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/* Global common subexpression elimination
and global constant/copy propagation for GNU compiler.
Copyright (C) 1997 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, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
/* TODO
- reordering of memory allocation and freeing to be more space efficient
- do rough calc of how many regs are needed in each block, and a rough
calc of how many regs are available in each class and use that to
throttle back the code in cases where RTX_COST is minimal.
- memory aliasing support
- ability to realloc sbitmap vectors would allow one initial computation
of reg_set_in_block with only subsequent additions, rather than
recomputing it for each pass
NOTES
- the classic gcse implementation is kept in for now for comparison
*/
/* References searched while implementing this.
This list will eventually be deleted but I wanted to have a record of it
for now.
Compilers Principles, Techniques and Tools
Aho, Sethi, Ullman
Addison-Wesley, 1988
Global Optimization by Suppression of Partial Redundancies
E. Morel, C. Renvoise
communications of the acm, Vol. 22, Num. 2, Feb. 1979
A Portable Machine-Independent Global Optimizer - Design and Measurements
Frederick Chow
Stanford Ph.D. thesis, Dec. 1983
xxx
Elimination Algorithms for Data Flow Analysis
B.G. Ryder, M.C. Paull
ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
reread
A Fast Algorithm for Code Movement Optimization
D.M. Dhamdhere
SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
A Solution to a Problem with Morel and Renvoise's
Global Optimization by Suppression of Partial Redundancies
K-H Drechsler, M.P. Stadel
ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
Practical Adaptation of the Global Optimization
Algorithm of Morel and Renvoise
D.M. Dhamdhere
ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
Efficiently Computing Static Single Assignment Form and the Control
Dependence Graph
R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
yyy
How to Analyze Large Programs Efficiently and Informatively
D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
Lazy Code Motion
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
What's In a Region? Or Computing Control Dependence Regions in Near-Linear
Time for Reducible Flow Control
Thomas Ball
ACM Letters on Programming Languages and Systems,
Vol. 2, Num. 1-4, Mar-Dec 1993
An Efficient Representation for Sparse Sets
Preston Briggs, Linda Torczon
ACM Letters on Programming Languages and Systems,
Vol. 2, Num. 1-4, Mar-Dec 1993
A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
K-H Drechsler, M.P. Stadel
ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
Partial Dead Code Elimination
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
Effective Partial Redundancy Elimination
P. Briggs, K.D. Cooper
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
The Program Structure Tree: Computing Control Regions in Linear Time
R. Johnson, D. Pearson, K. Pingali
ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
Optimal Code Motion: Theory and Practice
J. Knoop, O. Ruthing, B. Steffen
ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
The power of assignment motion
J. Knoop, O. Ruthing, B. Steffen
ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
Global code motion / global value numbering
C. Click
ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
Value Driven Redundancy Elimination
L.T. Simpson
Rice University Ph.D. thesis, Apr. 1996
Value Numbering
L.T. Simpson
Massively Scalar Compiler Project, Rice University, Sep. 1996
High Performance Compilers for Parallel Computing
Michael Wolfe
Addison-Wesley, 1996
People wishing to speed up the code here should read xxx, yyy.
People wishing to do something different can find various possibilities
in the above papers and elsewhere.
*/
#include "config.h"
/* Must precede rtl.h for FFS. */
#include "system.h"
#include "rtl.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "flags.h"
#include "real.h"
#include "insn-config.h"
#include "recog.h"
#include "basic-block.h"
#include "output.h"
#include "obstack.h"
#define obstack_chunk_alloc gmalloc
#define obstack_chunk_free free
/* Maximum number of passes to perform. */
#define MAX_PASSES 1
/* Propagate flow information through back edges and thus enable PRE's
moving loop invariant calculations out of loops.
Originally this tended to create worse overall code, but several
improvements during the development of PRE seem to have made following
back edges generally a win.
Note much of the loop invariant code motion done here would normally
be done by loop.c, which has more heuristics for when to move invariants
out of loops. At some point we might need to move some of those
heuristics into gcse.c. */
#define FOLLOW_BACK_EDGES 1
/* We support two GCSE implementations: Classic GCSE (i.e. Dragon Book)
and PRE (Partial Redundancy Elimination) GCSE (based on Fred Chow's thesis).
The default is PRE.
In either case we perform the following steps:
1) Compute basic block information.
2) Compute table of places where registers are set.
3) Perform copy/constant propagation.
4) Perform global cse.
5) Perform another pass of copy/constant propagation [only if PRE].
Two passes of copy/constant propagation are done because the first one
enables more GCSE and the second one helps to clean up the copies that
GCSE creates. This is needed more for PRE than for Classic because Classic
GCSE will try to use an existing register containing the common
subexpression rather than create a new one. This is harder to do for PRE
because of the code motion (which Classic GCSE doesn't do).
Expressions we are interested in GCSE-ing are of the form
(set (pseudo-reg) (expression)).
Function want_to_gcse_p says what these are.
PRE handles moving invariant expressions out of loops (by treating them as
partially redundant). This feature of PRE is disabled here (by not
propagating dataflow information along back edges) because loop.c has more
involved (and thus typically better) heuristics for what to move out of
loops.
Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
assignment) based GVN (global value numbering). L. T. Simpson's paper
(Rice University) on value numbering is a useful reference for this.
**********************
We used to support multiple passes but there are diminishing returns in
doing so. The first pass usually makes 90% of the changes that are doable.
A second pass can make a few more changes made possible by the first pass.
Experiments show any further passes don't make enough changes to justify
the expense.
A study of spec92 using an unlimited number of passes:
[1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
[6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
[12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
It was found doing copy propagation between each pass enables further
substitutions.
PRE is quite expensive in complicated functions because the DFA can take
awhile to converge. Hence we only perform one pass. Macro MAX_PASSES can
be modified if one wants to experiment.
**********************
The steps for PRE are:
1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
2) Perform the data flow analysis for PRE.
3) Delete the redundant instructions
4) Insert the required copies [if any] that make the partially
redundant instructions fully redundant.
5) For other reaching expressions, insert an instruction to copy the value
to a newly created pseudo that will reach the redundant instruction.
The deletion is done first so that when we do insertions we
know which pseudo reg to use.
Various papers have argued that PRE DFA is expensive (O(n^2)) and others
argue it is not. The number of iterations for the algorithm to converge
is typically 2-4 so I don't view it as that expensive (relatively speaking).
PRE GCSE depends heavily on the seconds CSE pass to clean up the copies
we create. To make an expression reach the place where it's redundant,
the result of the expression is copied to a new register, and the redundant
expression is deleted by replacing it with this new register. Classic GCSE
doesn't have this problem as much as it computes the reaching defs of
each register in each block and thus can try to use an existing register.
**********************
When -fclassic-gcse, we perform a classic global CSE pass.
It is based on the algorithms in the Dragon book, and is based on code
written by Devor Tevi at Intel.
The steps for Classic GCSE are:
1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
Also recorded are reaching definition "gen" statements (rd_gen)
2) Compute the reaching definitions (reaching_defs).
This is a bitmap for each basic block indexed by INSN_CUID that is 1
for each statement containing a definition that reaches the block.
3) Compute the available expressions (ae_in).
This is a bitmap for each basic block indexed by expression number
that is 1 for each expression that is available at the beginning of
the block.
4) Perform GCSE.
This is done by scanning each instruction looking for sets of the form
(set (pseudo-reg) (expression)) and checking if `expression' is in the
hash table. If it is, and if the expression is available, and if only
one computation of the expression reaches the instruction, we substitute
the expression for a register containing its value. If there is no
such register, but the expression is expensive enough we create an
instruction to copy the result of the expression into and use that.
**********************
A fair bit of simplicity is created by creating small functions for simple
tasks, even when the function is only called in one place. This may
measurably slow things down [or may not] by creating more function call
overhead than is necessary. The source is laid out so that it's trivial
to make the affected functions inline so that one can measure what speed
up, if any, can be achieved, and maybe later when things settle things can
be rearranged.
Help stamp out big monolithic functions! */
/* GCSE global vars. */
/* -dG dump file. */
static FILE *gcse_file;
/* Bitmaps are normally not included in debugging dumps.
However it's useful to be able to print them from GDB.
We could create special functions for this, but it's simpler to
just allow passing stderr to the dump_foo fns. Since stderr can
be a macro, we store a copy here. */
static FILE *debug_stderr;
/* An obstack for our working variables. */
static struct obstack gcse_obstack;
/* Non-zero for each mode that supports (set (reg) (reg)).
This is trivially true for integer and floating point values.
It may or may not be true for condition codes. */
static char can_copy_p[(int) NUM_MACHINE_MODES];
/* Non-zero if can_copy_p has been initialized. */
static int can_copy_init_p;
/* Element I is a list of I's predecessors/successors. */
static int_list_ptr *s_preds;
static int_list_ptr *s_succs;
/* Element I is the number of predecessors/successors of basic block I. */
static int *num_preds;
static int *num_succs;
/* Hash table of expressions. */
struct expr
{
/* The expression (SET_SRC for expressions, PATTERN for assignments). */
rtx expr;
/* Index in the available expression bitmaps. */
int bitmap_index;
/* Next entry with the same hash. */
struct expr *next_same_hash;
/* List of anticipatable occurrences in basic blocks in the function.
An "anticipatable occurrence" is one that is the first occurrence in the
basic block and the operands are not modified in the basic block prior
to the occurrence. */
struct occr *antic_occr;
/* List of available occurrence in basic blocks in the function.
An "available occurrence" is one that is the last occurrence in the
basic block and the operands are not modified by following statements in
the basic block [including this insn]. */
struct occr *avail_occr;
/* Non-null if the computation is PRE redundant.
The value is the newly created pseudo-reg to record a copy of the
expression in all the places that reach the redundant copy. */
rtx reaching_reg;
};
/* Occurrence of an expression.
There is one per basic block. If a pattern appears more than once the
last appearance is used [or first for anticipatable expressions]. */
struct occr
{
/* Next occurrence of this expression. */
struct occr *next;
/* The insn that computes the expression. */
rtx insn;
/* Non-zero if this [anticipatable] occurrence has been deleted. */
char deleted_p;
/* Non-zero if this [available] occurrence has been copied to
reaching_reg. */
/* ??? This is mutually exclusive with deleted_p, so they could share
the same byte. */
char copied_p;
};
/* Expression and copy propagation hash tables.
Each hash table is an array of buckets.
??? It is known that if it were an array of entries, structure elements
`next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
not clear whether in the final analysis a sufficient amount of memory would
be saved as the size of the available expression bitmaps would be larger
[one could build a mapping table without holes afterwards though].
Someday I'll perform the computation and figure it out.
*/
/* Total size of the expression hash table, in elements. */
static int expr_hash_table_size;
/* The table itself.
This is an array of `expr_hash_table_size' elements. */
static struct expr **expr_hash_table;
/* Total size of the copy propagation hash table, in elements. */
static int set_hash_table_size;
/* The table itself.
