RFR: 8304293: RISC-V: JDK-8276799 missed atomic intrinsic support for C1

[Feilong Jiang]

On Thu, 16 Mar 2023 09:35:10 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> The following intrinsics in C1 are controlled by supports_atomic_xxx, but they are not set properly on RISC-V:
>> - _getAndAddInt
>> - _getAndAddLong
>> - _getAndSetInt
>> - _getAndSetLong
>> - _getAndSetReference
>> 
>> RISC-V provides a set of atomic instructions [1], these intrinsics could be enabled by default.
>> 
>> Here is the HIR output of C1:
>> 
>> before:
>> 
>> 
>> B18 (V) [189, 196] -> B20 pred: B8 B17 
>> empty stack
>> inlining depth 0
>> __bci__use__tid____instr____________________________________
>>   0    0    a251   <instance 0x00000040a802fb98 klass=jdk/internal/misc/Unsafe>
>>   3    0    a252   null   
>>   4    0    l254   274954985816L
>>   7    0    l255   1L
>> . 8    0    l256   a251.invokespecial(a252, l254, l255)
>>                    jdk/internal/misc/Unsafe.getAndAddLong(Ljava/lang/Object;JJ)J
>> . 193  0    l258   a42._24 := l256 (J) tid
>> . 196  0     259   goto B20
>> 
>> 
>> after:
>> 
>> 
>> B18 (V) [189, 196] -> B20 pred: B8 B17 
>> empty stack
>> inlining depth 0
>> __bci__use__tid____instr____________________________________
>>   0    0    a251   <instance 0x00000040a802fb98 klass=jdk/internal/misc/Unsafe>
>>   3    0    a252   null   
>>   4    0    l254   274954985816L
>>   7    0    l255   1L
>> . 8    0    l256   UnsafeGetAndSet (add)(a252, l254, value l255)
>> . 193  0    l258   a42._24 := l256 (J) tid
>> . 196  0     259   goto B20
>> 
>> 
>> 1. https://github.com/riscv/riscv-isa-manual/blob/8b9047d8d20ef548f7996efee1550760d7bc1279/src/a.tex#L416-L422
>> 
>> Testing:
>> 
>> - [x] `hotspot_tier1` & `jdk_tier1` on Unmatched board (release build)
>
> Looks good. Thanks for finding this.

@RealFYang @yhzhu20 -- Thanks!

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PR: https://git.openjdk.org/jdk/pull/13053