RFR: 8374540: Add comment describing implementaiton choices of Math.fma [v2]

[Joe Darcy]

On Tue, 6 Jan 2026 07:29:30 GMT, Alan Bateman <alanb at openjdk.org> wrote:

> It will be used when in the interpreter too, which it think confuses people sometimes as they modify the Java code and see that the modified code executes.

FWIW, I've worked with the HotSpot team in years past and at least some of the java.lang.Math intrinsics are used under all VM compilation modes including the interpreter (if they are used at all on that platform, etc.). That is basically necessary for correctness of a method like Math.sin since the specification imposes consistency constraints on the return values of different calls to Math.sin. (In other words if there are two spec-compliant implementations of Math.sin, sampling between them won't necessarily yield a third spec compliant implementation.)

I'm not certain if use in the interpreter holds for Math.fma too, but I can update the comment to admit that possibility.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29044#discussion_r2665651877