PR 81292: ICE on related strlens after r249880

PR 81292: ICE on related strlens after r249880

[Richard Sandiford]

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.

Tested on x86_64-linux-gnu and aarch64-linux-gnu.  OK to install?

Sorry for the breakage.

Richard


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.

Index: gcc/tree-ssa-strlen.c
===================================================================
--- gcc/tree-ssa-strlen.c	2017-07-03 21:00:21.438433126 +0100
+++ gcc/tree-ssa-strlen.c	2017-07-03 21:00:34.971809881 +0100
@@ -1214,8 +1214,23 @@ handle_builtin_strlen (gimple_stmt_itera
 	      /* 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;
 	}
Index: gcc/testsuite/gcc.dg/pr81292-1.c
===================================================================
--- /dev/null	2017-07-03 19:11:31.344941082 +0100
+++ gcc/testsuite/gcc.dg/pr81292-1.c	2017-07-03 21:00:34.971809881 +0100
@@ -0,0 +1,35 @@
+/* { 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" } } */
Index: gcc/testsuite/gcc.dg/pr81292-2.c
===================================================================
--- /dev/null	2017-07-03 19:11:31.344941082 +0100
+++ gcc/testsuite/gcc.dg/pr81292-2.c	2017-07-03 21:00:34.971809881 +0100
@@ -0,0 +1,35 @@
+/* { 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" } } */

Re: PR 81292: ICE on related strlens after r249880

[Jakub Jelinek]

On Tue, Jul 04, 2017 at 12:14:48PM +0100, Richard Sandiford wrote:
> 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.
> 
> Tested on x86_64-linux-gnu and aarch64-linux-gnu.  OK to install?
> 
> Sorry for the breakage.
> 
> Richard
> 
> 
> 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.

Ok, thanks.

	Jakub