RFR: 8315612: RISC-V: intrinsic for unsignedMultiplyHigh [v2]

[Vladimir Kempik]

On Tue, 5 Sep 2023 07:04:06 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

>> Hello
>> Please review this simple patch, it add c2 implementation of intrinsic for unsignedMultiplyHigh.
>> The generated code changes from:
>> 
>>             0x0000003fbcfb12f8:   mulh	t4,t2,t3
>>    2.99%    0x0000003fbcfb12fc:   srai	t5,t2,0x3f
>>             0x0000003fbcfb1300:   and	t5,t5,t3
>>             0x0000003fbcfb1304:   srai	t3,t3,0x3f
>>             0x0000003fbcfb1308:   and	t2,t3,t2
>>             0x0000003fbcfb130c:   add	t4,t4,t5
>>             0x0000003fbcfb130e:   add	t2,t2,t4                    ;*ladd {reexecute=0 rethrow=0 return_oop=0}
>> 
>> to
>> 
>>             0x0000003fdcfb6668:   mulhu	t2,t2,t3                    ;*invokestatic unsignedMultiplyHigh {reexecute=0 rethrow=0 return_oop=0}
>> 
>> 
>> Clear code size reduction and potentially some performance boost.
>> on hifive I can see the perf boost:
>> 
>> before:
>> MathBench.unsignedMultiplyHighLongLong       0  thrpt    8  67459.527 ± 10110.941  ops/ms
>> 
>> after:
>> MathBench.unsignedMultiplyHighLongLong       0  thrpt    8  86207.949 ± 8636.131  ops/ms
>> 
>> However on thead the jmh benchmark unsignedMultiplyHighLongLong  didn't show any difference as the hottest place is the fence ( getfield isDone ):
>> 
>>             0x0000003fdcfb6660:   ld	t3,64(t4)
>>             0x0000003fdcfb6664:   ld	t2,56(t4)
>>             0x0000003fdcfb6668:   mulhu	t2,t2,t3                    ;*invokestatic unsignedMultiplyHigh {reexecute=0 rethrow=0 return_oop=0}
>>                                                                       ; - org.openjdk.bench.java.lang.MathBench::unsignedMultiplyHighLongLong at 8 (line 545)
>>                                                                       ; - org.openjdk.bench.java.lang.jmh_generated.MathBench_unsignedMultiplyHighLongLong_jmhTest::unsignedMultiplyHighLongLong_thrpt_jmhStub at 17 (line 119)
>>    3.12%    0x0000003fdcfb666c:   lbu	t3,148(s3)                  ;*invokestatic consumeCompiler {reexecute=0 rethrow=0 return_oop=0}
>>                                                                       ; - org.openjdk.jmh.infra.Blackhole::consume at 7 (line 393)
>>                                                                       ; - org.openjdk.bench.java.lang.jmh_generated.MathBench_unsignedMultiplyHighLongLong_jmhTest::unsignedMultiplyHighLongLong_thrpt_jmhStub at 20 (line 119)
>>             0x0000003fdcfb6670:   fence	ir,iorw                     ;*getfield isDone {reexecute=0 rethrow=0 return_oop=0}
>>                                                                       ; - or...
>
> Vladimir Kempik has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix nits

yes, -prof perfasm option to jmh

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PR Comment: https://git.openjdk.org/jdk/pull/15558#issuecomment-1792149606