This is an array of `set_hash_table_size' elements. */
static struct expr **set_hash_table;
/* Mapping of uids to cuids.
Only real insns get cuids. */
static int *uid_cuid;
/* Highest UID in UID_CUID. */
static int max_uid;
/* Get the cuid of an insn. */
#define INSN_CUID(INSN) (uid_cuid[INSN_UID (INSN)])
/* Number of cuids. */
static int max_cuid;
/* Mapping of cuids to insns. */
static rtx *cuid_insn;
/* Get insn from cuid. */
#define CUID_INSN(CUID) (cuid_insn[CUID])
/* Maximum register number in function prior to doing gcse + 1.
Registers created during this pass have regno >= max_gcse_regno.
This is named with "gcse" to not collide with global of same name. */
static int max_gcse_regno;
/* Maximum number of cse-able expressions found. */
static int n_exprs;
/* Maximum number of assignments for copy propagation found. */
static int n_sets;
/* Table of registers that are modified.
For each register, each element is a list of places where the pseudo-reg
is set.
For simplicity, GCSE is done on sets of pseudo-regs only. PRE GCSE only
requires knowledge of which blocks kill which regs [and thus could use
a bitmap instead of the lists `reg_set_table' uses]. The classic GCSE
uses the information in lists.
If the classic GCSE pass is deleted `reg_set_table' and could be turned
into an array of bitmaps (num-bbs x num-regs)
[however perhaps it may be useful to keep the data as is].
One advantage of recording things this way is that `reg_set_table' is
fairly sparse with respect to pseudo regs but for hard regs could be
fairly dense [relatively speaking].
And recording sets of pseudo-regs in lists speeds
up functions like compute_transp since in the case of pseudo-regs we only
need to iterate over the number of times a pseudo-reg is set, not over the
number of basic blocks [clearly there is a bit of a slow down in the cases
where a pseudo is set more than once in a block, however it is believed
that the net effect is to speed things up]. This isn't done for hard-regs
because recording call-clobbered hard-regs in `reg_set_table' at each
function call can consume a fair bit of memory, and iterating over hard-regs
stored this way in compute_transp will be more expensive. */
typedef struct reg_set {
/* The next setting of this register. */
struct reg_set *next;
/* The insn where it was set. */
rtx insn;
} reg_set;
static reg_set **reg_set_table;
/* Size of `reg_set_table'.
The table starts out at max_gcse_regno + slop, and is enlarged as
necessary. */
static int reg_set_table_size;
/* Amount to grow `reg_set_table' by when it's full. */
#define REG_SET_TABLE_SLOP 100
/* Bitmap containing one bit for each register in the program.
Used when performing GCSE to track which registers have been set since
the start of the basic block. */
static sbitmap reg_set_bitmap;
/* For each block, a bitmap of registers set in the block.
This is used by expr_killed_p and compute_transp.
It is computed during hash table computation and not by compute_sets
as it includes registers added since the last pass (or between cprop and
gcse) and it's currently not easy to realloc sbitmap vectors. */
static sbitmap *reg_set_in_block;
/* For each block, non-zero if memory is set in that block.
This is computed during hash table computation and is used by
expr_killed_p and compute_transp.
??? Handling of memory is very simple, we don't make any attempt
to optimize things (later).
??? This can be computed by compute_sets since the information
doesn't change. */
static char *mem_set_in_block;
/* Various variables for statistics gathering. */
/* Memory used in a pass.
This isn't intended to be absolutely precise. Its intent is only
to keep an eye on memory usage. */
static int bytes_used;
/* GCSE substitutions made. */
static int gcse_subst_count;
/* Number of copy instructions created. */
static int gcse_create_count;
/* Number of constants propagated. */
static int const_prop_count;
/* Number of copys propagated. */
static int copy_prop_count;
extern char *current_function_name;
extern int current_function_calls_setjmp;
extern int current_function_calls_longjmp;
/* These variables are used by classic GCSE.
Normally they'd be defined a bit later, but `rd_gen' needs to
be declared sooner. */
/* A bitmap of all ones for implementing the algorithm for available
expressions and reaching definitions. */
/* ??? Available expression bitmaps have a different size than reaching
definition bitmaps. This should be the larger of the two, however, it
is not currently used for reaching definitions. */
static sbitmap u_bitmap;
/* Each block has a bitmap of each type.
The length of each blocks bitmap is:
max_cuid - for reaching definitions
n_exprs - for available expressions
Thus we view the bitmaps as 2 dimensional arrays. i.e.
rd_kill[block_num][cuid_num]
ae_kill[block_num][expr_num]
*/
/* For reaching defs */
static sbitmap *rd_kill, *rd_gen, *reaching_defs, *rd_out;
/* for available exprs */
static sbitmap *ae_kill, *ae_gen, *ae_in, *ae_out;
static void compute_can_copy PROTO ((void));
static char *gmalloc PROTO ((unsigned int));
static char *grealloc PROTO ((char *, unsigned int));
static char *gcse_alloc PROTO ((unsigned long));
static void alloc_gcse_mem PROTO ((rtx));
static void free_gcse_mem PROTO ((void));
extern void dump_cuid_table PROTO ((FILE *));
static void alloc_reg_set_mem PROTO ((int));
static void free_reg_set_mem PROTO ((void));
static void record_one_set PROTO ((int, rtx));
static void record_set_info PROTO ((rtx, rtx));
static void compute_sets PROTO ((rtx));
static void hash_scan_insn PROTO ((rtx, int, int));
static void hash_scan_set PROTO ((rtx, rtx, int));
static void hash_scan_clobber PROTO ((rtx, rtx));
static void hash_scan_call PROTO ((rtx, rtx));
static void maybe_set_rd_gen PROTO ((int, rtx));
static int want_to_gcse_p PROTO ((rtx));
static int oprs_unchanged_p PROTO ((rtx, rtx, int));
static int oprs_anticipatable_p PROTO ((rtx, rtx));
static int oprs_available_p PROTO ((rtx, rtx));
static void insert_expr_in_table PROTO ((rtx, enum machine_mode, rtx, int, int));
static void insert_set_in_table PROTO ((rtx, rtx));
static unsigned int hash_expr PROTO ((rtx, enum machine_mode, int *, int));
static unsigned int hash_expr_1 PROTO ((rtx, enum machine_mode, int *));
static unsigned int hash_set PROTO ((int, int));
static int expr_equiv_p PROTO ((rtx, rtx));
static void record_last_reg_set_info PROTO ((rtx, int));
static void record_last_mem_set_info PROTO ((rtx));
static void record_last_set_info PROTO ((rtx, rtx));
static void compute_hash_table PROTO ((rtx, int));
static void alloc_set_hash_table PROTO ((int));
static void free_set_hash_table PROTO ((void));
static void compute_set_hash_table PROTO ((rtx));
static void alloc_expr_hash_table PROTO ((int));
static void free_expr_hash_table PROTO ((void));
static void compute_expr_hash_table PROTO ((rtx));
static void dump_hash_table PROTO ((FILE *, char *, struct expr **, int, int));
static struct expr *lookup_expr PROTO ((rtx));
static struct expr *lookup_set PROTO ((int, rtx));
static struct expr *next_set PROTO ((int, struct expr *));
static void reset_opr_set_tables PROTO ((void));
static int oprs_not_set_p PROTO ((rtx, rtx));
static void mark_call PROTO ((rtx, rtx));
static void mark_set PROTO ((rtx, rtx));
static void mark_clobber PROTO ((rtx, rtx));
static void mark_oprs_set PROTO ((rtx));
static void alloc_rd_mem PROTO ((int, int));
static void free_rd_mem PROTO ((void));
static void compute_kill_rd PROTO ((void));
static void handle_rd_kill_set PROTO ((rtx, int, int));
static void compute_rd PROTO ((void));
extern void dump_rd_table PROTO ((FILE *, char *, sbitmap *));
static void alloc_avail_expr_mem PROTO ((int, int));
static void free_avail_expr_mem PROTO ((void));
static void compute_ae_gen PROTO ((void));
static void compute_ae_kill PROTO ((void));
static int expr_killed_p PROTO ((rtx, int));
static void compute_available PROTO ((void));
static int expr_reaches_here_p PROTO ((struct occr *, struct expr *,
int, int, char *));
static rtx computing_insn PROTO ((struct expr *, rtx));
static int def_reaches_here_p PROTO ((rtx, rtx));
static int can_disregard_other_sets PROTO ((struct reg_set **, rtx, int));
static int handle_avail_expr PROTO ((rtx, struct expr *));
static int classic_gcse PROTO ((void));
static int one_classic_gcse_pass PROTO ((rtx, int));
static void alloc_cprop_mem PROTO ((int, int));
static void free_cprop_mem PROTO ((void));
extern void dump_cprop_data PROTO ((FILE *));
static void compute_transp PROTO ((rtx, int, sbitmap *, int));
static void compute_cprop_local_properties PROTO ((void));
static void compute_cprop_avinout PROTO ((void));
static void compute_cprop_data PROTO ((void));
static void find_used_regs PROTO ((rtx));
static int try_replace_reg PROTO ((rtx, rtx, rtx));
static struct expr *find_avail_set PROTO ((int, rtx));
static int cprop_insn PROTO ((rtx));
static int cprop PROTO ((void));
static int one_cprop_pass PROTO ((rtx, int));
static void alloc_pre_mem PROTO ((int, int));
static void free_pre_mem PROTO ((void));
extern void dump_pre_data PROTO ((FILE *));
static void compute_pre_local_properties PROTO ((void));
static void compute_pre_avinout PROTO ((void));
static void compute_pre_antinout PROTO ((void));
static void compute_pre_pavinout PROTO ((void));
static void compute_pre_ppinout PROTO ((void));
static void compute_pre_data PROTO ((void));
static int pre_expr_reaches_here_p PROTO ((struct occr *, struct expr *,
int, char *));
static void pre_insert_insn PROTO ((struct expr *, int));
static void pre_insert PROTO ((struct expr **));
static void pre_insert_copy_insn PROTO ((struct expr *, rtx));
static void pre_insert_copies PROTO ((void));
static int pre_delete PROTO ((void));
static int pre_gcse PROTO ((void));
static int one_pre_gcse_pass PROTO ((rtx, int));
static void add_label_notes PROTO ((rtx, rtx));
/* Entry point for global common subexpression elimination.
