std.math.exponential: Disable use of fyl2x and fyl2xp1 intrinsics on dmd/macOS port

[ibuclaw]

After some probing, looks like Apple M1 emulation of x86 instructions is bugged. Nothing we can do besides opening a ticket with Apple, so disabling use fyl2xp1 intrinsics on the target.

[dlang-bot]

Thanks for your pull request, @ibuclaw!

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Testing this PR locally

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dub run digger -- build "stable + phobos#8705"

[ibuclaw]

log1p(0x1p-16382): expected: 0x1p-16382 | got: 0x0p+0
****** FAIL release64 std.math.exponential
core.exception.AssertError@std/math/exponential.d(3765): Assertion failure
----------------

[ibuclaw]

The fyl2x{p1} instruction that dmd makes use of appears to have problems when emulated on macOS 13's version of Rosetta.

fabs(0x1p-16382) = 3.3621e-4932
fabs(0x1p-16382) <= 0.25 = true
yl2xp1(0x1p-16382) = 0x0p+0

Not a lot we can do other than disable it, and file a bug report against Apple, which they'll probably just ignore.

[WalterBright]

If you file a bug report with Apple, please include a link to it in the code. And mebbe a link to this PR in the code, too, so there's more of an explanation.

[ibuclaw]

If you file a bug report with Apple, please include a link to it in the code. And mebbe a link to this PR in the code, too, so there's more of an explanation.

I don't recall the site where dev issues are tracked, there was one raised for the ctor/dtor regression too.

[maxhaton]

There basically isn't a (public) bug tracker for apple things as far as I can tell.

[ibuclaw]

There basically isn't a (public) bug tracker for apple things as far as I can tell.

Radar was the tracker. I did have a url to the site at one point, but can't find it anymore. I'm pretty sure I previously linked to it for the macOS crt dtor bug either here or bugzilla.

[maxhaton]

Are you thinking of https://openradar.appspot.com/page/1 ?

[ibuclaw]

Are you thinking of https://openradar.appspot.com/page/1 ?

Aha, yes.

https://openradar.appspot.com/FB9733712

Issue still ignored after 2 years :-(

[maxhaton]

Note:

Reports posted here will not necessarily be seen by Apple. All problems should be submitted at bugreport.apple.com before they are posted here. Please only post information for Radars that you have filed yourself, and please do not include Apple confidential information in your posts. Thank you!

(Openradar is for telling people bug reports you have filed with apple, I think, apple don't maintain it although they'd be stupid to not look at it)