--- /dev/null
+# fma.m4 serial 1
+dnl Copyright (C) 2011 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_FUNC_FMA],
+[
+ AC_REQUIRE([gl_MATH_H_DEFAULTS])
+
+ dnl Determine FMA_LIBM.
+ gl_MATHFUNC([fma], [double], [(double, double, double)])
+ if test $gl_cv_func_fma_no_libm = yes \
+ || test $gl_cv_func_fma_in_libm = yes; then
+ gl_FUNC_FMA_WORKS
+ case "$gl_cv_func_fma_works" in
+ *no) REPLACE_FMA=1 ;;
+ esac
+ else
+ HAVE_FMA=0
+ fi
+ if test $HAVE_FMA = 0 || test $REPLACE_FMA = 1; then
+ dnl Find libraries needed to link lib/fmal.c.
+ AC_REQUIRE([gl_FUNC_FREXP])
+ AC_REQUIRE([gl_FUNC_LDEXP])
+ AC_REQUIRE([gl_FUNC_FEGETROUND])
+ FMA_LIBM=
+ dnl Append $FREXP_LIBM to FMA_LIBM, avoiding gratuitous duplicates.
+ case " $FMA_LIBM " in
+ *" $FREXP_LIBM "*) ;;
+ *) FMA_LIBM="$FMA_LIBM $FREXP_LIBM" ;;
+ esac
+ dnl Append $LDEXP_LIBM to FMA_LIBM, avoiding gratuitous duplicates.
+ case " $FMA_LIBM " in
+ *" $LDEXP_LIBM "*) ;;
+ *) FMA_LIBM="$FMA_LIBM $LDEXP_LIBM" ;;
+ esac
+ dnl Append $FEGETROUND_LIBM to FMA_LIBM, avoiding gratuitous duplicates.
+ case " $FMA_LIBM " in
+ *" $FEGETROUND_LIBM "*) ;;
+ *) FMA_LIBM="$FMA_LIBM $FEGETROUND_LIBM" ;;
+ esac
+ fi
+ AC_SUBST([FMA_LIBM])
+])
+
+dnl Test whether fma() has any of the 7 known bugs of glibc 2.11.3 on x86_64.
+AC_DEFUN([gl_FUNC_FMA_WORKS],
+[
+ AC_REQUIRE([AC_PROG_CC])
+ AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
+ AC_REQUIRE([gl_FUNC_LDEXP])
+ save_LIBS="$LIBS"
+ LIBS="$LIBS $FMA_LIBM $LDEXP_LIBM"
+ AC_CACHE_CHECK([whether fma works], [gl_cv_func_fma_works],
+ [
+ AC_RUN_IFELSE(
+ [AC_LANG_SOURCE([[
+#include <float.h>
+#include <math.h>
+double p0 = 0.0;
+int main()
+{
+ int failed_tests = 0;
+ /* These tests fail with glibc 2.11.3 on x86_64. */
+ {
+ volatile double x = 1.5; /* 3 * 2^-1 */
+ volatile double y = x;
+ volatile double z = ldexp (1.0, DBL_MANT_DIG + 1); /* 2^54 */
+ /* x * y + z with infinite precision: 2^54 + 9 * 2^-2.
+ Lies between (2^52 + 0) * 2^2 and (2^52 + 1) * 2^2
+ and is closer to (2^52 + 1) * 2^2, therefore the rounding
+ must round up and produce (2^52 + 1) * 2^2. */
+ volatile double expected = z + 4.0;
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 1;
+ }
+ {
+ volatile double x = 1.25; /* 2^0 + 2^-2 */
+ volatile double y = - x;
+ volatile double z = ldexp (1.0, DBL_MANT_DIG + 1); /* 2^54 */
+ /* x * y + z with infinite precision: 2^54 - 2^0 - 2^-1 - 2^-4.
