combine.c (try_widen_shift_mode): Factor out code to check if an integer…

combine.c (try_widen_shift_mode): Factor out code to check if an integer constant is a low-order bitmask from here ...

	* combine.c (try_widen_shift_mode): Factor out code to check if an
        integer constant is a low-order bitmask from here ...
	* rtlanal.c (low_bitmask_len): ... to here.
	* rtl.h (low_bitmask_len): Declare.

From-SVN: r150656

gcc/ChangeLog

+2009-08-11  Adam Nemet  <anemet@caviumnetworks.com>
+
+	* combine.c (try_widen_shift_mode): Factor out code to check if an
+        integer constant is a low-order bitmask from here ...
+	* rtlanal.c (low_bitmask_len): ... to here.
+	* rtl.h (low_bitmask_len): Declare.
+
 2009-08-11  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR target/8603

gcc/combine.c

@@ -9027,13 +9027,9 @@ try_widen_shift_mode (enum rtx_code code, rtx op, int count,
 
       /* We can also widen if the bits brought in will be masked off.  This
 	 operation is performed in ORIG_MODE.  */
-      if (outer_code == AND
-	  && GET_MODE_BITSIZE (orig_mode) <= HOST_BITS_PER_WIDE_INT)
+      if (outer_code == AND)
 	{
-	  int care_bits;
-
-	  outer_const &= GET_MODE_MASK (orig_mode);
-	  care_bits = exact_log2 (outer_const + 1);
+	  int care_bits = low_bitmask_len (orig_mode, outer_const);
 
 	  if (care_bits >= 0
 	      && GET_MODE_BITSIZE (orig_mode) - care_bits >= count)

gcc/rtl.h

@@ -1095,6 +1095,7 @@ extern unsigned HOST_WIDE_INT nonzero_bits (const_rtx, enum machine_mode);
 extern unsigned int num_sign_bit_copies (const_rtx, enum machine_mode);
 extern bool constant_pool_constant_p (rtx);
 extern bool truncated_to_mode (enum machine_mode, const_rtx);
+extern int low_bitmask_len (enum machine_mode, unsigned HOST_WIDE_INT);
 
 
 /* 1 if RTX is a subreg containing a reg that is already known to be

gcc/rtlanal.c

@@ -5032,3 +5032,20 @@ constant_pool_constant_p (rtx x)
   x = avoid_constant_pool_reference (x);
   return GET_CODE (x) == CONST_DOUBLE;
 }
+
+/* If M is a bitmask that selects a field of low-order bits within an item but
+   not the entire word, return the length of the field.  Return -1 otherwise.
+   M is used in machine mode MODE.  */
+
+int
+low_bitmask_len (enum machine_mode mode, unsigned HOST_WIDE_INT m)
+{
+  if (mode != VOIDmode)
+    {
+      if (GET_MODE_BITSIZE (mode) > HOST_BITS_PER_WIDE_INT)
+	return -1;
+      m &= GET_MODE_MASK (mode);
+    }
+
+  return exact_log2 (m + 1);
+}