Re: [PATCH] Don't fold nextafter/nexttoward if -ftrapping-math or -fmath-errno if they produce denormal results (PR c/86420)

[Marc Glisse]

On Sat, 7 Jul 2018, Jakub Jelinek wrote:

2018-07-07  Jakub Jelinek  <ja...@redhat.com>
        PR c/86420
        * real.c (real_nextafter): Return true if result is denormal.

I have a question on the side: would it be hard / useful, in cases where 
nextafter may set errno or some exception flag, to fold the result to a 
constant while keeping the function call (ignoring the value it returns)? 
To clarify, I mean replace

_2 = nextafter(DBL_DENORM_MIN, 0);

with

nextafter(DBL_DENORM_MIN, 0);
_2 = 0;

I think we already do that for some other calls, although I can't remember 
where. The point would be that we have the value of _2 and can keep 
folding its uses.

--
Marc Glisse