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

[Vladimir Kempik]

> 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}
>                                                                       ; - org.openjdk.bench.java.lang.jmh_generated.MathBench_unsignedMultiplyHighLongLo...

Vladimir Kempik has updated the pull request incrementally with one additional commit since the last revision:

  Fix nits

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/15558/files
  - new: https://git.openjdk.org/jdk/pull/15558/files/55f34287..1715f4f8

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15558&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15558&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/15558.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15558/head:pull/15558

PR: https://git.openjdk.org/jdk/pull/15558