[Mono-dev] How do I use scratch registers in op code implementation

[Rodrigo Kumpera]

You have to take it from the appropriate set (callee/caller) saved it
belongs to.
The regalloc ask the arch code for a mask of available registers so, for
example, pic code
can save a register for the GOT pointer.

On Tue, Aug 21, 2012 at 7:21 PM, Braddock Gaskill (Contractor) <
braddock.gaskill at apx-labs.com> wrote:

>  Hi Rodrigo,
>
> How do I take a general purpose register out of the available set for the
> register allocator?
>
> I see with xmm15 on amd64 that you cleared the corresponding bit in
> MONO_ARCH_CALLEE_FREGS.
>
> Can I just do the same with MONO_ARCH_CALLEE_REGS?  The allocator never
> touches callER saved regs?  (why not?)
>
> Thanks,
> Braddock
>
>
>  ------------------------------
> *From:* Rodrigo Kumpera [kumpera at gmail.com]
> *Sent:* Thursday, August 16, 2012 8:39 AM
> *To:* Braddock Gaskill (Contractor)
> *Cc:* mono-devel-list at lists.ximian.com
> *Subject:* Re: [Mono-dev] How do I use scratch registers in op code
> implementation
>
>  You can take a register out of the available set and the register
> allocator will never use it.
>
>  We do that with xmm reg 15 on amd64.
>
> On Thu, Aug 16, 2012 at 11:04 AM, Braddock Gaskill (Contractor) <
> braddock.gaskill at apx-labs.com> wrote:
>
>>  Hi folks,
>> We're working on the mono port to the Tilera TILE-Gx cpu.
>>
>> When implementing IR op codes in mono_arch_output_basic_block() we
>> sometimes need to use a scratch register.  For example, TILE-Gx has no
>> single membase + offset load instruction - we must do the address addition
>> as a separate step.
>>
>> How do we inform the runtime that we have/will clobber a register?  I
>> know that if we clobber a source register we can set the clob field in the
>> machine description file, but what if we use another register?  Is it
>> possible to reserve a register for this purpose?
>>
>> Thanks,
>> Braddock Gaskill
>>
>>
>> _______________________________________________
>> Mono-devel-list mailing list
>> Mono-devel-list at lists.ximian.com
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>>
>>
>
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