simplify.c (twos_complement): Calculate mask in GMP arithmetic.

2004-10-30  Tobias Schlueter  <tobias.schlueter@physik.uni-muenchen.de>

	* simplify.c (twos_complement): Calculate mask in GMP arithmetic.

From-SVN: r89888

gcc/fortran/ChangeLog

 2004-10-30  Tobias Schlueter  <tobias.schlueter@physik.uni-muenchen.de>
 
+	* simplify.c (twos_complement): Calculate mask in GMP arithmetic.
+
+2004-10-30  Tobias Schlueter  <tobias.schlueter@physik.uni-muenchen.de>
+
 	* trans.c (gfc_trans_code): Set global locus after recursing. Fix
 	comment typo.
 

gcc/fortran/simplify.c

@@ -146,19 +146,17 @@ static void
 twos_complement (mpz_t x, int bitsize)
 {
   mpz_t mask;
-  char mask_s[bitsize + 1];
 
   if (mpz_tstbit (x, bitsize - 1) == 1)
     {
-      /* The mpz_init_set_{u|s}i functions take a long argument, but
-	 the widest integer the target supports might be wider, so we
-	 have to go via an intermediate string.  */
-      memset (mask_s, '1', bitsize);
-      mask_s[bitsize] = '\0';
-      mpz_init_set_str (mask, mask_s, 2);
+      mpz_init_set_ui(mask, 1);
+      mpz_mul_2exp(mask, mask, bitsize);
+      mpz_sub_ui(mask, mask, 1);
 
-      /* We negate the number by hand, zeroing the high bits, and then
-	 have it negated by GMP.  */
+      /* We negate the number by hand, zeroing the high bits, that is
+        make it the corresponding positive number, and then have it
+        negated by GMP, giving the correct representation of the
+        negative number.  */
       mpz_com (x, x);
       mpz_add_ui (x, x, 1);
       mpz_and (x, x, mask);