1 files changed, 214 insertions, 25 deletions

diff --git a/gcc/tree-ssa-uninit.c b/gcc/tree-ssa-uninit.c
index ae30e24..bd46ddf 100644
--- a/gcc/tree-ssa-uninit.c
+++ b/gcc/tree-ssa-uninit.c
@@ -74,46 +74,173 @@ get_mask_first_set_bit (unsigned mask)
 }
 #define MASK_FIRST_SET_BIT(mask) get_mask_first_set_bit (mask)
 
-
 /* Return true if T, an SSA_NAME, has an undefined value.  */
-
-bool
-ssa_undefined_value_p (tree t)
+static bool
+has_undefined_value_p (tree t)
 {
-  tree var = SSA_NAME_VAR (t);
-
-  if (!var)
-    ;
-  /* Parameters get their initial value from the function entry.  */
-  else if (TREE_CODE (var) == PARM_DECL)
-    return false;
-  /* When returning by reference the return address is actually a hidden
-     parameter.  */
-  else if (TREE_CODE (var) == RESULT_DECL && DECL_BY_REFERENCE (var))
-    return false;
-  /* Hard register variables get their initial value from the ether.  */
-  else if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
-    return false;
-
-  /* The value is undefined iff its definition statement is empty.  */
-  return (gimple_nop_p (SSA_NAME_DEF_STMT (t))
+  return (ssa_undefined_value_p (t)
           || (possibly_undefined_names
               && pointer_set_contains (possibly_undefined_names, t)));
 }
 
-/* Like ssa_undefined_value_p, but don't return true if TREE_NO_WARNING
+
+
+/* Like has_undefined_value_p, but don't return true if TREE_NO_WARNING
    is set on SSA_NAME_VAR.  */
 
 static inline bool
-uninit_undefined_value_p (tree t)
-{
-  if (!ssa_undefined_value_p (t))
+uninit_undefined_value_p (tree t) {
+  if (!has_undefined_value_p (t))
     return false;
   if (SSA_NAME_VAR (t) && TREE_NO_WARNING (SSA_NAME_VAR (t)))
     return false;
   return true;
 }
 
