gcc/gcc/cfgloop.h

/* Natural loop functions
   Copyright (C) 1987, 1997, 1998, 1999, 2000, 2001, 2002, 2003
   Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 2, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING.  If not, write to the Free
Software Foundation, 59 Temple Place - Suite 330, Boston, MA
02111-1307, USA.  */

/* Structure to hold decision about unrolling/peeling.  */
enum lpt_dec
{
  LPT_NONE,
  LPT_PEEL_COMPLETELY,
  LPT_PEEL_SIMPLE,
  LPT_UNROLL_CONSTANT,
  LPT_UNROLL_RUNTIME,
  LPT_UNROLL_STUPID
};

struct lpt_decision
{
  enum lpt_dec decision;
  unsigned times;
};

/* Description of loop for simple loop unrolling.  */
struct loop_desc
{
  int postincr;		/* 1 if increment/decrement is done after loop exit condition.  */
  rtx stride;		/* Value added to VAR in each iteration.  */
  rtx var;		/* Loop control variable.  */
  rtx var_alts;		/* List of definitions of its initial value.  */
  rtx lim;		/* Expression var is compared with.  */
  rtx lim_alts;		/* List of definitions of its initial value.  */
  bool const_iter;      /* True if it iterates constant number of times.  */
  unsigned HOST_WIDE_INT niter;
			/* Number of iterations if it is constant.  */
  bool may_be_zero;     /* If we cannot determine that the first iteration will pass.  */
  enum rtx_code cond;	/* Exit condition.  */
  int neg;		/* Set to 1 if loop ends when condition is satisfied.  */
  edge out_edge;	/* The exit edge.  */
  edge in_edge;		/* And the other one.  */
  int n_branches;	/* Number of branches inside the loop.  */
};

/* Structure to hold information for each natural loop.  */
struct loop
{
  /* Index into loops array.  */
  int num;

  /* Basic block of loop header.  */
  basic_block header;

  /* Basic block of loop latch.  */
  basic_block latch;

  /* Basic block of loop preheader or NULL if it does not exist.  */
  basic_block pre_header;

  /* For loop unrolling/peeling decision.  */
  struct lpt_decision lpt_decision;

  /* Simple loop description.  */
  int simple;
  struct loop_desc desc;
  int has_desc;

  /* Number of loop insns.  */
  unsigned ninsns;

  /* Average number of executed insns per iteration.  */
  unsigned av_ninsns;

  /* Array of edges along the preheader extended basic block trace.
     The source of the first edge is the root node of preheader
     extended basic block, if it exists.  */
  edge *pre_header_edges;

  /* Number of edges along the pre_header extended basic block trace.  */
  int num_pre_header_edges;

  /* The first block in the loop.  This is not necessarily the same as
     the loop header.  */
  basic_block first;

  /* The last block in the loop.  This is not necessarily the same as
     the loop latch.  */
  basic_block last;

  /* Bitmap of blocks contained within the loop.  */
  sbitmap nodes;

  /* Number of blocks contained within the loop.  */
  unsigned num_nodes;

  /* Array of edges that enter the loop.  */
  edge *entry_edges;

  /* Number of edges that enter the loop.  */
  int num_entries;

  /* Array of edges that exit the loop.  */
  edge *exit_edges;

  /* Number of edges that exit the loop.  */
  int num_exits;

  /* Bitmap of blocks that dominate all exits of the loop.  */
  sbitmap exits_doms;

  /* The loop nesting depth.  */
  int depth;

  /* Superloops of the loop.  */
  struct loop **pred;

  /* The height of the loop (enclosed loop levels) within the loop
     hierarchy tree.  */
  int level;

  /* The outer (parent) loop or NULL if outermost loop.  */
  struct loop *outer;

  /* The first inner (child) loop or NULL if innermost loop.  */
  struct loop *inner;

  /* Link to the next (sibling) loop.  */
  struct loop *next;

  /* Loop that is copy of this loop.  */
  struct loop *copy;