F is the first instruction in the function. */
void
gcse_main (f, file)
rtx f;
FILE *file;
{
int changed, pass;
/* Bytes used at start of pass. */
int initial_bytes_used;
/* Maximum number of bytes used by a pass. */
int max_pass_bytes;
/* Point to release obstack data from for each pass. */
char *gcse_obstack_bottom;
/* It's impossible to construct a correct control flow graph in the
presense of setjmp, so just punt to be safe. */
if (current_function_calls_setjmp)
return;
/* For calling dump_foo fns from gdb. */
debug_stderr = stderr;
max_gcse_regno = max_reg_num ();
find_basic_blocks (f, max_gcse_regno, file, 0);
/* Return if there's nothing to do. */
if (n_basic_blocks <= 1)
{
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
return;
}
/* See what modes support reg/reg copy operations. */
if (! can_copy_init_p)
{
compute_can_copy ();
can_copy_init_p = 1;
}
gcc_obstack_init (&gcse_obstack);
gcse_file = file;
/* Allocate and compute predecessors/successors. */
s_preds = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
s_succs = (int_list_ptr *) alloca (n_basic_blocks * sizeof (int_list_ptr));
num_preds = (int *) alloca (n_basic_blocks * sizeof (int));
num_succs = (int *) alloca (n_basic_blocks * sizeof (int));
bytes_used = 4 * n_basic_blocks * sizeof (int_list_ptr);
compute_preds_succs (s_preds, s_succs, num_preds, num_succs);
if (file)
{
dump_bb_data (file, s_preds, s_succs);
}
/* Record where pseudo-registers are set.
This data is kept accurate during each pass.
??? We could also record hard-reg and memory information here
[since it's unchanging], however it is currently done during
hash table computation. */
alloc_reg_set_mem (max_gcse_regno);
compute_sets (f);
pass = 0;
initial_bytes_used = bytes_used;
max_pass_bytes = 0;
gcse_obstack_bottom = gcse_alloc (1);
changed = 1;
while (changed && pass < MAX_PASSES)
{
changed = 0;
if (file)
fprintf (file, "GCSE pass %d\n\n", pass + 1);
/* Initialize bytes_used to the space for the pred/succ lists,
and the reg_set_table data. */
bytes_used = initial_bytes_used;
/* Each pass may create new registers, so recalculate each time. */
max_gcse_regno = max_reg_num ();
alloc_gcse_mem (f);
changed = one_cprop_pass (f, pass + 1);
if (optimize_size)
changed |= one_classic_gcse_pass (f, pass + 1);
else
changed |= one_pre_gcse_pass (f, pass + 1);
if (max_pass_bytes < bytes_used)
max_pass_bytes = bytes_used;
free_gcse_mem ();
if (file)
{
fprintf (file, "\n");
fflush (file);
}
obstack_free (&gcse_obstack, gcse_obstack_bottom);
pass++;
}
/* If we're doing PRE, do one last pass of copy propagation. */
if (! optimize_size)
{
max_gcse_regno = max_reg_num ();
alloc_gcse_mem (f);
one_cprop_pass (f, pass + 1);
free_gcse_mem ();
}
if (file)
{
fprintf (file, "GCSE of %s: %d basic blocks, ",
current_function_name, n_basic_blocks);
fprintf (file, "%d pass%s, %d bytes\n\n",
pass, pass > 1 ? "es" : "", max_pass_bytes);
}
/* Free our obstack. */
obstack_free (&gcse_obstack, NULL_PTR);
/* Free reg_set_table. */
free_reg_set_mem ();
/* Free storage used to record predecessor/successor data. */
free_bb_mem ();
/* Free storage allocated by find_basic_blocks. */
free_basic_block_vars (0);
}
/* Misc. utilities. */
/* Compute which modes support reg/reg copy operations. */
static void
compute_can_copy ()
{
int i;
#ifndef AVOID_CCMODE_COPIES
rtx reg,insn;
#endif
char *free_point = (char *) oballoc (1);
bzero (can_copy_p, NUM_MACHINE_MODES);
start_sequence ();
for (i = 0; i < NUM_MACHINE_MODES; i++)
{
switch (GET_MODE_CLASS (i))
{
case MODE_CC :
#ifdef AVOID_CCMODE_COPIES
can_copy_p[i] = 0;
#else
reg = gen_rtx_REG ((enum machine_mode) i, LAST_VIRTUAL_REGISTER + 1);
insn = emit_insn (gen_rtx_SET (VOIDmode, reg, reg));
if (recog (PATTERN (insn), insn, NULL_PTR) >= 0)
can_copy_p[i] = 1;
#endif
break;
default :
can_copy_p[i] = 1;
break;
}
}
end_sequence ();
/* Free the objects we just allocated. */
obfree (free_point);
}
/* Cover function to xmalloc to record bytes allocated. */
static char *
gmalloc (size)
unsigned int size;
{
bytes_used += size;
return xmalloc (size);
}
/* Cover function to xrealloc.
We don't record the additional size since we don't know it.
It won't affect memory usage stats much anyway. */
static char *
grealloc (ptr, size)
char *ptr;
unsigned int size;
{
return xrealloc (ptr, size);
}
/* Cover function to obstack_alloc.
We don't need to record the bytes allocated here since
obstack_chunk_alloc is set to gmalloc. */
static char *
gcse_alloc (size)
unsigned long size;
{
return (char *) obstack_alloc (&gcse_obstack, size);
}
/* Allocate memory for the cuid mapping array,
and reg/memory set tracking tables.
This is called at the start of each pass. */
static void
alloc_gcse_mem (f)
rtx f;
{
int i,n;
rtx insn;
/* Find the largest UID and create a mapping from UIDs to CUIDs.
CUIDs are like UIDs except they increase monotonically, have no gaps,
and only apply to real insns. */
max_uid = get_max_uid ();
n = (max_uid + 1) * sizeof (int);
uid_cuid = (int *) gmalloc (n);
bzero ((char *) uid_cuid, n);
for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
INSN_CUID (insn) = i++;
else
INSN_CUID (insn) = i;
}
/* Create a table mapping cuids to insns. */
max_cuid = i;
n = (max_cuid + 1) * sizeof (rtx);
cuid_insn = (rtx *) gmalloc (n);
bzero ((char *) cuid_insn, n);
for (insn = f, i = 0; insn; insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
CUID_INSN (i) = insn;
i++;
}
}
/* Allocate vars to track sets of regs. */
reg_set_bitmap = (sbitmap) sbitmap_alloc (max_gcse_regno);
/* Allocate vars to track sets of regs, memory per block. */
reg_set_in_block = (sbitmap *) sbitmap_vector_alloc (n_basic_blocks,
max_gcse_regno);
mem_set_in_block = (char *) gmalloc (n_basic_blocks);
}
/* Free memory allocated by alloc_gcse_mem. */
static void
free_gcse_mem ()
{
free (uid_cuid);
free (cuid_insn);
free (reg_set_bitmap);
free (reg_set_in_block);
free (mem_set_in_block);
}
void
dump_cuid_table (file)
FILE *file;
{
int i,n;
fprintf (file, "CUID table\n");
for (i = n = 0; i < max_cuid; i++)
{
rtx insn = CUID_INSN (i);
if (n != 0 && n % 10 == 0)
fprintf (file, "\n");
if (insn != NULL)
fprintf (file, " %d", INSN_UID (insn));
}
fprintf (file, "\n\n");
}
/* Register set information.
`reg_set_table' records where each register is set or otherwise
modified. */
static struct obstack reg_set_obstack;
static void
alloc_reg_set_mem (n_regs)
int n_regs;
{
int n;
reg_set_table_size = n_regs + REG_SET_TABLE_SLOP;
n = reg_set_table_size * sizeof (struct reg_set *);
reg_set_table = (struct reg_set **) gmalloc (n);
bzero ((char *) reg_set_table, n);
gcc_obstack_init (&reg_set_obstack);
}
static void
free_reg_set_mem ()
{
free (reg_set_table);
obstack_free (&reg_set_obstack, NULL_PTR);
}
/* Record REGNO in the reg_set table. */
static void
record_one_set (regno, insn)
int regno;
rtx insn;
{
/* allocate a new reg_set element and link it onto the list */
struct reg_set *new_reg_info, *reg_info_ptr1, *reg_info_ptr2;
/* If the table isn't big enough, enlarge it. */
if (regno >= reg_set_table_size)
{
int new_size = regno + REG_SET_TABLE_SLOP;
reg_set_table = (struct reg_set **)
grealloc ((char *) reg_set_table,
new_size * sizeof (struct reg_set *));
bzero ((char *) (reg_set_table + reg_set_table_size),
(new_size - reg_set_table_size) * sizeof (struct reg_set *));
reg_set_table_size = new_size;
}
new_reg_info = (struct reg_set *) obstack_alloc (&reg_set_obstack,
sizeof (struct reg_set));
bytes_used += sizeof (struct reg_set);
new_reg_info->insn = insn;
new_reg_info->next = NULL;
if (reg_set_table[regno] == NULL)
reg_set_table[regno] = new_reg_info;
else
{
reg_info_ptr1 = reg_info_ptr2 = reg_set_table[regno];
/* ??? One could keep a "last" pointer to speed this up. */
while (reg_info_ptr1 != NULL)
{
reg_info_ptr2 = reg_info_ptr1;
reg_info_ptr1 = reg_info_ptr1->next;
}
reg_info_ptr2->next = new_reg_info;
}
}
/* For communication between next two functions (via note_stores). */
static rtx record_set_insn;
/* Called from compute_sets via note_stores to handle one
SET or CLOBBER in an insn. */
static void
record_set_info (dest, setter)
rtx dest, setter ATTRIBUTE_UNUSED;
{
if (GET_CODE (dest) == SUBREG)
dest = SUBREG_REG (dest);
if (GET_CODE (dest) == REG)
{
if (REGNO (dest) >= FIRST_PSEUDO_REGISTER)
record_one_set (REGNO (dest), record_set_insn);
}
}
/* Scan the function and record each set of each pseudo-register.
This is called once, at the start of the gcse pass.
See the comments for `reg_set_table' for further docs. */
static void
compute_sets (f)
rtx f;
{
rtx insn = f;
while (insn)
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
record_set_insn = insn;
note_stores (PATTERN (insn), record_set_info);
}
insn = NEXT_INSN (insn);
}
}
/* Hash table support. */
/* For each register, the cuid of the first/last insn in the block to set it,
or zero if not set. */
static int *reg_first_set;
static int *reg_last_set;
/* While computing "first/last set" info, this is the CUID of first/last insn
to set memory or zero if not set. `mem_last_set' is also used when
performing GCSE to record whether memory has been set since the beginning
of the block.
