RFC: gimple tuples data structures design

[Aldy Hernandez]

Hi folks.

Under Diego's loving whip, I've been taking a look at GIMPLE tuples, and
have come up with a possible layout for the data structures representing
the tuples.  It's a mix between what Mark and Diego's originally suggested
along with a few other things ;-).

Still missing are labels and gimple temporaries, but this should get the
ball going.

I'm anxious to see what people think and suggest.

Cheers.
Aldy


/* All tree structures, including the gimple IL, derive from this base
   structure.  */
struct tree_base GTY(())
{
  ENUM_BITFIELD(tree_code) code : 8;

  unsigned side_effects_flag : 1;
  unsigned constant_flag : 1;
  unsigned addressable_flag : 1;
  unsigned volatile_flag : 1;
  unsigned readonly_flag : 1;
  unsigned unsigned_flag : 1;
  unsigned asm_written_flag: 1;
  unsigned nowarning_flag : 1;

  unsigned used_flag : 1;
  unsigned nothrow_flag : 1;
  unsigned static_flag : 1;
  unsigned public_flag : 1;
  unsigned private_flag : 1;
  unsigned protected_flag : 1;
  unsigned deprecated_flag : 1;
  unsigned invariant_flag : 1;

  unsigned lang_flag_0 : 1;
  unsigned lang_flag_1 : 1;
  unsigned lang_flag_2 : 1;
  unsigned lang_flag_3 : 1;
  unsigned lang_flag_4 : 1;
  unsigned lang_flag_5 : 1;
  unsigned lang_flag_6 : 1;
  unsigned visited : 1;
};

/* This structure is for generic trees.  */
struct tree_common GTY(())
{
  struct tree_base base;
  tree chain;
  tree type;
  union tree_ann_d *ann;
};

/* Gimple statements.

   This includes modify statements (what GENERIC calls MODIFY_EXPR),
   labels, calls, gotos, etc, as well as OpenMP directives.  */
struct gimple_stmt GTY(())
{
  struct tree_base base;
  source_locus locus;
  struct tree_base *operands[1];
};

/* Gimple expressions.

   This includes binary and unary expressions, and conditional 
   expressions.  */
struct gimple_expr GTY(())
{
  struct tree_base base;
  tree type;
  struct gimple_expr *operands[1];
};

/* OpenMP clauses (error, private, shared, etc).  */
struct gimple_omp_clause GTY(())
{
  struct tree_base base;
  enum omp_clause_code code;
  union omp_clause_subcode {
    enum omp_clause_default_kind  default_kind;
    enum omp_clause_schedule_kind schedule_kind;
    enum tree_code                reduction_code;
  } GTY ((skip)) subcode;
  struct tree_base ops[1];
};

/* Gimple SSA names.

   This is the similar to ``tree_ssa_name'' in GENERIC except 
   we save a `tree_ann_d', and a `type'.  We also move `ptr_info'
   and `value_handle' to on-the-side arrays indexed by SSA names
   (or hash tables).  */
struct gimple_ssa_name
{
    struct tree_base base;
    tree var;
    /* `type' is in TREE_TYPE (var) */
    struct gimple_stmt def_stmt;
    unsigned int version;
    struct ssa_use_operand_d imm_uses;
};