RFR(S):8211251:Default mask register for avx512 instructions

[Viswanathan, Sandhya]

Hi Vladimir,

As you know the PostLoopMultiversioning needs to be fully redesigned and is currently disabled. 
That particular code should only be exercised when PostLoopMultiversioning is on.
I could change it with an assert statement if that looks ok to you.

Please let me know.

Best Regards,
Sandhya


-----Original Message-----
From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com] 
Sent: Thursday, September 27, 2018 3:24 PM
To: Viswanathan, Sandhya <sandhya.viswanathan at intel.com>; hotspot compiler <hotspot-compiler-dev at openjdk.java.net>
Subject: Re: RFR(S):8211251:Default mask register for avx512 instructions

Looks good except PostLoopMultiversioning flag guarded changes in macroAssembler_x86.cpp which 
should be explained too.

Thanks,
Vladimir

On 9/27/18 2:37 PM, Viswanathan, Sandhya wrote:
> Please find below a patch which cleans up K1 mask register handling for AVX 512 instructions.
> 
> Currently unmasked instructions are encoded using k1 register which requires k1 register to be 
> initialized properly and also reinitialized across JNI and Runtime calls.
> 
> This patch encodes AVX 512 instructions as unmasked instruction with K0 encoding where the explicit 
> mask register is not specified.
> 
> RFE: https://bugs.openjdk.java.net/browse/JDK-8211251
> 
> Webrev: http://cr.openjdk.java.net/~vdeshpande/k_register/webrev.00/ 
> <http://cr.openjdk.java.net/%7Evdeshpande/k_register/webrev.00/>
> 
> Best Regards,
> 
> Sandhya
>