mpq/div.c: Reduce memory use.

1 files changed, 36 insertions, 14 deletions

diff --git a/mpq/div.c b/mpq/div.c
index 7d91e0998..6c058a250 100644
--- a/mpq/div.c
+++ b/mpq/div.c
@@ -37,7 +37,6 @@ mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
 {
   mpz_t gcd1, gcd2;
   mpz_t tmp1, tmp2;
-  mpz_t numtmp;
   mp_size_t op1_num_size;
   mp_size_t op1_den_size;
   mp_size_t op2_num_size;
@@ -45,11 +44,40 @@ mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
   mp_size_t alloc;
   TMP_DECL;
 
-  op2_num_size = ABSIZ(NUM(op2));
+  op2_num_size = SIZ(NUM(op2));
 
   if (UNLIKELY (op2_num_size == 0))
     DIVIDE_BY_ZERO;
 
+  if (op1 == op2)
+    {
+      PTR(NUM(quot))[0] = 1;
+      SIZ(NUM(quot)) = 1;
+      PTR(DEN(quot))[0] = 1;
+      SIZ(DEN(quot)) = 1;
+      return;      
+    }
+
+  if (quot == op2)
+    {
+      /* We checked for op1 == op2: we are not in the x=x/x case.
+	 We compute x=y/x by computing x=inv(x)*y */
+      MPN_PTR_SWAP (PTR(NUM(quot)), ALLOC(NUM(quot)),
+		    PTR(DEN(quot)), ALLOC(DEN(quot)));
+      if (op2_num_size > 0)
+	{
+	  SIZ(NUM(quot)) = SIZ(DEN(quot));
+	  SIZ(DEN(quot)) = op2_num_size;
+	}
+      else
+	{
+	  SIZ(NUM(quot)) = - SIZ(DEN(quot));
+	  SIZ(DEN(quot)) = - op2_num_size;
+	}
+      mpq_mul (quot, quot, op1);
+      return;
+    }
+
   op1_num_size = ABSIZ(NUM(op1));
 
   if (op1_num_size == 0)
@@ -62,6 +90,7 @@ mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
       return;
     }
 
+  op2_num_size = ABS(op2_num_size);
   op2_den_size =   SIZ(DEN(op2));
   op1_den_size =   SIZ(DEN(op1));
 
@@ -79,13 +108,10 @@ mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
   alloc = MAX (op1_den_size, op2_den_size);
   MPZ_TMP_INIT (tmp2, alloc);
 
-  alloc = op1_num_size + op2_den_size;
-  MPZ_TMP_INIT (numtmp, alloc);
-
-  /* QUOT might be identical to either operand, so don't store the result there
-     until we are finished with the input operands.  We can overwrite the
-     numerator of QUOT when we are finished with the numerators of OP1 and
-     OP2.  */
+  /* QUOT might be identical to OP1, so don't store the result there
+     until we are finished with the input operand.  We can overwrite
+     the numerator of QUOT when we are finished with the numerator of
+     OP1. */
 
   mpz_gcd (gcd1, NUM(op1), NUM(op2));
   mpz_gcd (gcd2, DEN(op2), DEN(op1));
@@ -93,17 +119,13 @@ mpq_div (mpq_ptr quot, mpq_srcptr op1, mpq_srcptr op2)
   mpz_divexact_gcd (tmp1, NUM(op1), gcd1);
   mpz_divexact_gcd (tmp2, DEN(op2), gcd2);
 
-  mpz_mul (numtmp, tmp1, tmp2);
+  mpz_mul (NUM(quot), tmp1, tmp2);
 
   mpz_divexact_gcd (tmp1, NUM(op2), gcd1);
   mpz_divexact_gcd (tmp2, DEN(op1), gcd2);
 
   mpz_mul (DEN(quot), tmp1, tmp2);
 
-  /* We needed to go via NUMTMP to take care of QUOT being the same as OP2.
-     Now move NUMTMP to QUOT->_mp_num.  */
-  mpz_set (NUM(quot), numtmp);
-
   /* Keep the denominator positive.  */
   if (SIZ(DEN(quot)) < 0)
     {