[PATCH v2] Enable inlining issignalingf within glibc

[Joseph Myers]

On Fri, 27 Sep 2019, Paul A. Clarke wrote:

> From: "Paul A. Clarke" <pc@us.ibm.com>
> 
> issignalingf is a very small function used in some areas where
> better performance (and smaller code) might be helpful.
> 
> Establish a means to inline issignalingf, and use that for powerpc.

Please don't add any math_private.h includes for optimizing function 
calls, or any optimized definitions of math.h functions that only live in 
math_private.h.  (Optimized definitions of functions that are only 
declared in math_private.h, such as __ieee754_* functions, are OK.)

See my commit c52944e8ccb15158b7e44cbb75fb46d81400d75c.  Where code uses 
anything from math_private.h, we want it to be something *only* in 
math_private.h, so that a build failure results if a math_private.h 
include is missing, rather than silently having less optimized code.

I.e. any such optimized inlines belong in include/math.h like the one for 
__isinff128 for GCC before GCC 7.

-- 
Joseph S. Myers
joseph@codesourcery.com