Add SCM_LIKELY and SCM_UNLIKELY for optimization

* libguile/numbers.c (scm_abs, scm_quotient, scm_remainder, scm_modulo):
  Add SCM_LIKELY and SCM_UNLIKELY in several places for optimization.

  (scm_remainder): Add comment about C99 "%" semantics.
  Strip away a redundant set of braces.

diff --git a/libguile/numbers.c b/libguile/numbers.c
index 608cf7a..e15a6ac 100644 (file)
--- a/libguile/numbers.c
+++ b/libguile/numbers.c
@@ -774,18 +774,18 @@ SCM_GPROC (s_quotient, "quotient", 2, 0, 0, scm_quotient, g_quotient);
 SCM
 scm_quotient (SCM x, SCM y)
 {
-  if (SCM_I_INUMP (x))
+  if (SCM_LIKELY (SCM_I_INUMP (x)))
     {
       scm_t_inum xx = SCM_I_INUM (x);
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_quotient);
          else
            {
              scm_t_inum z = xx / yy;
-             if (SCM_FIXABLE (z))
+             if (SCM_LIKELY (SCM_FIXABLE (z)))
                return SCM_I_MAKINUM (z);
              else
                return scm_i_inum2big (z);
@@ -809,12 +809,12 @@ scm_quotient (SCM x, SCM y)
     }
   else if (SCM_BIGP (x))
     {
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_quotient);
-         else if (yy == 1)
+         else if (SCM_UNLIKELY (yy == 1))
            return x;
          else
            {
@@ -858,15 +858,18 @@ SCM_GPROC (s_remainder, "remainder", 2, 0, 0, scm_remainder, g_remainder);
 SCM
 scm_remainder (SCM x, SCM y)
 {
-  if (SCM_I_INUMP (x))
+  if (SCM_LIKELY (SCM_I_INUMP (x)))
     {
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_remainder);
          else
            {
+             /* C99 specifies that "%" is the remainder corresponding to a
+                 quotient rounded towards zero, and that's also traditional
+                 for machine division, so z here should be well defined.  */
              scm_t_inum z = SCM_I_INUM (x) % yy;
              return SCM_I_MAKINUM (z);
            }
@@ -889,10 +892,10 @@ scm_remainder (SCM x, SCM y)
     }
   else if (SCM_BIGP (x))
     {
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_remainder);
          else
            {
@@ -931,13 +934,13 @@ SCM_GPROC (s_modulo, "modulo", 2, 0, 0, scm_modulo, g_modulo);
 SCM
 scm_modulo (SCM x, SCM y)
 {
-  if (SCM_I_INUMP (x))
+  if (SCM_LIKELY (SCM_I_INUMP (x)))
     {
       scm_t_inum xx = SCM_I_INUM (x);
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_modulo);
          else
            {
@@ -1008,10 +1011,10 @@ scm_modulo (SCM x, SCM y)
     }
   else if (SCM_BIGP (x))
     {
-      if (SCM_I_INUMP (y))
+      if (SCM_LIKELY (SCM_I_INUMP (y)))
        {
          scm_t_inum yy = SCM_I_INUM (y);
-         if (yy == 0)
+         if (SCM_UNLIKELY (yy == 0))
            scm_num_overflow (s_modulo);
          else
            {
@@ -1029,22 +1032,20 @@ scm_modulo (SCM x, SCM y)
        }
       else if (SCM_BIGP (y))
        {
-           {
-             SCM result = scm_i_mkbig ();
-             int y_sgn = mpz_sgn (SCM_I_BIG_MPZ (y));
-             SCM pos_y = scm_i_clonebig (y, y_sgn >= 0);
-             mpz_mod (SCM_I_BIG_MPZ (result),
-                      SCM_I_BIG_MPZ (x),
-                      SCM_I_BIG_MPZ (pos_y));
+         SCM result = scm_i_mkbig ();
+         int y_sgn = mpz_sgn (SCM_I_BIG_MPZ (y));
+         SCM pos_y = scm_i_clonebig (y, y_sgn >= 0);
+         mpz_mod (SCM_I_BIG_MPZ (result),
+                  SCM_I_BIG_MPZ (x),
+                  SCM_I_BIG_MPZ (pos_y));
         
-             scm_remember_upto_here_1 (x);
-             if ((y_sgn < 0) && (mpz_sgn (SCM_I_BIG_MPZ (result)) != 0))
-               mpz_add (SCM_I_BIG_MPZ (result),
-                        SCM_I_BIG_MPZ (y),
-                        SCM_I_BIG_MPZ (result));
-             scm_remember_upto_here_2 (y, pos_y);
-             return scm_i_normbig (result);
-           }
+         scm_remember_upto_here_1 (x);
+         if ((y_sgn < 0) && (mpz_sgn (SCM_I_BIG_MPZ (result)) != 0))
+           mpz_add (SCM_I_BIG_MPZ (result),
+                    SCM_I_BIG_MPZ (y),
+                    SCM_I_BIG_MPZ (result));
+         scm_remember_upto_here_2 (y, pos_y);
+         return scm_i_normbig (result);
        }
       else
        SCM_WTA_DISPATCH_2 (g_modulo, x, y, SCM_ARG2, s_modulo);