Note that handling of memory is very simple, we don't make any attempt
to optimize things (later). */
static int mem_first_set;
static int mem_last_set;
/* Set the appropriate bit in `rd_gen' [the gen for reaching defs] if the
register set in this insn is not set after this insn in this block. */
static void
maybe_set_rd_gen (regno, insn)
int regno;
rtx insn;
{
if (reg_last_set[regno] <= INSN_CUID (insn))
SET_BIT (rd_gen[BLOCK_NUM (insn)], INSN_CUID (insn));
}
/* Perform a quick check whether X, the source of a set, is something
we want to consider for GCSE. */
static int
want_to_gcse_p (x)
rtx x;
{
enum rtx_code code = GET_CODE (x);
switch (code)
{
case REG:
case SUBREG:
case CONST_INT:
case CONST_DOUBLE:
case CALL:
return 0;
default:
break;
}
return 1;
}
/* Return non-zero if the operands of expression X are unchanged from the
start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
static int
oprs_unchanged_p (x, insn, avail_p)
rtx x, insn;
int avail_p;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case REG:
if (avail_p)
return (reg_last_set[REGNO (x)] == 0
|| reg_last_set[REGNO (x)] < INSN_CUID (insn));
else
return (reg_first_set[REGNO (x)] == 0
|| reg_first_set[REGNO (x)] >= INSN_CUID (insn));
case MEM:
if (avail_p)
{
if (mem_last_set != 0
&& mem_last_set >= INSN_CUID (insn))
return 0;
}
else
{
if (mem_first_set != 0
&& mem_first_set < INSN_CUID (insn))
return 0;
}
x = XEXP (x, 0);
goto repeat;
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
return 0;
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 1;
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
if (! oprs_unchanged_p (tem, insn, avail_p))
return 0;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
if (! oprs_unchanged_p (XVECEXP (x, i, j), insn, avail_p))
return 0;
}
}
}
return 1;
}
/* Return non-zero if the operands of expression X are unchanged from
the start of INSN's basic block up to but not including INSN. */
static int
oprs_anticipatable_p (x, insn)
rtx x, insn;
{
return oprs_unchanged_p (x, insn, 0);
}
/* Return non-zero if the operands of expression X are unchanged from
INSN to the end of INSN's basic block. */
static int
oprs_available_p (x, insn)
rtx x, insn;
{
return oprs_unchanged_p (x, insn, 1);
}
/* Hash expression X.
MODE is only used if X is a CONST_INT.
A boolean indicating if a volatile operand is found or if the expression
contains something we don't want to insert in the table is stored in
DO_NOT_RECORD_P.
??? One might want to merge this with canon_hash. Later. */
static unsigned int
hash_expr (x, mode, do_not_record_p, hash_table_size)
rtx x;
enum machine_mode mode;
int *do_not_record_p;
int hash_table_size;
{
unsigned int hash;
*do_not_record_p = 0;
hash = hash_expr_1 (x, mode, do_not_record_p);
return hash % hash_table_size;
}
/* Subroutine of hash_expr to do the actual work. */
static unsigned int
hash_expr_1 (x, mode, do_not_record_p)
rtx x;
enum machine_mode mode;
int *do_not_record_p;
{
int i, j;
unsigned hash = 0;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return hash;
code = GET_CODE (x);
switch (code)
{
case REG:
{
register int regno = REGNO (x);
hash += ((unsigned) REG << 7) + regno;
return hash;
}
case CONST_INT:
{
unsigned HOST_WIDE_INT tem = INTVAL (x);
hash += ((unsigned) CONST_INT << 7) + (unsigned) mode + tem;
return hash;
}
case CONST_DOUBLE:
/* This is like the general case, except that it only counts
the integers representing the constant. */
hash += (unsigned) code + (unsigned) GET_MODE (x);
if (GET_MODE (x) != VOIDmode)
for (i = 2; i < GET_RTX_LENGTH (CONST_DOUBLE); i++)
{
unsigned tem = XINT (x, i);
hash += tem;
}
else
hash += ((unsigned) CONST_DOUBLE_LOW (x)
+ (unsigned) CONST_DOUBLE_HIGH (x));
return hash;
/* Assume there is only one rtx object for any given label. */
case LABEL_REF:
/* We don't hash on the address of the CODE_LABEL to avoid bootstrap
differences and differences between each stage's debugging dumps. */
hash += ((unsigned) LABEL_REF << 7) + CODE_LABEL_NUMBER (XEXP (x, 0));
return hash;
case SYMBOL_REF:
{
/* Don't hash on the symbol's address to avoid bootstrap differences.
Different hash values may cause expressions to be recorded in
different orders and thus different registers to be used in the
final assembler. This also avoids differences in the dump files
between various stages. */
unsigned int h = 0;
unsigned char *p = (unsigned char *) XSTR (x, 0);
while (*p)
h += (h << 7) + *p++; /* ??? revisit */
hash += ((unsigned) SYMBOL_REF << 7) + h;
return hash;
}
case MEM:
if (MEM_VOLATILE_P (x))
{
*do_not_record_p = 1;
return 0;
}
hash += (unsigned) MEM;
x = XEXP (x, 0);
goto repeat;
case PRE_DEC:
case PRE_INC:
case POST_DEC:
case POST_INC:
case PC:
case CC0:
case CALL:
case UNSPEC_VOLATILE:
*do_not_record_p = 1;
return 0;
case ASM_OPERANDS:
if (MEM_VOLATILE_P (x))
{
*do_not_record_p = 1;
return 0;
}
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
hash += (unsigned) code + (unsigned) GET_MODE (x);
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
hash += hash_expr_1 (tem, 0, do_not_record_p);
if (*do_not_record_p)
return 0;
}
else if (fmt[i] == 'E')
for (j = 0; j < XVECLEN (x, i); j++)
{
hash += hash_expr_1 (XVECEXP (x, i, j), 0, do_not_record_p);
if (*do_not_record_p)
return 0;
}
else if (fmt[i] == 's')
{
register unsigned char *p = (unsigned char *) XSTR (x, i);
if (p)
while (*p)
hash += *p++;
}
else if (fmt[i] == 'i')
{
register unsigned tem = XINT (x, i);
hash += tem;
}
else
abort ();
}
return hash;
}
/* Hash a set of register REGNO.
Sets are hashed on the register that is set.
This simplifies the PRE copy propagation code.
??? May need to make things more elaborate. Later, as necessary. */
static unsigned int
hash_set (regno, hash_table_size)
int regno;
int hash_table_size;
{
unsigned int hash;
hash = regno;
return hash % hash_table_size;
}
/* Return non-zero if exp1 is equivalent to exp2.
??? Borrowed from cse.c. Might want to remerge with cse.c. Later. */
static int
expr_equiv_p (x, y)
rtx x, y;
{
register int i, j;
register enum rtx_code code;
register char *fmt;
if (x == y)
return 1;
if (x == 0 || y == 0)
return x == y;
code = GET_CODE (x);
if (code != GET_CODE (y))
return 0;
/* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent. */
if (GET_MODE (x) != GET_MODE (y))
return 0;
switch (code)
{
case PC:
case CC0:
return x == y;
case CONST_INT:
return INTVAL (x) == INTVAL (y);
case LABEL_REF:
return XEXP (x, 0) == XEXP (y, 0);
case SYMBOL_REF:
return XSTR (x, 0) == XSTR (y, 0);
case REG:
return REGNO (x) == REGNO (y);
/* For commutative operations, check both orders. */
case PLUS:
case MULT:
case AND:
case IOR:
case XOR:
case NE:
case EQ:
return ((expr_equiv_p (XEXP (x, 0), XEXP (y, 0))
&& expr_equiv_p (XEXP (x, 1), XEXP (y, 1)))
|| (expr_equiv_p (XEXP (x, 0), XEXP (y, 1))
&& expr_equiv_p (XEXP (x, 1), XEXP (y, 0))));
default:
break;
}
/* Compare the elements. If any pair of corresponding elements
fail to match, return 0 for the whole thing. */
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
switch (fmt[i])
{
case 'e':
if (! expr_equiv_p (XEXP (x, i), XEXP (y, i)))
return 0;
break;
case 'E':
if (XVECLEN (x, i) != XVECLEN (y, i))
return 0;
for (j = 0; j < XVECLEN (x, i); j++)
if (! expr_equiv_p (XVECEXP (x, i, j), XVECEXP (y, i, j)))
return 0;
break;
case 's':
if (strcmp (XSTR (x, i), XSTR (y, i)))
return 0;
break;
case 'i':
if (XINT (x, i) != XINT (y, i))
return 0;
break;
case 'w':
if (XWINT (x, i) != XWINT (y, i))
return 0;
break;
case '0':
break;
default:
abort ();
}
}
return 1;
}
/* Insert expression X in INSN in the hash table.
If it is already present, record it as the last occurrence in INSN's
basic block.
MODE is the mode of the value X is being stored into.
It is only used if X is a CONST_INT.
ANTIC_P is non-zero if X is an anticipatable expression.
AVAIL_P is non-zero if X is an available expression. */
static void
insert_expr_in_table (x, mode, insn, antic_p, avail_p)
rtx x;
enum machine_mode mode;
rtx insn;
int antic_p, avail_p;
{
int found, do_not_record_p;
unsigned int hash;
struct expr *cur_expr, *last_expr = NULL;
struct occr *antic_occr, *avail_occr;
struct occr *last_occr = NULL;
hash = hash_expr (x, mode, &do_not_record_p, expr_hash_table_size);
/* Do not insert expression in table if it contains volatile operands,
or if hash_expr determines the expression is something we don't want
to or can't handle. */
if (do_not_record_p)
return;
cur_expr = expr_hash_table[hash];
found = 0;
while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
{
/* If the expression isn't found, save a pointer to the end of
the list. */
last_expr = cur_expr;
cur_expr = cur_expr->next_same_hash;
}
if (! found)
{
cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
bytes_used += sizeof (struct expr);
if (expr_hash_table[hash] == NULL)
{
/* This is the first pattern that hashed to this index. */
expr_hash_table[hash] = cur_expr;
}
else
{
/* Add EXPR to end of this hash chain. */
last_expr->next_same_hash = cur_expr;
}
/* Set the fields of the expr element. */
cur_expr->expr = x;
cur_expr->bitmap_index = n_exprs++;
cur_expr->next_same_hash = NULL;
cur_expr->antic_occr = NULL;
cur_expr->avail_occr = NULL;
}
/* Now record the occurrence(s). */
if (antic_p)
{
antic_occr = cur_expr->antic_occr;
/* Search for another occurrence in the same basic block. */
while (antic_occr && BLOCK_NUM (antic_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = antic_occr;
antic_occr = antic_occr->next;
}
if (antic_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer the currently recorded one. We want the first one in the
block and the block is scanned from start to end. */
; /* nothing to do */
}
else
{
/* First occurrence of this expression in this basic block. */
antic_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->antic_occr == NULL)
cur_expr->antic_occr = antic_occr;
else
last_occr->next = antic_occr;
antic_occr->insn = insn;
antic_occr->next = NULL;
}
}
if (avail_p)
{
avail_occr = cur_expr->avail_occr;
/* Search for another occurrence in the same basic block. */
while (avail_occr && BLOCK_NUM (avail_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = avail_occr;
avail_occr = avail_occr->next;
}
if (avail_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer this occurrence to the currently recorded one. We want
the last one in the block and the block is scanned from start
to end. */
avail_occr->insn = insn;
}
else
{
/* First occurrence of this expression in this basic block. */
avail_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->avail_occr == NULL)
cur_expr->avail_occr = avail_occr;
else
last_occr->next = avail_occr;
avail_occr->insn = insn;
avail_occr->next = NULL;
}
}
}
/* Insert pattern X in INSN in the hash table.
