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/* RTL dead store elimination.
Copyright (C) 2005-2021 Free Software Foundation, Inc.
Contributed by Richard Sandiford <rsandifor@codesourcery.com>
and Kenneth Zadeck <zadeck@naturalbridge.com>
This file is part of GCC.
GCC 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 3, or (at your option) any later
version.
GCC 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 GCC; see the file COPYING3. If not see
<http://www.gnu.org/licenses/>. */
#undef BASELINE
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "target.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "predict.h"
#include "df.h"
#include "memmodel.h"
#include "tm_p.h"
#include "gimple-ssa.h"
#include "expmed.h"
#include "optabs.h"
#include "emit-rtl.h"
#include "recog.h"
#include "alias.h"
#include "stor-layout.h"
#include "cfgrtl.h"
#include "cselib.h"
#include "tree-pass.h"
#include "explow.h"
#include "expr.h"
#include "dbgcnt.h"
#include "rtl-iter.h"
#include "cfgcleanup.h"
#include "calls.h"
/* This file contains three techniques for performing Dead Store
Elimination (dse).
* The first technique performs dse locally on any base address. It
is based on the cselib which is a local value numbering technique.
This technique is local to a basic block but deals with a fairly
general addresses.
* The second technique performs dse globally but is restricted to
base addresses that are either constant or are relative to the
frame_pointer.
* The third technique, (which is only done after register allocation)
processes the spill slots. This differs from the second
technique because it takes advantage of the fact that spilling is
completely free from the effects of aliasing.
Logically, dse is a backwards dataflow problem. A store can be
deleted if it if cannot be reached in the backward direction by any
use of the value being stored. However, the local technique uses a
forwards scan of the basic block because cselib requires that the
block be processed in that order.
The pass is logically broken into 7 steps:
0) Initialization.
1) The local algorithm, as well as scanning the insns for the two
global algorithms.
2) Analysis to see if the global algs are necessary. In the case
of stores base on a constant address, there must be at least two
stores to that address, to make it possible to delete some of the
stores. In the case of stores off of the frame or spill related
stores, only one store to an address is necessary because those
stores die at the end of the function.
3) Set up the global dataflow equations based on processing the
info parsed in the first step.
4) Solve the dataflow equations.
5) Delete the insns that the global analysis has indicated are
unnecessary.
6) Delete insns that store the same value as preceding store
where the earlier store couldn't be eliminated.
7) Cleanup.
This step uses cselib and canon_rtx to build the largest expression
possible for each address. This pass is a forwards pass through
each basic block. From the point of view of the global technique,
the first pass could examine a block in either direction. The
forwards ordering is to accommodate cselib.
We make a simplifying assumption: addresses fall into four broad
categories:
1) base has rtx_varies_p == false, offset is constant.
2) base has rtx_varies_p == false, offset variable.
3) base has rtx_varies_p == true, offset constant.
4) base has rtx_varies_p == true, offset variable.
The local passes are able to process all 4 kinds of addresses. The
global pass only handles 1).
The global problem is formulated as follows:
A store, S1, to address A, where A is not relative to the stack
frame, can be eliminated if all paths from S1 to the end of the
function contain another store to A before a read to A.
If the address A is relative to the stack frame, a store S2 to A
can be eliminated if there are no paths from S2 that reach the
end of the function that read A before another store to A. In
this case S2 can be deleted if there are paths from S2 to the
end of the function that have no reads or writes to A. This
second case allows stores to the stack frame to be deleted that
would otherwise die when the function returns. This cannot be
done if stores_off_frame_dead_at_return is not true. See the doc
for that variable for when this variable is false.
The global problem is formulated as a backwards set union
dataflow problem where the stores are the gens and reads are the
kills. Set union problems are rare and require some special
handling given our representation of bitmaps. A straightforward
implementation requires a lot of bitmaps filled with 1s.
These are expensive and cumbersome in our bitmap formulation so
care has been taken to avoid large vectors filled with 1s. See
the comments in bb_info and in the dataflow confluence functions
for details.
There are two places for further enhancements to this algorithm:
1) The original dse which was embedded in a pass called flow also
did local address forwarding. For example in
A <- r100
... <- A
flow would replace the right hand side of the second insn with a
reference to r100. Most of the information is available to add this
to this pass. It has not done it because it is a lot of work in
the case that either r100 is assigned to between the first and
second insn and/or the second insn is a load of part of the value
stored by the first insn.
insn 5 in gcc.c-torture/compile/990203-1.c simple case.
insn 15 in gcc.c-torture/execute/20001017-2.c simple case.
insn 25 in gcc.c-torture/execute/20001026-1.c simple case.
insn 44 in gcc.c-torture/execute/20010910-1.c simple case.
2) The cleaning up of spill code is quite profitable. It currently
depends on reading tea leaves and chicken entrails left by reload.
This pass depends on reload creating a singleton alias set for each
spill slot and telling the next dse pass which of these alias sets
are the singletons. Rather than analyze the addresses of the
spills, dse's spill processing just does analysis of the loads and
stores that use those alias sets. There are three cases where this
falls short:
a) Reload sometimes creates the slot for one mode of access, and
then inserts loads and/or stores for a smaller mode. In this
case, the current code just punts on the slot. The proper thing
to do is to back out and use one bit vector position for each
byte of the entity associated with the slot. This depends on
KNOWING that reload always generates the accesses for each of the
bytes in some canonical (read that easy to understand several
passes after reload happens) way.
b) Reload sometimes decides that spill slot it allocated was not
large enough for the mode and goes back and allocates more slots
with the same mode and alias set. The backout in this case is a
little more graceful than (a). In this case the slot is unmarked
as being a spill slot and if final address comes out to be based
off the frame pointer, the global algorithm handles this slot.
c) For any pass that may prespill, there is currently no
mechanism to tell the dse pass that the slot being used has the
special properties that reload uses. It may be that all that is
required is to have those passes make the same calls that reload
does, assuming that the alias sets can be manipulated in the same
way. */
/* There are limits to the size of constant offsets we model for the
global problem. There are certainly test cases, that exceed this
limit, however, it is unlikely that there are important programs
that really have constant offsets this size. */
#define MAX_OFFSET (64 * 1024)
/* Obstack for the DSE dataflow bitmaps. We don't want to put these
on the default obstack because these bitmaps can grow quite large
(~2GB for the small (!) test case of PR54146) and we'll hold on to
all that memory until the end of the compiler run.
As a bonus, delete_tree_live_info can destroy all the bitmaps by just
releasing the whole obstack. */
static bitmap_obstack dse_bitmap_obstack;
/* Obstack for other data. As for above: Kinda nice to be able to
throw it all away at the end in one big sweep. */
static struct obstack dse_obstack;
/* Scratch bitmap for cselib's cselib_expand_value_rtx. */
static bitmap scratch = NULL;
struct insn_info_type;
/* This structure holds information about a candidate store. */
class store_info
{
public:
/* False means this is a clobber. */
bool is_set;
/* False if a single HOST_WIDE_INT bitmap is used for positions_needed. */
bool is_large;
/* The id of the mem group of the base address. If rtx_varies_p is
true, this is -1. Otherwise, it is the index into the group
table. */
int group_id;
/* This is the cselib value. */
cselib_val *cse_base;
/* This canonized mem. */
rtx mem;
/* Canonized MEM address for use by canon_true_dependence. */
rtx mem_addr;
/* The offset of the first byte associated with the operation. */
poly_int64 offset;
/* The number of bytes covered by the operation. This is always exact
and known (rather than -1). */
poly_int64 width;
union
{
/* A bitmask as wide as the number of bytes in the word that
contains a 1 if the byte may be needed. The store is unused if
all of the bits are 0. This is used if IS_LARGE is false. */
unsigned HOST_WIDE_INT small_bitmask;
struct
{
/* A bitmap with one bit per byte, or null if the number of
bytes isn't known at compile time. A cleared bit means
the position is needed. Used if IS_LARGE is true. */
bitmap bmap;
/* When BITMAP is nonnull, this counts the number of set bits
(i.e. unneeded bytes) in the bitmap. If it is equal to
WIDTH, the whole store is unused.
When BITMAP is null:
- the store is definitely not needed when COUNT == 1
- all the store is needed when COUNT == 0 and RHS is nonnull
- otherwise we don't know which parts of the store are needed. */
int count;
} large;
} positions_needed;
/* The next store info for this insn. */
class store_info *next;
/* The right hand side of the store. This is used if there is a
subsequent reload of the mems address somewhere later in the
basic block. */
rtx rhs;
/* If rhs is or holds a constant, this contains that constant,
otherwise NULL. */
rtx const_rhs;
/* Set if this store stores the same constant value as REDUNDANT_REASON
insn stored. These aren't eliminated early, because doing that
might prevent the earlier larger store to be eliminated. */
struct insn_info_type *redundant_reason;
};
/* Return a bitmask with the first N low bits set. */
static unsigned HOST_WIDE_INT
lowpart_bitmask (int n)
{
unsigned HOST_WIDE_INT mask = HOST_WIDE_INT_M1U;
return mask >> (HOST_BITS_PER_WIDE_INT - n);
}
static object_allocator<store_info> cse_store_info_pool ("cse_store_info_pool");
static object_allocator<store_info> rtx_store_info_pool ("rtx_store_info_pool");
/* This structure holds information about a load. These are only
built for rtx bases. */
class read_info_type
{
public:
/* The id of the mem group of the base address. */
int group_id;
/* The offset of the first byte associated with the operation. */
poly_int64 offset;
/* The number of bytes covered by the operation, or -1 if not known. */
poly_int64 width;
/* The mem being read. */
rtx mem;
/* The next read_info for this insn. */
class read_info_type *next;
};
typedef class read_info_type *read_info_t;
static object_allocator<read_info_type> read_info_type_pool ("read_info_pool");
/* One of these records is created for each insn. */
struct insn_info_type
{
/* Set true if the insn contains a store but the insn itself cannot
be deleted. This is set if the insn is a parallel and there is
more than one non dead output or if the insn is in some way
volatile. */
bool cannot_delete;
/* This field is only used by the global algorithm. It is set true
if the insn contains any read of mem except for a (1). This is
also set if the insn is a call or has a clobber mem. If the insn
contains a wild read, the use_rec will be null. */
bool wild_read;
/* This is true only for CALL instructions which could potentially read
any non-frame memory location. This field is used by the global
algorithm. */
bool non_frame_wild_read;
/* This field is only used for the processing of const functions.
