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From: Richard Allen <rsaxvc@rsaxvc.net>
To: newlib@sourceware.org
Subject: Re: [PATCH] Avoid extra float->double conversion
Date: Fri, 21 Apr 2017 13:30:00 -0000	[thread overview]
Message-ID: <CAMY0PLVybxoyVwUdsA4zzN1cpffDLBeNKXDAr=pnDTicXpuG0A@mail.gmail.com> (raw)
In-Reply-To: <10ded3d6-37d2-9b85-48f6-501254eaf7fe@LGSInnovations.com>

> And just wondering, did you check all of the "f" functions?  (I'd guess so
> since your 0/0 patch edits multiple files, but better to know for sure.)
> It would not be at all surprising if others (or even all) of the f forms had
> the same flaw.

Several of the "f" functions do similar things, mostly compares, but a few
arithmetic operations. This patch lets my particular project remove rint() at
link time. There will be a few more patches for those. There's also a few spots
where some operations are duplicated in if/elses, not sure if I'll go
after those.
Eventually, I'd like to get mathfp back up and running, but that's going to be a
much larger effort.

> This is better than the first one, with the catch on the constants. Have you
> checked what was linked to be certain that no other double things are still
> there?  (Perhaps easier than inspecting the source.)

The only float->double and double->float conversions remaining
are in the error handling when moving to/from exc.retval, exc.arg1, and
exc.arg2.

> To be the most gung-ho, isnan() should be isnanf() throughout--saves a
> conversion and might avoid a double function being linked.  (It seems odd
> that it does have isfinitef(), but not isnanf().)

In C99, isnan() became template-ey, and acts like a macro. newlib
implements it with __builtin_isnan(), which GCC inlines. Calling
isnanf() results in a function call, so I didn't change those.

-Richard

  reply	other threads:[~2017-04-21 13:30 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-19 23:53 Richard Allen
2017-04-20  0:03 ` Richard Allen
2017-04-20  0:36   ` Craig Howland
2017-04-21 13:30     ` Richard Allen [this message]
2017-05-18 23:58       ` Richard Allen

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