RFR(L): 8081247 AVX 512 extended support code review request

Berg, Michael C michael.c.berg at intel.com
Fri Jun 5 04:46:07 UTC 2015

Vladimir please find the following webrev with the suggested changes, I have added small signature functions which look like the old versions  in the assembler but manage the problem I need to handle, which is additional state for legacy only instructions. There is a new vm_version function which handles the cpuid checks with a conglomerate approach for the one scenario which had it.
The loop in the stub generator is now formed to alter the upper bound and execute in one path.



-----Original Message-----
From: Vladimir Kozlov [mailto:vladimir.kozlov at oracle.com] 
Sent: Wednesday, June 03, 2015 6:10 PM
To: Berg, Michael C; 'hotspot-compiler-dev at openjdk.java.net'
Subject: Re: RFR(L): 8081247 AVX 512 extended support code review request

Hi, Michael


I don't like that you replaced prefix method with few parameters with method which has a lot of them:

-  int encode = vex_prefix_0F38_and_encode_q(dst, src1, src2);
+  int encode = vex_prefix_and_encode(dst->encoding(), src1->encoding(),
+                                     VEX_SIMD_NONE, VEX_OPCODE_0F_38,
true, AVX_128bit,
+                                     true, false);

Why you did that?


Can we set different loop limit based on UseAVX instead of having 2 loops.


Instead of long condition expressions like next:

UseAVX > 0 && !VM_Version::supports_avx512vl() &&

May be have one VM_Version finction which does these checks.


On 6/2/15 9:38 PM, Berg, Michael C wrote:
> Hi Folks,
> I would like to contribute more AVX512 enabling to facilitate support 
> for machines which utilize EVEX encoding. I need two reviewers to 
> review this patch and comment as needed:
> Bug-id: https://bugs.openjdk.java.net/browse/JDK-8081247
> webrev:
> http://cr.openjdk.java.net/~mcberg/8081247/webrev.01/
> This patch enables BMI code on EVEX targets, improves replication 
> patterns to be more efficient on both EVEX enabled and legacy targets, 
> adds more CPUID based rules for correct code generation on various 
> EVEX enabled servers, extends more call save/restore functionality and 
> extends the vector space further for SIMD operations.  Please expedite 
> this review as there is a near term need for the support.
> Also, as I am not yet a committer, this code needs a sponsor as well.
> Thanks,
> Michael

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