X is a SET of a reg to either another reg or a constant.
If it is already present, record it as the last occurrence in INSN's
basic block. */
static void
insert_set_in_table (x, insn)
rtx x;
rtx insn;
{
int found;
unsigned int hash;
struct expr *cur_expr, *last_expr = NULL;
struct occr *cur_occr, *last_occr = NULL;
if (GET_CODE (x) != SET
|| GET_CODE (SET_DEST (x)) != REG)
abort ();
hash = hash_set (REGNO (SET_DEST (x)), set_hash_table_size);
cur_expr = set_hash_table[hash];
found = 0;
while (cur_expr && ! (found = expr_equiv_p (cur_expr->expr, x)))
{
/* If the expression isn't found, save a pointer to the end of
the list. */
last_expr = cur_expr;
cur_expr = cur_expr->next_same_hash;
}
if (! found)
{
cur_expr = (struct expr *) gcse_alloc (sizeof (struct expr));
bytes_used += sizeof (struct expr);
if (set_hash_table[hash] == NULL)
{
/* This is the first pattern that hashed to this index. */
set_hash_table[hash] = cur_expr;
}
else
{
/* Add EXPR to end of this hash chain. */
last_expr->next_same_hash = cur_expr;
}
/* Set the fields of the expr element.
We must copy X because it can be modified when copy propagation is
performed on its operands. */
/* ??? Should this go in a different obstack? */
cur_expr->expr = copy_rtx (x);
cur_expr->bitmap_index = n_sets++;
cur_expr->next_same_hash = NULL;
cur_expr->antic_occr = NULL;
cur_expr->avail_occr = NULL;
}
/* Now record the occurrence. */
cur_occr = cur_expr->avail_occr;
/* Search for another occurrence in the same basic block. */
while (cur_occr && BLOCK_NUM (cur_occr->insn) != BLOCK_NUM (insn))
{
/* If an occurrence isn't found, save a pointer to the end of
the list. */
last_occr = cur_occr;
cur_occr = cur_occr->next;
}
if (cur_occr)
{
/* Found another instance of the expression in the same basic block.
Prefer this occurrence to the currently recorded one. We want
the last one in the block and the block is scanned from start
to end. */
cur_occr->insn = insn;
}
else
{
/* First occurrence of this expression in this basic block. */
cur_occr = (struct occr *) gcse_alloc (sizeof (struct occr));
bytes_used += sizeof (struct occr);
/* First occurrence of this expression in any block? */
if (cur_expr->avail_occr == NULL)
cur_expr->avail_occr = cur_occr;
else
last_occr->next = cur_occr;
cur_occr->insn = insn;
cur_occr->next = NULL;
}
}
/* Scan pattern PAT of INSN and add an entry to the hash table.
If SET_P is non-zero, this is for the assignment hash table,
otherwise it is for the expression hash table. */
static void
hash_scan_set (pat, insn, set_p)
rtx pat, insn;
int set_p;
{
rtx src = SET_SRC (pat);
rtx dest = SET_DEST (pat);
if (GET_CODE (src) == CALL)
hash_scan_call (src, insn);
if (GET_CODE (dest) == REG)
{
int regno = REGNO (dest);
rtx tmp;
/* Only record sets of pseudo-regs in the hash table. */
if (! set_p
&& regno >= FIRST_PSEUDO_REGISTER
/* Don't GCSE something if we can't do a reg/reg copy. */
&& can_copy_p [GET_MODE (dest)]
/* Is SET_SRC something we want to gcse? */
&& want_to_gcse_p (src))
{
/* An expression is not anticipatable if its operands are
modified before this insn. */
int antic_p = ! optimize_size && oprs_anticipatable_p (src, insn);
/* An expression is not available if its operands are
subsequently modified, including this insn. */
int avail_p = oprs_available_p (src, insn);
insert_expr_in_table (src, GET_MODE (dest), insn, antic_p, avail_p);
}
/* Record sets for constant/copy propagation. */
else if (set_p
&& regno >= FIRST_PSEUDO_REGISTER
&& ((GET_CODE (src) == REG
&& REGNO (src) >= FIRST_PSEUDO_REGISTER
&& can_copy_p [GET_MODE (dest)])
/* ??? CONST_INT:wip */
|| GET_CODE (src) == CONST_INT)
/* A copy is not available if its src or dest is subsequently
modified. Here we want to search from INSN+1 on, but
oprs_available_p searches from INSN on. */
&& (insn == BLOCK_END (BLOCK_NUM (insn))
|| ((tmp = next_nonnote_insn (insn)) != NULL_RTX
&& oprs_available_p (pat, tmp))))
insert_set_in_table (pat, insn);
}
/* Check if first/last set in this block for classic gcse,
but not for copy/constant propagation. */
if (optimize_size && !set_p)
{
rtx dest = SET_DEST (pat);
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
if (GET_CODE (dest) == REG)
maybe_set_rd_gen (REGNO (dest), insn);
}
}
static void
hash_scan_clobber (x, insn)
rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
{
/* Currently nothing to do. */
}
static void
hash_scan_call (x, insn)
rtx x ATTRIBUTE_UNUSED, insn ATTRIBUTE_UNUSED;
{
/* Currently nothing to do. */
}
/* Process INSN and add hash table entries as appropriate.
Only available expressions that set a single pseudo-reg are recorded.
Single sets in a PARALLEL could be handled, but it's an extra complication
that isn't dealt with right now. The trick is handling the CLOBBERs that
are also in the PARALLEL. Later.
If SET_P is non-zero, this is for the assignment hash table,
otherwise it is for the expression hash table.
If IN_LIBCALL_BLOCK nonzero, we are in a libcall block, and should
not record any expressions. */
static void
hash_scan_insn (insn, set_p, in_libcall_block)
rtx insn;
int set_p;
int in_libcall_block;
{
rtx pat = PATTERN (insn);
/* Pick out the sets of INSN and for other forms of instructions record
what's been modified. */
if (GET_CODE (pat) == SET && ! in_libcall_block)
hash_scan_set (pat, insn, set_p);
else if (GET_CODE (pat) == PARALLEL)
{
int i;
for (i = 0; i < XVECLEN (pat, 0); i++)
{
rtx x = XVECEXP (pat, 0, i);
if (GET_CODE (x) == SET)
{
if (GET_CODE (SET_SRC (x)) == CALL)
hash_scan_call (SET_SRC (x), insn);
/* Check if first/last set in this block for classic
gcse, but not for constant/copy propagation. */
if (optimize_size && !set_p)
{
rtx dest = SET_DEST (x);
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
if (GET_CODE (dest) == REG)
maybe_set_rd_gen (REGNO (dest), insn);
}
}
else if (GET_CODE (x) == CLOBBER)
hash_scan_clobber (x, insn);
else if (GET_CODE (x) == CALL)
hash_scan_call (x, insn);
}
}
else if (GET_CODE (pat) == CLOBBER)
hash_scan_clobber (pat, insn);
else if (GET_CODE (pat) == CALL)
hash_scan_call (pat, insn);
}
static void
dump_hash_table (file, name, table, table_size, total_size)
FILE *file;
char *name;
struct expr **table;
int table_size, total_size;
{
int i;
/* Flattened out table, so it's printed in proper order. */
struct expr **flat_table = (struct expr **) alloca (total_size * sizeof (struct expr *));
unsigned int *hash_val = (unsigned int *) alloca (total_size * sizeof (unsigned int));
bzero ((char *) flat_table, total_size * sizeof (struct expr *));
for (i = 0; i < table_size; i++)
{
struct expr *expr;
for (expr = table[i]; expr != NULL; expr = expr->next_same_hash)
{
flat_table[expr->bitmap_index] = expr;
hash_val[expr->bitmap_index] = i;
}
}
fprintf (file, "%s hash table (%d buckets, %d entries)\n",
name, table_size, total_size);
for (i = 0; i < total_size; i++)
{
struct expr *expr = flat_table[i];
fprintf (file, "Index %d (hash value %d)\n ",
expr->bitmap_index, hash_val[i]);
print_rtl (file, expr->expr);
fprintf (file, "\n");
}
fprintf (file, "\n");
}
/* Record register first/last/block set information for REGNO in INSN.
reg_first_set records the first place in the block where the register
is set and is used to compute "anticipatability".
reg_last_set records the last place in the block where the register
is set and is used to compute "availability".
reg_set_in_block records whether the register is set in the block
and is used to compute "transparency". */
static void
record_last_reg_set_info (insn, regno)
rtx insn;
int regno;
{
if (reg_first_set[regno] == 0)
reg_first_set[regno] = INSN_CUID (insn);
reg_last_set[regno] = INSN_CUID (insn);
SET_BIT (reg_set_in_block[BLOCK_NUM (insn)], regno);
}
/* Record memory first/last/block set information for INSN. */
static void
record_last_mem_set_info (insn)
rtx insn;
{
if (mem_first_set == 0)
mem_first_set = INSN_CUID (insn);
mem_last_set = INSN_CUID (insn);
mem_set_in_block[BLOCK_NUM (insn)] = 1;
}
/* Used for communicating between next two routines. */
static rtx last_set_insn;
/* Called from compute_hash_table via note_stores to handle one
SET or CLOBBER in an insn. */
static void
record_last_set_info (dest, setter)
rtx dest, setter ATTRIBUTE_UNUSED;
{
if (GET_CODE (dest) == SUBREG)
dest = SUBREG_REG (dest);
if (GET_CODE (dest) == REG)
record_last_reg_set_info (last_set_insn, REGNO (dest));
else if (GET_CODE (dest) == MEM
/* Ignore pushes, they clobber nothing. */
&& ! push_operand (dest, GET_MODE (dest)))
record_last_mem_set_info (last_set_insn);
}
/* Top level function to create an expression or assignment hash table.
Expression entries are placed in the hash table if
- they are of the form (set (pseudo-reg) src),
- src is something we want to perform GCSE on,
- none of the operands are subsequently modified in the block
Assignment entries are placed in the hash table if
- they are of the form (set (pseudo-reg) src),
- src is something we want to perform const/copy propagation on,
- none of the operands or target are subsequently modified in the block
Currently src must be a pseudo-reg or a const_int.
F is the first insn.
SET_P is non-zero for computing the assignment hash table. */
static void
compute_hash_table (f, set_p)
rtx f ATTRIBUTE_UNUSED;
int set_p;
{
int bb;
/* While we compute the hash table we also compute a bit array of which
registers are set in which blocks.
We also compute which blocks set memory, in the absence of aliasing
support [which is TODO].
