433 lines
16 KiB
C
433 lines
16 KiB
C
/* Loop optimization definitions for GCC
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Copyright (C) 1991, 1995, 1998, 1999, 2000, 2001, 2002, 2003, 2004
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Free Software Foundation, Inc.
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 2, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with GCC; see the file COPYING. If not, write to the Free
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Software Foundation, 59 Temple Place - Suite 330, Boston, MA
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02111-1307, USA. */
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#include "bitmap.h"
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#include "sbitmap.h"
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#include "hard-reg-set.h"
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#include "basic-block.h"
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/* Flags passed to loop_optimize. */
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#define LOOP_UNROLL 1
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#define LOOP_BCT 2
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#define LOOP_PREFETCH 4
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#define LOOP_AUTO_UNROLL 8
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/* Get the loop info pointer of a loop. */
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#define LOOP_INFO(LOOP) ((struct loop_info *) (LOOP)->aux)
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/* Get a pointer to the loop movables structure. */
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#define LOOP_MOVABLES(LOOP) (&LOOP_INFO (LOOP)->movables)
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/* Get a pointer to the loop registers structure. */
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#define LOOP_REGS(LOOP) (&LOOP_INFO (LOOP)->regs)
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/* Get a pointer to the loop induction variables structure. */
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#define LOOP_IVS(LOOP) (&LOOP_INFO (LOOP)->ivs)
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/* Get the luid of an insn. Catch the error of trying to reference the LUID
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of an insn added during loop, since these don't have LUIDs. */
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#define INSN_LUID(INSN) \
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(INSN_UID (INSN) < max_uid_for_loop ? uid_luid[INSN_UID (INSN)] \
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: (abort (), -1))
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#define REGNO_FIRST_LUID(REGNO) \
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(REGNO_FIRST_UID (REGNO) < max_uid_for_loop \
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? uid_luid[REGNO_FIRST_UID (REGNO)] \
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: 0)
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#define REGNO_LAST_LUID(REGNO) \
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(REGNO_LAST_UID (REGNO) < max_uid_for_loop \
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? uid_luid[REGNO_LAST_UID (REGNO)] \
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: INT_MAX)
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/* A "basic induction variable" or biv is a pseudo reg that is set
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(within this loop) only by incrementing or decrementing it. */
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/* A "general induction variable" or giv is a pseudo reg whose
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value is a linear function of a biv. */
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/* Bivs are recognized by `basic_induction_var';
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Givs by `general_induction_var'. */
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/* An enum for the two different types of givs, those that are used
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as memory addresses and those that are calculated into registers. */
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enum g_types
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{
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DEST_ADDR,
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DEST_REG
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};
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/* A `struct induction' is created for every instruction that sets
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an induction variable (either a biv or a giv). */
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struct induction
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{
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rtx insn; /* The insn that sets a biv or giv */
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rtx new_reg; /* New register, containing strength reduced
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version of this giv. */
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rtx src_reg; /* Biv from which this giv is computed.
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(If this is a biv, then this is the biv.) */
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enum g_types giv_type; /* Indicate whether DEST_ADDR or DEST_REG */
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rtx dest_reg; /* Destination register for insn: this is the
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register which was the biv or giv.
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For a biv, this equals src_reg.
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For a DEST_ADDR type giv, this is 0. */
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rtx *location; /* Place in the insn where this giv occurs.
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If GIV_TYPE is DEST_REG, this is 0. */
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/* For a biv, this is the place where add_val
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was found. */
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enum machine_mode mode; /* The mode of this biv or giv */
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rtx mem; /* For DEST_ADDR, the memory object. */
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rtx mult_val; /* Multiplicative factor for src_reg. */
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rtx add_val; /* Additive constant for that product. */
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int benefit; /* Gain from eliminating this insn. */
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rtx final_value; /* If the giv is used outside the loop, and its
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final value could be calculated, it is put
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here, and the giv is made replaceable. Set
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the giv to this value before the loop. */
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unsigned combined_with; /* The number of givs this giv has been
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combined with. If nonzero, this giv
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cannot combine with any other giv. */
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unsigned replaceable : 1; /* 1 if we can substitute the strength-reduced
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variable for the original variable.
