This patch implements generic type query and conversion functions,

and applies them to the use of cgraph_node, varpool_node, and symtab_node.

The functions are:

bool is_a <TYPE> (pointer)
  Tests whether the pointer actually points to a more derived TYPE.

TYPE *as_a <TYPE> (pointer)
  Converts pointer to a TYPE*.

TYPE *dyn_cast <TYPE> (pointer)
  Converts pointer to TYPE* if and only if "is_a <TYPE> pointer".
  Otherwise, returns NULL.
  This function is essentially a checked down cast.

These functions reduce compile time and increase type safety when treating a
generic item as a more specific item.  In essence, the code change is from

  if (symtab_function_p (node))
    {
      struct cgraph_node *cnode = cgraph (node);
      ....
    }

to

  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
    {
      ....
    }

The necessary conditional test defines a variable that holds a known good
pointer to the specific item and avoids subsequent conversion calls and
the assertion checks that may come with them.

When, the property test is embedded within a larger condition, the variable
declaration gets pulled out of the condition.  (This leaves some room for
using the variable inappropriately.)

  if (symtab_variable_p (node)
      && varpool (node)->finalized)
    varpool_analyze_node (varpool (node));

becomes

  varpool_node *vnode = dyn_cast <varpool_node> (node);
  if (vnode && vnode->finalized)
    varpool_analyze_node (vnode);

Note that we have converted two sets of assertions in the calls to varpool
into safe and efficient use of a variable.


There are remaining calls to symtab_function_p and symtab_variable_p that
do not involve a pointer to a more specific type.  These have been converted
to calls to a functions is_a <cgraph_node> and is_a <varpool_node>.  The
original predicate functions have been removed.

The cgraph.h header defined both a struct and a function with the name
varpool_node.  This name overloading can cause some unintuitive error messages
when, as is common in C++, one omits the struct keyword when using the type.
I have renamed the function to varpool_node_for_decl.

Tested on x86_64.


Index: gcc/ChangeLog

2012-10-31  Lawrence Crowl  <crowl@google.com>

	* is-a.h: New.
	(is_a <T> (U*)): New.  Test for is-a relationship.
	(as_a <T> (U*)): New.  Treat as a derived type.
	(dyn_cast <T> (U*)): New.  Conditionally cast based on is_a.
	* cgraph.h (varpool_node): Rename to varpool_node_for_decl.
	Adjust callers to match.
	(is_a_helper <cgraph_node>::test (symtab_node_def *)): New.
	(is_a_helper <varpool_node>::test (symtab_node_def *)): New.
	(symtab_node_def::try_function): New.  Change most calls to
	symtab_function_p with calls to dyn_cast <cgraph_node> (p).
	(symtab_node_def::try_variable): New.  Change most calls to
	symtab_variable_p with calls to dyn_cast <varpool_node> (p).
	(symtab_function_p): Remove.  Change callers to use
        is_a <cgraph_node> (p) instead.
	(symtab_variable_p): Remove.  Change callers to use
        is_a <varpool_node> (p) instead.
	* cgraph.c (cgraph_node_for_asm): Remove redundant call to
	symtab_node_for_asm.
	* cgraphunit.c (symbol_finalized_and_needed): New.
	(symbol_finalized): New.
	(cgraph_analyze_functions): Split complicated conditionals out into
	above new functions.
	* Makefile.in (CGRAPH_H): Add is-a.h as used by cgraph.h.

From-SVN: r193051

1 files changed, 17 insertions, 16 deletions

diff --git a/gcc/symtab.c b/gcc/symtab.c
index c21edcb..39753e2 100644
--- a/gcc/symtab.c
+++ b/gcc/symtab.c
@@ -104,7 +104,7 @@ eq_assembler_name (const void *p1, const void *p2)
 static void
 insert_to_assembler_name_hash (symtab_node node)
 {
-  if (symtab_variable_p (node) && DECL_HARD_REGISTER (node->symbol.decl))
+  if (is_a <varpool_node> (node) && DECL_HARD_REGISTER (node->symbol.decl))
     return;
   gcc_checking_assert (!node->symbol.previous_sharing_asm_name
 		       && !node->symbol.next_sharing_asm_name);
@@ -252,8 +252,8 @@ symtab_unregister_node (symtab_node node)
   if (*slot == node)
     {
       symtab_node replacement_node = NULL;
-      if (symtab_function_p (node))
-	replacement_node = (symtab_node)cgraph_find_replacement_node (cgraph (node));
+      if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
+	replacement_node = (symtab_node)cgraph_find_replacement_node (cnode);
       if (!replacement_node)
 	htab_clear_slot (symtab_hash, slot);
       else
@@ -294,10 +294,10 @@ symtab_get_node (const_tree decl)
 void
 symtab_remove_node (symtab_node node)
 {
-  if (symtab_function_p (node))
-    cgraph_remove_node (cgraph (node));
-  else if (symtab_variable_p (node))
-    varpool_remove_node (varpool (node));
+  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
+    cgraph_remove_node (cnode);
+  else if (varpool_node *vnode = dyn_cast <varpool_node> (node))
+    varpool_remove_node (vnode);
 }
 
 /* Initalize asm name hash unless.  */
@@ -538,10 +538,10 @@ dump_symtab_base (FILE *f, symtab_node node)
 void
 dump_symtab_node (FILE *f, symtab_node node)
 {
-  if (symtab_function_p (node))
-    dump_cgraph_node (f, cgraph (node));
-  else if (symtab_variable_p (node))
-    dump_varpool_node (f, varpool (node));
+  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
+    dump_cgraph_node (f, cnode);
+  else if (varpool_node *vnode = dyn_cast <varpool_node> (node))
+    dump_varpool_node (f, vnode);
 }
 
 /* Dump symbol table.  */
@@ -579,7 +579,7 @@ verify_symtab_base (symtab_node node)
   bool error_found = false;
   symtab_node hashed_node;
 
-  if (symtab_function_p (node))
+  if (is_a <cgraph_node> (node))
     {
       if (TREE_CODE (node->symbol.decl) != FUNCTION_DECL)
 	{
@@ -587,7 +587,7 @@ verify_symtab_base (symtab_node node)
           error_found = true;
 	}
     }
-  else if (symtab_variable_p (node))
+  else if (is_a <varpool_node> (node))
     {
       if (TREE_CODE (node->symbol.decl) != VAR_DECL)
 	{
@@ -622,7 +622,8 @@ verify_symtab_base (symtab_node node)
 	  hashed_node = hashed_node->symbol.next_sharing_asm_name;
 	}
       if (!hashed_node
-          && !(symtab_variable_p (node) || DECL_HARD_REGISTER (node->symbol.decl)))
+          && !(is_a <varpool_node> (node)
+	       || DECL_HARD_REGISTER (node->symbol.decl)))
 	{
           error ("node not found in symtab assembler name hash");
           error_found = true;
@@ -676,8 +677,8 @@ verify_symtab_node (symtab_node node)
     return;
 
   timevar_push (TV_CGRAPH_VERIFY);
-  if (symtab_function_p (node))
-    verify_cgraph_node (cgraph (node));
+  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
+    verify_cgraph_node (cnode);
   else
     if (verify_symtab_base (node))
       {