RFR(M): 8181616: FMA Vectorization on x86

[Deshpande, Vivek R]

Hi Vladimir

Thanks for taking a look at the patch.
The FMA is introduced with Haswell microarchitecture along with AVX2. It is recommended to also check for AVX for using FMA instructions.

Regards,
Vivek
-----Original Message-----
From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com] 
Sent: Monday, June 5, 2017 4:53 PM
To: Deshpande, Vivek R; hotspot-compiler-dev at openjdk.java.net
Cc: Viswanathan, Sandhya
Subject: Re: RFR(M): 8181616: FMA Vectorization on x86

Thank you, Vivek

Why you restrict FMA to AVX?:

-  if (supports_fma() && UseSSE >= 2) {
+  if (supports_fma() && UseAVX > 0) {

Otherwise changes look good.

Thanks,
Vladimir

On 6/5/17 2:42 PM, Deshpande, Vivek R wrote:
> Hi All
>
>
>
> The enhancement generates Vector FMA instructions using SuperWord Analysis for X86.
>
> We observed upto 6x gain on Skylake and KNL using 512 bit Vector FMA instructions using FMA API operating on independent arrays.
>
> Webrev:
>
> http://cr.openjdk.java.net/~vdeshpande/8181616/webrev.00/
>
> I have also updated the JBS entry.
>
> https://bugs.openjdk.java.net/browse/JDK-8181616
>
> Would you please review and sponsor it.
>
>
>
> Regards,
>
> Vivek
>
>
>