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0 means they must be kept separate and the
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new one must be copied into the old pseudo
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reg each time the old one is set. */
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unsigned not_replaceable : 1; /* Used to prevent duplicating work. This is
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1 if we know that the giv definitely can
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not be made replaceable, in which case we
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don't bother checking the variable again
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even if further info is available.
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Both this and the above can be zero. */
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unsigned ignore : 1; /* 1 prohibits further processing of giv */
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unsigned always_computable : 1;/* 1 if this value is computable every
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iteration. */
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unsigned always_executed : 1; /* 1 if this set occurs each iteration. */
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unsigned maybe_multiple : 1; /* Only used for a biv and 1 if this biv
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update may be done multiple times per
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iteration. */
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unsigned cant_derive : 1; /* For giv's, 1 if this giv cannot derive
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another giv. This occurs in many cases
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where a giv's lifetime spans an update to
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a biv. */
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unsigned maybe_dead : 1; /* 1 if this giv might be dead. In that case,
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we won't use it to eliminate a biv, it
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would probably lose. */
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unsigned auto_inc_opt : 1; /* 1 if this giv had its increment output next
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to it to try to form an auto-inc address. */
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unsigned unrolled : 1; /* 1 if new register has been allocated and
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initialized in unrolled loop. */
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unsigned shared : 1;
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unsigned no_const_addval : 1; /* 1 if add_val does not contain a const. */
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int lifetime; /* Length of life of this giv */
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rtx derive_adjustment; /* If nonzero, is an adjustment to be
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subtracted from add_val when this giv
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derives another. This occurs when the
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giv spans a biv update by incrementation. */
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rtx ext_dependent; /* If nonzero, is a sign or zero extension
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if a biv on which this giv is dependent. */
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struct induction *next_iv; /* For givs, links together all givs that are
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based on the same biv. For bivs, links
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together all biv entries that refer to the
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same biv register. */
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struct induction *same; /* For givs, if the giv has been combined with
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another giv, this points to the base giv.
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The base giv will have COMBINED_WITH nonzero.
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For bivs, if the biv has the same LOCATION
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than another biv, this points to the base
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biv. */
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HOST_WIDE_INT const_adjust; /* Used by loop unrolling, when an address giv
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is split, and a constant is eliminated from
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the address, the -constant is stored here
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for later use. */
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struct induction *same_insn; /* If there are multiple identical givs in
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the same insn, then all but one have this
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field set, and they all point to the giv
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that doesn't have this field set. */
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rtx last_use; /* For a giv made from a biv increment, this is
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a substitute for the lifetime information. */
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};
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/* A `struct iv_class' is created for each biv. */
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struct iv_class
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{
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unsigned int regno; /* Pseudo reg which is the biv. */
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int biv_count; /* Number of insns setting this reg. */
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struct induction *biv; /* List of all insns that set this reg. */
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int giv_count; /* Number of DEST_REG givs computed from this
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biv. The resulting count is only used in
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check_dbra_loop. */
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struct induction *giv; /* List of all insns that compute a giv
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from this reg. */
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int total_benefit; /* Sum of BENEFITs of all those givs. */
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rtx initial_value; /* Value of reg at loop start. */
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rtx initial_test; /* Test performed on BIV before loop. */
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rtx final_value; /* Value of reg at loop end, if known. */
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struct iv_class *next; /* Links all class structures together. */
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rtx init_insn; /* insn which initializes biv, 0 if none. */
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rtx init_set; /* SET of INIT_INSN, if any. */
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unsigned incremented : 1; /* 1 if somewhere incremented/decremented */
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unsigned eliminable : 1; /* 1 if plausible candidate for
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elimination. */
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unsigned nonneg : 1; /* 1 if we added a REG_NONNEG note for
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this. */
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unsigned reversed : 1; /* 1 if we reversed the loop that this
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biv controls. */
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unsigned all_reduced : 1; /* 1 if all givs using this biv have
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been reduced. */
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};
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/* Definitions used by the basic induction variable discovery code. */
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enum iv_mode
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{
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UNKNOWN_INDUCT,
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BASIC_INDUCT,
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NOT_BASIC_INDUCT,
