[unix-history] / usr / src / contrib / gcc-2.3.3 / loop.h

/* Loop optimization definitions for GNU C-Compiler
   Copyright (C) 1991 Free Software Foundation, Inc.

This file is part of GNU CC.

GNU CC 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.

GNU CC 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 GNU CC; see the file COPYING.  If not, write to
the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  */

/* Get the luid of an insn.  Catch the error of trying to reference the LUID
   of an insn added during loop, since these don't have LUIDs.  */

#define INSN_LUID(INSN)			\
  (INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
   : (abort (), -1))

/* A "basic induction variable" or biv is a pseudo reg that is set
   (within this loop) only by incrementing or decrementing it.  */
/* A "general induction variable" or giv is a pseudo reg whose
   value is a linear function of a biv.  */

/* Bivs are recognized by `basic_induction_var';
   Givs by `general_induct_var'.  */

/* An enum for the two different types of givs, those that are used
   as memory addresses and those that are calculated into registers.  */
enum g_types { DEST_ADDR, DEST_REG };

/* A `struct induction' is created for every instruction that sets
   an induction variable (either a biv or a giv).  */

struct induction
{
  rtx insn;			/* The insn that sets a biv or giv */
  rtx new_reg;			/* New register, containing strength reduced
				   version of this giv.  */
  rtx src_reg;			/* Biv from which this giv is computed.
				   (If this is a biv, then this is the biv.) */
  enum g_types giv_type;	/* Indicate whether DEST_ADDR or DEST_REG */
  rtx dest_reg;			/* Destination register for insn: this is the
				   register which was the biv or giv.
				   For a biv, this equals src_reg.
				   For a DEST_ADDR type giv, this is 0.  */
  rtx *location;		/* Place in the insn where this giv occurs.
				   If GIV_TYPE is DEST_REG, this is 0.  */
  enum machine_mode mode;	/* The mode of this biv or giv */
  enum machine_mode mem_mode;	/* For DEST_ADDR, mode of the memory object. */
  rtx mult_val;			/* Multiplicative factor for src_reg.  */
  rtx add_val;			/* Additive constant for that product.  */
  int benefit;			/* Gain from eliminating this insn.  */
  rtx final_value;		/* If the giv is used outside the loop, and its
				   final value could be calculated, it is put
				   here, and the giv is made replaceable.  Set
				   the giv to this value before the loop.  */
  unsigned replaceable : 1;	/* 1 if we can substitute the strength-reduced
				   variable for the original variable.
				   0 means they must be kept separate and the
				   new one must be copied into the old pseudo
				   reg each time the old one is set.  */
  unsigned not_replaceable : 1;	/* Used to prevent duplicating work.  This is
				   1 if we know that the giv definitely can
				   not be made replaceable, in which case we
				   don't bother checking the variable again
				   even if further info is available.
				   Both this and the above can be zero.  */
  unsigned ignore : 1;		/* 1 prohibits further processing of giv */
  unsigned always_computable : 1;/* 1 if this set occurs each iteration */
  unsigned maybe_multiple : 1;	/* Only used for a biv and  1 if this biv
				   update may be done multiple times per
				   iteration. */
  unsigned cant_derive : 1;	/* For giv's, 1 if this giv cannot derive
				   another giv.  This occurs in many cases
				   where a giv's lifetime spans an update to
				   a biv. */
  unsigned combined_with : 1;	/* 1 if this giv has been combined with.  It
				   then cannot combine with any other giv.  */
  unsigned maybe_dead : 1;	/* 1 if this giv might be dead.  In that case,
				   we won't use it to eliminate a biv, it
				   would probably lose. */
  int lifetime;			/* Length of life of this giv */
  int times_used;		/* # times this giv is used. */
  rtx derive_adjustment;	/* If nonzero, is an adjustment to be
				   subtracted from add_val when this giv
				   derives another.  This occurs when the
				   giv spans a biv update by incrementation. */
  struct induction *next_iv;	/* For givs, links together all givs that are
				   based on the same biv.  For bivs, links
				   together all biv entries that refer to the
				   same biv register.  */
  struct induction *same;	/* If this giv has been combined with another
				   giv, this points to the base giv.  The base
				   giv will have COMBINED_WITH non-zero.  */
  HOST_WIDE_INT const_adjust;	/* Used by loop unrolling, when an address giv
				   is split, and a constant is eliminated from
				   the address, the -constant is stored here
				   for later use. */
};

