[newlib-cygwin] Fix rounding issues with sqrt/sqrtf

[newlib-cygwin] Fix rounding issues with sqrt/sqrtf

[Jeff Johnston]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=a9165ea07ce3a99bbfd294ada9c0fd54db738bb9

commit a9165ea07ce3a99bbfd294ada9c0fd54db738bb9
Author: Jeff Johnston <jjohnstn@redhat.com>
Date:   Fri Jun 4 14:36:38 2021 -0400

    Fix rounding issues with sqrt/sqrtf
    
    - compiler is sometimes optimizing out the rounding check in
      e_sqrt.c and ef_sqrt.c which uses two constants to create
      an inexact operation
    - there is a similar constant operation in s_tanh.c/sf_tanh.c
    - make the one and tiny constants volatile to stop this

Diff:
---
 newlib/libm/math/e_sqrt.c  | 4 ++--
 newlib/libm/math/ef_sqrt.c | 4 ++--
 newlib/libm/math/s_tanh.c  | 4 ++--
 newlib/libm/math/sf_tanh.c | 4 ++--
 4 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/newlib/libm/math/e_sqrt.c b/newlib/libm/math/e_sqrt.c
index 78fc52417..85dbdd1e7 100644
--- a/newlib/libm/math/e_sqrt.c
+++ b/newlib/libm/math/e_sqrt.c
@@ -86,9 +86,9 @@
 #ifndef _DOUBLE_IS_32BITS
 
 #ifdef __STDC__
-static	const double	one	= 1.0, tiny=1.0e-300;
+static	const volatile double	one	= 1.0, tiny=1.0e-300;
 #else
-static	double	one	= 1.0, tiny=1.0e-300;
+static	double	volatile one	= 1.0, tiny=1.0e-300;
 #endif
 
 #ifdef __STDC__
diff --git a/newlib/libm/math/ef_sqrt.c b/newlib/libm/math/ef_sqrt.c
index 80e7f360e..448e26e57 100644
--- a/newlib/libm/math/ef_sqrt.c
+++ b/newlib/libm/math/ef_sqrt.c
@@ -16,9 +16,9 @@
 #include "fdlibm.h"
 
 #ifdef __STDC__
-static	const float	one	= 1.0, tiny=1.0e-30;
+static	const volatile float	one	= 1.0, tiny=1.0e-30;
 #else
-static	float	one	= 1.0, tiny=1.0e-30;
+static	float	volatile one	= 1.0, tiny=1.0e-30;
 #endif
 
 #ifdef __STDC__
diff --git a/newlib/libm/math/s_tanh.c b/newlib/libm/math/s_tanh.c
index f7864306e..66018d7d0 100644
--- a/newlib/libm/math/s_tanh.c
+++ b/newlib/libm/math/s_tanh.c
@@ -73,9 +73,9 @@ PORTABILITY
 #ifndef _DOUBLE_IS_32BITS
 
 #ifdef __STDC__
-static const double one=1.0, two=2.0, tiny = 1.0e-300;
+static const volatile double one=1.0, two=2.0, tiny = 1.0e-300;
 #else
-static double one=1.0, two=2.0, tiny = 1.0e-300;
+static double volatile one=1.0, two=2.0, tiny = 1.0e-300;
 #endif
 
 #ifdef __STDC__
diff --git a/newlib/libm/math/sf_tanh.c b/newlib/libm/math/sf_tanh.c
index 1eb44a2ff..214bdb495 100644
--- a/newlib/libm/math/sf_tanh.c
+++ b/newlib/libm/math/sf_tanh.c
@@ -16,9 +16,9 @@
 #include "fdlibm.h"
 
 #ifdef __STDC__
-static const float one=1.0, two=2.0, tiny = 1.0e-30;
+static const volatile float one=1.0, two=2.0, tiny = 1.0e-30;
 #else
-static float one=1.0, two=2.0, tiny = 1.0e-30;
+static volatile float one=1.0, two=2.0, tiny = 1.0e-30;
 #endif
 
 #ifdef __STDC__