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GENERAL_INDUCT
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};
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/* A `struct iv' is created for every register. */
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struct iv
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{
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enum iv_mode type;
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union
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{
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struct iv_class *class;
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struct induction *info;
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} iv;
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};
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#define REG_IV_TYPE(ivs, n) ivs->regs[n].type
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#define REG_IV_INFO(ivs, n) ivs->regs[n].iv.info
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#define REG_IV_CLASS(ivs, n) ivs->regs[n].iv.class
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struct loop_ivs
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{
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/* Indexed by register number, contains pointer to `struct
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iv' if register is an induction variable. */
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struct iv *regs;
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/* Size of regs array. */
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unsigned int n_regs;
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/* The head of a list which links together (via the next field)
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every iv class for the current loop. */
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struct iv_class *list;
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};
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typedef struct loop_mem_info
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{
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rtx mem; /* The MEM itself. */
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rtx reg; /* Corresponding pseudo, if any. */
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int optimize; /* Nonzero if we can optimize access to this MEM. */
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} loop_mem_info;
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struct loop_reg
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{
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/* Number of times the reg is set during the loop being scanned.
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During code motion, a negative value indicates a reg that has
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been made a candidate; in particular -2 means that it is an
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candidate that we know is equal to a constant and -1 means that
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it is a candidate not known equal to a constant. After code
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motion, regs moved have 0 (which is accurate now) while the
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failed candidates have the original number of times set.
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Therefore, at all times, == 0 indicates an invariant register;
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< 0 a conditionally invariant one. */
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int set_in_loop;
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/* Original value of set_in_loop; same except that this value
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is not set negative for a reg whose sets have been made candidates
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and not set to 0 for a reg that is moved. */
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int n_times_set;
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/* Contains the insn in which a register was used if it was used
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exactly once; contains const0_rtx if it was used more than once. */
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rtx single_usage;
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/* Nonzero indicates that the register cannot be moved or strength
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reduced. */
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char may_not_optimize;
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/* Nonzero means reg N has already been moved out of one loop.
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This reduces the desire to move it out of another. */
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char moved_once;
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};
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struct loop_regs
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{
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int num; /* Number of regs used in table. */
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int size; /* Size of table. */
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struct loop_reg *array; /* Register usage info. array. */
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int multiple_uses; /* Nonzero if a reg has multiple uses. */
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};
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struct loop_movables
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{
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/* Head of movable chain. */
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struct movable *head;
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/* Last movable in chain. */
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struct movable *last;
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};
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/* Information pertaining to a loop. */
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struct loop_info
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{
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/* Nonzero if there is a subroutine call in the current loop. */
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int has_call;
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/* Nonzero if there is a libcall in the current loop. */
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int has_libcall;
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/* Nonzero if there is a non constant call in the current loop. */
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int has_nonconst_call;
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/* Nonzero if there is a prefetch instruction in the current loop. */
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int has_prefetch;
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/* Nonzero if there is a volatile memory reference in the current
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loop. */
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int has_volatile;
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/* Nonzero if there is a tablejump in the current loop. */
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int has_tablejump;
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/* Nonzero if there are ways to leave the loop other than falling
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off the end. */
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int has_multiple_exit_targets;
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/* Nonzero if there is an indirect jump in the current function. */
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int has_indirect_jump;
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/* Whether loop unrolling has emitted copies of the loop body so
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that the main loop needs no exit tests. */
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int preconditioned;
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/* Register or constant initial loop value. */
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rtx initial_value;
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/* Register or constant value used for comparison test. */
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rtx comparison_value;
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/* Register or constant approximate final value. */
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rtx final_value;
