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From: "vincent-gcc at vinc17 dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/91858] [9/10 Regression] Compile time hog w/ complex float trigonometric functions
Date: Wed, 01 Apr 2020 14:17:16 +0000	[thread overview]
Message-ID: <bug-91858-4-IZorWgFvB9@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-91858-4@http.gcc.gnu.org/bugzilla/>

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91858

--- Comment #10 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to rguenther@suse.de from comment #9)
> It's likely by us doing
> 
> mpfr_set_emin (-32990);
> mpfr_set_emax (32766);
> 
> during startup to work around a similar bug in MPC (IIRC it also
> was tan ...).

I suspect an internal overflow in the MPC computation, in which case doubling
the precision at each iteration won't solve the issue. Setting emax to 14425 or
below avoids the loop, but the real part of the result is slightly incorrect (0
instead of non-zero), though not affecting the binary32 exponent range, as this
value is tiny:

  1.0011111100101111e-28854

Changing the exponent range will solve the issue for some values, but I fear
that whatever the exponent range is chosen, there may remain values that will
trigger the bug.

Paul Zimmermann says that this bug is fixed in the MPC development version.

  parent reply	other threads:[~2020-04-01 14:17 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <bug-91858-4@http.gcc.gnu.org/bugzilla/>
2020-03-12 11:58 ` jakub at gcc dot gnu.org
2020-04-01 12:28 ` vincent-gcc at vinc17 dot net
2020-04-01 12:41 ` rguenth at gcc dot gnu.org
2020-04-01 13:17 ` vincent-gcc at vinc17 dot net
2020-04-01 13:33 ` vincent-gcc at vinc17 dot net
2020-04-01 13:38 ` rguenther at suse dot de
2020-04-01 14:17 ` vincent-gcc at vinc17 dot net [this message]
2020-04-01 14:33 ` vincent-gcc at vinc17 dot net
2020-04-01 15:53 ` vincent-gcc at vinc17 dot net
2020-04-03 12:23 ` rguenth at gcc dot gnu.org

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