??? This isn't needed during const/copy propagation, but it's cheap to
compute. Later. */
sbitmap_vector_zero (reg_set_in_block, n_basic_blocks);
bzero ((char *) mem_set_in_block, n_basic_blocks);
/* Some working arrays used to track first and last set in each block. */
/* ??? One could use alloca here, but at some size a threshold is crossed
beyond which one should use malloc. Are we at that threshold here? */
reg_first_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
reg_last_set = (int *) gmalloc (max_gcse_regno * sizeof (int));
for (bb = 0; bb < n_basic_blocks; bb++)
{
rtx insn;
int regno;
int in_libcall_block;
/* First pass over the instructions records information used to
determine when registers and memory are first and last set.
??? The mem_set_in_block and hard-reg reg_set_in_block computation
could be moved to compute_sets since they currently don't change. */
bzero ((char *) reg_first_set, max_gcse_regno * sizeof (int));
bzero ((char *) reg_last_set, max_gcse_regno * sizeof (int));
mem_first_set = 0;
mem_last_set = 0;
for (insn = basic_block_head[bb];
insn && insn != NEXT_INSN (basic_block_end[bb]);
insn = NEXT_INSN (insn))
{
#ifdef NON_SAVING_SETJMP
if (NON_SAVING_SETJMP && GET_CODE (insn) == NOTE
&& NOTE_LINE_NUMBER (insn) == NOTE_INSN_SETJMP)
{
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
record_last_reg_set_info (insn, regno);
continue;
}
#endif
if (GET_RTX_CLASS (GET_CODE (insn)) != 'i')
continue;
if (GET_CODE (insn) == CALL_INSN)
{
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
if (call_used_regs[regno])
record_last_reg_set_info (insn, regno);
if (! CONST_CALL_P (insn))
record_last_mem_set_info (insn);
}
last_set_insn = insn;
note_stores (PATTERN (insn), record_last_set_info);
}
/* The next pass builds the hash table. */
for (insn = basic_block_head[bb], in_libcall_block = 0;
insn && insn != NEXT_INSN (basic_block_end[bb]);
insn = NEXT_INSN (insn))
{
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
{
if (find_reg_note (insn, REG_LIBCALL, NULL_RTX))
in_libcall_block = 1;
else if (find_reg_note (insn, REG_RETVAL, NULL_RTX))
in_libcall_block = 0;
hash_scan_insn (insn, set_p, in_libcall_block);
}
}
}
free (reg_first_set);
free (reg_last_set);
/* Catch bugs early. */
reg_first_set = reg_last_set = 0;
}
/* Allocate space for the set hash table.
N_INSNS is the number of instructions in the function.
It is used to determine the number of buckets to use. */
static void
alloc_set_hash_table (n_insns)
int n_insns;
{
int n;
set_hash_table_size = n_insns / 4;
if (set_hash_table_size < 11)
set_hash_table_size = 11;
/* Attempt to maintain efficient use of hash table.
Making it an odd number is simplest for now.
??? Later take some measurements. */
set_hash_table_size |= 1;
n = set_hash_table_size * sizeof (struct expr *);
set_hash_table = (struct expr **) gmalloc (n);
}
/* Free things allocated by alloc_set_hash_table. */
static void
free_set_hash_table ()
{
free (set_hash_table);
}
/* Compute the hash table for doing copy/const propagation. */
static void
compute_set_hash_table (f)
rtx f;
{
/* Initialize count of number of entries in hash table. */
n_sets = 0;
bzero ((char *) set_hash_table, set_hash_table_size * sizeof (struct expr *));
compute_hash_table (f, 1);
}
/* Allocate space for the expression hash table.
N_INSNS is the number of instructions in the function.
It is used to determine the number of buckets to use. */
static void
alloc_expr_hash_table (n_insns)
int n_insns;
{
int n;
expr_hash_table_size = n_insns / 2;
/* Make sure the amount is usable. */
if (expr_hash_table_size < 11)
expr_hash_table_size = 11;
/* Attempt to maintain efficient use of hash table.
Making it an odd number is simplest for now.
??? Later take some measurements. */
expr_hash_table_size |= 1;
n = expr_hash_table_size * sizeof (struct expr *);
expr_hash_table = (struct expr **) gmalloc (n);
}
/* Free things allocated by alloc_expr_hash_table. */
static void
free_expr_hash_table ()
{
free (expr_hash_table);
}
/* Compute the hash table for doing GCSE. */
static void
compute_expr_hash_table (f)
rtx f;
{
/* Initialize count of number of entries in hash table. */
n_exprs = 0;
bzero ((char *) expr_hash_table, expr_hash_table_size * sizeof (struct expr *));
compute_hash_table (f, 0);
}
/* Expression tracking support. */
/* Lookup pattern PAT in the expression table.
The result is a pointer to the table entry, or NULL if not found. */
static struct expr *
lookup_expr (pat)
rtx pat;
{
int do_not_record_p;
unsigned int hash = hash_expr (pat, GET_MODE (pat), &do_not_record_p,
expr_hash_table_size);
struct expr *expr;
if (do_not_record_p)
return NULL;
expr = expr_hash_table[hash];
while (expr && ! expr_equiv_p (expr->expr, pat))
expr = expr->next_same_hash;
return expr;
}
/* Lookup REGNO in the set table.
If PAT is non-NULL look for the entry that matches it, otherwise return
the first entry for REGNO.
The result is a pointer to the table entry, or NULL if not found. */
static struct expr *
lookup_set (regno, pat)
int regno;
rtx pat;
{
unsigned int hash = hash_set (regno, set_hash_table_size);
struct expr *expr;
expr = set_hash_table[hash];
if (pat)
{
while (expr && ! expr_equiv_p (expr->expr, pat))
expr = expr->next_same_hash;
}
else
{
while (expr && REGNO (SET_DEST (expr->expr)) != regno)
expr = expr->next_same_hash;
}
return expr;
}
/* Return the next entry for REGNO in list EXPR. */
static struct expr *
next_set (regno, expr)
int regno;
struct expr *expr;
{
do
expr = expr->next_same_hash;
while (expr && REGNO (SET_DEST (expr->expr)) != regno);
return expr;
}
/* Reset tables used to keep track of what's still available [since the
start of the block]. */
static void
reset_opr_set_tables ()
{
/* Maintain a bitmap of which regs have been set since beginning of
the block. */
sbitmap_zero (reg_set_bitmap);
/* Also keep a record of the last instruction to modify memory.
For now this is very trivial, we only record whether any memory
location has been modified. */
mem_last_set = 0;
}
/* Return non-zero if the operands of X are not set before INSN in
INSN's basic block. */
static int
oprs_not_set_p (x, insn)
rtx x, insn;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case PC:
case CC0:
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 1;
case MEM:
if (mem_last_set != 0)
return 0;
x = XEXP (x, 0);
goto repeat;
case REG:
return ! TEST_BIT (reg_set_bitmap, REGNO (x));
default:
break;
}
fmt = GET_RTX_FORMAT (code);
for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
{
if (fmt[i] == 'e')
{
int not_set_p;
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = XEXP (x, 0);
goto repeat;
}
not_set_p = oprs_not_set_p (XEXP (x, i), insn);
if (! not_set_p)
return 0;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
int not_set_p = oprs_not_set_p (XVECEXP (x, i, j), insn);
if (! not_set_p)
return 0;
}
}
}
return 1;
}
/* Mark things set by a CALL. */
static void
mark_call (pat, insn)
rtx pat ATTRIBUTE_UNUSED, insn;
{
mem_last_set = INSN_CUID (insn);
}
/* Mark things set by a SET. */
static void
mark_set (pat, insn)
rtx pat, insn;
{
rtx dest = SET_DEST (pat);
while (GET_CODE (dest) == SUBREG
|| GET_CODE (dest) == ZERO_EXTRACT
|| GET_CODE (dest) == SIGN_EXTRACT
|| GET_CODE (dest) == STRICT_LOW_PART)
dest = XEXP (dest, 0);
if (GET_CODE (dest) == REG)
SET_BIT (reg_set_bitmap, REGNO (dest));
else if (GET_CODE (dest) == MEM)
mem_last_set = INSN_CUID (insn);
if (GET_CODE (SET_SRC (pat)) == CALL)
mark_call (SET_SRC (pat), insn);
}
/* Record things set by a CLOBBER. */
static void
mark_clobber (pat, insn)
rtx pat, insn;
{
rtx clob = XEXP (pat, 0);
while (GET_CODE (clob) == SUBREG || GET_CODE (clob) == STRICT_LOW_PART)
clob = XEXP (clob, 0);
if (GET_CODE (clob) == REG)
SET_BIT (reg_set_bitmap, REGNO (clob));
else
mem_last_set = INSN_CUID (insn);
}
/* Record things set by INSN.
This data is used by oprs_not_set_p. */
static void
mark_oprs_set (insn)
rtx insn;
{
rtx pat = PATTERN (insn);
if (GET_CODE (pat) == SET)
mark_set (pat, insn);
else if (GET_CODE (pat) == PARALLEL)
{
int i;
for (i = 0; i < XVECLEN (pat, 0); i++)
{
rtx x = XVECEXP (pat, 0, i);
if (GET_CODE (x) == SET)
mark_set (x, insn);
else if (GET_CODE (x) == CLOBBER)
mark_clobber (x, insn);
else if (GET_CODE (x) == CALL)
mark_call (x, insn);
}
}
else if (GET_CODE (pat) == CLOBBER)
mark_clobber (pat, insn);
else if (GET_CODE (pat) == CALL)
mark_call (pat, insn);
}
/* Classic GCSE reaching definition support. */
/* Allocate reaching def variables. */
static void
alloc_rd_mem (n_blocks, n_insns)
int n_blocks, n_insns;
{
rd_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_kill, n_basic_blocks);
rd_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_gen, n_basic_blocks);
reaching_defs = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (reaching_defs, n_basic_blocks);
rd_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_insns);
sbitmap_vector_zero (rd_out, n_basic_blocks);
}
/* Free reaching def variables. */
static void
free_rd_mem ()
{
free (rd_kill);
free (rd_gen);
free (reaching_defs);
free (rd_out);
}
/* Add INSN to the kills of BB.
