Re: [C++ PATCH] overloaded operator fns [6/N]

[Nathan Sidwell <nathan at acm dot org>]

This patch shrinks the lang_fn_decl's operator_code field from 16 to 6 
bits, by storing the compressed operator code instead of the tree_code.

I rename DECL_OVERLOADED_OPERATOR_CODE to 
DECL_OVERLOADED_OPERATOR_CODE_RAW, to remind that it's not a tree_code. 
DECL_OVERLOADED_OPERATOR_CODE_IS remains with checking a literal tree 
code.  It uses preprocessor concatenation to directly map the tree_code 
name to the compressed operator enumeration.  So no runtime indirection!

nathan

--
Nathan Sidwell

2017-11-01  Nathan Sidwell  <nathan@acm.org>

	gcc/cp/
	* cp-tree.h (assign_op_identifier, call_op_identifier): Use
	compressed code.
	(struct lang_decl_fn): Use compressed operator code.
	(DECL_OVERLOADED_OPERATOR_CODE): Replace with ...
	(DECL_OVERLOADED_OPERATOR_CODE_RAW): ... this.
	(DECL_OVERLOADED_OPERATOR_CODE_IS): Use it.
	* decl.c (duplicate_decls): Use DECL_OVERLOADED_OPERATOR_CODE_RAW.
	(build_library_fn): Likewise.
	(grok_op_properties): Likewise.
	* mangle.c (write_unqualified_name): Likewise.
	* method.c (implicitly_declare_fn): Likewise.
	* typeck.c (check_return_expr): Use DECL_OVERLOADED_OPERATOR_IS.

	libcc1/
	* libcp1plugin.cc (plugin_build_decl): Use
	DECL_OVERLOADED_OPERATOR_CODE_RAW.

Index: gcc/cp/cp-tree.h
===================================================================
--- gcc/cp/cp-tree.h	(revision 254311)
+++ gcc/cp/cp-tree.h	(working copy)
@@ -246,8 +246,8 @@ extern GTY(()) tree cp_global_trees[CPTI
 #define deleting_dtor_identifier	cp_global_trees[CPTI_DELETING_DTOR_IDENTIFIER]
 
 #define ovl_op_identifier(ISASS, CODE)  (OVL_OP_INFO(ISASS, CODE)->identifier)
-#define assign_op_identifier (ovl_op_identifier (true, NOP_EXPR))
-#define call_op_identifier (ovl_op_identifier (false, CALL_EXPR))
+#define assign_op_identifier (ovl_op_info[true][OVL_OP_NOP_EXPR].identifier)
+#define call_op_identifier (ovl_op_info[false][OVL_OP_CALL_EXPR].identifier)
 /* The name used for conversion operators -- but note that actual
    conversion functions use special identifiers outside the identifier
    table.  */
@@ -2479,26 +2479,24 @@ struct GTY(()) lang_decl_min {
 struct GTY(()) lang_decl_fn {
   struct lang_decl_min min;
 
-  /* In an overloaded operator, this is the value of
-     DECL_OVERLOADED_OPERATOR_P.
-     FIXME: We should really do better in compressing this.  */
-  ENUM_BITFIELD (tree_code) operator_code : 16;
-
+  /* In a overloaded operator, this is the compressed operator code.  */
+  unsigned ovl_op_code : 6;
   unsigned global_ctor_p : 1;
   unsigned global_dtor_p : 1;
+
   unsigned static_function : 1;
   unsigned pure_virtual : 1;
   unsigned defaulted_p : 1;
   unsigned has_in_charge_parm_p : 1;
   unsigned has_vtt_parm_p : 1;
   unsigned pending_inline_p : 1;
-
   unsigned nonconverting : 1;
   unsigned thunk_p : 1;
+
   unsigned this_thunk_p : 1;
   unsigned hidden_friend_p : 1;
   unsigned omp_declare_reduction_p : 1;
-  /* 3 spare bits.  */
+  unsigned spare : 13;
 