  /* Non-zero if the loop is invalid (e.g., contains setjmp.).  */
  int invalid;

  /* Auxiliary info specific to a pass.  */
  void *aux;

  /* The following are currently used by loop.c but they are likely to
     disappear as loop.c is converted to use the CFG.  */

  /* Non-zero if the loop has a NOTE_INSN_LOOP_VTOP.  */
  rtx vtop;

  /* Non-zero if the loop has a NOTE_INSN_LOOP_CONT.
     A continue statement will generate a branch to NEXT_INSN (cont).  */
  rtx cont;

  /* The dominator of cont.  */
  rtx cont_dominator;

  /* The NOTE_INSN_LOOP_BEG.  */
  rtx start;

  /* The NOTE_INSN_LOOP_END.  */
  rtx end;

  /* For a rotated loop that is entered near the bottom,
     this is the label at the top.  Otherwise it is zero.  */
  rtx top;

  /* Place in the loop where control enters.  */
  rtx scan_start;

  /* The position where to sink insns out of the loop.  */
  rtx sink;

  /* List of all LABEL_REFs which refer to code labels outside the
     loop.  Used by routines that need to know all loop exits, such as
     final_biv_value and final_giv_value.

     This does not include loop exits due to return instructions.
     This is because all bivs and givs are pseudos, and hence must be
     dead after a return, so the presence of a return does not affect
     any of the optimizations that use this info.  It is simpler to
     just not include return instructions on this list.  */
  rtx exit_labels;

  /* The number of LABEL_REFs on exit_labels for this loop and all
     loops nested inside it.  */
  int exit_count;
};

/* Flags for state of loop structure.  */
enum
{
  LOOPS_HAVE_PREHEADERS = 1,
  LOOPS_HAVE_SIMPLE_LATCHES = 2,
  LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS = 4
};

/* Structure to hold CFG information about natural loops within a function.  */
struct loops
{
  /* Number of natural loops in the function.  */
  unsigned num;

  /* Maximum nested loop level in the function.  */
  unsigned levels;

  /* Array of natural loop descriptors (scanning this array in reverse order
     will find the inner loops before their enclosing outer loops).  */
  struct loop *array;

  /* The above array is unused in new loop infrastructure and is kept only for
     purposes of the old loop optimizer.  Instead we store just pointers to
     loops here.  */
  struct loop **parray;

  /* Pointer to root of loop hierarchy tree.  */
  struct loop *tree_root;

  /* Information derived from the CFG.  */
  struct cfg
  {
    /* The bitmap vector of dominators or NULL if not computed.  */
    dominance_info dom;

    /* The ordering of the basic blocks in a depth first search.  */
    int *dfs_order;

    /* The reverse completion ordering of the basic blocks found in a
       depth first search.  */
    int *rc_order;
  } cfg;

  /* Headers shared by multiple loops that should be merged.  */
  sbitmap shared_headers;

  /* State of loops.  */
  int state;
};

/* Flags for loop discovery.  */

#define LOOP_TREE		1	/* Build loop hierarchy tree.  */
#define LOOP_PRE_HEADER		2	/* Analyze loop preheader.  */
#define LOOP_ENTRY_EDGES	4	/* Find entry edges.  */
#define LOOP_EXIT_EDGES		8	/* Find exit edges.  */
#define LOOP_EDGES		(LOOP_ENTRY_EDGES | LOOP_EXIT_EDGES)
#define LOOP_ALL	       15	/* All of the above  */

/* Loop recognition.  */
extern int flow_loops_find		PARAMS ((struct loops *, int flags));
extern int flow_loops_update		PARAMS ((struct loops *, int flags));
extern void flow_loops_free		PARAMS ((struct loops *));
extern void flow_loops_dump		PARAMS ((const struct loops *, FILE *,
						void (*)(const struct loop *,
						FILE *, int), int));
extern void flow_loop_dump		PARAMS ((const struct loop *, FILE *,
						void (*)(const struct loop *,
						FILE *, int), int));
extern int flow_loop_scan		PARAMS ((struct loops *,
						struct loop *, int));
extern void flow_loop_free		PARAMS ((struct loop *));
void mark_irreducible_loops		PARAMS ((struct loops *));

