RFR: 8323115: x86-32: Incorrect predicates for cmov instruct transforms with UseSSE

[Aleksey Shipilev]

On Mon, 8 Jan 2024 10:29:35 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> The fix looks good to me but it's concerning that we never hit this in testing. Maybe it never fails because the expanded instructions are guarded by `predicate (UseSSE ...` as well.

In my experience fixing bugs in these FPU-related match rules is that it takes a combination of code shape and relevant hardware (that defaults for unusual `UseSSE <= 2`), or specific testing that runs with lower `UseSSE`. I think I was one of the few remaining people who ran x86_32 with `-XX:UseSSE=0`, for example, but finally stopped. I think going forward we would just need to require `UseSSE >= 2` for x86_32, like for x86_64, making these issues go away.

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PR Comment: https://git.openjdk.org/jdk/pull/17296#issuecomment-1880883043