[Bug middle-end/91858] [9/10 Regression] Compile time hog w/ complex float trigonometric functions

[rguenther at suse dot de]

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

--- Comment #9 from rguenther at suse dot de <rguenther at suse dot de> ---
On Wed, 1 Apr 2020, vincent-gcc at vinc17 dot net wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91858
> 
> --- Comment #7 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
> (In reply to Richard Biener from comment #6)
> > I guess there's only one limb, the rest looks garbage.
> 
> Yes, and 11258999068426240000 with _mpfr_exp = 14 corresponds to 10000 as
> expected (11258999068426240000 = 10000*2^50).
> 
> And even when reusing the input
> 
>   mpc_init2 (x, 24);
>   mpc_set_ui_ui (x, 10000, 10000, MPC_RNDNN);
>   mpc_tan (x, x, 0);
> 
> the program terminates immediately.
> 
> I'm going to look at this more closely with gdb. But I confirm I can see
> mpc_tan in the backtrace.

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 ...).