These functions cannot read memory, but they can read the stack
because that is where they may get their parms. We need to be
this conservative because, like the store motion pass, we don't
consider CALL_INSN_FUNCTION_USAGE when processing call insns.
Moreover, we need to distinguish two cases:
1. Before reload (register elimination), the stores related to
outgoing arguments are stack pointer based and thus deemed
of non-constant base in this pass. This requires special
handling but also means that the frame pointer based stores
need not be killed upon encountering a const function call.
2. After reload, the stores related to outgoing arguments can be
either stack pointer or hard frame pointer based. This means
that we have no other choice than also killing all the frame
pointer based stores upon encountering a const function call.
This field is set after reload for const function calls and before
reload for const tail function calls on targets where arg pointer
is the frame pointer. Having this set is less severe than a wild
read, it just means that all the frame related stores are killed
rather than all the stores. */
bool frame_read;
/* This field is only used for the processing of const functions.
It is set if the insn may contain a stack pointer based store. */
bool stack_pointer_based;
/* This is true if any of the sets within the store contains a
cselib base. Such stores can only be deleted by the local
algorithm. */
bool contains_cselib_groups;
/* The insn. */
rtx_insn *insn;
/* The list of mem sets or mem clobbers that are contained in this
insn. If the insn is deletable, it contains only one mem set.
But it could also contain clobbers. Insns that contain more than
one mem set are not deletable, but each of those mems are here in
order to provide info to delete other insns. */
store_info *store_rec;
/* The linked list of mem uses in this insn. Only the reads from
rtx bases are listed here. The reads to cselib bases are
completely processed during the first scan and so are never
created. */
read_info_t read_rec;
/* The live fixed registers. We assume only fixed registers can
cause trouble by being clobbered from an expanded pattern;
storing only the live fixed registers (rather than all registers)
means less memory needs to be allocated / copied for the individual
stores. */
regset fixed_regs_live;
/* The prev insn in the basic block. */
struct insn_info_type * prev_insn;
/* The linked list of insns that are in consideration for removal in
the forwards pass through the basic block. This pointer may be
trash as it is not cleared when a wild read occurs. The only
time it is guaranteed to be correct is when the traversal starts
at active_local_stores. */
struct insn_info_type * next_local_store;
};
typedef struct insn_info_type *insn_info_t;
static object_allocator<insn_info_type> insn_info_type_pool ("insn_info_pool");
/* The linked list of stores that are under consideration in this
basic block. */
static insn_info_t active_local_stores;
static int active_local_stores_len;
struct dse_bb_info_type
{
/* Pointer to the insn info for the last insn in the block. These
are linked so this is how all of the insns are reached. During
scanning this is the current insn being scanned. */
insn_info_t last_insn;
/* The info for the global dataflow problem. */
/* This is set if the transfer function should and in the wild_read
bitmap before applying the kill and gen sets. That vector knocks
out most of the bits in the bitmap and thus speeds up the
operations. */
bool apply_wild_read;
/* The following 4 bitvectors hold information about which positions
of which stores are live or dead. They are indexed by
get_bitmap_index. */
/* The set of store positions that exist in this block before a wild read. */
bitmap gen;
/* The set of load positions that exist in this block above the
same position of a store. */
bitmap kill;
/* The set of stores that reach the top of the block without being
killed by a read.
Do not represent the in if it is all ones. Note that this is
what the bitvector should logically be initialized to for a set
intersection problem. However, like the kill set, this is too
expensive. So initially, the in set will only be created for the
exit block and any block that contains a wild read. */
bitmap in;
/* The set of stores that reach the bottom of the block from it's
successors.
Do not represent the in if it is all ones. Note that this is
what the bitvector should logically be initialized to for a set
intersection problem. However, like the kill and in set, this is
too expensive. So what is done is that the confluence operator
just initializes the vector from one of the out sets of the
successors of the block. */
bitmap out;
/* The following bitvector is indexed by the reg number. It
contains the set of regs that are live at the current instruction
being processed. While it contains info for all of the
registers, only the hard registers are actually examined. It is used
to assure that shift and/or add sequences that are inserted do not
accidentally clobber live hard regs. */
bitmap regs_live;
};
typedef struct dse_bb_info_type *bb_info_t;
static object_allocator<dse_bb_info_type> dse_bb_info_type_pool
("bb_info_pool");
/* Table to hold all bb_infos. */
static bb_info_t *bb_table;
/* There is a group_info for each rtx base that is used to reference
memory. There are also not many of the rtx bases because they are
very limited in scope. */
struct group_info
{
/* The actual base of the address. */
rtx rtx_base;
/* The sequential id of the base. This allows us to have a
canonical ordering of these that is not based on addresses. */
int id;
/* True if there are any positions that are to be processed
globally. */
bool process_globally;
/* True if the base of this group is either the frame_pointer or
hard_frame_pointer. */
bool frame_related;
/* A mem wrapped around the base pointer for the group in order to do
read dependency. It must be given BLKmode in order to encompass all
the possible offsets from the base. */
rtx base_mem;
/* Canonized version of base_mem's address. */
rtx canon_base_addr;
/* These two sets of two bitmaps are used to keep track of how many
stores are actually referencing that position from this base. We
only do this for rtx bases as this will be used to assign
positions in the bitmaps for the global problem. Bit N is set in
store1 on the first store for offset N. Bit N is set in store2
for the second store to offset N. This is all we need since we
only care about offsets that have two or more stores for them.
The "_n" suffix is for offsets less than 0 and the "_p" suffix is
for 0 and greater offsets.
There is one special case here, for stores into the stack frame,
we will or store1 into store2 before deciding which stores look
at globally. This is because stores to the stack frame that have
no other reads before the end of the function can also be
deleted. */
bitmap store1_n, store1_p, store2_n, store2_p;
/* These bitmaps keep track of offsets in this group escape this function.
An offset escapes if it corresponds to a named variable whose
addressable flag is set. */
bitmap escaped_n, escaped_p;
/* The positions in this bitmap have the same assignments as the in,
out, gen and kill bitmaps. This bitmap is all zeros except for
the positions that are occupied by stores for this group. */
bitmap group_kill;
/* The offset_map is used to map the offsets from this base into
positions in the global bitmaps. It is only created after all of
the all of stores have been scanned and we know which ones we
care about. */
int *offset_map_n, *offset_map_p;
int offset_map_size_n, offset_map_size_p;
};
static object_allocator<group_info> group_info_pool ("rtx_group_info_pool");
/* Index into the rtx_group_vec. */
static int rtx_group_next_id;
static vec<group_info *> rtx_group_vec;
/* This structure holds the set of changes that are being deferred
when removing read operation. See replace_read. */
struct deferred_change
{
/* The mem that is being replaced. */
rtx *loc;
/* The reg it is being replaced with. */
rtx reg;
struct deferred_change *next;
};
static object_allocator<deferred_change> deferred_change_pool
("deferred_change_pool");
static deferred_change *deferred_change_list = NULL;
/* This is true except if cfun->stdarg -- i.e. we cannot do
this for vararg functions because they play games with the frame. */
static bool stores_off_frame_dead_at_return;
/* Counter for stats. */
static int globally_deleted;
static int locally_deleted;
static bitmap all_blocks;
/* Locations that are killed by calls in the global phase. */
static bitmap kill_on_calls;
/* The number of bits used in the global bitmaps. */
static unsigned int current_position;
/* Print offset range [OFFSET, OFFSET + WIDTH) to FILE. */
static void
print_range (FILE *file, poly_int64 offset, poly_int64 width)
{
fprintf (file, "[");
print_dec (offset, file, SIGNED);
fprintf (file, "..");
print_dec (offset + width, file, SIGNED);
fprintf (file, ")");
}
/*----------------------------------------------------------------------------
Zeroth step.
Initialization.
