RFR: 8308340: C2: Idealize Fma nodes [v4]

[Richard Reingruber]

On Thu, 20 Jul 2023 09:34:27 GMT, Fei Gao <fgao at openjdk.org> wrote:

>> Thanks. How are `FmaV` nodes with mask handled then? Are they transformed into equivalent nodes without mask?
>
> Actually, there is no handling on `FmaV` nodes **with mask** in this patch, whether in the C2 mid-end or codegen backend. The gvn transformation just skips them. And I suppose `FmaV` nodes with mask can't be transformed into nodes **without mask**, except that C2 can guarantee that the mask is all true (this transformation has not been supported by current C2). Thanks.

I guess I would have to dig deeper into the vector api implementation to really understand how it works.
Thanks for your patience.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14576#discussion_r1269230335