+ Lies between (2^53 - 1) * 2^1 and 2^53 * 2^1
+ and is closer to (2^53 - 1) * 2^1, therefore the rounding
+ must round down and produce (2^53 - 1) * 2^1. */
+ volatile double expected = (ldexp (1.0, DBL_MANT_DIG) - 1.0) * 2.0;
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 2;
+ }
+ {
+ volatile double x = 1.0 + ldexp (1.0, 1 - DBL_MANT_DIG); /* 2^0 + 2^-52 */
+ volatile double y = x;
+ volatile double z = 4.0; /* 2^2 */
+ /* x * y + z with infinite precision: 2^2 + 2^0 + 2^-51 + 2^-104.
+ Lies between (2^52 + 2^50) * 2^-50 and (2^52 + 2^50 + 1) * 2^-50
+ and is closer to (2^52 + 2^50 + 1) * 2^-50, therefore the rounding
+ must round up and produce (2^52 + 2^50 + 1) * 2^-50. */
+ volatile double expected = 4.0 + 1.0 + ldexp (1.0, 3 - DBL_MANT_DIG);
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 4;
+ }
+ {
+ volatile double x = 1.0 + ldexp (1.0, 1 - DBL_MANT_DIG); /* 2^0 + 2^-52 */
+ volatile double y = - x;
+ volatile double z = 8.0; /* 2^3 */
+ /* x * y + z with infinite precision: 2^2 + 2^1 + 2^0 - 2^-51 - 2^-104.
+ Lies between (2^52 + 2^51 + 2^50 - 1) * 2^-50 and
+ (2^52 + 2^51 + 2^50) * 2^-50 and is closer to
+ (2^52 + 2^51 + 2^50 - 1) * 2^-50, therefore the rounding
+ must round down and produce (2^52 + 2^51 + 2^50 - 1) * 2^-50. */
+ volatile double expected = 7.0 - ldexp (1.0, 3 - DBL_MANT_DIG);
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 8;
+ }
+ {
+ volatile double x = 1.25; /* 2^0 + 2^-2 */
+ volatile double y = - 0.75; /* - 2^0 + 2^-2 */
+ volatile double z = ldexp (1.0, DBL_MANT_DIG); /* 2^53 */
+ /* x * y + z with infinite precision: 2^53 - 2^0 + 2^-4.
+ Lies between (2^53 - 2^0) and 2^53 and is closer to (2^53 - 2^0),
+ therefore the rounding must round down and produce (2^53 - 2^0). */
+ volatile double expected = ldexp (1.0, DBL_MANT_DIG) - 1.0;
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 16;
+ }
+ if ((DBL_MANT_DIG % 2) == 1)
+ {
+ volatile double x = 1.0 + ldexp (1.0, - (DBL_MANT_DIG + 1) / 2); /* 2^0 + 2^-27 */
+ volatile double y = 1.0 - ldexp (1.0, - (DBL_MANT_DIG + 1) / 2); /* 2^0 - 2^-27 */
+ volatile double z = - ldexp (1.0, DBL_MIN_EXP - DBL_MANT_DIG); /* - 2^-1074 */
+ /* x * y + z with infinite precision: 2^0 - 2^-54 - 2^-1074.
+ Lies between (2^53 - 1) * 2^-53 and 2^53 * 2^-53 and is closer to
+ (2^53 - 1) * 2^-53, therefore the rounding must round down and
+ produce (2^53 - 1) * 2^-53. */
+ volatile double expected = 1.0 - ldexp (1.0, - DBL_MANT_DIG);
+ volatile double result = fma (x, y, z);
+ if (result != expected)
+ failed_tests |= 32;
+ }
+ {
+ double minus_inf = -1.0 / p0;
+ volatile double x = ldexp (1.0, DBL_MAX_EXP - 1);
+ volatile double y = ldexp (1.0, DBL_MAX_EXP - 1);
+ volatile double z = minus_inf;
+ volatile double result = fma (x, y, z);
+ if (!(result == minus_inf))
+ failed_tests |= 64;
+ }
+ return failed_tests;
+}]])],
+ [gl_cv_func_fma_works=yes],
+ [gl_cv_func_fma_works=no],
+ [dnl Guess no, even on glibc systems.
+ gl_cv_func_fma_works="guessing no"
+ ])
+ ])
+ LIBS="$save_LIBS"
+])
+
+# Prerequisites of lib/fma.c.
+AC_DEFUN([gl_PREREQ_FMA], [:])
projects / gnulib.git / blobdiff