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/globals_x86.hpp line 218:

> 216:                                                                             \
> 217:   /* Autodetected, see vm_version_x86.cpp */                                \
> 218:   product(bool, DoEcoreOpt, false, DIAGNOSTIC,                              \

Change to name to DoEcoreOpt -> DoEcoreOpts or EnableX86ECoreOpts

src/hotspot/cpu/x86/x86.ad line 7443:

> 7441:   ins_encode %{
> 7442:     int vlen_enc = vector_length_encoding(this);
> 7443:     InternalAddress new_mxcsr = $constantaddress((jint)(DoEcoreOpt ? 0x3FBF : 0x3F80));

You can define a preprocessor macro for conditional selection pattern

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PR Review Comment: https://git.openjdk.org/jdk/pull/16504#discussion_r1384293766
PR Review Comment: https://git.openjdk.org/jdk/pull/16504#discussion_r1384292566