RFR: 8319429: Resetting MXCSR flags degrades ecore [v2]

[Jatin Bhateja]

On Mon, 6 Nov 2023 23:55:59 GMT, Volodymyr Paprotski <duke at openjdk.org> wrote:

>> Improves vector rounding on ECore about 10x
>> 
>> (BEFORE) FpRoundingBenchmark.test_round_float        2048  thrpt    3  40.912 ± 0.044  ops/ms
>> (AFTER ) FpRoundingBenchmark.test_round_float        2048  thrpt    3  431.682 ± 0.727  ops/ms
>
> Volodymyr Paprotski has updated the pull request incrementally with one additional commit since the last revision:
> 
>   move option to x86-specific section

src/hotspot/cpu/x86/vm_version_x86.cpp line 862:

> 860:   // Check if processor has Intel Ecore
> 861:   if (FLAG_IS_DEFAULT(DoEcoreOpt) && is_intel() && cpu_family() == 6 &&
> 862:     (_model == 0x97 || _model == 0xAC || _model == 0xAF)) {

Model 0x97 corresponds to ADL Hybrid Core converged ISA target where DoEcodeOpt enabling will depend on the core over which VM initialization thread executes.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16504#discussion_r1384290564