REGNO, set in BB, is killed by INSN. */
static void
handle_rd_kill_set (insn, regno, bb)
rtx insn;
int regno, bb;
{
struct reg_set *this_reg = reg_set_table[regno];
while (this_reg)
{
if (BLOCK_NUM (this_reg->insn) != BLOCK_NUM (insn))
SET_BIT (rd_kill[bb], INSN_CUID (this_reg->insn));
this_reg = this_reg->next;
}
}
void
dump_rd_table (file, title, bmap)
FILE *file;
char *title;
sbitmap *bmap;
{
int bb,cuid,i,j,n;
fprintf (file, "%s\n", title);
for (bb = 0; bb < n_basic_blocks; bb++)
{
fprintf (file, "BB %d\n", bb);
dump_sbitmap (file, bmap[bb]);
for (i = n = cuid = 0; i < bmap[bb]->size; i++)
{
for (j = 0; j < SBITMAP_ELT_BITS; j++, cuid++)
{
if ((bmap[bb]->elms[i] & (1 << j)) != 0)
{
if (n % 10 == 0)
fprintf (file, " ");
fprintf (file, " %d", INSN_UID (CUID_INSN (cuid)));
n++;
}
}
}
if (n != 0)
fprintf (file, "\n");
}
fprintf (file, "\n");
}
/* Compute the set of kill's for reaching definitions. */
static void
compute_kill_rd ()
{
int bb,cuid;
/* For each block
For each set bit in `gen' of the block (i.e each insn which
generates a definition in the block)
Call the reg set by the insn corresponding to that bit regx
Look at the linked list starting at reg_set_table[regx]
For each setting of regx in the linked list, which is not in
this block
Set the bit in `kill' corresponding to that insn
*/
for (bb = 0; bb < n_basic_blocks; bb++)
{
for (cuid = 0; cuid < max_cuid; cuid++)
{
if (TEST_BIT (rd_gen[bb], cuid))
{
rtx insn = CUID_INSN (cuid);
rtx pat = PATTERN (insn);
if (GET_CODE (insn) == CALL_INSN)
{
int regno;
for (regno = 0; regno < FIRST_PSEUDO_REGISTER; regno++)
{
if (call_used_regs[regno])
handle_rd_kill_set (insn, regno, bb);
}
}
if (GET_CODE (pat) == PARALLEL)
{
int i;
/* We work backwards because ... */
for (i = XVECLEN (pat, 0) - 1; i >= 0; i--)
{
enum rtx_code code = GET_CODE (XVECEXP (pat, 0, i));
if ((code == SET || code == CLOBBER)
&& GET_CODE (XEXP (XVECEXP (pat, 0, i), 0)) == REG)
handle_rd_kill_set (insn,
REGNO (XEXP (XVECEXP (pat, 0, i), 0)),
bb);
}
}
else if (GET_CODE (pat) == SET)
{
if (GET_CODE (SET_DEST (pat)) == REG)
{
/* Each setting of this register outside of this block
must be marked in the set of kills in this block. */
handle_rd_kill_set (insn, REGNO (SET_DEST (pat)), bb);
}
}
/* FIXME: CLOBBER? */
}
}
}
}
/* Compute the reaching definitions as in
Compilers Principles, Techniques, and Tools. Aho, Sethi, Ullman,
Chapter 10. It is the same algorithm as used for computing available
expressions but applied to the gens and kills of reaching definitions. */
static void
compute_rd ()
{
int bb, changed, passes;
for (bb = 0; bb < n_basic_blocks; bb++)
sbitmap_copy (rd_out[bb] /*dst*/, rd_gen[bb] /*src*/);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
for (bb = 0; bb < n_basic_blocks; bb++)
{
sbitmap_union_of_predecessors (reaching_defs[bb], rd_out,
bb, s_preds);
changed |= sbitmap_union_of_diff (rd_out[bb], rd_gen[bb],
reaching_defs[bb], rd_kill[bb]);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "reaching def computation: %d passes\n", passes);
}
/* Classic GCSE available expression support. */
/* Allocate memory for available expression computation. */
static void
alloc_avail_expr_mem (n_blocks, n_exprs)
int n_blocks, n_exprs;
{
ae_kill = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_kill, n_basic_blocks);
ae_gen = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_gen, n_basic_blocks);
ae_in = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_in, n_basic_blocks);
ae_out = (sbitmap *) sbitmap_vector_alloc (n_blocks, n_exprs);
sbitmap_vector_zero (ae_out, n_basic_blocks);
u_bitmap = (sbitmap) sbitmap_alloc (n_exprs);
sbitmap_ones (u_bitmap);
}
static void
free_avail_expr_mem ()
{
free (ae_kill);
free (ae_gen);
free (ae_in);
free (ae_out);
free (u_bitmap);
}
/* Compute the set of available expressions generated in each basic block. */
static void
compute_ae_gen ()
{
int i;
/* For each recorded occurrence of each expression, set ae_gen[bb][expr].
This is all we have to do because an expression is not recorded if it
is not available, and the only expressions we want to work with are the
ones that are recorded. */
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr = expr_hash_table[i];
while (expr != NULL)
{
struct occr *occr = expr->avail_occr;
while (occr != NULL)
{
SET_BIT (ae_gen[BLOCK_NUM (occr->insn)], expr->bitmap_index);
occr = occr->next;
}
expr = expr->next_same_hash;
}
}
}
/* Return non-zero if expression X is killed in BB. */
static int
expr_killed_p (x, bb)
rtx x;
int bb;
{
int i;
enum rtx_code code;
char *fmt;
/* repeat is used to turn tail-recursion into iteration. */
repeat:
if (x == 0)
return 1;
code = GET_CODE (x);
switch (code)
{
case REG:
return TEST_BIT (reg_set_in_block[bb], REGNO (x));
case MEM:
if (mem_set_in_block[bb])
return 1;
x = XEXP (x, 0);
goto repeat;
case PC:
case CC0: /*FIXME*/
case CONST:
case CONST_INT:
case CONST_DOUBLE:
case SYMBOL_REF:
case LABEL_REF:
case ADDR_VEC:
case ADDR_DIFF_VEC:
return 0;
default:
break;
}
i = GET_RTX_LENGTH (code) - 1;
fmt = GET_RTX_FORMAT (code);
for (; i >= 0; i--)
{
if (fmt[i] == 'e')
{
rtx tem = XEXP (x, i);
/* If we are about to do the last recursive call
needed at this level, change it into iteration.
This function is called enough to be worth it. */
if (i == 0)
{
x = tem;
goto repeat;
}
if (expr_killed_p (tem, bb))
return 1;
}
else if (fmt[i] == 'E')
{
int j;
for (j = 0; j < XVECLEN (x, i); j++)
{
if (expr_killed_p (XVECEXP (x, i, j), bb))
return 1;
}
}
}
return 0;
}
/* Compute the set of available expressions killed in each basic block. */
static void
compute_ae_kill ()
{
int bb,i;
for (bb = 0; bb < n_basic_blocks; bb++)
{
for (i = 0; i < expr_hash_table_size; i++)
{
struct expr *expr = expr_hash_table[i];
for ( ; expr != NULL; expr = expr->next_same_hash)
{
/* Skip EXPR if generated in this block. */
if (TEST_BIT (ae_gen[bb], expr->bitmap_index))
continue;
if (expr_killed_p (expr->expr, bb))
SET_BIT (ae_kill[bb], expr->bitmap_index);
}
}
}
}
/* Compute available expressions.
Implement the algorithm to find available expressions
as given in the Aho Sethi Ullman book, pages 627-631. */
static void
compute_available ()
{
int bb, changed, passes;
sbitmap_zero (ae_in[0]);
sbitmap_copy (ae_out[0] /*dst*/, ae_gen[0] /*src*/);
for (bb = 1; bb < n_basic_blocks; bb++)
sbitmap_difference (ae_out[bb], u_bitmap, ae_kill[bb]);
passes = 0;
changed = 1;
while (changed)
{
changed = 0;
for (bb = 1; bb < n_basic_blocks; bb++)
{
sbitmap_intersect_of_predecessors (ae_in[bb], ae_out,
bb, s_preds);
changed |= sbitmap_union_of_diff (ae_out[bb], ae_gen[bb],
ae_in[bb], ae_kill[bb]);
}
passes++;
}
if (gcse_file)
fprintf (gcse_file, "avail expr computation: %d passes\n", passes);
}
/* Actually perform the Classic GCSE optimizations. */
/* Return non-zero if occurrence OCCR of expression EXPR reaches block BB.
CHECK_SELF_LOOP is non-zero if we should consider a block reaching itself
as a positive reach. We want to do this when there are two computations
of the expression in the block.
VISITED is a pointer to a working buffer for tracking which BB's have
been visited. It is NULL for the top-level call.
We treat reaching expressions that go through blocks containing the same
reaching expression as "not reaching". E.g. if EXPR is generated in blocks
2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
2 as not reaching. The intent is to improve the probability of finding
only one reaching expression and to reduce register lifetimes by picking
the closest such expression. */
static int
expr_reaches_here_p (occr, expr, bb, check_self_loop, visited)
struct occr *occr;
struct expr *expr;
int bb;
int check_self_loop;
char *visited;
{
int_list_ptr pred;
if (visited == NULL)
{
visited = (char *) alloca (n_basic_blocks);
bzero (visited, n_basic_blocks);
}
for (pred = s_preds[bb]; pred != NULL; pred = pred->next)
{
int pred_bb = INT_LIST_VAL (pred);
if (visited[pred_bb])
{
/* This predecessor has already been visited.
Nothing to do. */
;
}
else if (pred_bb == bb)
{
/* BB loops on itself. */
if (check_self_loop
&& TEST_BIT (ae_gen[pred_bb], expr->bitmap_index)
&& BLOCK_NUM (occr->insn) == pred_bb)
return 1;
visited[pred_bb] = 1;
}
/* Ignore this predecessor if it kills the expression. */
else if (TEST_BIT (ae_kill[pred_bb], expr->bitmap_index))
visited[pred_bb] = 1;
/* Does this predecessor generate this expression? */
else if (TEST_BIT (ae_gen[pred_bb], expr->bitmap_index))
{
/* Is this the occurrence we're looking for?
Note that there's only one generating occurrence per block
so we just need to check the block number. */
if (BLOCK_NUM (occr->insn) == pred_bb)
return 1;
visited[pred_bb] = 1;
}
/* Neither gen nor kill. */
else
{
visited[pred_bb] = 1;
if (expr_reaches_here_p (occr, expr, pred_bb, check_self_loop, visited))
return 1;
}
}
/* All paths have been checked. */
return 0;
}
/* Return the instruction that computes EXPR that reaches INSN's basic block.
If there is more than one such instruction, return NULL.
Called only by handle_avail_expr. */
static rtx
computing_insn (expr, insn)
struct expr *expr;
rtx insn;
{
int bb = BLOCK_NUM (insn);
if (expr->avail_occr->next == NULL)
{
if (BLOCK_NUM (expr->avail_occr->insn) == bb)
{
/* The available expression is actually itself
(i.e. a loop in the flow graph) so do nothing. */
return NULL;
}
/* (FIXME) Case that we found a pattern that was created by
a substitution that took place. */
return expr->avail_occr->insn;
}
else
{
/* Pattern is computed more than once.
Search backwards from this insn to see how many of these
computations actually reach this insn. */
struct occr *occr;
rtx insn_computes_expr = NULL;
int can_reach = 0;
for (occr = expr->avail_occr; occr != NULL; occr = occr->next)
{
if (BLOCK_NUM (occr->insn) == bb)
{
/* The expression is generated in this block.
The only time we care about this is when the expression
is generated later in the block [and thus there's a loop].
