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Re: [PATCH 1/8] Document signaling for min, max and ltgt operations


On Tue, Aug 20, 2019 at 05:19:46PM +0200, Ilya Leoshkevich wrote:
> > Am 20.08.2019 um 17:04 schrieb Segher Boessenkool <segher@kernel.crashing.org>:
> > The < and > operators separately already can cause exceptions, unless
> > you use -fno-trapping-math, in which case you cannot have LTGT at all.
> 
> Hmm, I've just tried compiling:
> 
>     int foo(float a, float b) { return ((a < b) || (a > b)); }
> 
> with -ftrapping-math and -fno-trapping-math with gcc 8.0.1, and got LTGT
> on tree and rtl levels in both cases:
> 
>     232t.optimized: _1 = a_2(D) <> b_3(D);
>     312r.final:        (if_then_else:SI (ltgt (reg:CCS 33 %cc)

Hrm, it seems to need -ffinite-math-only, even?  Or just -ffast-math
of course.  (That'll teach me to post without testing for another year
or two, sorry!)


Segher


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