[PATCH] Improves __ieee754_exp() performance by greater than 5x on sparc/x86.

[Joseph Myers]

On Fri, 20 Oct 2017, Szabolcs Nagy wrote:

> decimal floats are not even required to be correctly rounded by
> the compiler in iso c, they are only faithfully rounded, so
> this is a portability bug in the original source too, you can
> silently get completely wrong code generation because of it.

GCC 4.9 (the minimum version for building glibc) and later correctly round 
decimal floating-point constants for binary formats (see GCC bug 21718).  
Before that we did at least once have an issue with a decimal constant 
where someone had computed a value exactly half way between two 
representable values and different compilers rounded it differently 
(glibc bug 14803).

-- 
Joseph S. Myers
joseph@codesourcery.com