+/* Emit warnings for uninitialized variables.  This is done in two passes.
+
+   The first pass notices real uses of SSA names with undefined values.
+   Such uses are unconditionally uninitialized, and we can be certain that
+   such a use is a mistake.  This pass is run before most optimizations,
+   so that we catch as many as we can.
+
+   The second pass follows PHI nodes to find uses that are potentially
+   uninitialized.  In this case we can't necessarily prove that the use
+   is really uninitialized.  This pass is run after most optimizations,
+   so that we thread as many jumps and possible, and delete as much dead
+   code as possible, in order to reduce false positives.  We also look
+   again for plain uninitialized variables, since optimization may have
+   changed conditionally uninitialized to unconditionally uninitialized.  */
+
+/* Emit a warning for EXPR based on variable VAR at the point in the
+   program T, an SSA_NAME, is used being uninitialized.  The exact
+   warning text is in MSGID and LOCUS may contain a location or be null.
+   WC is the warning code.  */
+
+static void
+warn_uninit (enum opt_code wc, tree t,
+	     tree expr, tree var, const char *gmsgid, void *data)
+{
+  gimple context = (gimple) data;
+  location_t location, cfun_loc;
+  expanded_location xloc, floc;
+
+  if (!has_undefined_value_p (t))
+    return;
+
+  /* TREE_NO_WARNING either means we already warned, or the front end
+     wishes to suppress the warning.  */
+  if ((context
+       && (gimple_no_warning_p (context)
+	   || (gimple_assign_single_p (context)
+	       && TREE_NO_WARNING (gimple_assign_rhs1 (context)))))
+      || TREE_NO_WARNING (expr))
+    return;
+
+  location = (context != NULL && gimple_has_location (context))
+	     ? gimple_location (context)
+	     : DECL_SOURCE_LOCATION (var);
+  location = linemap_resolve_location (line_table, location,
+				       LRK_SPELLING_LOCATION,
+				       NULL);
+  cfun_loc = DECL_SOURCE_LOCATION (cfun->decl);
+  xloc = expand_location (location);
+  floc = expand_location (cfun_loc);
+  if (warning_at (location, wc, gmsgid, expr))
+    {
+      TREE_NO_WARNING (expr) = 1;
+
+      if (location == DECL_SOURCE_LOCATION (var))
+	return;
+      if (xloc.file != floc.file
+	  || linemap_location_before_p (line_table,
+					location, cfun_loc)
+	  || linemap_location_before_p (line_table,
+					cfun->function_end_locus,
+					location))
+	inform (DECL_SOURCE_LOCATION (var), "%qD was declared here", var);
+    }
+}
+
+static unsigned int
+warn_uninitialized_vars (bool warn_possibly_uninitialized)
+{
+  gimple_stmt_iterator gsi;
+  basic_block bb;
+
+  FOR_EACH_BB (bb)
+    {
+      bool always_executed = dominated_by_p (CDI_POST_DOMINATORS,
+					     single_succ (ENTRY_BLOCK_PTR), bb);
+      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+	{
+	  gimple stmt = gsi_stmt (gsi);
+	  use_operand_p use_p;
+	  ssa_op_iter op_iter;
+	  tree use;
+
+	  if (is_gimple_debug (stmt))
+	    continue;
+
+	  /* We only do data flow with SSA_NAMEs, so that's all we
+	     can warn about.  */
+	  FOR_EACH_SSA_USE_OPERAND (use_p, stmt, op_iter, SSA_OP_USE)
+	    {
+	      use = USE_FROM_PTR (use_p);
+	      if (always_executed)
+		warn_uninit (OPT_Wuninitialized, use,
+			     SSA_NAME_VAR (use), SSA_NAME_VAR (use),
+			     "%qD is used uninitialized in this function",
+			     stmt);
+	      else if (warn_possibly_uninitialized)
+		warn_uninit (OPT_Wmaybe_uninitialized, use,
+			     SSA_NAME_VAR (use), SSA_NAME_VAR (use),
+			     "%qD may be used uninitialized in this function",
+			     stmt);
+	    }
+
+	  /* For memory the only cheap thing we can do is see if we
+	     have a use of the default def of the virtual operand.
+	     ???  Note that at -O0 we do not have virtual operands.
+	     ???  Not so cheap would be to use the alias oracle via
+	     walk_aliased_vdefs, if we don't find any aliasing vdef
+	     warn as is-used-uninitialized, if we don't find an aliasing
+	     vdef that kills our use (stmt_kills_ref_p), warn as
+	     may-be-used-uninitialized.  But this walk is quadratic and
+	     so must be limited which means we would miss warning
+	     opportunities.  */
+	  use = gimple_vuse (stmt);
+	  if (use
+	      && gimple_assign_single_p (stmt)
+	      && !gimple_vdef (stmt)
+	      && SSA_NAME_IS_DEFAULT_DEF (use))
+	    {
+	      tree rhs = gimple_assign_rhs1 (stmt);
+	      tree base = get_base_address (rhs);
+
+	      /* Do not warn if it can be initialized outside this function.  */
+	      if (TREE_CODE (base) != VAR_DECL
+		  || DECL_HARD_REGISTER (base)
+		  || is_global_var (base))
+		continue;
+
+	      if (always_executed)
+		warn_uninit (OPT_Wuninitialized, use, 
+			     gimple_assign_rhs1 (stmt), base,
+			     "%qE is used uninitialized in this function",
+			     stmt);
+	      else if (warn_possibly_uninitialized)
+		warn_uninit (OPT_Wmaybe_uninitialized, use,
+			     gimple_assign_rhs1 (stmt), base,
+			     "%qE may be used uninitialized in this function",
+			     stmt);
+	    }
+	}
+    }
+
+  return 0;
+}
+
 /* Checks if the operand OPND of PHI is defined by 
    another phi with one operand defined by this PHI, 
    but the rest operands are all defined. If yes, 
@@ -2084,3 +2211,65 @@ make_pass_late_warn_uninitialized (gcc::context *ctxt)
 {
   return new pass_late_warn_uninitialized (ctxt);
 }
+
+
+static unsigned int
+execute_early_warn_uninitialized (void)
+{
+  /* Currently, this pass runs always but
+     execute_late_warn_uninitialized only runs with optimization. With
+     optimization we want to warn about possible uninitialized as late
+     as possible, thus don't do it here.  However, without
+     optimization we need to warn here about "may be uninitialized".
+  */
+  calculate_dominance_info (CDI_POST_DOMINATORS);
+
+  warn_uninitialized_vars (/*warn_possibly_uninitialized=*/!optimize);
+
+  /* Post-dominator information can not be reliably updated. Free it
+     after the use.  */
+
+  free_dominance_info (CDI_POST_DOMINATORS);
+  return 0;
+}
+
+
+namespace {
+
+const pass_data pass_data_early_warn_uninitialized =
+{
+  GIMPLE_PASS, /* type */
+  "*early_warn_uninitialized", /* name */
+  OPTGROUP_NONE, /* optinfo_flags */
+  true, /* has_gate */
+  true, /* has_execute */
+  TV_TREE_UNINIT, /* tv_id */
+  PROP_ssa, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  0, /* todo_flags_finish */
+};
+
+class pass_early_warn_uninitialized : public gimple_opt_pass
+{
+public:
+  pass_early_warn_uninitialized(gcc::context *ctxt)
+    : gimple_opt_pass(pass_data_early_warn_uninitialized, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  bool gate () { return gate_warn_uninitialized (); }
+  unsigned int execute () { return execute_early_warn_uninitialized (); }
+
+}; // class pass_early_warn_uninitialized
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_early_warn_uninitialized (gcc::context *ctxt)
+{
+  return new pass_early_warn_uninitialized (ctxt);
+}
+
+