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/* Register or constant initial loop value with term common to
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final_value removed. */
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rtx initial_equiv_value;
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/* Register or constant final loop value with term common to
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initial_value removed. */
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rtx final_equiv_value;
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/* Register corresponding to iteration variable. */
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rtx iteration_var;
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/* Constant loop increment. */
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rtx increment;
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enum rtx_code comparison_code;
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/* Holds the number of loop iterations. It is zero if the number
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could not be calculated. Must be unsigned since the number of
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iterations can be as high as 2^wordsize - 1. For loops with a
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wider iterator, this number will be zero if the number of loop
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iterations is too large for an unsigned integer to hold. */
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unsigned HOST_WIDE_INT n_iterations;
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/* The number of times the loop body was unrolled. */
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unsigned int unroll_number;
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int used_count_register;
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/* The loop iterator induction variable. */
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struct iv_class *iv;
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/* List of MEMs that are stored in this loop. */
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rtx store_mems;
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/* Array of MEMs that are used (read or written) in this loop, but
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cannot be aliased by anything in this loop, except perhaps
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themselves. In other words, if mems[i] is altered during
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the loop, it is altered by an expression that is rtx_equal_p to
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it. */
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loop_mem_info *mems;
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/* The index of the next available slot in MEMS. */
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int mems_idx;
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/* The number of elements allocated in MEMS. */
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int mems_allocated;
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/* Nonzero if we don't know what MEMs were changed in the current
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loop. This happens if the loop contains a call (in which case
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`has_call' will also be set) or if we store into more than
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NUM_STORES MEMs. */
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int unknown_address_altered;
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/* The above doesn't count any readonly memory locations that are
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stored. This does. */
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int unknown_constant_address_altered;
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/* Count of memory write instructions discovered in the loop. */
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int num_mem_sets;
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/* The insn where the first of these was found. */
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rtx first_loop_store_insn;
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/* The chain of movable insns in loop. */
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struct loop_movables movables;
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/* The registers used the in loop. */
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struct loop_regs regs;
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/* The induction variable information in loop. */
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struct loop_ivs ivs;
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/* Nonzero if call is in pre_header extended basic block. */
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int pre_header_has_call;
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};
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/* Variables declared in loop.c, but also needed in unroll.c. */
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extern int *uid_luid;
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extern int max_uid_for_loop;
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extern unsigned int max_reg_before_loop;
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extern struct loop **uid_loop;
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extern FILE *loop_dump_stream;
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/* Forward declarations for non-static functions declared in loop.c and
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unroll.c. */
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extern int loop_invariant_p (const struct loop *, rtx);
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extern rtx get_condition_for_loop (const struct loop *, rtx);
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extern void loop_iv_add_mult_hoist (const struct loop *, rtx, rtx, rtx, rtx);
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extern void loop_iv_add_mult_sink (const struct loop *, rtx, rtx, rtx, rtx);
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extern void loop_iv_add_mult_emit_before (const struct loop *, rtx, rtx,
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rtx, rtx, basic_block, rtx);
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extern rtx express_from (struct induction *, struct induction *);
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extern rtx extend_value_for_giv (struct induction *, rtx);
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extern void unroll_loop (struct loop *, int, int);
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extern rtx biv_total_increment (const struct iv_class *);
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extern unsigned HOST_WIDE_INT loop_iterations (struct loop *);
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extern int precondition_loop_p (const struct loop *, rtx *, rtx *, rtx *,
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enum machine_mode *mode);
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extern rtx final_biv_value (const struct loop *, struct iv_class *);
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extern rtx final_giv_value (const struct loop *, struct induction *);
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extern void emit_unrolled_add (rtx, rtx, rtx);
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extern int back_branch_in_range_p (const struct loop *, rtx);
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extern int loop_insn_first_p (rtx, rtx);
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typedef rtx (*loop_insn_callback) (struct loop *, rtx, int, int);
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extern void for_each_insn_in_loop (struct loop *, loop_insn_callback);
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extern rtx loop_insn_emit_before (const struct loop *, basic_block, rtx, rtx);
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extern rtx loop_insn_sink (const struct loop *, rtx);
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extern rtx loop_insn_hoist (const struct loop *, rtx);
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/* Forward declarations for non-static functions declared in doloop.c. */
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extern rtx doloop_condition_get (rtx);
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extern int doloop_optimize (const struct loop *);
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