x86-64 stub calling convention

[Vladimir Kozlov]

Deneau, Tom wrote:
> I am trying to understand the stub setup on windows x64.
> (I have code that is working OK on linux x64).
> 
> Trying to understand the need for setup_arg_regs() and restore_arg_regs().
> It seems like these only needed if you use explicit register names
> in the interior of your stub routine, so you need to have the incoming args map
> the same way on windows and linux.
> 
> But if I have 4 or fewer incoming integer register arguments and I am willing to use c_arg0, c_arg1, etc,
> does that mean I can avoid these calls altogether?

Correct. You still can use explicit registers if they are never used for arguments.

Vladimir

> 
> -- Tom
> 
> 
> -----Original Message-----
> From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com] 
> Sent: Sunday, July 01, 2012 6:45 PM
> To: Deneau, Tom
> Cc: Krystal Mok; hotspot-compiler-dev at openjdk.java.net
> Subject: Re: x86-64 stub calling convention
> 
> It is only used in 32-bit VM to avoid additional code to handle x87 FPU stack around the call to a method which does not 
> use FPU. In 64-bit VM it is NOP. Look on mach nodes definitions for CallLeaf and CallLeafNoFP in .ad files. So in your 
> case you can set RC_NO_FP flag since you don't use FPU.
> 
> Vladimir
> 
> On 7/1/12 2:48 PM, Deneau, Tom wrote:
>> A related question...
>>
>> In what cases can the flag bit RC_NO_FP be set when used with make_runtime_call?
>> Can it be set when xmm registers are used, but they are only used for integer operations?
>>
>> -- Tom
>>
>>
>> -----Original Message-----
>> From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
>> Sent: Saturday, June 30, 2012 9:35 PM
>> To: Deneau, Tom
>> Cc: Krystal Mok; hotspot-compiler-dev at openjdk.java.net
>> Subject: Re: x86-64 stub calling convention
>>
>> Currently we use CallRuntime nodes for calling stubs and we use it for calls into runtime (C compiled code) that is why
>> it uses C calling convention. We have RFE to create special calling convention for stubs to pass arguments in registers
>> even in 32-bit VM but we never had time to do it.
>>
>> Vladimir
>>
>> On 6/30/12 7:08 PM, Deneau, Tom wrote:
>>> OK, thanks, Vladimir.
>>> Is there a good reason for using the OS's C calling convention for stubs?
>>> (as opposed to, say, using whatever makes the most sense for Java).
>>>
>>> -- Tom
>>>
>>>
>>> -----Original Message-----
>>> From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
>>> Sent: Friday, June 29, 2012 10:46 PM
>>> To: Krystal Mok
>>> Cc: Deneau, Tom; hotspot-compiler-dev at openjdk.java.net
>>> Subject: Re: x86-64 stub calling convention
>>>
>>> I was not right that you can use all XMM registers. On windows64 only xmm0-xmm5 are available free, the rest are SOE
>>> (save on entry). For stabs calls we use C calling convention. It is described in .ad file where XMM registers are
>>> defined (second parameter):
>>>
>>> // Linux ABI:   No register preserved across function calls
>>> //              XMM0-XMM7 might hold parameters
>>> // Windows ABI: XMM6-XMM15 preserved across function calls
>>> //              XMM0-XMM3 might hold parameters
>>>
>>> reg_def XMM5   (SOC, SOC, Op_RegF,  5, xmm5->as_VMReg());
>>> reg_def XMM5_H (SOC, SOC, Op_RegF,  5, xmm5->as_VMReg()->next());
>>>
>>> #ifdef _WIN64
>>>
>>> reg_def XMM6   (SOC, SOE, Op_RegF,  6, xmm6->as_VMReg());
>>> reg_def XMM6_H (SOC, SOE, Op_RegF,  6, xmm6->as_VMReg()->next());
>>> ...
>>>
>>> #else
>>>
>>> reg_def XMM6   (SOC, SOC, Op_RegF,  6, xmm6->as_VMReg());
>>> reg_def XMM6_H (SOC, SOC, Op_RegF,  6, xmm6->as_VMReg()->next());
>>>
>>> Vladimir
>>>
>>> On 6/29/12 7:25 PM, Krystal Mok wrote:
>>>> Hi Tom,
>>>>
>>>> This is something I'd like to get an answer to, too. I did see in a comment in one of the older changes [1][2] that:
>>>>
>>>> +       // Spill because stubs can use any register they like and it's
>>>> +       // easier to restore just those that we care about.
>>>>
>>>> Which doesn't really sound reassuring...
>>>>
>>>> - Kris
>>>>
>>>> [1]: http://hg.openjdk.java.net/hsx/hotspot-comp/hotspot/rev/28263a73ebfb
>>>> [2]: http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2011-May/005623.html
>>>>
>>>> On Sat, Jun 30, 2012 at 9:27 AM, Deneau, Tom<tom.deneau at amd.com<mailto:tom.deneau at amd.com>>   wrote:
>>>>
>>>>       Hi --
>>>>
>>>>       Can someone point me to the x86-64 calling convention for stubs created
>>>>       by stubGenerator?  In particular, which xmm registers if any must be preserved
>>>>       and which are volatile.
>>>>
>>>>       -- Tom Deneau
>>>>
>>>>
>>>
>>
> 
>