it's unnecessary.

Why was the untyped_call part unnecessary?

>> I'm a bit surprised that it doesn't work at -O1 for a simple test
>> like this though.  What goes wrong?
>>
>
> AFAIU now the problem is that the optimization doesn't trigger for -O0
> and -01, because the register allocator behaves more conservatively.

Hmm, is that just because -fcaller-saves is -O2 and above?  If so,
should -fuse-caller-save imply -fcaller-saves?

Thanks,
Richard


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