re PR sanitizer/63316 (False asan positive)

	PR sanitizer/63316
	* asan.c (asan_expand_check_ifn): Fix up align >= 8 optimization.

	* c-c++-common/asan/pr63316.c: New test.

From-SVN: r215547

gcc/ChangeLog

+2014-09-24  Jakub Jelinek  <jakub@redhat.com>
+
+	PR sanitizer/63316
+	* asan.c (asan_expand_check_ifn): Fix up align >= 8 optimization.
+
 2014-09-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	PR tree-optimization/63266

gcc/asan.c

@@ -2585,19 +2585,26 @@ asan_expand_check_ifn (gimple_stmt_iterator *iter, bool use_calls)
 	  gimple shadow_test = build_assign (NE_EXPR, shadow, 0);
 	  gimple_seq seq = NULL;
 	  gimple_seq_add_stmt (&seq, shadow_test);
-	  /* Aligned (>= 8 bytes) access do not need & 7.  */
+	  /* Aligned (>= 8 bytes) can test just
+	     (real_size_in_bytes - 1 >= shadow), as base_addr & 7 is known
+	     to be 0.  */
 	  if (align < 8)
-	    gimple_seq_add_stmt (&seq, build_assign (BIT_AND_EXPR,
-						     base_addr, 7));
-	  gimple_seq_add_stmt (&seq, build_type_cast (shadow_type,
-						      gimple_seq_last (seq)));
-	  if (real_size_in_bytes > 1)
-	    gimple_seq_add_stmt (&seq,
-				 build_assign (PLUS_EXPR, gimple_seq_last (seq),
-					       real_size_in_bytes - 1));
-	  gimple_seq_add_stmt (&seq, build_assign (GE_EXPR,
+	    {
+	      gimple_seq_add_stmt (&seq, build_assign (BIT_AND_EXPR,
+						       base_addr, 7));
+	      gimple_seq_add_stmt (&seq,
+				   build_type_cast (shadow_type,
+						    gimple_seq_last (seq)));
+	      if (real_size_in_bytes > 1)
+		gimple_seq_add_stmt (&seq,
+				     build_assign (PLUS_EXPR,
 						   gimple_seq_last (seq),
-						   shadow));
+						   real_size_in_bytes - 1));
+	      t = gimple_assign_lhs (gimple_seq_last_stmt (seq));
+	    }
+	  else
+	    t = build_int_cst (shadow_type, real_size_in_bytes - 1);
+	  gimple_seq_add_stmt (&seq, build_assign (GE_EXPR, t, shadow));
 	  gimple_seq_add_stmt (&seq, build_assign (BIT_AND_EXPR, shadow_test,
 						   gimple_seq_last (seq)));
 	  t = gimple_assign_lhs (gimple_seq_last (seq));

gcc/testsuite/ChangeLog

+2014-09-24  Jakub Jelinek  <jakub@redhat.com>
+
+	PR sanitizer/63316
+	* c-c++-common/asan/pr63316.c: New test.
+
 2014-09-24  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	PR tree-optimization/63266

gcc/testsuite/c-c++-common/asan/pr63316.c

+/* PR sanitizer/63316 */
+/* { dg-do run } */
+/* { dg-options "-fsanitize=address -O2" } */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+extern void *malloc (__SIZE_TYPE__);
+extern void free (void *);
+#ifdef __cplusplus
+}
+#endif
+
+int
+main ()
+{
+  int *p = (int *) malloc (sizeof (int));
+  *p = 3;
+  asm volatile ("" : : "r" (p) : "memory");
+  free (p);
+  return 0;
+}