lib/53027: macro renaming of functions discourages optimization

[coypu%sdf.org@localhost]

>Number:         53027
>Category:       lib
>Synopsis:       macro renaming of functions discourages optimization
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Feb 14 12:35:00 +0000 2018
>Originator:     coypu
>Release:        NetBSD 8.99.12
>Organization:
>Environment:
NetBSD planets 8.99.12 NetBSD 8.99.12 (GENERIC) #0: Thu Feb  8 00:38:03 IST 2018  fly@planets:/usr/src/sys/arch/amd64/compile/GENERIC amd64

>Description:
These two files generate different code in netbsd if compiled with:
gcc -O3 test.c -shared -fPIC

-----------------------------------------------------------------------
With header (#define isnan __isnan ..)
#include <math.h>
int dummy(float x) { return isnan(x); }

00000000000004ec <dummy>:
 4ec:	e9 0f ff ff ff       	jmpq   400 <__isnanf@plt>


-----------------------------------------------------------------------
Without the header

int dummy(float x) { return isnan(x); }

000000000000049c <dummy>:
 49c:	31 c0                	xor    %eax,%eax
 49e:	0f 2e c0             	ucomiss %xmm0,%xmm0
 4a1:	0f 9a c0             	setp   %al
 4a4:	c3                   	retq   

it is replaced by builtin.
>How-To-Repeat:

>Fix: