[PATCH] tree-ssa-strlen improvements (PR tree-optimization/71625)

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

This is just first small step towards this PR.
It brings the ADDR_EXPR of DECL_P bases roughly on the same level as
SSA_NAMEs pointers - so get_stridx_plus_constant works for them, and
more importantly, before this patch there was a very severe bug in
addr_stridxptr (missing list = list->next; in the loop), which meant that
inside of a single decl we were tracking at most one string length, rather
than the former 16 (or now 32) limit.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

As a follow-up, I'd like to introduce string length at least N, where we
don't know the exact string length, but we know there are no '\0' chars
within N bytes.

2016-06-28  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/71625
	* tree-ssa-strlen.c (get_addr_stridx): Add PTR argument.  Assume list
	is sorted by ascending list->offset.  If PTR is non-NULL and there is
	previous strinfo, call get_stridx_plus_constant.
	(get_stridx): Pass exp as second argument to get_addr_stridx.
	(addr_stridxptr): Add missing list = list->next, so that there can be
	more than one entries in the list.  Bump limit from 16 to 32.  Ensure
	the list is sorted by ascending list->offset.
	(get_stridx_plus_constant): Adjust so that it can be also called with
	ADDR_EXPR instead of SSA_NAME as PTR.
	(handle_char_store): Pass NULL_TREE as second argument to
	get_addr_stridx.

	* gcc.dg/strlenopt-28.c: New test.

--- gcc/tree-ssa-strlen.c.jj	2016-06-28 10:21:22.103693623 +0200
+++ gcc/tree-ssa-strlen.c	2016-06-28 13:41:56.797718522 +0200
@@ -159,10 +159,10 @@ get_strinfo (int idx)
 /* Helper function for get_stridx.  */
 
 static int
-get_addr_stridx (tree exp)
+get_addr_stridx (tree exp, tree ptr)
 {
   HOST_WIDE_INT off;
-  struct stridxlist *list;
+  struct stridxlist *list, *last = NULL;
   tree base;
 
   if (!decl_to_stridxlist_htab)
@@ -180,9 +180,22 @@ get_addr_stridx (tree exp)
     {
       if (list->offset == off)
 	return list->idx;
+      if (list->offset > off)
+	return 0;
+      last = list;
       list = list->next;
     }
   while (list);
+
+  if (ptr && last && last->idx > 0)
+    {
+      strinfo *si = get_strinfo (last->idx);
+      if (si
+	  && si->length
+	  && TREE_CODE (si->length) == INTEGER_CST
+	  && compare_tree_int (si->length, off - last->offset) != -1)
+	return get_stridx_plus_constant (si, off - last->offset, ptr);
+    }
   return 0;
 }
 
@@ -234,7 +247,7 @@ get_stridx (tree exp)
 
   if (TREE_CODE (exp) == ADDR_EXPR)
     {
-      int idx = get_addr_stridx (TREE_OPERAND (exp, 0));
+      int idx = get_addr_stridx (TREE_OPERAND (exp, 0), exp);
       if (idx != 0)
 	return idx;
     }
@@ -304,15 +317,29 @@ addr_stridxptr (tree exp)
   if (existed)
     {
       int i;
-      for (i = 0; i < 16; i++)
+      stridxlist *before = NULL;
+      for (i = 0; i < 32; i++)
 	{
 	  if (list->offset == off)
 	    return &list->idx;
+	  if (list->offset > off && before == NULL)
+	    before = list;
 	  if (list->next == NULL)
 	    break;
+	  list = list->next;
 	}
-      if (i == 16)
+      if (i == 32)
 	return NULL;
+      if (before)
+	{
+	  list = before;
+	  before = XOBNEW (&stridx_obstack, struct stridxlist);
+	  *before = *list;
+	  list->next = before;
+	  list->offset = off;
+	  list->idx = 0;
+	  return &list->idx;
+	}
       list->next = XOBNEW (&stridx_obstack, struct stridxlist);
       list = list->next;
     }
@@ -613,9 +640,7 @@ verify_related_strinfos (strinfo *origsi
 static int
 get_stridx_plus_constant (strinfo *basesi, HOST_WIDE_INT off, tree ptr)
 {
-  gcc_checking_assert (TREE_CODE (ptr) == SSA_NAME);
-
-  if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ptr))
+  if (TREE_CODE (ptr) == SSA_NAME && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (ptr))
     return 0;
 
   if (basesi->length == NULL_TREE
@@ -633,7 +658,8 @@ get_stridx_plus_constant (strinfo *bases
       || TREE_CODE (si->length) != INTEGER_CST)
     return 0;
 
-  if (ssa_ver_to_stridx.length () <= SSA_NAME_VERSION (ptr))
+  if (TREE_CODE (ptr) == SSA_NAME
+      && ssa_ver_to_stridx.length () <= SSA_NAME_VERSION (ptr))
     ssa_ver_to_stridx.safe_grow_cleared (num_ssa_names);
 
   gcc_checking_assert (compare_tree_int (si->length, off) != -1);
@@ -651,6 +677,7 @@ get_stridx_plus_constant (strinfo *bases
 	{
 	  if (r == 0)
 	    {
+	      gcc_assert (TREE_CODE (ptr) == SSA_NAME);
 	      ssa_ver_to_stridx[SSA_NAME_VERSION (ptr)] = si->idx;
 	      return si->idx;
 	    }
@@ -2063,7 +2090,7 @@ handle_char_store (gimple_stmt_iterator
 	}
     }
   else
-    idx = get_addr_stridx (lhs);
+    idx = get_addr_stridx (lhs, NULL_TREE);
 
   if (idx > 0)
     {
--- gcc/testsuite/gcc.dg/strlenopt-28.c.jj	2016-06-28 13:57:06.768016510 +0200
+++ gcc/testsuite/gcc.dg/strlenopt-28.c	2016-06-28 13:55:01.000000000 +0200
@@ -0,0 +1,59 @@
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-strlen" } */
+
+#include "strlenopt.h"
+
+volatile int v;
+
+size_t
+f1 (void)
+{
+  char a[30];
+  v += 1;
+  memcpy (a, "1234567", 8);
+  memcpy (a + 7, "89abcdefg", 10);
+  memcpy (a + 16, "h", 2);
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+size_t
+f2 (void)
+{
+  char a[30];
+  v += 2;
+  strcpy (a, "1234567");
+  strcpy (a + 7, "89abcdefg");
+  strcpy (a + 16, "h");
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+size_t
+f3 (char *a)
+{
+  v += 3;
+  memcpy (a, "1234567", 8);
+  memcpy (a + 7, "89abcdefg", 10);
+  memcpy (a + 16, "h", 2);
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+size_t
+f4 (char *a)
+{
+  v += 4;
+  strcpy (a, "1234567");
+  strcpy (a + 7, "89abcdefg");
+  strcpy (a + 16, "h");
+  return strlen (a);	// This strlen should be optimized into 17.
+}
+
+int
+main ()
+{
+  char a[30];
+  if (f1 () != 17 || f2 () != 17 || f3 (a) != 17 || f4 (a) != 17)
+    abort ();
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "strlen \\(" 0 "strlen" } } */

	Jakub