re PR middle-end/64516 (arm: wrong unaligned load generated)

2016-06-13  Richard Biener  <rguenther@suse.de>

	PR middle-end/64516
	* fold-const.c (fold_unary_loc): Preserve alignment when
	folding a VIEW_CONVERT_EXPR into a MEM_REF.

	* gcc.dg/align-3.c: New testcase.

From-SVN: r237355

gcc/ChangeLog

+2016-06-13  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/64516
+	* fold-const.c (fold_unary_loc): Preserve alignment when
+	folding a VIEW_CONVERT_EXPR into a MEM_REF.
+
 2016-06-13  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/71458

gcc/fold-const.c

@@ -7975,6 +7975,8 @@ fold_unary_loc (location_t loc, enum tree_code code, tree type, tree op0)
     case VIEW_CONVERT_EXPR:
       if (TREE_CODE (op0) == MEM_REF)
         {
+	  if (TYPE_ALIGN (TREE_TYPE (op0)) != TYPE_ALIGN (type))
+	    type = build_aligned_type (type, TYPE_ALIGN (TREE_TYPE (op0)));
 	  tem = fold_build2_loc (loc, MEM_REF, type,
 				 TREE_OPERAND (op0, 0), TREE_OPERAND (op0, 1));
 	  REF_REVERSE_STORAGE_ORDER (tem) = REF_REVERSE_STORAGE_ORDER (op0);

gcc/testsuite/ChangeLog

+2016-06-13  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/64516
+	* gcc.dg/align-3.c: New testcase.
+
 2016-06-13  Martin Liska  <mliska@suse.cz>
 
 	* gcc.target/i386/pr71458.c: New test.

gcc/testsuite/gcc.dg/align-3.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-expand" } */
+
+typedef struct { char a[2]; } __attribute__((__packed__)) TU2;
+unsigned short get16_unaligned(const void *p) {
+    unsigned short v;
+    *(TU2 *)(void *)(&v) = *(const TU2 *)p;
+    return v;
+}
+
+/* { dg-final { scan-rtl-dump "MEM\[^\n\r\]*A8\\\]" "expand" } } */