Can GMP be replaced by trees?

[Tobias Schlüter]

Paul Brook wrote:
By changing the core GCC code (for anything more than +-*/) to use MPFR,
rather than going the other way, support for folding particular functions
is naturally shared by all languages supporting those functions - for
example, you get constant folding for most of the C99 <math.h> and
<complex.h> functions "for free" (as MPFR already implements computing
0.5ulp correctly rounded values for those functions).  (You also fix the
well-known problem that sqrtl can be folded with incorrect rounding on
systems with 106-bit long double.)  Contributions to MPFR to support
functions not already supported help more than just GCC.


This would be my preferred solution.

Tobi: The existing routines for real arithmetic are in real.{c,h}, and do not 
involve tree nodes. These would probably be useable as a replacement for GMP. 
However I think the best solution would be to convert everything to use MPFR 
as described above.

Ok, (I missed that gcc's real.[ch] don't operate on trees).

I openend PR 15515 which is meant to track any efforts in that 
direction. We can change this to a non-Fortran bug if people think that 
the benefit of this work is not specific to Fortran.

- Tobi