1 /* Loop optimization definitions for GNU C-Compiler
2 Copyright (C) 1991, 1995, 1998, 1999 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. */
22 #include "basic-block.h"
24 /* Get the luid of an insn. Catch the error of trying to reference the LUID
25 of an insn added during loop, since these don't have LUIDs. */
27 #define INSN_LUID(INSN) \
28 (INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
31 /* A "basic induction variable" or biv is a pseudo reg that is set
32 (within this loop) only by incrementing or decrementing it. */
33 /* A "general induction variable" or giv is a pseudo reg whose
34 value is a linear function of a biv. */
36 /* Bivs are recognized by `basic_induction_var';
37 Givs by `general_induct_var'. */
39 /* An enum for the two different types of givs, those that are used
40 as memory addresses and those that are calculated into registers. */
41 enum g_types { DEST_ADDR, DEST_REG };
43 /* A `struct induction' is created for every instruction that sets
44 an induction variable (either a biv or a giv). */
48 rtx insn; /* The insn that sets a biv or giv */
49 rtx new_reg; /* New register, containing strength reduced
50 version of this giv. */
51 rtx src_reg; /* Biv from which this giv is computed.
52 (If this is a biv, then this is the biv.) */
53 enum g_types giv_type; /* Indicate whether DEST_ADDR or DEST_REG */
54 rtx dest_reg; /* Destination register for insn: this is the
55 register which was the biv or giv.
56 For a biv, this equals src_reg.
57 For a DEST_ADDR type giv, this is 0. */
58 rtx *location; /* Place in the insn where this giv occurs.
59 If GIV_TYPE is DEST_REG, this is 0. */
60 /* For a biv, this is the place where add_val
62 enum machine_mode mode; /* The mode of this biv or giv */
63 enum machine_mode mem_mode; /* For DEST_ADDR, mode of the memory object. */
64 rtx mult_val; /* Multiplicative factor for src_reg. */
65 rtx add_val; /* Additive constant for that product. */
66 int benefit; /* Gain from eliminating this insn. */
67 rtx final_value; /* If the giv is used outside the loop, and its
68 final value could be calculated, it is put
69 here, and the giv is made replaceable. Set
70 the giv to this value before the loop. */
71 unsigned combined_with; /* The number of givs this giv has been
72 combined with. If nonzero, this giv
73 cannot combine with any other giv. */
74 unsigned replaceable : 1; /* 1 if we can substitute the strength-reduced
75 variable for the original variable.
76 0 means they must be kept separate and the
77 new one must be copied into the old pseudo
78 reg each time the old one is set. */
79 unsigned not_replaceable : 1; /* Used to prevent duplicating work. This is
80 1 if we know that the giv definitely can
81 not be made replaceable, in which case we
82 don't bother checking the variable again
83 even if further info is available.
84 Both this and the above can be zero. */
85 unsigned ignore : 1; /* 1 prohibits further processing of giv */
86 unsigned always_computable : 1;/* 1 if this value is computable every
88 unsigned always_executed : 1; /* 1 if this set occurs each iteration. */
89 unsigned maybe_multiple : 1; /* Only used for a biv and 1 if this biv
90 update may be done multiple times per
92 unsigned cant_derive : 1; /* For giv's, 1 if this giv cannot derive
93 another giv. This occurs in many cases
94 where a giv's lifetime spans an update to
96 unsigned maybe_dead : 1; /* 1 if this giv might be dead. In that case,
97 we won't use it to eliminate a biv, it
98 would probably lose. */
99 unsigned auto_inc_opt : 1; /* 1 if this giv had its increment output next
100 to it to try to form an auto-inc address. */
101 unsigned unrolled : 1; /* 1 if new register has been allocated and
102 initialized in unrolled loop. */
104 unsigned no_const_addval : 1; /* 1 if add_val does not contain a const. */
105 unsigned multi_insn_incr : 1; /* 1 if multiple insns updated the biv. */
106 int lifetime; /* Length of life of this giv */
107 rtx derive_adjustment; /* If nonzero, is an adjustment to be
108 subtracted from add_val when this giv
109 derives another. This occurs when the
110 giv spans a biv update by incrementation. */
111 struct induction *next_iv; /* For givs, links together all givs that are
112 based on the same biv. For bivs, links
113 together all biv entries that refer to the
114 same biv register. */
115 struct induction *same; /* If this giv has been combined with another
116 giv, this points to the base giv. The base
117 giv will have COMBINED_WITH non-zero. */
118 struct induction *derived_from;/* For a giv, if we decided to derive this
119 giv from another one. */
120 HOST_WIDE_INT const_adjust; /* Used by loop unrolling, when an address giv
121 is split, and a constant is eliminated from
122 the address, the -constant is stored here
124 int ix; /* Used by recombine_givs, as n index into
126 struct induction *same_insn; /* If there are multiple identical givs in
127 the same insn, then all but one have this
128 field set, and they all point to the giv
129 that doesn't have this field set. */
130 rtx last_use; /* For a giv made from a biv increment, this is
131 a substitute for the lifetime information. */
134 /* A `struct iv_class' is created for each biv. */
137 int regno; /* Pseudo reg which is the biv. */
138 int biv_count; /* Number of insns setting this reg. */
139 struct induction *biv; /* List of all insns that set this reg. */
140 int giv_count; /* Number of DEST_REG givs computed from this
141 biv. The resulting count is only used in
143 struct induction *giv; /* List of all insns that compute a giv
145 int total_benefit; /* Sum of BENEFITs of all those givs */
146 rtx initial_value; /* Value of reg at loop start */
147 rtx initial_test; /* Test performed on BIV before loop */
148 struct iv_class *next; /* Links all class structures together */
149 rtx init_insn; /* insn which initializes biv, 0 if none. */
150 rtx init_set; /* SET of INIT_INSN, if any. */
151 unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
152 unsigned eliminable : 1; /* 1 if plausible candidate for elimination. */
153 unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for this. */
154 unsigned reversed : 1; /* 1 if we reversed the loop that this
158 /* Information required to calculate the number of loop iterations.
