llvm dev - Aug 2015 - preserve registers across function call

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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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
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
>
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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
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
>
>
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>
>
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