/* A `struct iv_class' is created for each biv.  */

struct iv_class {
  int regno;			/* Pseudo reg which is the biv.  */
  int biv_count;		/* Number of insns setting this reg.  */
  struct induction *biv;	/* List of all insns that set this reg.  */
  int giv_count;		/* Number of DEST_REG givs computed from this
				   biv.  The resulting count is only used in
				   check_dbra_loop.  */
  struct induction *giv;	/* List of all insns that compute a giv
				   from this reg.  */
  int total_benefit;		/* Sum of BENEFITs of all those givs */
  rtx initial_value;		/* Value of reg at loop start */
  rtx initial_test;		/* Test performed on BIV before loop */
  struct iv_class *next;	/* Links all class structures together */
  rtx init_insn;		/* insn which initializes biv, 0 if none. */
  rtx init_set;			/* SET of INIT_INSN, if any. */
  unsigned incremented : 1;	/* 1 if somewhere incremented/decremented */
  unsigned eliminable : 1;	/* 1 if plausible candidate for elimination. */
  unsigned nonneg : 1;		/* 1 if we added a REG_NONNEG note for this. */
  unsigned reversed : 1;	/* 1 if we reversed the loop that this
				   biv controls. */
};

/* Definitions used by the basic induction variable discovery code.  */
enum iv_mode { UNKNOWN_INDUCT, BASIC_INDUCT, NOT_BASIC_INDUCT,
		 GENERAL_INDUCT };

/* Variables declared in loop.c, but also needed in unroll.c.  */

extern int *uid_luid;
extern int max_uid_for_loop;
extern int *uid_loop_num;
extern int *loop_outer_loop;
extern rtx *loop_number_exit_labels;
extern unsigned HOST_WIDE_INT loop_n_iterations;
extern int max_reg_before_loop;

extern FILE *loop_dump_stream;

extern enum iv_mode *reg_iv_type;
extern struct induction **reg_iv_info;
extern struct iv_class **reg_biv_class;
extern struct iv_class *loop_iv_list;

/* Forward declarations for non-static functions declared in loop.c and
   unroll.c.  */
int invariant_p ();
rtx get_condition_for_loop ();
void emit_iv_add_mult ();

/* Forward declarations for non-static functions declared in stmt.c.  */
void find_loop_tree_blocks ();
void unroll_block_trees ();

