PR tree-optimization/86914 - wrong code with strlen() of poor-man's flexible…

PR tree-optimization/86914 - wrong code with strlen() of poor-man's flexible array member plus offset

gcc/ChangeLog:

	PR tree-optimization/86914
	* tree-ssa-strlen.c (maybe_set_strlen_range): Avoid MEM_REF.

gcc/testsuite/ChangeLog:

	PR tree-optimization/86914
	* gcc.dg/strlenopt-57.c: New test.

From-SVN: r263905

gcc/ChangeLog

 2018-08-27  Martin Sebor  <msebor@redhat.com>
 
+	PR tree-optimization/86914
+	* tree-ssa-strlen.c (maybe_set_strlen_range): Avoid MEM_REF.
+
+2018-08-27  Martin Sebor  <msebor@redhat.com>
+
 	PR tree-optimization/87112
 	* builtins.c (expand_builtin_strnlen): Convert c_strlen result to
 	the type of the bound argument.

gcc/testsuite/ChangeLog

 2018-08-27  Martin Sebor  <msebor@redhat.com>
 
+	PR tree-optimization/86914
+	* gcc.dg/strlenopt-57.c: New test.
+
+2018-08-27  Martin Sebor  <msebor@redhat.com>
+
 	PR tree-optimization/87112
 	* gcc.dg/pr87112.c: New test.
 

gcc/testsuite/gcc.dg/strlenopt-57.c

+/* PR tree-optimization/86914 - wrong code with strlen() of poor-man's
+   flexible array member plus offset
+   { dg-do compile }
+   { dg-options "-O2 -Wall -fdump-tree-optimized" } */
+
+#include "strlenopt.h"
+
+struct A0 { char i, a[0]; };
+struct A1 { char i, a[1]; };
+struct A9 { char i, a[9]; };
+struct Ax { char i, a[]; };
+
+extern int a[];
+
+extern struct A0 a0;
+extern struct A1 a1;
+extern struct A9 a9;
+extern struct Ax ax;
+
+void test_var_flexarray_cst_off (void)
+{
+  /* Use arbitrary constants greater than 16 in case GCC ever starts
+     unrolling strlen() calls with small array arguments.  */
+  a[0] = 17 < strlen (a0.a + 1);
+  a[1] = 19 < strlen (a1.a + 1);
+  a[2] = 23 < strlen (a9.a + 9);
+  a[3] = 29 < strlen (ax.a + 3);
+}
+
+void test_ptr_flexarray_cst_off (struct A0 *p0, struct A1 *p1,
+				 struct A9 *p9, struct Ax *px)
+{
+  a[0] = 17 < strlen (p0->a + 1);
+  a[1] = 19 < strlen (p1->a + 1);
+  a[2] = 23 < strlen (p9->a + 9);
+  a[3] = 29 < strlen (px->a + 3);
+}
+
+void test_ptr_flexarray_var_off (struct A0 *p0, struct A1 *p1,
+				 struct A9 *p9, struct Ax *px,
+				 int i)
+{
+  a[0] = 17 < strlen (p0->a + i);
+  a[1] = 19 < strlen (p1->a + i);
+  a[2] = 23 < strlen (p9->a + i);
+  a[3] = 29 < strlen (px->a + i);
+}
+
+/* { dg-final { scan-tree-dump-times "strlen" 12 "optimized" } } */

gcc/tree-ssa-strlen.c

@@ -1160,7 +1160,9 @@ maybe_set_strlen_range (tree lhs, tree src, tree bound)
 	 suggests if it's treated as a poor-man's flexible array member.  */
       src = TREE_OPERAND (src, 0);
       bool src_is_array = TREE_CODE (TREE_TYPE (src)) == ARRAY_TYPE;
-      if (src_is_array && !array_at_struct_end_p (src))
+      if (src_is_array
+	  && TREE_CODE (src) != MEM_REF
+	  && !array_at_struct_end_p (src))
 	{
 	  tree type = TREE_TYPE (src);
 	  if (tree size = TYPE_SIZE_UNIT (type))