RFR: 8332533: RISC-V: Enable vector variable shift instructions for machines with RVV [v2]

[Hamlin Li]

On Tue, 21 May 2024 14:32:30 GMT, Gui Cao <gcao at openjdk.org> wrote:

>> Hi, I noticed the following warning in the Opto JIT Code for the Vector API in the `test/jdk/jdk/incubator/vector/Byte256VectorTests.java: ASHRByte256VectorTests` test:
>> 
>> --------------------------------------------------------------------------------
>>   ** Rejected vector op (RShiftVB,byte,32) because architecture does not support variable vector shifts
>>   ** not supported: arity=2 opc=405 vlen=32 etype=byte ismask=0 is_masked_op=0
>> ``` 
>> the reason is because Matcher::supports_vector_ variable_shifts returns false. the port of RISC-V Vector API now supports the vector shifts, so this should return with UseRVV.  By the Way, the Matcher::supports_vector_variable_shifts function was introduced by Vector API, and I think forgot to modify the Matcher::supports_vector_variable_shifts function when implementing vector shift.
>> After the fix, the test passes normally and generates the Opto JIT Code such as:
>> 
>> 1c2     loadV V1, [R7]  # vector (rvv)
>> 1ca     lwu  R28, [R28, #12]    # loadN, compressed ptr, #@loadN ! Field: jdk/internal/vm/vector/VectorSupport$VectorPayload.payload (constant)
>> 1ce     decode_heap_oop  R7, R28    #@decodeHeapOop
>> 1d2     addi  R7, R7, #16   # ptr, #@addP_reg_imm
>> 1d4     loadV V2, [R7]  # vector (rvv)
>> 1dc     vand_immI V1, V1, #7
>> 1e4     spill [sp, #48] -> R7    # spill size = 32
>> 1e6     # castII of R7, #@castII
>> 1e6     vasrB V3, V2, V1
>> 1fa     spill [sp, #96] -> R29   # spill size = 32
>> 1fc     bgeu  R7, R29, B101 #@cmpU_branch  P=0.000001 C=-1.000000
>> 
>> 
>> ### Testing:
>> qemu 8.1.50 with UseRVV:
>> - [x] Run tier1-3 tests (release)
>> - [x] Run test/jdk/jdk/incubator/vector (fastdebug)
>
> Gui Cao has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove constexpr in Matcher::supports_vector_variable_shifts

Thanks, still good.

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Marked as reviewed by mli (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19313#pullrequestreview-2068931037