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AC_DEFUN([AC_USE_SSEMATH],
[
AC_REQUIRE([AC_PROG_CC])
AC_MSG_CHECKING([for sse based math flag])
sm_save_CFLAGS="$CFLAGS"
CFLAGS="-mfpmath=sse $CFLAGS"
AC_TRY_COMPILE(
[],
[],
gl_cv_cc_ssemath=yes,
gl_cv_cc_ssemath=no)
CFLAGS="$sm_save_CFLAGS"
if test $gl_cv_cc_ssemath = yes; then
CFLAGS="-mfpmath=sse $CFLAGS"
fi
AC_MSG_RESULT([$gl_cv_cc_ssemath])
AC_SUBST([CFLAGS])
])
AC_DEFUN([AC_CHECK_IEEE_FLOAT_ROUND],
[
AC_REQUIRE([AC_USE_SSEMATH])
AC_MSG_CHECKING([FPU rounding behavior])
HAVE_IEEE_FLOAT_ROUND=-1
AC_RUN_IFELSE([AC_LANG_PROGRAM([[double a = 3.0, b = 7.0;]],
[[volatile double c = a / b;]
[return (c == a/b) ? 0 : 1;]])],
[AC_MSG_RESULT([correct IEEE behavior])
HAVE_IEEE_FLOAT_ROUND=1],
[AC_MSG_ERROR([Bad FPU rounding behavior.
The rounding behavior of your FPU does not follow IEEE standards.
There are three ways (among others) to enforce the expected behavior (best solutions first):
- Specify a CPU architecture providing SSE2 supported by your CPU
(If gcc is used, add -march=pentium4 or even better -march=native to compiler flags)
- Force use of SSE2 instruction set if your CPU supports it
(If gcc is used, add -msse2 and -mfpmath=sse to compiler flags)
- Do not store floating point variables in registers
(If gcc is used, add -ffloat-store to compiler flags)])
HAVE_IEEE_FLOAT_ROUND=0],
AC_MSG_RESULT([unable to test]))
])
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