----------------------------------------------------------------------------*/
/* Hashtable callbacks for maintaining the "bases" field of
store_group_info, given that the addresses are function invariants. */
struct invariant_group_base_hasher : nofree_ptr_hash <group_info>
{
static inline hashval_t hash (const group_info *);
static inline bool equal (const group_info *, const group_info *);
};
inline bool
invariant_group_base_hasher::equal (const group_info *gi1,
const group_info *gi2)
{
return rtx_equal_p (gi1->rtx_base, gi2->rtx_base);
}
inline hashval_t
invariant_group_base_hasher::hash (const group_info *gi)
{
int do_not_record;
return hash_rtx (gi->rtx_base, Pmode, &do_not_record, NULL, false);
}
/* Tables of group_info structures, hashed by base value. */
static hash_table<invariant_group_base_hasher> *rtx_group_table;
/* Get the GROUP for BASE. Add a new group if it is not there. */
static group_info *
get_group_info (rtx base)
{
struct group_info tmp_gi;
group_info *gi;
group_info **slot;
gcc_assert (base != NULL_RTX);
/* Find the store_base_info structure for BASE, creating a new one
if necessary. */
tmp_gi.rtx_base = base;
slot = rtx_group_table->find_slot (&tmp_gi, INSERT);
gi = *slot;
if (gi == NULL)
{
*slot = gi = group_info_pool.allocate ();
gi->rtx_base = base;
gi->id = rtx_group_next_id++;
gi->base_mem = gen_rtx_MEM (BLKmode, base);
gi->canon_base_addr = canon_rtx (base);
gi->store1_n = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->store1_p = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->store2_n = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->store2_p = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->escaped_p = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->escaped_n = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->group_kill = BITMAP_ALLOC (&dse_bitmap_obstack);
gi->process_globally = false;
gi->frame_related =
(base == frame_pointer_rtx) || (base == hard_frame_pointer_rtx);
gi->offset_map_size_n = 0;
gi->offset_map_size_p = 0;
gi->offset_map_n = NULL;
gi->offset_map_p = NULL;
rtx_group_vec.safe_push (gi);
}
return gi;
}
/* Initialization of data structures. */
static void
dse_step0 (void)
{
locally_deleted = 0;
globally_deleted = 0;
bitmap_obstack_initialize (&dse_bitmap_obstack);
gcc_obstack_init (&dse_obstack);
scratch = BITMAP_ALLOC (&reg_obstack);
kill_on_calls = BITMAP_ALLOC (&dse_bitmap_obstack);
rtx_group_table = new hash_table<invariant_group_base_hasher> (11);
bb_table = XNEWVEC (bb_info_t, last_basic_block_for_fn (cfun));
rtx_group_next_id = 0;
stores_off_frame_dead_at_return = !cfun->stdarg;
init_alias_analysis ();
}
/*----------------------------------------------------------------------------
First step.
Scan all of the insns. Any random ordering of the blocks is fine.
Each block is scanned in forward order to accommodate cselib which
is used to remove stores with non-constant bases.
----------------------------------------------------------------------------*/
/* Delete all of the store_info recs from INSN_INFO. */
static void
free_store_info (insn_info_t insn_info)
{
store_info *cur = insn_info->store_rec;
while (cur)
{
store_info *next = cur->next;
if (cur->is_large)
BITMAP_FREE (cur->positions_needed.large.bmap);
if (cur->cse_base)
cse_store_info_pool.remove (cur);
else
rtx_store_info_pool.remove (cur);
cur = next;
}
insn_info->cannot_delete = true;
insn_info->contains_cselib_groups = false;
insn_info->store_rec = NULL;
}
struct note_add_store_info
{
rtx_insn *first, *current;
regset fixed_regs_live;
bool failure;
};
/* Callback for emit_inc_dec_insn_before via note_stores.
Check if a register is clobbered which is live afterwards. */
static void
note_add_store (rtx loc, const_rtx expr ATTRIBUTE_UNUSED, void *data)
{
rtx_insn *insn;
note_add_store_info *info = (note_add_store_info *) data;
if (!REG_P (loc))
return;
/* If this register is referenced by the current or an earlier insn,
that's OK. E.g. this applies to the register that is being incremented
with this addition. */
for (insn = info->first;
insn != NEXT_INSN (info->current);
insn = NEXT_INSN (insn))
if (reg_referenced_p (loc, PATTERN (insn)))
return;
/* If we come here, we have a clobber of a register that's only OK
if that register is not live. If we don't have liveness information
available, fail now. */
if (!info->fixed_regs_live)
{
info->failure = true;
return;
}
/* Now check if this is a live fixed register. */
unsigned int end_regno = END_REGNO (loc);
for (unsigned int regno = REGNO (loc); regno < end_regno; ++regno)
if (REGNO_REG_SET_P (info->fixed_regs_live, regno))
info->failure = true;
}
/* Callback for for_each_inc_dec that emits an INSN that sets DEST to
SRC + SRCOFF before insn ARG. */
static int
emit_inc_dec_insn_before (rtx mem ATTRIBUTE_UNUSED,
rtx op ATTRIBUTE_UNUSED,
rtx dest, rtx src, rtx srcoff, void *arg)
{
insn_info_t insn_info = (insn_info_t) arg;
rtx_insn *insn = insn_info->insn, *new_insn, *cur;
note_add_store_info info;
/* We can reuse all operands without copying, because we are about
to delete the insn that contained it. */
if (srcoff)
{
start_sequence ();
emit_insn (gen_add3_insn (dest, src, srcoff));
new_insn = get_insns ();
end_sequence ();
}
else
new_insn = gen_move_insn (dest, src);
info.first = new_insn;
info.fixed_regs_live = insn_info->fixed_regs_live;
info.failure = false;
for (cur = new_insn; cur; cur = NEXT_INSN (cur))
{
info.current = cur;
note_stores (cur, note_add_store, &info);
}
/* If a failure was flagged above, return 1 so that for_each_inc_dec will
return it immediately, communicating the failure to its caller. */
if (info.failure)
return 1;
emit_insn_before (new_insn, insn);
return 0;
}
/* Before we delete INSN_INFO->INSN, make sure that the auto inc/dec, if it
is there, is split into a separate insn.
Return true on success (or if there was nothing to do), false on failure. */
static bool
check_for_inc_dec_1 (insn_info_t insn_info)
{
rtx_insn *insn = insn_info->insn;
rtx note = find_reg_note (insn, REG_INC, NULL_RTX);
if (note)
return for_each_inc_dec (PATTERN (insn), emit_inc_dec_insn_before,
insn_info) == 0;
/* Punt on stack pushes, those don't have REG_INC notes and we are
unprepared to deal with distribution of REG_ARGS_SIZE notes etc. */
subrtx_iterator::array_type array;
FOR_EACH_SUBRTX (iter, array, PATTERN (insn), NONCONST)
{
const_rtx x = *iter;
if (GET_RTX_CLASS (GET_CODE (x)) == RTX_AUTOINC)
return false;
}
return true;
}
/* Entry point for postreload. If you work on reload_cse, or you need this
anywhere else, consider if you can provide register liveness information
and add a parameter to this function so that it can be passed down in
insn_info.fixed_regs_live. */
bool
check_for_inc_dec (rtx_insn *insn)
{
insn_info_type insn_info;
rtx note;
insn_info.insn = insn;
insn_info.fixed_regs_live = NULL;
note = find_reg_note (insn, REG_INC, NULL_RTX);
if (note)
return for_each_inc_dec (PATTERN (insn), emit_inc_dec_insn_before,
&insn_info) == 0;
/* Punt on stack pushes, those don't have REG_INC notes and we are
unprepared to deal with distribution of REG_ARGS_SIZE notes etc. */
subrtx_iterator::array_type array;
FOR_EACH_SUBRTX (iter, array, PATTERN (insn), NONCONST)
{
const_rtx x = *iter;
if (GET_RTX_CLASS (GET_CODE (x)) == RTX_AUTOINC)
return false;
}
return true;
}
/* Delete the insn and free all of the fields inside INSN_INFO. */
static void
delete_dead_store_insn (insn_info_t insn_info)
{
read_info_t read_info;
if (!dbg_cnt (dse))
return;
if (!check_for_inc_dec_1 (insn_info))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Locally deleting insn %d\n",
INSN_UID (insn_info->insn));
free_store_info (insn_info);
read_info = insn_info->read_rec;
while (read_info)
{
read_info_t next = read_info->next;
read_info_type_pool.remove (read_info);
read_info = next;
}
insn_info->read_rec = NULL;
delete_insn (insn_info->insn);
locally_deleted++;
insn_info->insn = NULL;
insn_info->wild_read = false;
}
/* Return whether DECL, a local variable, can possibly escape the current
function scope. */
static bool
local_variable_can_escape (tree decl)
{
if (TREE_ADDRESSABLE (decl))
return true;
/* If this is a partitioned variable, we need to consider all the variables
in the partition. This is necessary because a store into one of them can
be replaced with a store into another and this may not change the outcome
of the escape analysis. */
if (cfun->gimple_df->decls_to_pointers != NULL)
{
tree *namep = cfun->gimple_df->decls_to_pointers->get (decl);
if (namep)
return TREE_ADDRESSABLE (*namep);
}
return false;
}
/* Return whether EXPR can possibly escape the current function scope. */
static bool
can_escape (tree expr)
{
tree base;
if (!expr)
return true;
base = get_base_address (expr);
if (DECL_P (base)
&& !may_be_aliased (base)
&& !(VAR_P (base)
&& !DECL_EXTERNAL (base)
&& !TREE_STATIC (base)
&& local_variable_can_escape (base)))
return false;
return true;
}
/* Set the store* bitmaps offset_map_size* fields in GROUP based on
OFFSET and WIDTH. */
static void
set_usage_bits (group_info *group, poly_int64 offset, poly_int64 width,
tree expr)
{
/* Non-constant offsets and widths act as global kills, so there's no point
trying to use them to derive global DSE candidates. */
HOST_WIDE_INT i, const_offset, const_width;
bool expr_escapes = can_escape (expr);
if (offset.is_constant (&const_offset)
&& width.is_constant (&const_width)
&& const_offset > -MAX_OFFSET
&& const_offset + const_width < MAX_OFFSET)
for (i = const_offset; i < const_offset + const_width; ++i)
{
bitmap store1;
bitmap store2;
bitmap escaped;
int ai;
if (i < 0)
{
store1 = group->store1_n;
store2 = group->store2_n;
escaped = group->escaped_n;
ai = -i;
}
else
{
store1 = group->store1_p;
store2 = group->store2_p;
escaped = group->escaped_p;
ai = i;
}
if (!bitmap_set_bit (store1, ai))
bitmap_set_bit (store2, ai);
else
{
if (i < 0)
{
if (group->offset_map_size_n < ai)
group->offset_map_size_n = ai;
}
else
{
if (group->offset_map_size_p < ai)
group->offset_map_size_p = ai;
}
}
if (expr_escapes)
bitmap_set_bit (escaped, ai);
}
}
static void
reset_active_stores (void)
{
active_local_stores = NULL;
active_local_stores_len = 0;
}
/* Free all READ_REC of the LAST_INSN of BB_INFO. */
static void
free_read_records (bb_info_t bb_info)
{
insn_info_t insn_info = bb_info->last_insn;
read_info_t *ptr = &insn_info->read_rec;
while (*ptr)
{
read_info_t next = (*ptr)->next;
read_info_type_pool.remove (*ptr);
*ptr = next;
}
}
/* Set the BB_INFO so that the last insn is marked as a wild read. */
static void
add_wild_read (bb_info_t bb_info)
{
insn_info_t insn_info = bb_info->last_insn;
insn_info->wild_read = true;
free_read_records (bb_info);
reset_active_stores ();
}
/* Set the BB_INFO so that the last insn is marked as a wild read of
non-frame locations. */
static void
add_non_frame_wild_read (bb_info_t bb_info)
{
insn_info_t insn_info = bb_info->last_insn;
insn_info->non_frame_wild_read = true;
free_read_records (bb_info);
reset_active_stores ();
}
/* Return true if X is a constant or one of the registers that behave
as a constant over the life of a function. This is equivalent to
!rtx_varies_p for memory addresses. */
static bool
const_or_frame_p (rtx x)
{
if (CONSTANT_P (x))
return true;
if (GET_CODE (x) == REG)
{
/* Note that we have to test for the actual rtx used for the frame
and arg pointers and not just the register number in case we have
eliminated the frame and/or arg pointer and are using it
for pseudos. */
if (x == frame_pointer_rtx || x == hard_frame_pointer_rtx
/* The arg pointer varies if it is not a fixed register. */
|| (x == arg_pointer_rtx && fixed_regs[ARG_POINTER_REGNUM])
|| x == pic_offset_table_rtx)
return true;
return false;
}
return false;
}
/* Take all reasonable action to put the address of MEM into the form
that we can do analysis on.
The gold standard is to get the address into the form: address +
OFFSET where address is something that rtx_varies_p considers a
constant. When we can get the address in this form, we can do
global analysis on it. Note that for constant bases, address is
not actually returned, only the group_id. The address can be
obtained from that.
If that fails, we try cselib to get a value we can at least use
locally. If that fails we return false.
The GROUP_ID is set to -1 for cselib bases and the index of the
group for non_varying bases.
FOR_READ is true if this is a mem read and false if not. */
static bool
canon_address (rtx mem,
int *group_id,
poly_int64 *offset,
cselib_val **base)
{
machine_mode address_mode = get_address_mode (mem);
rtx mem_address = XEXP (mem, 0);
rtx expanded_address, address;
int expanded;
cselib_lookup (mem_address, address_mode, 1, GET_MODE (mem));
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " mem: ");
print_inline_rtx (dump_file, mem_address, 0);
fprintf (dump_file, "\n");
}
/* First see if just canon_rtx (mem_address) is const or frame,
if not, try cselib_expand_value_rtx and call canon_rtx on that. */
address = NULL_RTX;
for (expanded = 0; expanded < 2; expanded++)
{
if (expanded)
{
/* Use cselib to replace all of the reg references with the full
expression. This will take care of the case where we have
r_x = base + offset;
val = *r_x;
by making it into
val = *(base + offset); */
expanded_address = cselib_expand_value_rtx (mem_address,
scratch, 5);
/* If this fails, just go with the address from first
iteration. */
if (!expanded_address)
break;
}
else
expanded_address = mem_address;
/* Split the address into canonical BASE + OFFSET terms. */
address = canon_rtx (expanded_address);
*offset = 0;
if (dump_file && (dump_flags & TDF_DETAILS))
{
if (expanded)
{
fprintf (dump_file, "\n after cselib_expand address: ");
print_inline_rtx (dump_file, expanded_address, 0);
fprintf (dump_file, "\n");
}
fprintf (dump_file, "\n after canon_rtx address: ");
print_inline_rtx (dump_file, address, 0);
fprintf (dump_file, "\n");
}
if (GET_CODE (address) == CONST)
address = XEXP (address, 0);
address = strip_offset_and_add (address, offset);
if (ADDR_SPACE_GENERIC_P (MEM_ADDR_SPACE (mem))
&& const_or_frame_p (address))
{
group_info *group = get_group_info (address);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " gid=%d offset=", group->id);
print_dec (*offset, dump_file);
fprintf (dump_file, "\n");
}
*base = NULL;
*group_id = group->id;
return true;
}
}
*base = cselib_lookup (address, address_mode, true, GET_MODE (mem));
*group_id = -1;
if (*base == NULL)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " no cselib val - should be a wild read.\n");
return false;
}
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " varying cselib base=%u:%u offset = ",
(*base)->uid, (*base)->hash);
print_dec (*offset, dump_file);
fprintf (dump_file, "\n");
}
return true;
}
/* Clear the rhs field from the active_local_stores array. */
static void
clear_rhs_from_active_local_stores (void)
{
insn_info_t ptr = active_local_stores;
while (ptr)
{
store_info *store_info = ptr->store_rec;
/* Skip the clobbers. */
while (!store_info->is_set)
store_info = store_info->next;
store_info->rhs = NULL;
store_info->const_rhs = NULL;
ptr = ptr->next_local_store;
}
}
/* Mark byte POS bytes from the beginning of store S_INFO as unneeded. */
static inline void
set_position_unneeded (store_info *s_info, int pos)
{
if (__builtin_expect (s_info->is_large, false))
{
if (bitmap_set_bit (s_info->positions_needed.large.bmap, pos))
s_info->positions_needed.large.count++;
}
else
s_info->positions_needed.small_bitmask
&= ~(HOST_WIDE_INT_1U << pos);
}
/* Mark the whole store S_INFO as unneeded. */
static inline void
set_all_positions_unneeded (store_info *s_info)
{
if (__builtin_expect (s_info->is_large, false))
{
HOST_WIDE_INT width;
if (s_info->width.is_constant (&width))
{
bitmap_set_range (s_info->positions_needed.large.bmap, 0, width);
s_info->positions_needed.large.count = width;
}
else
{
gcc_checking_assert (!s_info->positions_needed.large.bmap);
s_info->positions_needed.large.count = 1;
}
}
else
s_info->positions_needed.small_bitmask = HOST_WIDE_INT_0U;
}
/* Return TRUE if any bytes from S_INFO store are needed. */
static inline bool
any_positions_needed_p (store_info *s_info)
{
if (__builtin_expect (s_info->is_large, false))
{
HOST_WIDE_INT width;
if (s_info->width.is_constant (&width))
{
gcc_checking_assert (s_info->positions_needed.large.bmap);
return s_info->positions_needed.large.count < width;
}
else
{
gcc_checking_assert (!s_info->positions_needed.large.bmap);
return s_info->positions_needed.large.count == 0;
}
}
else
return (s_info->positions_needed.small_bitmask != HOST_WIDE_INT_0U);
}
/* Return TRUE if all bytes START through START+WIDTH-1 from S_INFO
store are known to be needed. */
static inline bool
all_positions_needed_p (store_info *s_info, poly_int64 start,
poly_int64 width)
{
gcc_assert (s_info->rhs);
if (!s_info->width.is_constant ())
{
gcc_assert (s_info->is_large
&& !s_info->positions_needed.large.bmap);
return s_info->positions_needed.large.count == 0;
}
/* Otherwise, if START and WIDTH are non-constant, we're asking about
a non-constant region of a constant-sized store. We can't say for
sure that all positions are needed. */
HOST_WIDE_INT const_start, const_width;
if (!start.is_constant (&const_start)
|| !width.is_constant (&const_width))
return false;
if (__builtin_expect (s_info->is_large, false))
{
for (HOST_WIDE_INT i = const_start; i < const_start + const_width; ++i)
if (bitmap_bit_p (s_info->positions_needed.large.bmap, i))
return false;
return true;
}
else
{
unsigned HOST_WIDE_INT mask
= lowpart_bitmask (const_width) << const_start;
return (s_info->positions_needed.small_bitmask & mask) == mask;
}
}
static rtx get_stored_val (store_info *, machine_mode, poly_int64,
poly_int64, basic_block, bool);
/* BODY is an instruction pattern that belongs to INSN. Return 1 if
there is a candidate store, after adding it to the appropriate
local store group if so. */
static int
record_store (rtx body, bb_info_t bb_info)
{
rtx mem, rhs, const_rhs, mem_addr;
poly_int64 offset = 0;
poly_int64 width = 0;
insn_info_t insn_info = bb_info->last_insn;
store_info *store_info = NULL;
int group_id;
cselib_val *base = NULL;
insn_info_t ptr, last, redundant_reason;
bool store_is_unused;
if (GET_CODE (body) != SET && GET_CODE (body) != CLOBBER)
return 0;
mem = SET_DEST (body);
/* If this is not used, then this cannot be used to keep the insn
from being deleted. On the other hand, it does provide something
that can be used to prove that another store is dead. */
store_is_unused
= (find_reg_note (insn_info->insn, REG_UNUSED, mem) != NULL);
/* Check whether that value is a suitable memory location. */
if (!MEM_P (mem))
{
/* If the set or clobber is unused, then it does not effect our
ability to get rid of the entire insn. */
if (!store_is_unused)
insn_info->cannot_delete = true;
return 0;
}
/* At this point we know mem is a mem. */
if (GET_MODE (mem) == BLKmode)
{
HOST_WIDE_INT const_size;