We let the normal cse pass handle the other cases. */
if (INSN_CUID (insn) < INSN_CUID (occr->insn))
{
if (expr_reaches_here_p (occr, expr, bb, 1, NULL))
{
can_reach++;
if (can_reach > 1)
return NULL;
insn_computes_expr = occr->insn;
}
}
}
else /* Computation of the pattern outside this block. */
{
if (expr_reaches_here_p (occr, expr, bb, 0, NULL))
{
can_reach++;
if (can_reach > 1)
return NULL;
insn_computes_expr = occr->insn;
}
}
}
if (insn_computes_expr == NULL)
abort ();
return insn_computes_expr;
}
}
/* Return non-zero if the definition in DEF_INSN can reach INSN.
Only called by can_disregard_other_sets. */
static int
def_reaches_here_p (insn, def_insn)
rtx insn, def_insn;
{
rtx reg;
if (TEST_BIT (reaching_defs[BLOCK_NUM (insn)], INSN_CUID (def_insn)))
return 1;
if (BLOCK_NUM (insn) == BLOCK_NUM (def_insn))
{
if (INSN_CUID (def_insn) < INSN_CUID (insn))
{
if (GET_CODE (PATTERN (def_insn)) == PARALLEL)
return 1;
if (GET_CODE (PATTERN (def_insn)) == CLOBBER)
reg = XEXP (PATTERN (def_insn), 0);
else if (GET_CODE (PATTERN (def_insn)) == SET)
reg = SET_DEST (PATTERN (def_insn));
else
abort ();
return ! reg_set_between_p (reg, NEXT_INSN (def_insn), insn);
}
else
return 0;
}
return 0;
}
/* Return non-zero if *ADDR_THIS_REG can only have one value at INSN.
The value returned is the number of definitions that reach INSN.
Returning a value of zero means that [maybe] more than one definition
reaches INSN and the caller can't perform whatever optimization it is
trying. i.e. it is always safe to return zero. */
static int
can_disregard_other_sets (addr_this_reg, insn, for_combine)
struct reg_set **addr_this_reg;
rtx insn;
int for_combine;
{
int number_of_reaching_defs = 0;
struct reg_set *this_reg = *addr_this_reg;
while (this_reg)
{
if (def_reaches_here_p (insn, this_reg->insn))
{
number_of_reaching_defs++;
/* Ignore parallels for now. */
if (GET_CODE (PATTERN (this_reg->insn)) == PARALLEL)
return 0;
if (!for_combine
&& (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER
|| ! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
SET_SRC (PATTERN (insn)))))
{
/* A setting of the reg to a different value reaches INSN. */
return 0;
}
if (number_of_reaching_defs > 1)
{
/* If in this setting the value the register is being
set to is equal to the previous value the register
was set to and this setting reaches the insn we are
trying to do the substitution on then we are ok. */
if (GET_CODE (PATTERN (this_reg->insn)) == CLOBBER)
return 0;
if (! rtx_equal_p (SET_SRC (PATTERN (this_reg->insn)),
SET_SRC (PATTERN (insn))))
return 0;
}
*addr_this_reg = this_reg;
}
/* prev_this_reg = this_reg; */
this_reg = this_reg->next;
}
return number_of_reaching_defs;
}
/* Expression computed by insn is available and the substitution is legal,
so try to perform the substitution.
The result is non-zero if any changes were made. */
static int
handle_avail_expr (insn, expr)
rtx insn;
struct expr *expr;
{
rtx pat, insn_computes_expr;
rtx to;
struct reg_set *this_reg;
int found_setting, use_src;
int changed = 0;
/* We only handle the case where one computation of the expression
reaches this instruction. */
insn_computes_expr = computing_insn (expr, insn);
if (insn_computes_expr == NULL)
return 0;
found_setting = 0;
use_src = 0;
/* At this point we know only one computation of EXPR outside of this
block reaches this insn. Now try to find a register that the
expression is computed into. */
if (GET_CODE (SET_SRC (PATTERN (insn_computes_expr))) == REG)
{
/* This is the case when the available expression that reaches
here has already been handled as an available expression. */
int regnum_for_replacing = REGNO (SET_SRC (PATTERN (insn_computes_expr)));
/* If the register was created by GCSE we can't use `reg_set_table',
however we know it's set only once. */
if (regnum_for_replacing >= max_gcse_regno
/* If the register the expression is computed into is set only once,
or only one set reaches this insn, we can use it. */
|| (((this_reg = reg_set_table[regnum_for_replacing]),
this_reg->next == NULL)
|| can_disregard_other_sets (&this_reg, insn, 0)))
{
use_src = 1;
found_setting = 1;
}
}
if (!found_setting)
{
int regnum_for_replacing = REGNO (SET_DEST (PATTERN (insn_computes_expr)));
/* This shouldn't happen. */
if (regnum_for_replacing >= max_gcse_regno)
abort ();
this_reg = reg_set_table[regnum_for_replacing];
/* If the register the expression is computed into is set only once,
or only one set reaches this insn, use it. */
if (this_reg->next == NULL
|| can_disregard_other_sets (&this_reg, insn, 0))
found_setting = 1;
}
if (found_setting)
{
pat = PATTERN (insn);
if (use_src)
to = SET_SRC (PATTERN (insn_computes_expr));
else
to = SET_DEST (PATTERN (insn_computes_expr));
changed = validate_change (insn, &SET_SRC (pat), to, 0);
/* We should be able to ignore the return code from validate_change but
to play it safe we check. */
if (changed)
{
gcse_subst_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d %s insn %d\n",
INSN_UID (insn), REGNO (to),
use_src ? "from" : "set in",
INSN_UID (insn_computes_expr));
}
}
}
/* The register that the expr is computed into is set more than once. */
else if (1 /*expensive_op(this_pattrn->op) && do_expensive_gcse)*/)
{
/* Insert an insn after insnx that copies the reg set in insnx
into a new pseudo register call this new register REGN.
From insnb until end of basic block or until REGB is set
replace all uses of REGB with REGN. */
rtx new_insn;
to = gen_reg_rtx (GET_MODE (SET_DEST (PATTERN (insn_computes_expr))));
/* Generate the new insn. */
/* ??? If the change fails, we return 0, even though we created
an insn. I think this is ok. */
new_insn
= emit_insn_after (gen_rtx_SET (VOIDmode, to,
SET_DEST (PATTERN (insn_computes_expr))),
insn_computes_expr);
/* Keep block number table up to date. */
set_block_num (new_insn, BLOCK_NUM (insn_computes_expr));
/* Keep register set table up to date. */
record_one_set (REGNO (to), new_insn);
gcse_create_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Creating insn %d to copy value of reg %d, computed in insn %d,\n",
INSN_UID (NEXT_INSN (insn_computes_expr)),
REGNO (SET_SRC (PATTERN (NEXT_INSN (insn_computes_expr)))),
INSN_UID (insn_computes_expr));
fprintf (gcse_file, " into newly allocated reg %d\n", REGNO (to));
}
pat = PATTERN (insn);
/* Do register replacement for INSN. */
changed = validate_change (insn, &SET_SRC (pat),
SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr))),
0);
/* We should be able to ignore the return code from validate_change but
to play it safe we check. */
if (changed)
{
gcse_subst_count++;
if (gcse_file != NULL)
{
fprintf (gcse_file, "GCSE: Replacing the source in insn %d with reg %d set in insn %d\n",
INSN_UID (insn),
REGNO (SET_DEST (PATTERN (NEXT_INSN (insn_computes_expr)))),
INSN_UID (insn_computes_expr));
}
}
}
return changed;
}
/* Perform classic GCSE.
This is called by one_classic_gcse_pass after all the dataflow analysis
has been done.
The result is non-zero if a change was made. */
static int
classic_gcse ()
{
int bb, changed;
rtx insn;
/* Note we start at block 1. */
changed = 0;
for (bb = 1; bb < n_basic_blocks; bb++)
{
/* Reset tables used to keep track of what's still valid [since the
start of the block]. */
reset_opr_set_tables ();
for (insn = basic_block_head[bb];
insn != NULL && insn != NEXT_INSN (basic_block_end[bb]);
insn = NEXT_INSN (insn))
{
/* Is insn of form (set (pseudo-reg) ...)? */
if (GET_CODE (insn) == INSN
&& GET_CODE (PATTERN (insn)) == SET
&& GET_CODE (SET_DEST (PATTERN (insn))) == REG
&& REGNO (SET_DEST (PATTERN (insn))) >= FIRST_PSEUDO_REGISTER)
{
rtx pat = PATTERN (insn);
rtx src = SET_SRC (pat);
struct expr *expr;
if (want_to_gcse_p (src)
/* Is the expression recorded? */
&& ((expr = lookup_expr (src)) != NULL)
/* Is the expression available [at the start of the
block]? */
&& TEST_BIT (ae_in[bb], expr->bitmap_index)
/* Are the operands unchanged since the start of the
block? */
&& oprs_not_set_p (src, insn))
changed |= handle_avail_expr (insn, expr);
}
/* Keep track of everything modified by this insn. */
/* ??? Need to be careful w.r.t. mods done to INSN. */
if (GET_RTX_CLASS (GET_CODE (insn)) == 'i')
mark_oprs_set (insn);
}
}
return changed;
}
/* Top level routine to perform one classic GCSE pass.
Return non-zero if a change was made. */
static int
one_classic_gcse_pass (f, pass)
rtx f;
int pass;
{
int changed = 0;
gcse_subst_count = 0;
gcse_create_count = 0;
alloc_expr_hash_table (max_cuid);
alloc_rd_mem (n_basic_blocks, max_cuid);
compute_expr_hash_table (f);
if (gcse_file)
dump_hash_table (gcse_file, "Expression", expr_hash_table,
expr_hash_table_size, n_exprs);
if (n_exprs > 0)
{
compute_kill_rd ();
compute_rd ();
alloc_avail_expr_mem (n_basic_blocks, n_exprs);
compute_ae_gen ();
compute_ae_kill ();
compute_available ();
changed = classic_gcse ();
free_avail_expr_mem ();
}
free_rd_mem ();
free_expr_hash_table ();
if (gcse_file)
{
fprintf (gcse_file, "\n");
fprintf (gcse_file, "GCSE of %s, pass %d: %d bytes needed, %d substs, %d insns created\n",
current_function_name, pass,
bytes_used, gcse_subst_count, gcse_create_count);
}
return changed;
}
/* Compute copy/constant propagation working variables. */
/* Local properties of assignments. */
static sbitmap *cprop_pavloc;
static sbitmap *cprop_absaltered;
/* Global properties of assignments (computed from the local properties). */
static sbitmap *cprop_avin;
static sbitmap *cprop_avout;
/* Allocate vars used for copy/const propagation.
N_BLOCKS is the number of basic blocks.
N_SETS is the number of sets. */
static void
alloc_cprop_mem (n_blocks, n_sets)
int n_blocks, n_sets;
{
cprop_pavloc = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_absaltered = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_avin = sbitmap_vector_alloc (n_blocks, n_sets);
cprop_avout = sbitmap_vector_alloc (n_blocks, n_sets);
}
/* Free vars used by copy/const propagation. */
static void