   /* 32-bits padding on 64-bit host.  */
 
@@ -2814,14 +2812,14 @@ struct GTY(()) lang_decl {
   IDENTIFIER_ASSIGN_OP_P (DECL_NAME (NODE))
 
 /* NODE is a function_decl for an overloaded operator.  Return its
-   operator code.   */
-#define DECL_OVERLOADED_OPERATOR_CODE(NODE)			\
-  (LANG_DECL_FN_CHECK (NODE)->operator_code)
+   compressed (raw) operator code.  Note that this is not a TREE_CODE.  */
+#define DECL_OVERLOADED_OPERATOR_CODE_RAW(NODE)		\
+  (LANG_DECL_FN_CHECK (NODE)->ovl_op_code)
 
 /* DECL is an overloaded operator.  Test whether it is for TREE_CODE
    (a literal constant).  */
 #define DECL_OVERLOADED_OPERATOR_IS(DECL, CODE)			\
-  (DECL_OVERLOADED_OPERATOR_CODE (DECL) == CODE)
+  (DECL_OVERLOADED_OPERATOR_CODE_RAW (DECL) == OVL_OP_##CODE)
 
 /* For FUNCTION_DECLs: nonzero means that this function is a
    constructor or a destructor with an extra in-charge parameter to
@@ -5526,7 +5524,8 @@ extern GTY(()) unsigned char ovl_op_mapp
 extern GTY(()) unsigned char ovl_op_alternate[OVL_OP_MAX];
 
 /* Given an ass_op_p boolean and a tree code, return a pointer to its
-   overloaded operator info.  */
+   overloaded operator info.  Tree codes for non-overloaded operators
+   map to the error-operator.  */
 #define OVL_OP_INFO(IS_ASS_P, TREE_CODE)			\
   (&ovl_op_info[(IS_ASS_P) != 0][ovl_op_mapping[(TREE_CODE)]])
 /* Overloaded operator info for an identifier for which
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 254311)
+++ gcc/cp/decl.c	(working copy)
@@ -1920,8 +1920,8 @@ next_arg:;
       DECL_OVERRIDE_P (newdecl) |= DECL_OVERRIDE_P (olddecl);
       DECL_THIS_STATIC (newdecl) |= DECL_THIS_STATIC (olddecl);
       if (DECL_OVERLOADED_OPERATOR_P (olddecl))
-	DECL_OVERLOADED_OPERATOR_CODE (newdecl)
-	  = DECL_OVERLOADED_OPERATOR_CODE (olddecl);
+	DECL_OVERLOADED_OPERATOR_CODE_RAW (newdecl)
+	  = DECL_OVERLOADED_OPERATOR_CODE_RAW (olddecl);
       new_defines_function = DECL_INITIAL (newdecl) != NULL_TREE;
 
       /* Optionally warn about more than one declaration for the same
@@ -4444,7 +4444,8 @@ build_library_fn (tree name, enum tree_c
   DECL_EXTERNAL (fn) = 1;
   TREE_PUBLIC (fn) = 1;
   DECL_ARTIFICIAL (fn) = 1;
-  DECL_OVERLOADED_OPERATOR_CODE (fn) = operator_code;
+  DECL_OVERLOADED_OPERATOR_CODE_RAW (fn)
+    = OVL_OP_INFO (false, operator_code)->ovl_op_code;
   SET_DECL_LANGUAGE (fn, lang_c);
   /* Runtime library routines are, by definition, available in an
      external shared object.  */
@@ -12902,7 +12903,7 @@ grok_op_properties (tree decl, bool comp
       operator_code = ovl_op->tree_code;
       op_flags = ovl_op->flags;
       gcc_checking_assert (operator_code != ERROR_MARK);
-      DECL_OVERLOADED_OPERATOR_CODE (decl) = operator_code;
+      DECL_OVERLOADED_OPERATOR_CODE_RAW (decl) = ovl_op->ovl_op_code;
     }
 
