RFR 8078563 - add profitability tests for reductions

Berg, Michael C michael.c.berg at intel.com
Wed Apr 29 17:23:55 UTC 2015

Christian, do you have any additional comments or does the code look ok?


From: Christian Thalinger [mailto:christian.thalinger at oracle.com]
Sent: Monday, April 27, 2015 9:49 AM
To: Berg, Michael C
Cc: hotspot-compiler-dev at openjdk.java.net
Subject: Re: RFR 8078563 - add profitability tests for reductions

+       // Length 2 reductions of INT/LONG do not offer performance benefits

+       if (((arith_type->basic_type() == T_INT) || (arith_type->basic_type() == T_LONG)) && (size == 2)) {

I don’t know that code very well but can there be reductions with size == 1?

On Apr 23, 2015, at 5:53 PM, Berg, Michael C <michael.c.berg at intel.com<mailto:michael.c.berg at intel.com>> wrote:

Hi Folks,

We (Intel) would like to add profitability tests to superword to gate scenarios where reduction optimization overhead is roughly equal to the benefit gained by vectorization.
We would like to do this for all x86 enabled microarchitectures that support reductions and superword.  This new constraint was tested on SSE and AVX (1,2) enabled platforms.
The contribution as referenced by RFR 8078563 is defined by the information at the links below.

Please review this bug entry and its code and comment as needed:


And its code and test addition (this is a small patch):


Vladimir Koslov has offered to sponsor this patch.


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