RFR: 8287139: aarch64 intrinsic for unsignedMultiplyHigh

[Nick Gasson]

On Mon, 23 May 2022 11:59:02 GMT, Raffaello Giulietti <duke at openjdk.java.net> wrote:

> Adds aarch64 intrinsic support for `Math.unsignedMultiplyHigh()`

Looks fine apart from the tiny cosmetic issue. Did you try the `MathBench.unsignedMultiplyHighLongLong` JMH benchmark introduced with the x86 implementation?

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.

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