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

2 files changed, 25 insertions, 22 deletions

diff --git a/gcc/lto/lto-partition.c b/gcc/lto/lto-partition.c
index 32243fb83d3..a642a6c5f17 100644
--- a/gcc/lto/lto-partition.c
+++ b/gcc/lto/lto-partition.c
@@ -55,22 +55,22 @@ get_symbol_class (symtab_node node)
 {
   /* Inline clones are always duplicated.
      This include external delcarations.   */
-  if (symtab_function_p (node)
-      && cgraph (node)->global.inlined_to)
+  cgraph_node *cnode = dyn_cast <cgraph_node> (node);
+  if (cnode && cnode->global.inlined_to)
     return SYMBOL_DUPLICATE;
 
   /* External declarations are external.  */
   if (DECL_EXTERNAL (node->symbol.decl))
     return SYMBOL_EXTERNAL;
 
-  if (symtab_variable_p (node))
+  if (varpool_node *vnode = dyn_cast <varpool_node> (node))
     {
       /* Constant pool references use local symbol names that can not
          be promoted global.  We should never put into a constant pool
          objects that can not be duplicated across partitions.  */
       if (DECL_IN_CONSTANT_POOL (node->symbol.decl))
 	return SYMBOL_DUPLICATE;
-      gcc_checking_assert (varpool (node)->analyzed);
+      gcc_checking_assert (vnode->analyzed);
     }
   /* Functions that are cloned may stay in callgraph even if they are unused.
      Handle them as external; compute_ltrans_boundary take care to make
@@ -145,7 +145,7 @@ add_references_to_partition (ltrans_partition part, symtab_node node)
     /* References to a readonly variable may be constant foled into its value.
        Recursively look into the initializers of the constant variable and add
        references, too.  */
-    else if (symtab_variable_p (ref->referred)
+    else if (is_a <varpool_node> (ref->referred)
 	     && const_value_known_p (ref->referred->symbol.decl)
 	     && !lto_symtab_encoder_in_partition_p (part->encoder, ref->referred))
       {
@@ -196,9 +196,8 @@ add_symbol_to_partition_1 (ltrans_partition part, symtab_node node)
     }
   node->symbol.aux = (void *)((size_t)node->symbol.aux + 1);
 
-  if (symtab_function_p (node))
+  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
     {
-      struct cgraph_node *cnode = cgraph (node);
       struct cgraph_edge *e;
       part->insns += inline_summary (cnode)->self_size;
 
@@ -247,15 +246,15 @@ contained_in_symbol (symtab_node node)
   if (lookup_attribute ("weakref",
 			DECL_ATTRIBUTES (node->symbol.decl)))
     return node;
-  if (symtab_function_p (node))
+  if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
     {
-      struct cgraph_node *cnode = cgraph_function_node (cgraph (node), NULL);
+      cnode = cgraph_function_node (cnode, NULL);
       if (cnode->global.inlined_to)
 	cnode = cnode->global.inlined_to;
       return (symtab_node) cnode;
     }
-  else if (symtab_variable_p (node))
-    return (symtab_node) varpool_variable_node (varpool (node), NULL);
+  else if (varpool_node *vnode = dyn_cast <varpool_node> (node))
+    return (symtab_node) varpool_variable_node (vnode, NULL);
   return node;
 }
 
@@ -302,8 +301,8 @@ undo_partition (ltrans_partition partition, unsigned int n_nodes)
 	pointer_set_destroy (partition->initializers_visited);
       partition->initializers_visited = NULL;
 
-      if (symtab_function_p (node))
-        partition->insns -= inline_summary (cgraph (node))->self_size;
+      if (cgraph_node *cnode = dyn_cast <cgraph_node> (node))
+        partition->insns -= inline_summary (cnode)->self_size;
       lto_symtab_encoder_delete_node (partition->encoder, node);
       node->symbol.aux = (void *)((size_t)node->symbol.aux - 1);
     }
@@ -555,11 +554,10 @@ lto_balanced_map (void)
 	  symtab_node snode = lto_symtab_encoder_deref (partition->encoder,
 							last_visited_node);
 
-	  if (symtab_function_p (snode))
+	  if (cgraph_node *node = dyn_cast <cgraph_node> (snode))
 	    {
 	      struct cgraph_edge *edge;
 
-	      node = cgraph (snode);
 	      refs = &node->symbol.ref_list;
 
 	      last_visited_node++;
@@ -611,7 +609,7 @@ lto_balanced_map (void)
 	  /* Compute boundary cost of IPA REF edges and at the same time look into
 	     variables referenced from current partition and try to add them.  */
 	  for (j = 0; ipa_ref_list_reference_iterate (refs, j, ref); j++)
-	    if (symtab_variable_p (ref->referred))
+	    if (is_a <varpool_node> (ref->referred))
 	      {
 		int index;
 
@@ -645,7 +643,7 @@ lto_balanced_map (void)
 		  cost++;
 	      }
 	  for (j = 0; ipa_ref_list_referring_iterate (refs, j, ref); j++)
-	    if (symtab_variable_p (ref->referring))
+	    if (is_a <varpool_node> (ref->referring))
 	      {
 		int index;
 
diff --git a/gcc/lto/lto.c b/gcc/lto/lto.c
index 7f64daee219..857e8f6032b 100644
--- a/gcc/lto/lto.c
+++ b/gcc/lto/lto.c
@@ -2671,12 +2671,17 @@ lto_wpa_write_files (void)
 	      if (!lto_symtab_encoder_in_partition_p (part->encoder, node))
 		{
 	          fprintf (cgraph_dump_file, "%s ", symtab_node_asm_name (node));
-		  if (symtab_function_p (node)
-		      && lto_symtab_encoder_encode_body_p (part->encoder, cgraph (node)))
+		  cgraph_node *cnode = dyn_cast <cgraph_node> (node);
+		  if (cnode
+		      && lto_symtab_encoder_encode_body_p (part->encoder, cnode))
 		    fprintf (cgraph_dump_file, "(body included)");
-		  else if (symtab_variable_p (node)
-		           && lto_symtab_encoder_encode_initializer_p (part->encoder, varpool (node)))
-		    fprintf (cgraph_dump_file, "(initializer included)");
+		  else
+		    {
+		      varpool_node *vnode = dyn_cast <varpool_node> (node);
+		      if (vnode
+			  && lto_symtab_encoder_encode_initializer_p (part->encoder, vnode))
+			fprintf (cgraph_dump_file, "(initializer included)");
+		    }
 		}
 	    }
 	  fprintf (cgraph_dump_file, "\n");