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Deprecate nwfpe emulation?


From: Richard Henderson
Subject: Deprecate nwfpe emulation?
Date: Mon, 27 Jan 2025 13:02:56 -0800
User-agent: Mozilla Thunderbird

On 1/27/25 09:46, Peter Maydell wrote:
On Mon, 27 Jan 2025 at 17:27, Philippe Mathieu-Daudé <philmd@linaro.org> wrote:
On 27/1/25 12:27, Peter Maydell wrote:
We have one test case in check-tcg which purports to be checking
iwMMXt. In fact it is doing no such thing: it runs the test without
selecting an iwMMXt CPU, which means the iwMMXt insns are interpreted
as FPA11 insns by the linux-user emulate_arm_fpa11() code. So the test
prints garbage and then succeeds anyway.

Uh...

It had me confused for a while, because I'd convinced myself
by code inspection that we only enabled iwMMXt if you
manually asked for a pxa2xx CPU and not in the default 'max'
CPU, and then I found this test case that we were running
with the default CPU type and which was apparently passing :-)

Any chance we can deprecate the fpa11 stuff too?

I see it's still enabled by the kernel for some boards,
but it depends on really old configury:

config FPE_NWFPE
        bool "NWFPE math emulation"
        depends on (!AEABI || OABI_COMPAT) && !THUMB2_KERNEL
        help
          Say Y to include the NWFPE floating point emulator in the kernel.
          This is necessary to run most binaries. Linux does not currently
          support floating point hardware so you need to say Y here even if
          your machine has an FPA or floating point co-processor podule.

No thumb2, no eabi, and oabi_compat enabled.
I suspect that's a very rare configuration these days.

I'll note the help message is somewhat dated.  :-)


r~



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