/* Loop datastructure manipulation/querying.  */
extern void flow_loop_tree_node_add	PARAMS ((struct loop *, struct loop *));
extern void flow_loop_tree_node_remove	PARAMS ((struct loop *));
extern bool flow_loop_outside_edge_p	PARAMS ((const struct loop *, edge));
extern bool flow_loop_nested_p		PARAMS ((const struct loop *,
						const struct loop *));
extern bool flow_bb_inside_loop_p	PARAMS ((const struct loop *,
						const basic_block));
extern struct loop * find_common_loop	PARAMS ((struct loop *, struct loop *));
extern int num_loop_insns		PARAMS ((struct loop *));
extern int average_num_loop_insns	PARAMS ((struct loop *));

/* Loops & cfg manipulation.  */
extern basic_block *get_loop_body	PARAMS ((const struct loop *));
extern edge *get_loop_exit_edges	PARAMS ((const struct loop *, unsigned *));

extern edge loop_preheader_edge		PARAMS ((const struct loop *));
extern edge loop_latch_edge		PARAMS ((const struct loop *));

extern void add_bb_to_loop		PARAMS ((basic_block, struct loop *));
extern void remove_bb_from_loops	PARAMS ((basic_block));

extern void cancel_loop			PARAMS ((struct loops *, struct loop *));
extern void cancel_loop_tree		PARAMS ((struct loops *, struct loop *));

extern basic_block loop_split_edge_with PARAMS ((edge, rtx, struct loops *));
extern int fix_loop_placement		PARAMS ((struct loop *));

enum
{
  CP_SIMPLE_PREHEADERS = 1,
  CP_INSIDE_CFGLAYOUT = 2
};

extern void create_preheaders		PARAMS ((struct loops *, int));
extern void force_single_succ_latches	PARAMS ((struct loops *));

extern void verify_loop_structure	PARAMS ((struct loops *));

/* Loop analysis.  */
extern bool simple_loop_p		PARAMS ((struct loops *, struct loop *,
						struct loop_desc *));
extern rtx count_loop_iterations	PARAMS ((struct loop_desc *, rtx, rtx));
extern bool just_once_each_iteration_p	PARAMS ((struct loops *,struct loop *,
						 basic_block));
extern unsigned expected_loop_iterations PARAMS ((const struct loop *));

/* Loop manipulation.  */
extern bool can_duplicate_loop_p	PARAMS ((struct loop *loop));

#define DLTHE_FLAG_UPDATE_FREQ	1	/* Update frequencies in
					   duplicate_loop_to_header_edge.  */

extern int duplicate_loop_to_header_edge PARAMS ((struct loop *, edge,
						struct loops *, unsigned,
						sbitmap, edge, edge *,
						unsigned *, int));
extern struct loop *loopify		PARAMS ((struct loops *, edge,
						edge, basic_block));
extern void unloop			PARAMS ((struct loops *, struct loop *));
extern bool remove_path			PARAMS ((struct loops *, edge));
extern edge split_loop_bb		PARAMS ((struct loops *, basic_block,
						rtx));

/* Loop optimizer initialization.  */
extern struct loops *loop_optimizer_init PARAMS ((FILE *));
extern void loop_optimizer_finalize	PARAMS ((struct loops *, FILE *));

/* Optimization passes.  */
extern void unswitch_loops		PARAMS ((struct loops *));

enum
{
  UAP_PEEL = 1,		/* Enables loop peeling.  */
  UAP_UNROLL = 2,	/* Enables peeling of loops if it seems profitable.  */
  UAP_UNROLL_ALL = 4	/* Enables peeling of all loops.  */
};

extern void unroll_and_peel_loops	PARAMS ((struct loops *, int));