RFR: 8283232: x86: Improve vector broadcast operations [v12]

[Jatin Bhateja]

On Fri, 29 Jul 2022 07:51:04 GMT, Jatin Bhateja <jbhateja at openjdk.org> wrote:

>> Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   unnecessary TEMP dst
>
> src/hotspot/share/opto/machnode.cpp line 478:
> 
>> 476:   // Stretching lots of inputs - don't do it.
>> 477:   // A MachContant has the last input being the constant base
>> 478:   if (req() > (is_MachConstant() ? 3U : 2U)) {
> 
> Earlier some of the nodes like add/sub/mul/divF_imm which were carrying 3 inputs were not getting cloned, now with change we may see them getting rematerialized before uses which may increase code size but of course it will reduced interferences. With earlier cap of 2 only Replicates were passing this check.

Saving a spill at the cost of re-materialization using a comparatively cheaper instruction like add/sub/mul looks better for divD may be costly.

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PR: https://git.openjdk.org/jdk/pull/7832