void unroll_loop ();
rtx biv_total_increment ();
unsigned HOST_WIDE_INT loop_iterations ();
rtx final_biv_value ();
rtx final_giv_value ();
void emit_unrolled_add ();
Commit	Line	Data
e59aa719 C	1	/* Loop optimization definitions for GNU C-Compiler
	2	Copyright (C) 1991 Free Software Foundation, Inc.
	3
	4	This file is part of GNU CC.
	5
	6	GNU CC is free software; you can redistribute it and/or modify
	7	it under the terms of the GNU General Public License as published by
	8	the Free Software Foundation; either version 2, or (at your option)
	9	any later version.
	10
	11	GNU CC is distributed in the hope that it will be useful,
	12	but WITHOUT ANY WARRANTY; without even the implied warranty of
	13	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	14	GNU General Public License for more details.
	15
	16	You should have received a copy of the GNU General Public License
	17	along with GNU CC; see the file COPYING. If not, write to
	18	the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
	19
	20	/* Get the luid of an insn. Catch the error of trying to reference the LUID
	21	of an insn added during loop, since these don't have LUIDs. */
	22
	23	#define INSN_LUID(INSN) \
	24	(INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
	25	: (abort (), -1))
	26
	27	/* A "basic induction variable" or biv is a pseudo reg that is set
	28	(within this loop) only by incrementing or decrementing it. */
	29	/* A "general induction variable" or giv is a pseudo reg whose
	30	value is a linear function of a biv. */
	31
	32	/* Bivs are recognized by `basic_induction_var';
	33	Givs by `general_induct_var'. */
	34
	35	/* An enum for the two different types of givs, those that are used
	36	as memory addresses and those that are calculated into registers. */
	37	enum g_types { DEST_ADDR, DEST_REG };
	38
	39	/* A `struct induction' is created for every instruction that sets
	40	an induction variable (either a biv or a giv). */
	41
	42	struct induction
	43	{
	44	rtx insn; /* The insn that sets a biv or giv */
	45	rtx new_reg; /* New register, containing strength reduced
	46	version of this giv. */
	47	rtx src_reg; /* Biv from which this giv is computed.
	48	(If this is a biv, then this is the biv.) */
	49	enum g_types giv_type; /* Indicate whether DEST_ADDR or DEST_REG */
	50	rtx dest_reg; /* Destination register for insn: this is the
	51	register which was the biv or giv.
	52	For a biv, this equals src_reg.
	53	For a DEST_ADDR type giv, this is 0. */
	54	rtx location; / Place in the insn where this giv occurs.
	55	If GIV_TYPE is DEST_REG, this is 0. */
	56	enum machine_mode mode; /* The mode of this biv or giv */
	57	enum machine_mode mem_mode; /* For DEST_ADDR, mode of the memory object. */
	58	rtx mult_val; /* Multiplicative factor for src_reg. */
	59	rtx add_val; /* Additive constant for that product. */
	60	int benefit; /* Gain from eliminating this insn. */
	61	rtx final_value; /* If the giv is used outside the loop, and its
	62	final value could be calculated, it is put
	63	here, and the giv is made replaceable. Set
	64	the giv to this value before the loop. */
65	unsigned replaceable : 1; /* 1 if we can substitute the strength-reduced
66	variable for the original variable.
67	0 means they must be kept separate and the
68	new one must be copied into the old pseudo
69	reg each time the old one is set. */
70	unsigned not_replaceable : 1; /* Used to prevent duplicating work. This is
71	1 if we know that the giv definitely can
72	not be made replaceable, in which case we
73	don't bother checking the variable again
74	even if further info is available.
75	Both this and the above can be zero. */
76	unsigned ignore : 1; /* 1 prohibits further processing of giv */
77	unsigned always_computable : 1;/* 1 if this set occurs each iteration */
78	unsigned maybe_multiple : 1; /* Only used for a biv and 1 if this biv
79	update may be done multiple times per
80	iteration. */
81	unsigned cant_derive : 1; /* For giv's, 1 if this giv cannot derive
82	another giv. This occurs in many cases
83	where a giv's lifetime spans an update to
84	a biv. */
85	unsigned combined_with : 1; /* 1 if this giv has been combined with. It
86	then cannot combine with any other giv. */
87	unsigned maybe_dead : 1; /* 1 if this giv might be dead. In that case,
88	we won't use it to eliminate a biv, it
89	would probably lose. */
90	int lifetime; /* Length of life of this giv */
91	int times_used; /* # times this giv is used. */
92	rtx derive_adjustment; /* If nonzero, is an adjustment to be
93	subtracted from add_val when this giv
94	derives another. This occurs when the
95	giv spans a biv update by incrementation. */
96	struct induction next_iv; / For givs, links together all givs that are
97	based on the same biv. For bivs, links
98	together all biv entries that refer to the
99	same biv register. */
100	struct induction same; / If this giv has been combined with another
101	giv, this points to the base giv. The base
102	giv will have COMBINED_WITH non-zero. */
103	HOST_WIDE_INT const_adjust; /* Used by loop unrolling, when an address giv
104	is split, and a constant is eliminated from
105	the address, the -constant is stored here
106	for later use. */
107	};
108
109	/* A `struct iv_class' is created for each biv. */
110
111	struct iv_class {
112	int regno; /* Pseudo reg which is the biv. */
113	int biv_count; /* Number of insns setting this reg. */
114	struct induction biv; / List of all insns that set this reg. */
115	int giv_count; /* Number of DEST_REG givs computed from this
116	biv. The resulting count is only used in
117	check_dbra_loop. */
118	struct induction giv; / List of all insns that compute a giv
119	from this reg. */
120	int total_benefit; /* Sum of BENEFITs of all those givs */
121	rtx initial_value; /* Value of reg at loop start */
122	rtx initial_test; /* Test performed on BIV before loop */
123	struct iv_class next; / Links all class structures together */
124	rtx init_insn; /* insn which initializes biv, 0 if none. */
125	rtx init_set; /* SET of INIT_INSN, if any. */
126	unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
127	unsigned eliminable : 1; /* 1 if plausible candidate for elimination. */
128	unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for this. */
129	unsigned reversed : 1; /* 1 if we reversed the loop that this
130	biv controls. */
131	};
132
133	/* Definitions used by the basic induction variable discovery code. */
134	enum iv_mode { UNKNOWN_INDUCT, BASIC_INDUCT, NOT_BASIC_INDUCT,
135	GENERAL_INDUCT };
136
137	/* Variables declared in loop.c, but also needed in unroll.c. */
138
139	extern int *uid_luid;
140	extern int max_uid_for_loop;
141	extern int *uid_loop_num;
142	extern int *loop_outer_loop;
143	extern rtx *loop_number_exit_labels;
144	extern unsigned HOST_WIDE_INT loop_n_iterations;
145	extern int max_reg_before_loop;
146
147	extern FILE *loop_dump_stream;
148
149	extern enum iv_mode *reg_iv_type;
150	extern struct induction **reg_iv_info;
151	extern struct iv_class **reg_biv_class;
152	extern struct iv_class *loop_iv_list;
153
154	/* Forward declarations for non-static functions declared in loop.c and
155	unroll.c. */
156	int invariant_p ();
157	rtx get_condition_for_loop ();
158	void emit_iv_add_mult ();
159
160	/* Forward declarations for non-static functions declared in stmt.c. */
161	void find_loop_tree_blocks ();
162	void unroll_block_trees ();
163
164	void unroll_loop ();
165	rtx biv_total_increment ();
166	unsigned HOST_WIDE_INT loop_iterations ();
167	rtx final_biv_value ();
168	rtx final_giv_value ();
169	void emit_unrolled_add ();