RFR: 8287139: aarch64 intrinsic for unsignedMultiplyHigh

[Raffaello Giulietti]

On Mon, 23 May 2022 12:41:25 GMT, Nick Gasson <ngasson at openjdk.org> wrote:

>> Adds aarch64 intrinsic support for `Math.unsignedMultiplyHigh()`
>
> src/hotspot/cpu/aarch64/aarch64.ad line 11151:
> 
>> 11149: 
>> 11150:   ins_cost(INSN_COST * 7);
>> 11151:   format %{ "umulh   $dst, $src1, $src2, \t# umulhi" %}
> 
> There's an unnecessary trailing comma here and in the `smulh` pattern above.

I didn't run the benchmark.
Isn't a single instruction supposed to be faster anyway, as opposed to the java method?

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PR: https://git.openjdk.java.net/jdk/pull/8840