if (GET_CODE (XEXP (mem, 0)) == SCRATCH)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " adding wild read for (clobber (mem:BLK (scratch))\n");
add_wild_read (bb_info);
insn_info->cannot_delete = true;
return 0;
}
/* Handle (set (mem:BLK (addr) [... S36 ...]) (const_int 0))
as memset (addr, 0, 36); */
else if (!MEM_SIZE_KNOWN_P (mem)
|| maybe_le (MEM_SIZE (mem), 0)
/* This is a limit on the bitmap size, which is only relevant
for constant-sized MEMs. */
|| (MEM_SIZE (mem).is_constant (&const_size)
&& const_size > MAX_OFFSET)
|| GET_CODE (body) != SET
|| !CONST_INT_P (SET_SRC (body)))
{
if (!store_is_unused)
{
/* If the set or clobber is unused, then it does not effect our
ability to get rid of the entire insn. */
insn_info->cannot_delete = true;
clear_rhs_from_active_local_stores ();
}
return 0;
}
}
/* We can still process a volatile mem, we just cannot delete it. */
if (MEM_VOLATILE_P (mem))
insn_info->cannot_delete = true;
if (!canon_address (mem, &group_id, &offset, &base))
{
clear_rhs_from_active_local_stores ();
return 0;
}
if (GET_MODE (mem) == BLKmode)
width = MEM_SIZE (mem);
else
width = GET_MODE_SIZE (GET_MODE (mem));
if (!endpoint_representable_p (offset, width))
{
clear_rhs_from_active_local_stores ();
return 0;
}
if (known_eq (width, 0))
return 0;
if (group_id >= 0)
{
/* In the restrictive case where the base is a constant or the
frame pointer we can do global analysis. */
group_info *group
= rtx_group_vec[group_id];
tree expr = MEM_EXPR (mem);
store_info = rtx_store_info_pool.allocate ();
set_usage_bits (group, offset, width, expr);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " processing const base store gid=%d",
group_id);
print_range (dump_file, offset, width);
fprintf (dump_file, "\n");
}
}
else
{
if (may_be_sp_based_p (XEXP (mem, 0)))
insn_info->stack_pointer_based = true;
insn_info->contains_cselib_groups = true;
store_info = cse_store_info_pool.allocate ();
group_id = -1;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " processing cselib store ");
print_range (dump_file, offset, width);
fprintf (dump_file, "\n");
}
}
const_rhs = rhs = NULL_RTX;
if (GET_CODE (body) == SET
/* No place to keep the value after ra. */
&& !reload_completed
&& (REG_P (SET_SRC (body))
|| GET_CODE (SET_SRC (body)) == SUBREG
|| CONSTANT_P (SET_SRC (body)))
&& !MEM_VOLATILE_P (mem)
/* Sometimes the store and reload is used for truncation and
rounding. */
&& !(FLOAT_MODE_P (GET_MODE (mem)) && (flag_float_store)))
{
rhs = SET_SRC (body);
if (CONSTANT_P (rhs))
const_rhs = rhs;
else if (body == PATTERN (insn_info->insn))
{
rtx tem = find_reg_note (insn_info->insn, REG_EQUAL, NULL_RTX);
if (tem && CONSTANT_P (XEXP (tem, 0)))
const_rhs = XEXP (tem, 0);
}
if (const_rhs == NULL_RTX && REG_P (rhs))
{
rtx tem = cselib_expand_value_rtx (rhs, scratch, 5);
if (tem && CONSTANT_P (tem))
const_rhs = tem;
}
}
/* Check to see if this stores causes some other stores to be
dead. */
ptr = active_local_stores;
last = NULL;
redundant_reason = NULL;
mem = canon_rtx (mem);
if (group_id < 0)
mem_addr = base->val_rtx;
else
{
group_info *group = rtx_group_vec[group_id];
mem_addr = group->canon_base_addr;
}
if (maybe_ne (offset, 0))
mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
while (ptr)
{
insn_info_t next = ptr->next_local_store;
class store_info *s_info = ptr->store_rec;
bool del = true;
/* Skip the clobbers. We delete the active insn if this insn
shadows the set. To have been put on the active list, it
has exactly on set. */
while (!s_info->is_set)
s_info = s_info->next;
if (s_info->group_id == group_id && s_info->cse_base == base)
{
HOST_WIDE_INT i;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " trying store in insn=%d gid=%d",
INSN_UID (ptr->insn), s_info->group_id);
print_range (dump_file, s_info->offset, s_info->width);
fprintf (dump_file, "\n");
}
/* Even if PTR won't be eliminated as unneeded, if both
PTR and this insn store the same constant value, we might
eliminate this insn instead. */
if (s_info->const_rhs
&& const_rhs
&& known_subrange_p (offset, width,
s_info->offset, s_info->width)
&& all_positions_needed_p (s_info, offset - s_info->offset,
width)
/* We can only remove the later store if the earlier aliases
at least all accesses the later one. */
&& ((MEM_ALIAS_SET (mem) == MEM_ALIAS_SET (s_info->mem)
|| alias_set_subset_of (MEM_ALIAS_SET (mem),
MEM_ALIAS_SET (s_info->mem)))
&& (!MEM_EXPR (s_info->mem)
|| refs_same_for_tbaa_p (MEM_EXPR (s_info->mem),
MEM_EXPR (mem)))))
{
if (GET_MODE (mem) == BLKmode)
{
if (GET_MODE (s_info->mem) == BLKmode
&& s_info->const_rhs == const_rhs)
redundant_reason = ptr;
}
else if (s_info->const_rhs == const0_rtx
&& const_rhs == const0_rtx)
redundant_reason = ptr;
else
{
rtx val;
start_sequence ();
val = get_stored_val (s_info, GET_MODE (mem), offset, width,
BLOCK_FOR_INSN (insn_info->insn),
true);
if (get_insns () != NULL)
val = NULL_RTX;
end_sequence ();
if (val && rtx_equal_p (val, const_rhs))
redundant_reason = ptr;
}
}
HOST_WIDE_INT begin_unneeded, const_s_width, const_width;
if (known_subrange_p (s_info->offset, s_info->width, offset, width))
/* The new store touches every byte that S_INFO does. */
set_all_positions_unneeded (s_info);
else if ((offset - s_info->offset).is_constant (&begin_unneeded)
&& s_info->width.is_constant (&const_s_width)
&& width.is_constant (&const_width))
{
HOST_WIDE_INT end_unneeded = begin_unneeded + const_width;
begin_unneeded = MAX (begin_unneeded, 0);
end_unneeded = MIN (end_unneeded, const_s_width);
for (i = begin_unneeded; i < end_unneeded; ++i)
set_position_unneeded (s_info, i);
}
else
{
/* We don't know which parts of S_INFO are needed and
which aren't, so invalidate the RHS. */
s_info->rhs = NULL;
s_info->const_rhs = NULL;
}
}
else if (s_info->rhs)
/* Need to see if it is possible for this store to overwrite
the value of store_info. If it is, set the rhs to NULL to
keep it from being used to remove a load. */
{
if (canon_output_dependence (s_info->mem, true,
mem, GET_MODE (mem),
mem_addr))
{
s_info->rhs = NULL;
s_info->const_rhs = NULL;
}
}
/* An insn can be deleted if every position of every one of
its s_infos is zero. */
if (any_positions_needed_p (s_info))
del = false;
if (del)
{
insn_info_t insn_to_delete = ptr;
active_local_stores_len--;
if (last)
last->next_local_store = ptr->next_local_store;
else
active_local_stores = ptr->next_local_store;
if (!insn_to_delete->cannot_delete)
delete_dead_store_insn (insn_to_delete);
}
else
last = ptr;
ptr = next;
}
/* Finish filling in the store_info. */
store_info->next = insn_info->store_rec;
insn_info->store_rec = store_info;
store_info->mem = mem;
store_info->mem_addr = mem_addr;
store_info->cse_base = base;
HOST_WIDE_INT const_width;
if (!width.is_constant (&const_width))
{
store_info->is_large = true;
store_info->positions_needed.large.count = 0;
store_info->positions_needed.large.bmap = NULL;
}
else if (const_width > HOST_BITS_PER_WIDE_INT)
{
store_info->is_large = true;
store_info->positions_needed.large.count = 0;
store_info->positions_needed.large.bmap = BITMAP_ALLOC (&dse_bitmap_obstack);
}
else
{
store_info->is_large = false;
store_info->positions_needed.small_bitmask
= lowpart_bitmask (const_width);
}
store_info->group_id = group_id;
store_info->offset = offset;
store_info->width = width;
store_info->is_set = GET_CODE (body) == SET;
store_info->rhs = rhs;
store_info->const_rhs = const_rhs;
store_info->redundant_reason = redundant_reason;
/* If this is a clobber, we return 0. We will only be able to
delete this insn if there is only one store USED store, but we
can use the clobber to delete other stores earlier. */
return store_info->is_set ? 1 : 0;
}
static void
dump_insn_info (const char * start, insn_info_t insn_info)
{
fprintf (dump_file, "%s insn=%d %s\n", start,
INSN_UID (insn_info->insn),
insn_info->store_rec ? "has store" : "naked");
}
/* If the modes are different and the value's source and target do not
line up, we need to extract the value from lower part of the rhs of
the store, shift it, and then put it into a form that can be shoved
into the read_insn. This function generates a right SHIFT of a
value that is at least ACCESS_SIZE bytes wide of READ_MODE. The
shift sequence is returned or NULL if we failed to find a
shift. */
static rtx
find_shift_sequence (poly_int64 access_size,
store_info *store_info,
machine_mode read_mode,
poly_int64 shift, bool speed, bool require_cst)
{
machine_mode store_mode = GET_MODE (store_info->mem);
scalar_int_mode new_mode;
rtx read_reg = NULL;
/* If a constant was stored into memory, try to simplify it here,
otherwise the cost of the shift might preclude this optimization
e.g. at -Os, even when no actual shift will be needed. */
if (store_info->const_rhs)
{
auto new_mode = smallest_int_mode_for_size (access_size * BITS_PER_UNIT);
auto byte = subreg_lowpart_offset (new_mode, store_mode);
rtx ret
= simplify_subreg (new_mode, store_info->const_rhs, store_mode, byte);
if (ret && CONSTANT_P (ret))
{
rtx shift_rtx = gen_int_shift_amount (new_mode, shift);
ret = simplify_const_binary_operation (LSHIFTRT, new_mode, ret,
shift_rtx);
if (ret && CONSTANT_P (ret))
{
byte = subreg_lowpart_offset (read_mode, new_mode);
ret = simplify_subreg (read_mode, ret, new_mode, byte);
if (ret && CONSTANT_P (ret)
&& (set_src_cost (ret, read_mode, speed)
<= COSTS_N_INSNS (1)))
return ret;
}
}
}
if (require_cst)
return NULL_RTX;
/* Some machines like the x86 have shift insns for each size of
operand. Other machines like the ppc or the ia-64 may only have
shift insns that shift values within 32 or 64 bit registers.
