(force_to_mode, case ASHIFTRT): Properly handle mask wider than

HOST_WIDE_INT.

From-SVN: r10534

diff --git a/gcc/combine.c b/gcc/combine.c
index 323db6b..e622b16 100644 (file)
--- a/gcc/combine.c
+++ b/gcc/combine.c
@@ -6035,8 +6035,30 @@ force_to_mode (x, mode, mask, reg, just_select)
        {
          int i = -1;
 
-         nonzero = GET_MODE_MASK (GET_MODE (x));
-         nonzero >>= INTVAL (XEXP (x, 1));
+         /* If the considered data is wider then HOST_WIDE_INT, we can't
+            represent a mask for all its bits in a single scalar.
+            But we only care about the lower bits, so calculate these.  */
+
+         if (GET_MODE_SIZE (GET_MODE (x)) > sizeof (HOST_WIDE_INT))
+           {
+             nonzero = ~(HOST_WIDE_INT)0;
+
+             /* GET_MODE_BITSIZE (GET_MODE (x)) - INTVAL (XEXP (x, 1))
+                is the number of bits a full-width mask would have set.
+                We need only shift if these are fewer than nonzero can
+                hold.  If not, we must keep all bits set in nonzero.  */
+
+             if (GET_MODE_BITSIZE (GET_MODE (x)) - INTVAL (XEXP (x, 1))
+                 < HOST_BITS_PER_WIDE_INT)
+               nonzero >>= INTVAL (XEXP (x, 1))
+                           + HOST_BITS_PER_WIDE_INT
+                           - GET_MODE_BITSIZE (GET_MODE (x)) ;
+           }
+         else
+           {
+             nonzero = GET_MODE_MASK (GET_MODE (x));
+             nonzero >>= INTVAL (XEXP (x, 1));
+           }
 
          if ((mask & ~ nonzero) == 0
              || (i = exact_log2 (mask)) >= 0)