Rewrite, as per Marc Glisse's suggestion.

1 files changed, 46 insertions, 54 deletions

diff --git a/mpz/divegcd.c b/mpz/divegcd.c
index 49257aec2..c67e76972 100644
--- a/mpz/divegcd.c
+++ b/mpz/divegcd.c
@@ -49,62 +49,77 @@ static void
 mpz_divexact_by3 (mpz_ptr q, mpz_srcptr a)
 {
   mp_size_t  size = SIZ(a);
-  if (size == 0)
-    {
-      SIZ(q) = 0;
-      return;
-    }
-  else
-    {
-      mp_size_t  abs_size = ABS(size);
-      mp_ptr     qp;
+  mp_size_t  abs_size = ABS(size);
+  mp_ptr     qp;
 
-      MPZ_REALLOC (q, abs_size);
+  MPZ_REALLOC (q, abs_size);
 
-      qp = PTR(q);
-      mpn_bdiv_dbm1 (qp, PTR(a), abs_size, GMP_NUMB_MASK / 3);
+  qp = PTR(q);
+  mpn_bdiv_dbm1 (qp, PTR(a), abs_size, GMP_NUMB_MASK / 3);
 
-      abs_size -= (qp[abs_size-1] == 0);
-      SIZ(q) = (size>0 ? abs_size : -abs_size);
-    }
+  abs_size -= (qp[abs_size-1] == 0);
+  SIZ(q) = (size>0 ? abs_size : -abs_size);
 }
 #endif
+
 #if GMP_NUMB_BITS % 4 == 0
 static void
 mpz_divexact_by5 (mpz_ptr q, mpz_srcptr a)
 {
   mp_size_t  size = SIZ(a);
-  if (size == 0)
-    {
-      SIZ(q) = 0;
-      return;
-    }
-  else
-    {
-      mp_size_t  abs_size = ABS(size);
-      mp_ptr     qp;
+  mp_size_t  abs_size = ABS(size);
+  mp_ptr     qp;
 
-      MPZ_REALLOC (q, abs_size);
+  MPZ_REALLOC (q, abs_size);
 
-      qp = PTR(q);
-      mpn_bdiv_dbm1 (qp, PTR(a), abs_size, GMP_NUMB_MASK / 5);
+  qp = PTR(q);
+  mpn_bdiv_dbm1 (qp, PTR(a), abs_size, GMP_NUMB_MASK / 5);
 
-      abs_size -= (qp[abs_size-1] == 0);
-      SIZ(q) = (size>0 ? abs_size : -abs_size);
-    }
+  abs_size -= (qp[abs_size-1] == 0);
+  SIZ(q) = (size>0 ? abs_size : -abs_size);
 }
 #endif
 
+static void
+mpz_divexact_limb (mpz_ptr q, mpz_srcptr a, mp_limb_t d)
+{
+  mp_size_t  size = SIZ(a);
+  mp_size_t  abs_size = ABS(size);
+  mp_ptr     qp;
+
+  MPZ_REALLOC (q, abs_size);
+
+  qp = PTR(q);
+  mpn_divexact_1 (qp, PTR(a), abs_size, d);
+
+  abs_size -= (qp[abs_size-1] == 0);
+  SIZ(q) = (size>0 ? abs_size : -abs_size);
+}
+
 void
 mpz_divexact_gcd (mpz_ptr q, mpz_srcptr a, mpz_srcptr d)
 {
   ASSERT (mpz_sgn (d) > 0);
 
+  if (SIZ(a) == 0)
+    {
+      SIZ(q) = 0;
+      return;
+    }
+
   if (SIZ(d) == 1)
     {
       mp_limb_t  dl = PTR(d)[0];
       int        twos;
 
+      if ((dl & 1) == 0)
+	{
+	  count_trailing_zeros (twos, dl);
+	  dl >>= twos;
+	  mpz_tdiv_q_2exp (q, a, twos);
+	  a = q;
+	}
+
       if (dl == 1)
 	{
 	  if (q != a)
@@ -126,30 +141,7 @@ mpz_divexact_gcd (mpz_ptr q, mpz_srcptr a, mpz_srcptr d)
 	}
 #endif
 
-      count_trailing_zeros (twos, dl);
-      dl >>= twos;
-      mpz_tdiv_q_2exp (q, a, twos);
-
-      if (dl == 1)
-	{
-	  return;
-	}
-#if GMP_NUMB_BITS % 2 == 0
-      if (dl == 3)
-	{
-	  mpz_divexact_by3 (q, q);
-	  return;
-	}
-#endif
-#if GMP_NUMB_BITS % 4 == 0
-      if (dl == 5)
-	{
-	  mpz_divexact_by5 (q, q);
-	  return;
-	}
-#endif
-
-      mpz_divexact_ui (q, q, dl);
+      mpz_divexact_limb (q, a, dl);
       return;
     }