RFR(S): x86: 8190494: fix for different results with UseAVX=3 when calling AVX-512 native function via JNI.

[Deshpande, Vivek R]

Hi Vladimir

We need no_mask_reg set as true for  vector word instructions: pblendw, vphaddw, phaddw.
For rest of the instructions we don’t need to remove mask register encoding.

Regards,
Vivek

-----Original Message-----
From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com] 
Sent: Thursday, November 30, 2017 3:44 PM
To: Deshpande, Vivek R <vivek.r.deshpande at intel.com>; hotspot-compiler-dev at openjdk.java.net
Cc: Viswanathan, Sandhya <sandhya.viswanathan at intel.com>
Subject: Re: RFR(S): x86: 8190494: fix for different results with UseAVX=3 when calling AVX-512 native function via JNI.

On 11/30/17 2:51 PM, Deshpande, Vivek R wrote:
> HI Vladimir
> 
> We are removing the mask register encoding from the scalar instructions as it is not needed. The JIT is not doing any masked scalar operations.

Does it affect execution if we don't remove mask register encoding?

Thanks,
Vladimir

> 
> Regards,
> Vivek
> 
> -----Original Message-----
> From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com]
> Sent: Thursday, November 30, 2017 8:56 AM
> To: Deshpande, Vivek R <vivek.r.deshpande at intel.com>; 
> hotspot-compiler-dev at openjdk.java.net
> Cc: Viswanathan, Sandhya <sandhya.viswanathan at intel.com>
> Subject: Re: RFR(S): x86: 8190494: fix for different results with UseAVX=3 when calling AVX-512 native function via JNI.
> 
> Thank you, Vivek
> 
> Changes looks good based on your description.
> 
> Please, explain why using mask register in scalar instructions is bad.
> 
> I will start pre-integration testing and let you know results.
> 
> Thanks,
> Vladimir
> 
> On 11/30/17 7:28 AM, Deshpande, Vivek R wrote:
>> Hi
>>
>> I have bug fix for 8190494: Different results with UseAVX=3 when calling AVX-512 native function via JNI.
>>
>> Mask register not being reset after JNI and the scalar floating point 
>> instructions using the mask register encoding with AVX 512 in the assembler causing this problem.
>>
>> I have tested it with jtreg on hotspot/compiler and SPECjvm2008 on knights landing and skylake.
>>
>> Webrev:
>>
>> http://cr.openjdk.java.net/~vdeshpande/8190494/webrev.00/
>>
>> I have also updated the JBS entry.
>>
>> https://bugs.openjdk.java.net/browse/JDK-8190494
>>
>> Would you please review and sponsor it.
>>
>> Regards,
>>
>> Vivek
>>