Merge common usage of mul_split function

A number of files share identical code for the
mul_split function.

This moves the duplicated function mul_split into its
own header, and refactors the fma usage into a single
selection macro.  Likewise, mul_split when used by a
long double implementation is renamed mul_splitl for
clarity.

1 files changed, 1 insertions, 31 deletions

diff --git a/sysdeps/ieee754/ldbl-128ibm/x2y2m1l.c b/sysdeps/ieee754/ldbl-128ibm/x2y2m1l.c
index da2e929175..a8b489530d 100644
--- a/sysdeps/ieee754/ldbl-128ibm/x2y2m1l.c
+++ b/sysdeps/ieee754/ldbl-128ibm/x2y2m1l.c
@@ -18,7 +18,7 @@
 
 #include <math.h>
 #include <math_private.h>
-#include <float.h>
+#include <mul_split.h>
 #include <stdlib.h>
 
 /* Calculate X + Y exactly and store the result in *HI + *LO.  It is
@@ -33,36 +33,6 @@ add_split (double *hi, double *lo, double x, double y)
   *lo = (x - *hi) + y;
 }
 
-/* Calculate X * Y exactly and store the result in *HI + *LO.  It is
-   given that the values are small enough that no overflow occurs and
-   large enough (or zero) that no underflow occurs.  */
-
-static inline void
-mul_split (double *hi, double *lo, double x, double y)
-{
-#ifdef __FP_FAST_FMA
-  /* Fast built-in fused multiply-add.  */
-  *hi = x * y;
-  *lo = __builtin_fma (x, y, -*hi);
-#elif defined FP_FAST_FMA
-  /* Fast library fused multiply-add, compiler before GCC 4.6.  */
-  *hi = x * y;
-  *lo = __fma (x, y, -*hi);
-#else
-  /* Apply Dekker's algorithm.  */
-  *hi = x * y;
-# define C ((1 << (DBL_MANT_DIG + 1) / 2) + 1)
-  double x1 = x * C;
-  double y1 = y * C;
-# undef C
-  x1 = (x - x1) + x1;
-  y1 = (y - y1) + y1;
-  double x2 = x - x1;
-  double y2 = y - y1;
-  *lo = (((x1 * y1 - *hi) + x1 * y2) + x2 * y1) + x2 * y2;
-#endif
-}
-
 /* Compare absolute values of floating-point values pointed to by P
    and Q for qsort.  */