[fixed-point] Fix left shfit when the shift amount == the width

["Fu, Chao-Ying" <fu at mips dot com>]

Hi,

  This patch fixes the case when the shift amount is
the same as the full width for the 128-bit unsigned fract type.

  Thanks!

Regards,
Chao-ying

2007-02-02  Chao-ying Fu  <fu@mips.com>

	* fixed-value.c (do_fixed_divide): Check the left shift amount to
	just copy data directly when it is the same as the width.
	This hits a corner case for the 128-bit unsigned fract type.
	(do_fixed_shift): Likewise.
	(fixed_convert_from_int): Likewise.

Index: fixed-value.c
===================================================================
--- fixed-value.c       (revision 121327)
+++ fixed-value.c       (working copy)
@@ -539,14 +539,23 @@
        pos_b = b->data;

       /* Left shift pos_a to {r, s} by FBIT.  */
-      lshift_double (pos_a.low, pos_a.high,
-                    GET_MODE_FBIT (f->mode),
-                    2 * HOST_BITS_PER_WIDE_INT,
-                    &s.low, &s.high, 0);
-      lshift_double (pos_a.low, pos_a.high,
-                    - (2 * HOST_BITS_PER_WIDE_INT - GET_MODE_FBIT (f->mode)),
-                    2 * HOST_BITS_PER_WIDE_INT,
-                    &r.low, &r.high, 0);
+      if (GET_MODE_FBIT (f->mode) == 2 * HOST_BITS_PER_WIDE_INT)
+       {
+         r = pos_a;
+         s.high = 0;
+         s.low = 0;
+       }
+      else
+       {
+         lshift_double (pos_a.low, pos_a.high,
+                        GET_MODE_FBIT (f->mode),
+                        2 * HOST_BITS_PER_WIDE_INT,
+                        &s.low, &s.high, 0);
+         lshift_double (pos_a.low, pos_a.high,
+                        - (2 * HOST_BITS_PER_WIDE_INT - GET_MODE_FBIT (f->mode)
),
+                        2 * HOST_BITS_PER_WIDE_INT,
+                        &r.low, &r.high, 0);
+       }

       /* Divide r by pos_b to quo_r.  The remanider is in mod.  */
       div_and_round_double (TRUNC_DIV_EXPR, 1, r.low, r.high, pos_b.low,
@@ -639,15 +648,24 @@
   else /* We need two double_int to store the left-shift result.  */
     {
       double_int temp_high, temp_low;
-      lshift_double (a->data.low, a->data.high,
-                    b->data.low,
-                    2 * HOST_BITS_PER_WIDE_INT,
-                    &temp_low.low, &temp_low.high, !unsignedp);
-      /* Logical shift right to temp_high.  */
-      lshift_double (a->data.low, a->data.high,
-                    b->data.low - 2 * HOST_BITS_PER_WIDE_INT,
-                    2 * HOST_BITS_PER_WIDE_INT,
-                    &temp_high.low, &temp_high.high, 0);
+      if (b->data.low == 2 * HOST_BITS_PER_WIDE_INT)
+       {
+         temp_high = a->data;
+         temp_low.high = 0;
+         temp_low.low = 0;
+       }
+      else
+       {
+         lshift_double (a->data.low, a->data.high,
+                        b->data.low,
+                        2 * HOST_BITS_PER_WIDE_INT,
+                        &temp_low.low, &temp_low.high, !unsignedp);
+         /* Logical shift right to temp_high.  */
+         lshift_double (a->data.low, a->data.high,
+                        b->data.low - 2 * HOST_BITS_PER_WIDE_INT,
+                        2 * HOST_BITS_PER_WIDE_INT,
+                        &temp_high.low, &temp_high.high, 0);
+       }
       if (!unsignedp && a->data.high < 0) /* Signed-extend temp_high.  */
        temp_high = double_int_ext (temp_high, b->data.low, unsignedp);
       f->data = temp_low;
@@ -953,6 +971,14 @@
   /* Left shift a to temp_high, temp_low.  */
   double_int temp_high, temp_low;
   int amount = GET_MODE_FBIT (mode);
+  if (amount == 2 * HOST_BITS_PER_WIDE_INT)
+    {
+       temp_high = a;
+       temp_low.low = 0;
+       temp_low.high = 0;
+    }
+  else
+    {
+      lshift_double (a.low, a.high,
+                    amount,
+                    2 * HOST_BITS_PER_WIDE_INT,
+                    &temp_low.low, &temp_low.high, 0);

-  /* Logical shift right to temp_high.  */
-  lshift_double (a.low, a.high,
-                amount - 2 * HOST_BITS_PER_WIDE_INT,
-                2 * HOST_BITS_PER_WIDE_INT,
-                &temp_high.low, &temp_high.high, 0);
+      /* Logical shift right to temp_high.  */
+      lshift_double (a.low, a.high,
+                    amount - 2 * HOST_BITS_PER_WIDE_INT,
+                    2 * HOST_BITS_PER_WIDE_INT,
+                    &temp_high.low, &temp_high.high, 0);
+    }