re PR tree-optimization/52395 (Too conservative alignment info from SRA)

2012-02-28  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/52395
	* tree-sra.c (build_ref_for_offset): Also look at the base
	TYPE_ALIGN when figuring out the alignment of the replacement.

From-SVN: r184620

gcc/ChangeLog

 2012-02-28  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/52395
+	* tree-sra.c (build_ref_for_offset): Also look at the base
+	TYPE_ALIGN when figuring out the alignment of the replacement.
+
+2012-02-28  Richard Guenther  <rguenther@suse.de>
+
 	PR tree-optimization/52402
 	* ipa-prop.c (ipa_modify_call_arguments): Properly use
 	mis-aligned types when creating the accesses at the call site.

gcc/tree-sra.c

@@ -1526,10 +1526,12 @@ build_ref_for_offset (location_t loc, tree base, HOST_WIDE_INT offset,
      we can extract more optimistic alignment information
      by looking at the access mode.  That would constrain the
      alignment of base + base_offset which we would need to
-     adjust according to offset.
-     ???  But it is not at all clear that prev_base is an access
-     that was in the IL that way, so be conservative for now.  */
+     adjust according to offset.  */
   align = get_pointer_alignment_1 (base, &misalign);
+  if (misalign == 0
+      && (TREE_CODE (prev_base) == MEM_REF
+	  || TREE_CODE (prev_base) == TARGET_MEM_REF))
+    align = MAX (align, TYPE_ALIGN (TREE_TYPE (prev_base)));
   misalign += (double_int_sext (tree_to_double_int (off),
 				TYPE_PRECISION (TREE_TYPE (off))).low
 	       * BITS_PER_UNIT);