x86-64 stub calling convention

[Deneau, Tom]

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
>>
>>
>
>