RFR: 8325821: [REDO] use "dmb.ishst+dmb.ishld" for release barrier [v2]

[kuaiwei]

On Wed, 22 May 2024 10:25:55 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> kuaiwei has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Make MacroAssembler::merge more clear
>
> src/hotspot/cpu/aarch64/globals_aarch64.hpp line 127:
> 
>> 125:   product(ccstr, UseBranchProtection, "none",                           \
>> 126:           "Branch Protection to use: none, standard, pac-ret")          \
>> 127:   product(bool, AlwaysMergeDMB, true, DIAGNOSTIC,                      \
> 
> Suggestion:
> 
>   product(bool, AlwaysMergeDMB, true, DIAGNOSTIC,                       \

Fixed

> test/hotspot/gtest/aarch64/test_assembler_aarch64.cpp line 93:
> 
>> 91: }
>> 92: 
>> 93: TEST_VM(AssemblerAArch64, merge_dmb) {
> 
> Given the previous experience with barrier merges that prompted the backout, I would prefer to have a more comprehensive test here, maybe an additional one. I am thinking something like the exhaustive combination of 4 back-to-back barriers of each of 5 types. This gives us 5^4 = 625 test cases, which I think is still manageable.

Test is added as merge_dmb_all_kinds

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PR Review Comment: https://git.openjdk.org/jdk/pull/19278#discussion_r1611041488
PR Review Comment: https://git.openjdk.org/jdk/pull/19278#discussion_r1611040971