re PR rtl-optimization/68636 (unnecessary unaligned load on mips o32)

2015-12-04  Richard Biener  <rguenther@suse.de>

	PR middle-end/68636
	* builtins.c (get_pointer_alignment_1): Take care of byte to
	bit alignment computation overflow.

From-SVN: r231246

gcc/ChangeLog

 2015-12-04  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/68636
+	* builtins.c (get_pointer_alignment_1): Take care of byte to
+	bit alignment computation overflow.
+
+2015-12-04  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/67438
 	* match.pd: Guard ~X cmp ~Y -> Y cmp X and the variant with
 	a constant with single_use.

gcc/builtins.c

@@ -458,6 +458,10 @@ get_pointer_alignment_1 (tree exp, unsigned int *alignp,
 	{
 	  *bitposp = ptr_misalign * BITS_PER_UNIT;
 	  *alignp = ptr_align * BITS_PER_UNIT;
+	  /* Make sure to return a sensible alignment when the multiplication
+	     by BITS_PER_UNIT overflowed.  */
+	  if (*alignp == 0)
+	    *alignp = 1u << (HOST_BITS_PER_INT - 1);
 	  /* We cannot really tell whether this result is an approximation.  */
 	  return true;
 	}