RFR: 8265491: Math Signum optimization for x86 [v2]

[Marcus G K Williams]

On Wed, 21 Apr 2021 16:47:20 GMT, Marcus G K Williams <github.com+168222+mgkwill at openjdk.org> wrote:

>> src/hotspot/cpu/x86/x86.ad line 5780:
>> 
>>> 5778: // --------------------------------- Signum ---------------------------
>>> 5779: 
>>> 5780: instruct signumF_reg(regF dst, regF zero, regF one, rFlagsReg cr) %{
>> 
>> Do we need `predicate(UseSSE>=2);` here?
>
> It seems ucomiss is SSE, but ucomisd is SSE2. I will add a SSE predicate to `instruct signumF_reg` and an SSE2 predicate to `instruct signumD_reg`. Thanks for the suggestion.

It looks like subss, subsd are also SSE, SSE2 respectively.

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PR: https://git.openjdk.java.net/jdk/pull/3581