[llvm-dev] preserve registers across function call

[Xiaochu Liu via llvm-dev]

Thank you so much, Marcello!

Regards,
Xiaochu


On Wed, Aug 26, 2015 at 9:51 PM Marcello Maggioni <mmaggioni at apple.com>
wrote:

> Yes, RegMask is what you should use for the CallPreservedMask.
> It means that the registers set as 1 are preserved from the Call (the
> callee saved) and the ones marked as 0 need to be saved instead.
>
> Cheers,
> Marcello
>
> On 26 Aug 2015, at 18:51, Xiaochu Liu <xiaochu1122 at gmail.com> wrote:
>
> Hi Marcello,
>
> Thanks for your reply. I will try to pass down the mask!
> I have one more question. In my backend I return CSR_RegMask in
> getCallPreservedMask and return CSR_SaveList in getCalleeSavedRegs. Is
> that a correct setup? I dumped the regmask and found that callee saved regs
> are marked 1 and non-callee saved regs are 0.
>
> Thanks,
> Xiaochu
>
>
>
> On Wed, Aug 26, 2015 at 5:58 PM Marcello Maggioni <mmaggioni at apple.com>
> wrote:
>
>> Is the preserved mask passed down to your Call instruction in LowerCall ?
>>
>> Marcello
>>
>> On 26 Aug 2015, at 17:52, Xiaochu Liu via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>>
>> Dear there,
>>
>> I was wondering how to preserve registers (caller saved) across calls. I
>> implemented getCalleeSavedRegs and getCallPreservedMask. But the
>> non-callee-saved registers are still not saved by caller. I want to spill
>> these registers in use on stack right before the call. From my
>> understanding, the register allocator in llvm will do the spill and
>> restoring automatically? Is there anything I was supposed to do to make it
>> happen?
>>
>> Thanks,
>> Xiaochu
>>
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