[Vm-dev] VM Maker: VMMaker.oscog-eem.1465.mcz

[Ryan Macnak]

Ah. In Dart, we let compiled code use the ABI registers and spill them at
runtime calls. Runtime calls are probably more frequent in Cog though, for
the interpreter/jit and stack page transitions.

On Thu, Sep 24, 2015 at 9:11 PM, Eliot Miranda <eliot.miranda at gmail.com>
wrote:

>
> Hi Ryan,
>
>     great question.  The answer is here:
>
> Name: VMMaker.oscog-eem.1466
> ...
> Revise upwards the max machine code size (for MoveRAw/AwR).
> Implement some of the calling convention machinery.
> Hence hit the first problem (in genPassReg:asArgument:).  The Cogit
> assumes the C argument registers are distinct from the other abstract
> registers, but on x64 these are rdi, rsi, rdx & rcx, all of which we like
> to use (for Arg1Reg, Arg0Reg, ReceiverResultReg & ClassReg respectively).
> So it's probably time to revise the abstract to concrete register mapping
> to avoid the conflict.  But I want to sleep on it first.
>
>
> So I have yet to dedicate the needle four argument registers to calls from
> machine code into the runtime.  Once this happens x64 should be down to 2
> scratch registers :-(.  I would love to be able to overlap the argument
> regs with allocate able registers but I've not written the necessary
> management code to flush allocated registers when runtime calls are made.
> I'm very open to suggestions here as losing those registers to runtime
> calls is a big hit.
>
> _,,,^..^,,,_ (phone)
>
> On Sep 24, 2015, at 7:34 PM, Ryan Macnak <rmacnak at gmail.com> wrote:
>
> Why does ARM get so many fewer scratch registers than X64? I would expect
> them only to differ by two (LR and PC).
>
> On Wed, Sep 23, 2015 at 11:08 AM, <commits at source.squeak.org> wrote:
>
>>
>> Eliot Miranda uploaded a new version of VMMaker to project VM Maker:
>> http://source.squeak.org/VMMaker/VMMaker.oscog-eem.1465.mcz
>>
>> ==================== Summary ====================
>>
>> Name: VMMaker.oscog-eem.1465
>> Author: eem
>> Time: 23 September 2015, 11:07:41.674 am
>> UUID: abda63f2-d72f-486d-8163-d23e6a7ebaeb
>> Ancestors: VMMaker.oscog-eem.1464
>>
>> Cogit:
>> Extend the abstract register scheme to include 8 scratch registers.
>> Allow ARMv6 use one, and x64 use 6.  Hence nuke the ill-thought-out
>> GPRegMax GPRegMin, and coincidentally, the unused MulCqR MulCwR MulRR.
>>
>> Add in-image compilation support for x64.
>
>
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