RFR: 8279508: Auto-vectorize Math.round API [v15]

[Jatin Bhateja]

On Sun, 13 Mar 2022 00:06:07 GMT, Quan Anh Mai <duke at openjdk.java.net> wrote:

>> src/hotspot/cpu/x86/c2_MacroAssembler_x86.cpp line 4161:
>> 
>>> 4159:   movl(scratch, 1056964608);
>>> 4160:   movq(xtmp1, scratch);
>>> 4161:   vbroadcastss(xtmp1, xtmp1, vec_enc);
>> 
>> An `evpbroadcastd` would reduce this by one instruction I guess?
>
> Anyway an `evpbroadcastd xmm, r` has around 5 latency on the gpr so I think you could just put the constant in the constant table and use `vbroadcastsd`

It was done to save redundant floating point to integer domain switch over penalties.

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PR: https://git.openjdk.java.net/jdk/pull/7094