PR 81292: ICE on related strlens after r249880

r249880 installed the result of a strlen in a strinfo if the strinfo
wasn't previously a full string.  But as Jakub says in the PR comments,
we can't just do that in isolation, because there are no vdefs on the
call that would invalidate any related strinfos.

This patch updates the related strinfos if the adjustment is simple and
invalidates them otherwise.  As elsewhere, we treat adjustments of the
form strlen +/- INTEGER_CST as simple but anything else as too complex.

2017-07-04  Richard Sandiford  <richard.sandiford@linaro.org>

gcc/
	PR tree-optimization/81292
	* tree-ssa-strlen.c (handle_builtin_strlen): When setting
	full_string_p, also call adjust_related_strinfos if the adjustment
	is simple, otherwise invalidate related strinfos.

gcc/testsuite/
	PR tree-optimization/81292
	* gcc.dg/pr81292-1.c: New test.
	* gcc.dg/pr81292-2.c: Likewise.

From-SVN: r249961

gcc/ChangeLog

+2017-07-04  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR tree-optimization/81292
+	* tree-ssa-strlen.c (handle_builtin_strlen): When setting
+	full_string_p, also call adjust_related_strinfos if the adjustment
+	is simple, otherwise invalidate related strinfos.
+
 2017-07-04  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/81040

gcc/testsuite/ChangeLog

+2017-07-04  Richard Sandiford  <richard.sandiford@linaro.org>
+
+	PR tree-optimization/81292
+	* gcc.dg/pr81292-1.c: New test.
+	* gcc.dg/pr81292-2.c: Likewise.
+
 2017-07-04  Martin Liska  <mliska@suse.cz>
 
 	PR sanitizer/81040

gcc/testsuite/gcc.dg/pr81292-1.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+char a[10];
+
+int __attribute__ ((noinline, noclone))
+f1 (int n)
+{
+  a[0] = '1';
+  a[1] = '2';
+  return strlen (a + 1) < n ? strlen (a) : 100;
+}
+
+int __attribute__ ((noinline, noclone))
+f2 (char *a, int n)
+{
+  a[0] = '1';
+  a[1] = '2';
+  return strlen (a + 1) < n ? strlen (a) : 100;
+}
+
+int
+main (void)
+{
+  char b[10];
+  strcpy (a + 2, "345");
+  strcpy (b + 2, "34567");
+  if (f1 (100) != 5 || f2 (b, 100) != 7)
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 2 "strlen" } } */

gcc/testsuite/gcc.dg/pr81292-2.c

+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+char a[] = { 0, 'a', 0, 'b', 'c', 0, 'd', 'e', 'f', 0 };
+
+int __attribute__ ((noinline, noclone))
+f1 (void)
+{
+  a[0] = '1';
+  a[strlen (a)] = '2';
+  a[strlen (a)] = '3';
+  return strlen (a);
+}
+
+int __attribute__ ((noinline, noclone))
+f2 (char *a)
+{
+  a[0] = '1';
+  a[strlen (a)] = '2';
+  a[strlen (a)] = '3';
+  return strlen (a);
+}
+
+int
+main (void)
+{
+  char b[] = { 0, 0, 'a', 'b', 0, 0 };
+  if (f1 () != 9 || f2 (b) != 5)
+    __builtin_abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 6 "strlen" } } */

gcc/tree-ssa-strlen.c

@@ -1214,8 +1214,23 @@ handle_builtin_strlen (gimple_stmt_iterator *gsi)
 	      /* Until now we only had a lower bound on the string length.
 		 Install LHS as the actual length.  */
 	      si = unshare_strinfo (si);
+	      tree old = si->nonzero_chars;
 	      si->nonzero_chars = lhs;
 	      si->full_string_p = true;
+	      if (TREE_CODE (old) == INTEGER_CST)
+		{
+		  location_t loc = gimple_location (stmt);
+		  old = fold_convert_loc (loc, TREE_TYPE (lhs), old);
+		  tree adj = fold_build2_loc (loc, MINUS_EXPR,
+					      TREE_TYPE (lhs), lhs, old);
+		  adjust_related_strinfos (loc, si, adj);
+		}
+	      else
+		{
+		  si->first = 0;
+		  si->prev = 0;
+		  si->next = 0;
+		}
 	    }
 	  return;
 	}