   if (op_flags & OVL_OP_FLAG_ALLOC)
@@ -13046,7 +13047,7 @@ grok_op_properties (tree decl, bool comp
 	  const ovl_op_info_t *ovl_op = &ovl_op_info[false][alt];
 	  gcc_checking_assert (ovl_op->flags == OVL_OP_FLAG_UNARY);
 	  operator_code = ovl_op->tree_code;
-	  DECL_OVERLOADED_OPERATOR_CODE (decl) = operator_code;
+	  DECL_OVERLOADED_OPERATOR_CODE_RAW (decl) = ovl_op->ovl_op_code;
 	}
       else if (arity != 2)
 	{
Index: gcc/cp/mangle.c
===================================================================
--- gcc/cp/mangle.c	(revision 254311)
+++ gcc/cp/mangle.c	(working copy)
@@ -1321,8 +1321,8 @@ write_unqualified_name (tree decl)
       else if (DECL_OVERLOADED_OPERATOR_P (decl))
 	{
 	  const char *mangled_name
-	    = (OVL_OP_INFO (DECL_ASSIGNMENT_OPERATOR_P (decl),
-	       DECL_OVERLOADED_OPERATOR_CODE (decl))->mangled_name);
+	    = (ovl_op_info[DECL_ASSIGNMENT_OPERATOR_P (decl)]
+	       [DECL_OVERLOADED_OPERATOR_CODE_RAW (decl)].mangled_name);
 	  write_string (mangled_name);
 	}
       else if (UDLIT_OPER_P (DECL_NAME (decl)))
Index: gcc/cp/method.c
===================================================================
--- gcc/cp/method.c	(revision 254311)
+++ gcc/cp/method.c	(working copy)
@@ -2078,7 +2078,7 @@ implicitly_declare_fn (special_function_
 
   if (!IDENTIFIER_CDTOR_P (name))
     /* Assignment operator.  */
-    DECL_OVERLOADED_OPERATOR_CODE (fn) = NOP_EXPR;
+    DECL_OVERLOADED_OPERATOR_CODE_RAW (fn) = OVL_OP_NOP_EXPR;
   else if (IDENTIFIER_CTOR_P (name))
     DECL_CXX_CONSTRUCTOR_P (fn) = true;
   else
Index: gcc/cp/typeck.c
===================================================================
--- gcc/cp/typeck.c	(revision 254311)
+++ gcc/cp/typeck.c	(working copy)
@@ -9074,9 +9074,8 @@ check_return_expr (tree retval, bool *no
 
   /* Only operator new(...) throw(), can return NULL [expr.new/13].  */
   if (DECL_OVERLOADED_OPERATOR_P (current_function_decl)
-      && (DECL_OVERLOADED_OPERATOR_CODE (current_function_decl) == NEW_EXPR
-	  || (DECL_OVERLOADED_OPERATOR_CODE (current_function_decl)
-	      == VEC_NEW_EXPR))
+      && (DECL_OVERLOADED_OPERATOR_IS (current_function_decl,  NEW_EXPR)
+	  || DECL_OVERLOADED_OPERATOR_IS (current_function_decl, VEC_NEW_EXPR))
       && !TYPE_NOTHROW_P (TREE_TYPE (current_function_decl))
       && ! flag_check_new
       && retval && null_ptr_cst_p (retval))
Index: libcc1/libcp1plugin.cc
===================================================================
--- libcc1/libcp1plugin.cc	(revision 254311)
+++ libcc1/libcp1plugin.cc	(working copy)
@@ -1412,7 +1412,7 @@ plugin_build_decl (cc1_plugin::connectio
 	DECL_CXX_DESTRUCTOR_P (decl) = 1;
       else if ((sym_flags & GCC_CP_FLAG_SPECIAL_FUNCTION)
 	       && opcode != ERROR_MARK)
-	DECL_OVERLOADED_OPERATOR_CODE (decl) = opcode;
+	DECL_OVERLOADED_OPERATOR_CODE_RAW (decl) = ovl_op_mapping[opcode];
     }
   else if (RECORD_OR_UNION_CODE_P (code))
     {