fixed horrible hack yp[-1]

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@274 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 19 insertions, 11 deletions

diff --git a/div_ui.c b/div_ui.c
index 489740df6..700e7d19b 100644
--- a/div_ui.c
+++ b/div_ui.c
@@ -18,11 +18,13 @@ mpfr_div_ui(y, x, u, rnd_mode)
      unsigned char rnd_mode; 
 #endif
 {
-  int xn, yn, dif, sh, i; mp_limb_t *xp, *yp, c, d;
+  int xn, yn, dif, sh, i; mp_limb_t *xp, *yp, *tmp, c, d;
+  TMP_DECL(marker);
 
   if (FLAG_NAN(x)) { SET_NAN(y); return 1; }
   if (u==0) { printf("infinity\n"); return 1; }
 
+  TMP_MARK(marker);
   xn = (PREC(x)-1)/BITS_PER_MP_LIMB + 1;
   yn = (PREC(y)-1)/BITS_PER_MP_LIMB + 1;
 
@@ -33,24 +35,29 @@ mpfr_div_ui(y, x, u, rnd_mode)
 
   /* save limb yp[-1] that will be used to store an extra limb of
      the quotient */
-  d = yp[-1];
   dif = yn+1-xn;
 #ifdef DEBUG
-  printf("dif=%d u=%lu\n",dif,u);
+  printf("dif=%d u=%lu xn=%d\n",dif,u,xn);
   printf("x="); mpfr_print_raw(x); putchar('\n');
 #endif
+
+  /* we need to store yn+1 = xn + dif limbs of the quotient */
+  if (ABSSIZE(y)>=yn+1) tmp=yp;
+  else tmp=TMP_ALLOC((yn+1)*BYTES_PER_MP_LIMB);
+
   if (dif>=0)
-    c = mpn_divrem_1(yp-1, dif, xp, xn, u);
+    c = mpn_divrem_1(tmp, dif, xp, xn, (mp_limb_t) u);
   else /* dif < 0 i.e. xn > yn */
-    c = mpn_divrem_1(yp-1, 0, xp-dif, yn, u);
-#ifdef DEBUG
-printf("y="); mpfr_print_raw(y); putchar('\n');
-#endif
+    c = mpn_divrem_1(tmp, 0, xp-dif, yn, (mp_limb_t) u);
 
   /* shift left to normalize */
-  count_leading_zeros(sh, yp[yn-1]);
-  if (sh) { mpn_lshift(yp-1, yp-1, yn+1, sh); EXP(y) -= sh; }
-  yp[-1] = d; /* restore value of yp[-1] */
+  count_leading_zeros(sh, tmp[yn]);
+  if (sh) {
+    mpn_lshift(yp, tmp+1, yn, sh);
+    yp[0] += tmp[0] >> (BITS_PER_MP_LIMB-sh);
+    EXP(y) -= sh; 
+  }
+  else MPN_COPY(yp, tmp+1, yn);
 #ifdef DEBUG
 printf("y="); mpfr_print_raw(y); putchar('\n');
 #endif
@@ -61,6 +68,7 @@ printf("y="); mpfr_print_raw(y); putchar('\n');
   d = *yp & (((mp_limb_t)1 << sh) - 1);
   *yp ^= d; /* set to zero lowest sh bits */
 
+  TMP_FREE(marker);
   if ((c | d)==0) {
     for (i=0; i<-dif && xp[i]==0; i++);
     if (i>=-dif) return 0; /* result is exact */