RFR: JDK-8314056 Remove runtime platform check from frem/drem [v3]

[Jatin Bhateja]

On Wed, 23 Aug 2023 23:17:00 GMT, Scott Gibbons <sgibbons at openjdk.org> wrote:

>> Remove platform check and move code to stubGenerator.  This fix increases performance by ~4.5%.
>> 
>> UPDATE: Subsequent commits increase performance gain to ~2x for AVX2, with no significant change to AVX512.
>> 
>> Tested tier1.
>
> Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:
> 
>   mxcsr fix; address review comments

Changes looks good to me, you may also include the results of following benchmark.
./test/micro/org/openjdk/bench/vm/compiler/pea/Blender.java

src/hotspot/cpu/x86/stubGenerator_x86_64_fmod.cpp line 473:

> 471:     __ ucomisd(xmm0, xmm1);
> 472:     __ movapd(xmm4, xmm0);
> 473:     __ jccb(Assembler::aboveEqual, L_117f);

This is a bounded label jump, Assembler::jcc should automatically optimize it with short jump encoding, but its not a blocker.

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PR Review: https://git.openjdk.org/jdk/pull/15210#pullrequestreview-1600272296
PR Review Comment: https://git.openjdk.org/jdk/pull/15210#discussion_r1308729157