Use of MPFR_UNLIKELY and MPFR_IS_SINGULAR for fast detection of special values (Nan, Inf or Zero).

Start to encapsulate the sign to be independant of the reprensation (Must be 1 or -1).


git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@2525 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 30 insertions, 29 deletions

diff --git a/log.c b/log.c
index f92eca156..43198f937 100644
--- a/log.c
+++ b/log.c
@@ -51,50 +51,51 @@ mpfr_log (mpfr_ptr r, mpfr_srcptr a, mp_rnd_t rnd_mode)
   double ref;
   TMP_DECL(marker);
 
-  /* If a is NaN, the result is NaN */
-  if (MPFR_IS_NAN(a))
+  /* Special cases */
+  if (MPFR_UNLIKELY( MPFR_IS_SINGULAR(a) ))
     {
-      MPFR_SET_NAN(r);
-      MPFR_RET_NAN;
-    }
-
-  MPFR_CLEAR_NAN(r);
-
-  /* check for infinity before zero */
-  if (MPFR_IS_INF(a))
-    {
-      if (MPFR_SIGN(a) < 0) /* log(-Inf) = NaN */
+      /* If a is NaN, the result is NaN */
+      if (MPFR_IS_NAN(a))
 	{
 	  MPFR_SET_NAN(r);
-          MPFR_RET_NAN;
+	  MPFR_RET_NAN;
 	}
-      else /* log(+Inf) = +Inf */
+      MPFR_CLEAR_NAN(r);
+      /* check for infinity before zero */
+      if (MPFR_IS_INF(a))
+	{
+	  if (MPFR_IS_NEG(a)) 
+	    /* log(-Inf) = NaN */
+	    {
+	      MPFR_SET_NAN(r);
+	      MPFR_RET_NAN;
+	    }
+	  else /* log(+Inf) = +Inf */
+	    {
+	      MPFR_SET_INF(r);
+	      MPFR_SET_POS(r);
+	      MPFR_RET(0);
+	    }
+	}      
+      /* Now we can clear the flags without damage even if r == a */
+      MPFR_CLEAR_INF(r);
+      if (MPFR_IS_ZERO(a))
 	{
 	  MPFR_SET_INF(r);
-          MPFR_SET_POS(r);
-          MPFR_RET(0);
+	  MPFR_SET_NEG(r);
+	  MPFR_RET(0); /* log(0) is an exact -infinity */
 	}
     }
-
-  /* Now we can clear the flags without damage even if r == a */
-  MPFR_CLEAR_INF(r);
-
-  if (MPFR_IS_ZERO(a))
-    {
-      MPFR_SET_INF(r);
-      MPFR_SET_NEG(r);
-      MPFR_RET(0); /* log(0) is an exact -infinity */
-    }
-
+  
   /* If a is negative, the result is NaN */
-  if (MPFR_SIGN(a) < 0)
+  if (MPFR_UNLIKELY( MPFR_IS_NEG(a) ))
     {
       MPFR_SET_NAN(r);
       MPFR_RET_NAN;
     }
 
   /* If a is 1, the result is 0 */
-  if (mpfr_cmp_ui (a, 1) == 0)
+  if (MPFR_UNLIKELY( mpfr_cmp_ui (a, 1) == 0) )
     {
       MPFR_SET_ZERO(r);
       MPFR_SET_POS(r);