1 /* Loop optimization definitions for GNU C-Compiler
2 Copyright (C) 1991, 1995, 1998 Free Software Foundation, Inc.
4 This file is part of GNU CC.
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)
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.
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, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* Get the luid of an insn. Catch the error of trying to reference the LUID
22 of an insn added during loop, since these don't have LUIDs. */
24 #define INSN_LUID(INSN) \
25 (INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
28 /* A "basic induction variable" or biv is a pseudo reg that is set
29 (within this loop) only by incrementing or decrementing it. */
30 /* A "general induction variable" or giv is a pseudo reg whose
31 value is a linear function of a biv. */
33 /* Bivs are recognized by `basic_induction_var';
34 Givs by `general_induct_var'. */
36 /* An enum for the two different types of givs, those that are used
37 as memory addresses and those that are calculated into registers. */
38 enum g_types { DEST_ADDR, DEST_REG };
40 /* A `struct induction' is created for every instruction that sets
41 an induction variable (either a biv or a giv). */
45 rtx insn; /* The insn that sets a biv or giv */
46 rtx new_reg; /* New register, containing strength reduced
47 version of this giv. */
48 rtx src_reg; /* Biv from which this giv is computed.
49 (If this is a biv, then this is the biv.) */
50 enum g_types giv_type; /* Indicate whether DEST_ADDR or DEST_REG */
51 rtx dest_reg; /* Destination register for insn: this is the
52 register which was the biv or giv.
53 For a biv, this equals src_reg.
54 For a DEST_ADDR type giv, this is 0. */
55 rtx *location; /* Place in the insn where this giv occurs.
56 If GIV_TYPE is DEST_REG, this is 0. */
57 enum machine_mode mode; /* The mode of this biv or giv */
58 enum machine_mode mem_mode; /* For DEST_ADDR, mode of the memory object. */
59 rtx mult_val; /* Multiplicative factor for src_reg. */
60 rtx add_val; /* Additive constant for that product. */
61 int benefit; /* Gain from eliminating this insn. */
62 rtx final_value; /* If the giv is used outside the loop, and its
63 final value could be calculated, it is put
64 here, and the giv is made replaceable. Set
65 the giv to this value before the loop. */
66 unsigned replaceable : 1; /* 1 if we can substitute the strength-reduced
67 variable for the original variable.
68 0 means they must be kept separate and the
69 new one must be copied into the old pseudo
70 reg each time the old one is set. */
71 unsigned not_replaceable : 1; /* Used to prevent duplicating work. This is
72 1 if we know that the giv definitely can
73 not be made replaceable, in which case we
74 don't bother checking the variable again
75 even if further info is available.
76 Both this and the above can be zero. */
77 unsigned ignore : 1; /* 1 prohibits further processing of giv */
78 unsigned always_computable : 1;/* 1 if this value is computable every
80 unsigned always_executed : 1; /* 1 if this set occurs each iteration. */
81 unsigned maybe_multiple : 1; /* Only used for a biv and 1 if this biv
82 update may be done multiple times per
84 unsigned cant_derive : 1; /* For giv's, 1 if this giv cannot derive
85 another giv. This occurs in many cases
86 where a giv's lifetime spans an update to
88 unsigned combined_with : 1; /* 1 if this giv has been combined with. It
89 then cannot combine with any other giv. */
90 unsigned maybe_dead : 1; /* 1 if this giv might be dead. In that case,
91 we won't use it to eliminate a biv, it
92 would probably lose. */
93 unsigned auto_inc_opt : 1; /* 1 if this giv had its increment output next
94 to it to try to form an auto-inc address. */
95 unsigned unrolled : 1; /* 1 if new register has been allocated and
96 initialized in unrolled loop. */
98 unsigned no_const_addval : 1; /* 1 if add_val does not contain a const. */
99 int lifetime; /* Length of life of this giv */
100 int times_used; /* # times this giv is used. */
101 rtx derive_adjustment; /* If nonzero, is an adjustment to be
102 subtracted from add_val when this giv
103 derives another. This occurs when the
104 giv spans a biv update by incrementation. */
105 struct induction *next_iv; /* For givs, links together all givs that are
106 based on the same biv. For bivs, links
107 together all biv entries that refer to the
108 same biv register. */
