[PATCH] Avoid static initialization in the strlen pass

[Jakub Jelinek <jakub at redhat dot com>]

Hi!

All the hash_maps in tree-ssa-strlen.c except for the newly added one
were pointers to hash maps, which were constructed either lazily or during
the pass.  But strlen_to_stridx is now constructed at the compiler start,
which is something I'd prefer to avoid, it affects even -O0 that way and
empty/small file compilation, something e.g. the kernel folks care so much
about.

Apparently the hash map is only needed when one of the two warnings
is enabled, so this patch initializes it only in that case and otherwise
doesn't fill it or query it.

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

2017-11-20  Jakub Jelinek  <jakub@redhat.com>

	* tree-ssa-strlen.c (strlen_to_stridx): Change into a pointer to
	hash_map.
	(handle_builtin_strlen, strlen_optimize_stmt): Only access it
	if non-NULL, instead of . use ->.
	(handle_builtin_stxncpy): Return early if strlen_to_stridx
	is NULL.  Spelling fix.  Instead of . use ->.
	(pass_strlen::execute): Allocate strlen_to_stridx if
	warn_stringop_{truncation,overflow}.  Instead of calling empty on it
	delete it and clear it at the end of the pass.

--- gcc/tree-ssa-strlen.c.jj	2017-11-15 09:40:03.000000000 +0100
+++ gcc/tree-ssa-strlen.c	2017-11-20 18:10:42.565458585 +0100
@@ -153,7 +153,7 @@ struct decl_stridxlist_map
 static hash_map<tree_decl_hash, stridxlist> *decl_to_stridxlist_htab;
 
 typedef std::pair<int, location_t> stridx_strlenloc;
-static hash_map<tree, stridx_strlenloc> strlen_to_stridx;
+static hash_map<tree, stridx_strlenloc> *strlen_to_stridx;
 
 /* Obstack for struct stridxlist and struct decl_stridxlist_map.  */
 static struct obstack stridx_obstack;
@@ -1207,8 +1207,11 @@ handle_builtin_strlen (gimple_stmt_itera
 	      gcc_assert (si->full_string_p);
 	    }
 
-	  location_t loc = gimple_location (stmt);
-	  strlen_to_stridx.put (lhs, stridx_strlenloc (idx, loc));
+	  if (strlen_to_stridx)
+	    {
+	      location_t loc = gimple_location (stmt);
+	      strlen_to_stridx->put (lhs, stridx_strlenloc (idx, loc));
+	    }
 	  return;
 	}
     }
@@ -1253,8 +1256,11 @@ handle_builtin_strlen (gimple_stmt_itera
       set_strinfo (idx, si);
       find_equal_ptrs (src, idx);
 
-      location_t loc = gimple_location (stmt);
-      strlen_to_stridx.put (lhs, stridx_strlenloc (idx, loc));
+      if (strlen_to_stridx)
+	{
+	  location_t loc = gimple_location (stmt);
+	  strlen_to_stridx->put (lhs, stridx_strlenloc (idx, loc));
+	}
     }
 }
 
@@ -1909,6 +1915,9 @@ maybe_diag_stxncpy_trunc (gimple_stmt_it
 static void
 handle_builtin_stxncpy (built_in_function, gimple_stmt_iterator *gsi)
 {
+  if (strlen_to_stridx == NULL)
+    return;
+
   gimple *stmt = gsi_stmt (*gsi);
 
   bool with_bounds = gimple_call_with_bounds_p (stmt);
@@ -1917,9 +1926,9 @@ handle_builtin_stxncpy (built_in_functio
   tree len = gimple_call_arg (stmt, with_bounds ? 3 : 2);
 
   /* If the length argument was computed from strlen(S) for some string
-     S retrieve the strinfo index for the string (PSS->FIRST) alonng with
+     S retrieve the strinfo index for the string (PSS->FIRST) along with
      the location of the strlen() call (PSS->SECOND).  */
-  stridx_strlenloc *pss = strlen_to_stridx.get (len);
+  stridx_strlenloc *pss = strlen_to_stridx->get (len);
   if (!pss || pss->first <= 0)
     {
       if (maybe_diag_stxncpy_trunc (*gsi, src, len))
@@ -2966,9 +2975,12 @@ strlen_optimize_stmt (gimple_stmt_iterat
 	  fold_strstr_to_strncmp (gimple_assign_rhs1 (stmt),
 				  gimple_assign_rhs2 (stmt), stmt);
 
-	tree rhs1 = gimple_assign_rhs1 (stmt);
-	if (stridx_strlenloc *ps = strlen_to_stridx.get (rhs1))
-	  strlen_to_stridx.put (lhs, stridx_strlenloc (*ps));
+	if (strlen_to_stridx)
+	  {
+	    tree rhs1 = gimple_assign_rhs1 (stmt);
+	    if (stridx_strlenloc *ps = strlen_to_stridx->get (rhs1))
+	      strlen_to_stridx->put (lhs, stridx_strlenloc (*ps));
+	  }
       }
     else if (TREE_CODE (lhs) != SSA_NAME && !TREE_SIDE_EFFECTS (lhs))
 	{
@@ -3202,6 +3214,9 @@ pass_strlen::execute (function *fun)
   ssa_ver_to_stridx.safe_grow_cleared (num_ssa_names);
   max_stridx = 1;
 
+  if (warn_stringop_truncation || warn_stringop_overflow)
+    strlen_to_stridx = new hash_map<tree, stridx_strlenloc> (64);
+
   calculate_dominance_info (CDI_DOMINATORS);
 
   /* String length optimization is implemented as a walk of the dominator
@@ -3220,7 +3235,11 @@ pass_strlen::execute (function *fun)
   laststmt.len = NULL_TREE;
   laststmt.stridx = 0;
 
-  strlen_to_stridx.empty ();
+  if (strlen_to_stridx)
+    {
+      delete strlen_to_stridx;
+      strlen_to_stridx = NULL;
+    }
 
   return 0;
 }

	Jakub