This loop tries to find the smallest shift insn that will right
justify the value we want to read but is available in one insn on
the machine. */
opt_scalar_int_mode new_mode_iter;
FOR_EACH_MODE_IN_CLASS (new_mode_iter, MODE_INT)
{
rtx target, new_reg, new_lhs;
rtx_insn *shift_seq, *insn;
int cost;
new_mode = new_mode_iter.require ();
if (GET_MODE_BITSIZE (new_mode) > BITS_PER_WORD)
break;
if (maybe_lt (GET_MODE_SIZE (new_mode), GET_MODE_SIZE (read_mode)))
continue;
/* Try a wider mode if truncating the store mode to NEW_MODE
requires a real instruction. */
if (maybe_lt (GET_MODE_SIZE (new_mode), GET_MODE_SIZE (store_mode))
&& !TRULY_NOOP_TRUNCATION_MODES_P (new_mode, store_mode))
continue;
/* Also try a wider mode if the necessary punning is either not
desirable or not possible. */
if (!CONSTANT_P (store_info->rhs)
&& !targetm.modes_tieable_p (new_mode, store_mode))
continue;
if (multiple_p (shift, GET_MODE_BITSIZE (new_mode))
&& known_le (GET_MODE_SIZE (new_mode), GET_MODE_SIZE (store_mode)))
{
/* Try to implement the shift using a subreg. */
poly_int64 offset
= subreg_offset_from_lsb (new_mode, store_mode, shift);
rtx rhs_subreg = simplify_gen_subreg (new_mode, store_info->rhs,
store_mode, offset);
if (rhs_subreg)
{
read_reg
= extract_low_bits (read_mode, new_mode, copy_rtx (rhs_subreg));
break;
}
}
if (maybe_lt (GET_MODE_SIZE (new_mode), access_size))
continue;
new_reg = gen_reg_rtx (new_mode);
start_sequence ();
/* In theory we could also check for an ashr. Ian Taylor knows
of one dsp where the cost of these two was not the same. But
this really is a rare case anyway. */
target = expand_binop (new_mode, lshr_optab, new_reg,
gen_int_shift_amount (new_mode, shift),
new_reg, 1, OPTAB_DIRECT);
shift_seq = get_insns ();
end_sequence ();
if (target != new_reg || shift_seq == NULL)
continue;
cost = 0;
for (insn = shift_seq; insn != NULL_RTX; insn = NEXT_INSN (insn))
if (INSN_P (insn))
cost += insn_cost (insn, speed);
/* The computation up to here is essentially independent
of the arguments and could be precomputed. It may
not be worth doing so. We could precompute if
worthwhile or at least cache the results. The result
technically depends on both SHIFT and ACCESS_SIZE,
but in practice the answer will depend only on ACCESS_SIZE. */
if (cost > COSTS_N_INSNS (1))
continue;
new_lhs = extract_low_bits (new_mode, store_mode,
copy_rtx (store_info->rhs));
if (new_lhs == NULL_RTX)
continue;
/* We found an acceptable shift. Generate a move to
take the value from the store and put it into the
shift pseudo, then shift it, then generate another
move to put in into the target of the read. */
emit_move_insn (new_reg, new_lhs);
emit_insn (shift_seq);
read_reg = extract_low_bits (read_mode, new_mode, new_reg);
break;
}
return read_reg;
}
/* Call back for note_stores to find the hard regs set or clobbered by
insn. Data is a bitmap of the hardregs set so far. */
static void
look_for_hardregs (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
{
bitmap regs_set = (bitmap) data;
if (REG_P (x)
&& HARD_REGISTER_P (x))
bitmap_set_range (regs_set, REGNO (x), REG_NREGS (x));
}
/* Helper function for replace_read and record_store.
Attempt to return a value of mode READ_MODE stored in STORE_INFO,
consisting of READ_WIDTH bytes starting from READ_OFFSET. Return NULL
if not successful. If REQUIRE_CST is true, return always constant. */
static rtx
get_stored_val (store_info *store_info, machine_mode read_mode,
poly_int64 read_offset, poly_int64 read_width,
basic_block bb, bool require_cst)
{
machine_mode store_mode = GET_MODE (store_info->mem);
poly_int64 gap;
rtx read_reg;
/* To get here the read is within the boundaries of the write so
shift will never be negative. Start out with the shift being in
bytes. */
if (store_mode == BLKmode)
gap = 0;
else if (BYTES_BIG_ENDIAN)
gap = ((store_info->offset + store_info->width)
- (read_offset + read_width));
else
gap = read_offset - store_info->offset;
if (gap.is_constant () && maybe_ne (gap, 0))
{
poly_int64 shift = gap * BITS_PER_UNIT;
poly_int64 access_size = GET_MODE_SIZE (read_mode) + gap;
read_reg = find_shift_sequence (access_size, store_info, read_mode,
shift, optimize_bb_for_speed_p (bb),
require_cst);
}
else if (store_mode == BLKmode)
{
/* The store is a memset (addr, const_val, const_size). */
gcc_assert (CONST_INT_P (store_info->rhs));
scalar_int_mode int_store_mode;
if (!int_mode_for_mode (read_mode).exists (&int_store_mode))
read_reg = NULL_RTX;
else if (store_info->rhs == const0_rtx)
read_reg = extract_low_bits (read_mode, int_store_mode, const0_rtx);
else if (GET_MODE_BITSIZE (int_store_mode) > HOST_BITS_PER_WIDE_INT
|| BITS_PER_UNIT >= HOST_BITS_PER_WIDE_INT)
read_reg = NULL_RTX;
else
{
unsigned HOST_WIDE_INT c
= INTVAL (store_info->rhs)
& ((HOST_WIDE_INT_1 << BITS_PER_UNIT) - 1);
int shift = BITS_PER_UNIT;
while (shift < HOST_BITS_PER_WIDE_INT)
{
c |= (c << shift);
shift <<= 1;
}
read_reg = gen_int_mode (c, int_store_mode);
read_reg = extract_low_bits (read_mode, int_store_mode, read_reg);
}
}
else if (store_info->const_rhs
&& (require_cst
|| GET_MODE_CLASS (read_mode) != GET_MODE_CLASS (store_mode)))
read_reg = extract_low_bits (read_mode, store_mode,
copy_rtx (store_info->const_rhs));
else
read_reg = extract_low_bits (read_mode, store_mode,
copy_rtx (store_info->rhs));
if (require_cst && read_reg && !CONSTANT_P (read_reg))
read_reg = NULL_RTX;
return read_reg;
}
/* Take a sequence of:
A <- r1
...
... <- A
and change it into
r2 <- r1
A <- r1
...
... <- r2
or
r3 <- extract (r1)
r3 <- r3 >> shift
r2 <- extract (r3)
... <- r2
or
r2 <- extract (r1)
... <- r2
Depending on the alignment and the mode of the store and
subsequent load.