109 struct induction *same; /* If this giv has been combined with another
110 giv, this points to the base giv. The base
111 giv will have COMBINED_WITH non-zero. */
112 HOST_WIDE_INT const_adjust; /* Used by loop unrolling, when an address giv
113 is split, and a constant is eliminated from
114 the address, the -constant is stored here
116 struct induction *same_insn; /* If there are multiple identical givs in
117 the same insn, then all but one have this
118 field set, and they all point to the giv
119 that doesn't have this field set. */
122 /* A `struct iv_class' is created for each biv. */
125 int regno; /* Pseudo reg which is the biv. */
126 int biv_count; /* Number of insns setting this reg. */
127 struct induction *biv; /* List of all insns that set this reg. */
128 int giv_count; /* Number of DEST_REG givs computed from this
129 biv. The resulting count is only used in
131 struct induction *giv; /* List of all insns that compute a giv
133 int total_benefit; /* Sum of BENEFITs of all those givs */
134 rtx initial_value; /* Value of reg at loop start */
135 rtx initial_test; /* Test performed on BIV before loop */
136 struct iv_class *next; /* Links all class structures together */
137 rtx init_insn; /* insn which initializes biv, 0 if none. */
138 rtx init_set; /* SET of INIT_INSN, if any. */
139 unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
140 unsigned eliminable : 1; /* 1 if plausible candidate for elimination. */
141 unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for this. */
142 unsigned reversed : 1; /* 1 if we reversed the loop that this
146 /* Information required to calculate the number of loop iterations.
147 This is set by loop_iterations. */
151 /* Register or constant initial loop value. */
153 /* Register or constant value used for comparison test. */
154 rtx comparison_value;
155 /* Register or constant approximate final value. */
157 /* Register or constant initial loop value with term common to
158 final_value removed. */
159 rtx initial_equiv_value;
160 /* Register or constant final loop value with term common to
161 initial_value removed. */
162 rtx final_equiv_value;
163 /* Register corresponding to iteration variable. */
165 /* Constant loop increment. */
167 enum rtx_code comparison_code;
168 /* Holds the number of loop iterations. It is zero if the number
169 could not be calculated. Must be unsigned since the number of
170 iterations can be as high as 2^wordsize - 1. For loops with a
171 wider iterator, this number will be zero if the number of loop
172 iterations is too large for an unsigned integer to hold. */
173 unsigned HOST_WIDE_INT n_iterations;
174 /* The loop unrolling factor.
178 -1: completely unrolled
179 >0: holds the unroll exact factor. */
183 /* Definitions used by the basic induction variable discovery code. */
184 enum iv_mode { UNKNOWN_INDUCT, BASIC_INDUCT, NOT_BASIC_INDUCT,
187 /* Variables declared in loop.c, but also needed in unroll.c. */
189 extern int *uid_luid;
190 extern int max_uid_for_loop;
191 extern int *uid_loop_num;
192 extern int *loop_outer_loop;
193 extern rtx *loop_number_exit_labels;
194 extern int *loop_number_exit_count;
195 extern int max_reg_before_loop;
197 extern FILE *loop_dump_stream;
199 extern enum iv_mode *reg_iv_type;
200 extern struct induction **reg_iv_info;
201 extern struct iv_class **reg_biv_class;
202 extern struct iv_class *loop_iv_list;
204 /* Forward declarations for non-static functions declared in loop.c and
206 int invariant_p PROTO((rtx));
207 rtx get_condition_for_loop PROTO((rtx));
208 void emit_iv_add_mult PROTO((rtx, rtx, rtx, rtx, rtx));
210 /* Forward declarations for non-static functions declared in stmt.c. */
211 void find_loop_tree_blocks PROTO((void));
212 void unroll_block_trees PROTO((void));
214 void unroll_loop PROTO((rtx, int, rtx, rtx, struct loop_info *, int));
215 rtx biv_total_increment PROTO((struct iv_class *, rtx, rtx));
216 unsigned HOST_WIDE_INT loop_iterations PROTO((rtx, rtx, struct loop_info *));
217 int precondition_loop_p PROTO((rtx, struct loop_info *,
219 enum machine_mode *mode));
220 rtx final_biv_value PROTO((struct iv_class *, rtx, rtx,
221 unsigned HOST_WIDE_INT));
222 rtx final_giv_value PROTO((struct induction *, rtx, rtx,
223 unsigned HOST_WIDE_INT));
224 void emit_unrolled_add PROTO((rtx, rtx, rtx));
225 int back_branch_in_range_p PROTO((rtx, rtx, rtx));
227 extern int *loop_unroll_number;