combine.c (simplify_shift_const): Revert previous two changes.

        * combine.c (simplify_shift_const): Revert previous two
        changes.  If SHIFT_COUNT_TRUNCATED, crop the shift count
        before the main loop.

From-SVN: r35742

gcc/ChangeLog

+2000-08-16  Richard Henderson  <rth@cygnus.com>
+
+	* combine.c (simplify_shift_const): Revert previous two
+	changes.  If SHIFT_COUNT_TRUNCATED, crop the shift count
+	before the main loop.
+
 2000-08-15  Richard Henderson  <rth@cygnus.com>
 
 	* combine.c (simplify_shift_const): Bound shift count when

gcc/combine.c

@@ -8851,6 +8851,14 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
 
   count = input_count;
 
+  /* Make sure and truncate the "natural" shift on the way in.  We don't
+     want to do this inside the loop as it makes it more difficult to
+     combine shifts.  */
+#ifdef SHIFT_COUNT_TRUNCATED
+  if (SHIFT_COUNT_TRUNCATED)
+    count %= GET_MODE_BITSIZE (mode);
+#endif
+
   /* Unless one of the branches of the `if' in this loop does a `continue',
      we will `break' the loop after the `if'.  */
 
@@ -8879,11 +8887,10 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
 	   ? result_mode : mode);
 
       /* Handle cases where the count is greater than the size of the mode
-	 minus 1.  If SHIFT_COUNT_TRUNCATED, there aren't really any such
-	 cases.  Otherwise, for ASHIFT, use the size minus one as the count
-	 (this can occur when simplifying (lshiftrt (ashiftrt ..))).  For
-	 rotates, take the count modulo the size.  For other shifts, the
-	 result is zero.
+	 minus 1.  For ASHIFT, use the size minus one as the count (this can
+	 occur when simplifying (lshiftrt (ashiftrt ..))).  For rotates,
+	 take the count modulo the size.  For other shifts, the result is
+	 zero.
 
 	 Since these shifts are being produced by the compiler by combining
 	 multiple operations, each of which are defined, we know what the
@@ -8891,11 +8898,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
 
       if (count > GET_MODE_BITSIZE (shift_mode) - 1)
 	{
-#ifdef SHIFT_COUNT_TRUNCATED
-	  if (SHIFT_COUNT_TRUNCATED)
-	    count %= GET_MODE_BITSIZE (shift_mode);
-	  else
-#endif
 	  if (code == ASHIFTRT)
 	    count = GET_MODE_BITSIZE (shift_mode) - 1;
 	  else if (code == ROTATE || code == ROTATERT)
@@ -9149,8 +9151,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
 		    break;
 
 		  count += first_count;
-		  if (count >= GET_MODE_BITSIZE (shift_mode))
-		    count = GET_MODE_BITSIZE (shift_mode) - 1;
 		  varop = XEXP (varop, 0);
 		  continue;
 		}
@@ -9204,9 +9204,6 @@ simplify_shift_const (x, code, result_mode, varop, input_count)
 	      else
 		count = signed_count;
 
-	      if (count >= GET_MODE_BITSIZE (shift_mode))
-		count = GET_MODE_BITSIZE (shift_mode) - 1;
-
 	      varop = XEXP (varop, 0);
 	      continue;
 	    }