The STORE_INFO and STORE_INSN are for the store and READ_INFO
and READ_INSN are for the read. Return true if the replacement
went ok. */
static bool
replace_read (store_info *store_info, insn_info_t store_insn,
read_info_t read_info, insn_info_t read_insn, rtx *loc)
{
machine_mode store_mode = GET_MODE (store_info->mem);
machine_mode read_mode = GET_MODE (read_info->mem);
rtx_insn *insns, *this_insn;
rtx read_reg;
basic_block bb;
if (!dbg_cnt (dse))
return false;
/* Create a sequence of instructions to set up the read register.
This sequence goes immediately before the store and its result
is read by the load.
We need to keep this in perspective. We are replacing a read
with a sequence of insns, but the read will almost certainly be
in cache, so it is not going to be an expensive one. Thus, we
are not willing to do a multi insn shift or worse a subroutine
call to get rid of the read. */
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "trying to replace %smode load in insn %d"
" from %smode store in insn %d\n",
GET_MODE_NAME (read_mode), INSN_UID (read_insn->insn),
GET_MODE_NAME (store_mode), INSN_UID (store_insn->insn));
start_sequence ();
bb = BLOCK_FOR_INSN (read_insn->insn);
read_reg = get_stored_val (store_info,
read_mode, read_info->offset, read_info->width,
bb, false);
if (read_reg == NULL_RTX)
{
end_sequence ();
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " -- could not extract bits of stored value\n");
return false;
}
/* Force the value into a new register so that it won't be clobbered
between the store and the load. */
read_reg = copy_to_mode_reg (read_mode, read_reg);
insns = get_insns ();
end_sequence ();
if (insns != NULL_RTX)
{
/* Now we have to scan the set of new instructions to see if the
sequence contains and sets of hardregs that happened to be
live at this point. For instance, this can happen if one of
the insns sets the CC and the CC happened to be live at that
point. This does occasionally happen, see PR 37922. */
bitmap regs_set = BITMAP_ALLOC (&reg_obstack);
for (this_insn = insns;
this_insn != NULL_RTX; this_insn = NEXT_INSN (this_insn))
{
if (insn_invalid_p (this_insn, false))
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " -- replacing the loaded MEM with ");
print_simple_rtl (dump_file, read_reg);
fprintf (dump_file, " led to an invalid instruction\n");
}
BITMAP_FREE (regs_set);
return false;
}
note_stores (this_insn, look_for_hardregs, regs_set);
}
if (store_insn->fixed_regs_live)
bitmap_and_into (regs_set, store_insn->fixed_regs_live);
if (!bitmap_empty_p (regs_set))
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "abandoning replacement because sequence "
"clobbers live hardregs:");
df_print_regset (dump_file, regs_set);
}
BITMAP_FREE (regs_set);
return false;
}
BITMAP_FREE (regs_set);
}
subrtx_iterator::array_type array;
FOR_EACH_SUBRTX (iter, array, *loc, NONCONST)
{
const_rtx x = *iter;
if (GET_RTX_CLASS (GET_CODE (x)) == RTX_AUTOINC)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " -- replacing the MEM failed due to address "
"side-effects\n");
return false;
}
}
if (validate_change (read_insn->insn, loc, read_reg, 0))
{
deferred_change *change = deferred_change_pool.allocate ();
/* Insert this right before the store insn where it will be safe
from later insns that might change it before the read. */
emit_insn_before (insns, store_insn->insn);
/* And now for the kludge part: cselib croaks if you just
return at this point. There are two reasons for this:
1) Cselib has an idea of how many pseudos there are and
that does not include the new ones we just added.
2) Cselib does not know about the move insn we added
above the store_info, and there is no way to tell it
about it, because it has "moved on".
Problem (1) is fixable with a certain amount of engineering.
Problem (2) is requires starting the bb from scratch. This
could be expensive.
So we are just going to have to lie. The move/extraction
insns are not really an issue, cselib did not see them. But
the use of the new pseudo read_insn is a real problem because
cselib has not scanned this insn. The way that we solve this
problem is that we are just going to put the mem back for now
and when we are finished with the block, we undo this. We
keep a table of mems to get rid of. At the end of the basic
block we can put them back. */
*loc = read_info->mem;
change->next = deferred_change_list;
deferred_change_list = change;
change->loc = loc;
change->reg = read_reg;
/* Get rid of the read_info, from the point of view of the
rest of dse, play like this read never happened. */
read_insn->read_rec = read_info->next;
read_info_type_pool.remove (read_info);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " -- replaced the loaded MEM with ");
print_simple_rtl (dump_file, read_reg);
fprintf (dump_file, "\n");
}
return true;
}
else
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " -- replacing the loaded MEM with ");
print_simple_rtl (dump_file, read_reg);
fprintf (dump_file, " led to an invalid instruction\n");
}
return false;
}
}
/* Check the address of MEM *LOC and kill any appropriate stores that may
be active. */
static void
check_mem_read_rtx (rtx *loc, bb_info_t bb_info)
{
rtx mem = *loc, mem_addr;
insn_info_t insn_info;
poly_int64 offset = 0;
poly_int64 width = 0;
cselib_val *base = NULL;
int group_id;
read_info_t read_info;
insn_info = bb_info->last_insn;
if ((MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
|| MEM_VOLATILE_P (mem))
{
if (crtl->stack_protect_guard
&& (MEM_EXPR (mem) == crtl->stack_protect_guard
|| (crtl->stack_protect_guard_decl
&& MEM_EXPR (mem) == crtl->stack_protect_guard_decl))
&& MEM_VOLATILE_P (mem))
{
/* This is either the stack protector canary on the stack,
which ought to be written by a MEM_VOLATILE_P store and
thus shouldn't be deleted and is read at the very end of
function, but shouldn't conflict with any other store.
Or it is __stack_chk_guard variable or TLS or whatever else
MEM holding the canary value, which really shouldn't be
ever modified in -fstack-protector* protected functions,
otherwise the prologue store wouldn't match the epilogue
check. */
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " stack protector canary read ignored.\n");
insn_info->cannot_delete = true;
return;
}
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " adding wild read, volatile or barrier.\n");
add_wild_read (bb_info);
insn_info->cannot_delete = true;
return;
}
/* If it is reading readonly mem, then there can be no conflict with
another write. */
if (MEM_READONLY_P (mem))
return;
if (!canon_address (mem, &group_id, &offset, &base))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " adding wild read, canon_address failure.\n");
add_wild_read (bb_info);
return;
}
if (GET_MODE (mem) == BLKmode)
width = -1;
else
width = GET_MODE_SIZE (GET_MODE (mem));
if (!endpoint_representable_p (offset, known_eq (width, -1) ? 1 : width))
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " adding wild read, due to overflow.\n");
add_wild_read (bb_info);
return;
}
read_info = read_info_type_pool.allocate ();
read_info->group_id = group_id;
read_info->mem = mem;
read_info->offset = offset;
read_info->width = width;
read_info->next = insn_info->read_rec;
insn_info->read_rec = read_info;
if (group_id < 0)
mem_addr = base->val_rtx;
else
{
group_info *group = rtx_group_vec[group_id];
mem_addr = group->canon_base_addr;
}
if (maybe_ne (offset, 0))
mem_addr = plus_constant (get_address_mode (mem), mem_addr, offset);
/* Avoid passing VALUE RTXen as mem_addr to canon_true_dependence
which will over and over re-create proper RTL and re-apply the
offset above. See PR80960 where we almost allocate 1.6GB of PLUS
RTXen that way. */
mem_addr = get_addr (mem_addr);
if (group_id >= 0)
{
/* This is the restricted case where the base is a constant or
the frame pointer and offset is a constant. */
insn_info_t i_ptr = active_local_stores;
insn_info_t last = NULL;
if (dump_file && (dump_flags & TDF_DETAILS))
{
if (!known_size_p (width))
fprintf (dump_file, " processing const load gid=%d[BLK]\n",
group_id);
else
{
fprintf (dump_file, " processing const load gid=%d", group_id);
print_range (dump_file, offset, width);
fprintf (dump_file, "\n");
}
}
while (i_ptr)
{
bool remove = false;
store_info *store_info = i_ptr->store_rec;
/* Skip the clobbers. */
while (!store_info->is_set)
store_info = store_info->next;
/* There are three cases here. */
if (store_info->group_id < 0)
/* We have a cselib store followed by a read from a
const base. */
remove
= canon_true_dependence (store_info->mem,
GET_MODE (store_info->mem),
store_info->mem_addr,
mem, mem_addr);
else if (group_id == store_info->group_id)
{
/* This is a block mode load. We may get lucky and
canon_true_dependence may save the day. */
if (!known_size_p (width))
remove
= canon_true_dependence (store_info->mem,
GET_MODE (store_info->mem),
store_info->mem_addr,
mem, mem_addr);
/* If this read is just reading back something that we just
stored, rewrite the read. */
else
{
if (store_info->rhs
&& known_subrange_p (offset, width, store_info->offset,
store_info->width)
&& all_positions_needed_p (store_info,
offset - store_info->offset,
width)
&& replace_read (store_info, i_ptr, read_info,
insn_info, loc))
return;
/* The bases are the same, just see if the offsets
could overlap. */
if (ranges_maybe_overlap_p (offset, width,
store_info->offset,
store_info->width))
remove = true;
}
}
/* else
The else case that is missing here is that the
bases are constant but different. There is nothing
to do here because there is no overlap. */
if (remove)
{
if (dump_file && (dump_flags & TDF_DETAILS))
dump_insn_info ("removing from active", i_ptr);
active_local_stores_len--;
if (last)
last->next_local_store = i_ptr->next_local_store;
else
active_local_stores = i_ptr->next_local_store;
}
else
last = i_ptr;
i_ptr = i_ptr->next_local_store;
}
}
else
{
insn_info_t i_ptr = active_local_stores;
insn_info_t last = NULL;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, " processing cselib load mem:");
print_inline_rtx (dump_file, mem, 0);
fprintf (dump_file, "\n");
}
while (i_ptr)
{
bool remove = false;
store_info *store_info = i_ptr->store_rec;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, " processing cselib load against insn %d\n",
INSN_UID (i_ptr->insn));
/* Skip the clobbers. */
while (!store_info->is_set)
store_info = store_info->next;
/* If this read is just reading back something that we just
stored, rewrite the read. */
if (store_info->rhs
&& store_info->group_id == -1
&& store_info->cse_base == base
&& known_subrange_p (offset, width, store_info->offset,
store_info->width)
&& all_positions_needed_p (store_info,
offset - store_info->offset, width)
&& replace_read (store_info, i_ptr, read_info, insn_info, loc))
return;
remove = canon_true_dependence (store_info->mem,
GET_MODE (store_info->mem),
store_info->mem_addr,
mem, mem_addr);
if (remove)
{
if (dump_file && (dump_flags & TDF_DETAILS))
dump_insn_info ("removing from active", i_ptr);
active_local_stores_len--;
if (last)
last->next_local_store = i_ptr->next_local_store;
else
active_local_stores = i_ptr->next_local_store;
}
else
last = i_ptr;
i_ptr = i_ptr->next_local_store;
}
}
}
/* A note_uses callback in which DATA points the INSN_INFO for
as check_mem_read_rtx. Nullify the pointer if i_m_r_m_r returns
true for any part of *LOC. */
static void
check_mem_read_use (rtx *loc, void *data)
{
subrtx_ptr_iterator::array_type array;
FOR_EACH_SUBRTX_PTR (iter, array, loc, NONCONST)
{
rtx *loc = *iter;
if (MEM_P (*loc))
check_mem_read_rtx (loc, (bb_info_t) data);
}
}
/* Get arguments passed to CALL_INSN. Return TRUE if successful.