159 This is set by loop_iterations. */
163 /* Nonzero if there is a subroutine call in the current loop. */
165 /* Nonzero if there is a volatile memory reference in the current
168 /* Nonzero if there is a tablejump in the current loop. */
170 /* Nonzero if there are ways to leave the loop other than falling
172 int has_multiple_exit_targets;
173 /* Nonzero if there is an indirect jump in the current function. */
174 int has_indirect_jump;
175 /* Register or constant initial loop value. */
177 /* Register or constant value used for comparison test. */
178 rtx comparison_value;
179 /* Register or constant approximate final value. */
181 /* Register or constant initial loop value with term common to
182 final_value removed. */
183 rtx initial_equiv_value;
184 /* Register or constant final loop value with term common to
185 initial_value removed. */
186 rtx final_equiv_value;
187 /* Register corresponding to iteration variable. */
189 /* Constant loop increment. */
191 enum rtx_code comparison_code;
192 /* Holds the number of loop iterations. It is zero if the number
193 could not be calculated. Must be unsigned since the number of
194 iterations can be as high as 2^wordsize - 1. For loops with a
195 wider iterator, this number will be zero if the number of loop
196 iterations is too large for an unsigned integer to hold. */
197 unsigned HOST_WIDE_INT n_iterations;
198 /* The number of times the loop body was unrolled. */
199 unsigned int unroll_number;
200 int used_count_register;
203 /* Definitions used by the basic induction variable discovery code. */
204 enum iv_mode { UNKNOWN_INDUCT, BASIC_INDUCT, NOT_BASIC_INDUCT,
207 /* Variables declared in loop.c, but also needed in unroll.c. */
209 extern int *uid_luid;
210 extern int max_uid_for_loop;
211 extern int max_reg_before_loop;
212 extern struct loop **uid_loop;
213 extern FILE *loop_dump_stream;
215 extern varray_type reg_iv_type;
216 extern varray_type reg_iv_info;
218 #define REG_IV_TYPE(n) \
219 (*(enum iv_mode *) &VARRAY_INT(reg_iv_type, (n)))
220 #define REG_IV_INFO(n) \
221 (*(struct induction **) &VARRAY_GENERIC_PTR(reg_iv_info, (n)))
223 extern struct iv_class **reg_biv_class;
224 extern struct iv_class *loop_iv_list;
226 extern int first_increment_giv, last_increment_giv;
228 /* Forward declarations for non-static functions declared in loop.c and
230 int invariant_p PROTO((rtx));
231 rtx get_condition_for_loop PROTO((rtx));
232 void emit_iv_add_mult PROTO((rtx, rtx, rtx, rtx, rtx));
233 rtx express_from PROTO((struct induction *, struct induction *));
235 void unroll_loop PROTO((struct loop *, int, rtx, int));
236 rtx biv_total_increment PROTO((struct iv_class *, rtx, rtx));
237 unsigned HOST_WIDE_INT loop_iterations PROTO((struct loop *));
238 int precondition_loop_p PROTO((rtx, struct loop_info *,
240 enum machine_mode *mode));
241 rtx final_biv_value PROTO((struct iv_class *, rtx, rtx,
242 unsigned HOST_WIDE_INT));
243 rtx final_giv_value PROTO((struct induction *, rtx, rtx,
244 unsigned HOST_WIDE_INT));
245 void emit_unrolled_add PROTO((rtx, rtx, rtx));
246 int back_branch_in_range_p PROTO((rtx, rtx, rtx));
248 int loop_insn_first_p PROTO((rtx, rtx));
250 /* Forward declarations for non-static functions declared in stmt.c. */
251 void find_loop_tree_blocks PROTO((void));
252 void unroll_block_trees PROTO((void));