The variable 'bigendian' denotes whether the sign bit is in the first or
second 64-bit word of the 'long double'. But in the usual case (namely,
when not cross-compiling), the 'signbit' module already has determined at
configure time the location of the sign bit. With this knowledge, it is
possible to optimize the code somewhat.
2023-10-04 Bruno Haible <br...@clisp.org>
totalorderl: Optimize.
* modules/totalorderl (Files): Add m4/signbit.m4.
* m4/totalorder.m4 (gl_FUNC_TOTALORDERL): Invoke
gl_LONG_DOUBLE_SIGN_LOCATION.
* lib/totalorderl.c (totalorderl): If LDBL_SIGNBIT_WORD is known,
use it, so that 'bigendian' becomes a constant.
diff --git a/lib/totalorderl.c b/lib/totalorderl.c
index 84fed3c4d1..cf7da088ac 100644
--- a/lib/totalorderl.c
+++ b/lib/totalorderl.c
@@ -73,8 +73,14 @@ totalorderl (long double const *x, long double const *y)
/* Determine in which of the two 'unsigned long long' words the sign bit
is located. */
+ bool bigendian;
+#if defined LDBL_SIGNBIT_WORD
+ /* We have already determined the sign bit location at configure time. */
+ bigendian = (LDBL_SIGNBIT_WORD < 2);
+#else
zu.f = -zu.f;
- bool bigendian = !!zu.i[0];
+ bigendian = !!zu.i[0];
+#endif
unsigned long long
xhi = xu.i[!bigendian] ^ extended_sign,
diff --git a/m4/totalorder.m4 b/m4/totalorder.m4
index 0bbd252675..95aab65f19 100644
--- a/m4/totalorder.m4
+++ b/m4/totalorder.m4
@@ -81,6 +81,9 @@ AC_DEFUN([gl_FUNC_TOTALORDERL]
else
REPLACE_TOTALORDERL=1
fi
- TOTALORDERL_LIBM='$(ISNANL_LIBM)'])
+ TOTALORDERL_LIBM='$(ISNANL_LIBM)'
+ dnl Prerequisite of lib/totalorderl.c.
+ gl_LONG_DOUBLE_SIGN_LOCATION
+ ])
AC_SUBST([TOTALORDERL_LIBM])
])
diff --git a/modules/totalorderl b/modules/totalorderl
index d684c8c69c..ed6f801130 100644
--- a/modules/totalorderl
+++ b/modules/totalorderl
@@ -5,6 +5,7 @@ Files:
lib/totalorderl.c
m4/mathfunc.m4
m4/totalorder.m4
+m4/signbit.m4
Depends-on:
math