So far it only handles arguments passed in registers. */
static bool
get_call_args (rtx call_insn, tree fn, rtx *args, int nargs)
{
CUMULATIVE_ARGS args_so_far_v;
cumulative_args_t args_so_far;
tree arg;
int idx;
INIT_CUMULATIVE_ARGS (args_so_far_v, TREE_TYPE (fn), NULL_RTX, 0, 3);
args_so_far = pack_cumulative_args (&args_so_far_v);
arg = TYPE_ARG_TYPES (TREE_TYPE (fn));
for (idx = 0;
arg != void_list_node && idx < nargs;
arg = TREE_CHAIN (arg), idx++)
{
scalar_int_mode mode;
rtx reg, link, tmp;
if (!is_int_mode (TYPE_MODE (TREE_VALUE (arg)), &mode))
return false;
function_arg_info arg (mode, /*named=*/true);
reg = targetm.calls.function_arg (args_so_far, arg);
if (!reg || !REG_P (reg) || GET_MODE (reg) != mode)
return false;
for (link = CALL_INSN_FUNCTION_USAGE (call_insn);
link;
link = XEXP (link, 1))
if (GET_CODE (XEXP (link, 0)) == USE)
{
scalar_int_mode arg_mode;
args[idx] = XEXP (XEXP (link, 0), 0);
if (REG_P (args[idx])
&& REGNO (args[idx]) == REGNO (reg)
&& (GET_MODE (args[idx]) == mode
|| (is_int_mode (GET_MODE (args[idx]), &arg_mode)
&& (GET_MODE_SIZE (arg_mode) <= UNITS_PER_WORD)
&& (GET_MODE_SIZE (arg_mode) > GET_MODE_SIZE (mode)))))
break;
}
if (!link)
return false;
tmp = cselib_expand_value_rtx (args[idx], scratch, 5);
if (GET_MODE (args[idx]) != mode)
{
if (!tmp || !CONST_INT_P (tmp))
return false;
tmp = gen_int_mode (INTVAL (tmp), mode);
}
if (tmp)
args[idx] = tmp;
targetm.calls.function_arg_advance (args_so_far, arg);
}
if (arg != void_list_node || idx != nargs)
return false;
return true;
}
/* Return a bitmap of the fixed registers contained in IN. */
static bitmap
copy_fixed_regs (const_bitmap in)
{
bitmap ret;
ret = ALLOC_REG_SET (NULL);
bitmap_and (ret, in, bitmap_view<HARD_REG_SET> (fixed_reg_set));
return ret;
}
/* Apply record_store to all candidate stores in INSN. Mark INSN
if some part of it is not a candidate store and assigns to a
non-register target. */
static void
scan_insn (bb_info_t bb_info, rtx_insn *insn, int max_active_local_stores)
{
rtx body;
insn_info_type *insn_info = insn_info_type_pool.allocate ();
int mems_found = 0;
memset (insn_info, 0, sizeof (struct insn_info_type));
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\n**scanning insn=%d\n",
INSN_UID (insn));
insn_info->prev_insn = bb_info->last_insn;
insn_info->insn = insn;
bb_info->last_insn = insn_info;
if (DEBUG_INSN_P (insn))
{
insn_info->cannot_delete = true;
return;
}
/* Look at all of the uses in the insn. */
note_uses (&PATTERN (insn), check_mem_read_use, bb_info);
if (CALL_P (insn))
{
bool const_call;
rtx call, sym;
tree memset_call = NULL_TREE;
insn_info->cannot_delete = true;
/* Const functions cannot do anything bad i.e. read memory,
however, they can read their parameters which may have
been pushed onto the stack.
memset and bzero don't read memory either. */
const_call = RTL_CONST_CALL_P (insn);
if (!const_call
&& (call = get_call_rtx_from (insn))
&& (sym = XEXP (XEXP (call, 0), 0))
&& GET_CODE (sym) == SYMBOL_REF
&& SYMBOL_REF_DECL (sym)
&& TREE_CODE (SYMBOL_REF_DECL (sym)) == FUNCTION_DECL
&& fndecl_built_in_p (SYMBOL_REF_DECL (sym), BUILT_IN_MEMSET))
memset_call = SYMBOL_REF_DECL (sym);
if (const_call || memset_call)
{
insn_info_t i_ptr = active_local_stores;
insn_info_t last = NULL;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "%s call %d\n",
const_call ? "const" : "memset", INSN_UID (insn));
/* See the head comment of the frame_read field. */
if (reload_completed
/* Tail calls are storing their arguments using
arg pointer. If it is a frame pointer on the target,
even before reload we need to kill frame pointer based
stores. */
|| (SIBLING_CALL_P (insn)
&& HARD_FRAME_POINTER_IS_ARG_POINTER))
insn_info->frame_read = true;
/* Loop over the active stores and remove those which are
killed by the const function call. */
while (i_ptr)
{
bool remove_store = false;
/* The stack pointer based stores are always killed. */
if (i_ptr->stack_pointer_based)
remove_store = true;
/* If the frame is read, the frame related stores are killed. */
else if (insn_info->frame_read)
{
store_info *store_info = i_ptr->store_rec;
/* Skip the clobbers. */
while (!store_info->is_set)
store_info = store_info->next;
if (store_info->group_id >= 0
&& rtx_group_vec[store_info->group_id]->frame_related)
remove_store = true;
}
if (remove_store)
{
if (dump_file && (dump_flags & TDF_DETAILS))
dump_insn_info ("removing from active", i_ptr);
active_local_stores_len--;
if (last)
last->next_local_store = i_ptr->next_local_store;
else
active_local_stores = i_ptr->next_local_store;
}
else
last = i_ptr;
i_ptr = i_ptr->next_local_store;
}
if (memset_call)
{
rtx args[3];
if (get_call_args (insn, memset_call, args, 3)
&& CONST_INT_P (args[1])
&& CONST_INT_P (args[2])
&& INTVAL (args[2]) > 0)
{
rtx mem = gen_rtx_MEM (BLKmode, args[0]);
set_mem_size (mem, INTVAL (args[2]));
body = gen_rtx_SET (mem, args[1]);
mems_found += record_store (body, bb_info);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "handling memset as BLKmode store\n");
if (mems_found == 1)
{
if (active_local_stores_len++ >= max_active_local_stores)
{
active_local_stores_len = 1;
active_local_stores = NULL;
}
insn_info->fixed_regs_live
= copy_fixed_regs (bb_info->regs_live);
insn_info->next_local_store = active_local_stores;
active_local_stores = insn_info;
}
}
else
clear_rhs_from_active_local_stores ();
}
}
else if (SIBLING_CALL_P (insn)
&& (reload_completed || HARD_FRAME_POINTER_IS_ARG_POINTER))
/* Arguments for a sibling call that are pushed to memory are passed
using the incoming argument pointer of the current function. After
reload that might be (and likely is) frame pointer based. And, if
it is a frame pointer on the target, even before reload we need to
kill frame pointer based stores. */
add_wild_read (bb_info);
else
/* Every other call, including pure functions, may read any memory
that is not relative to the frame. */
add_non_frame_wild_read (bb_info);
return;
}
/* Assuming that there are sets in these insns, we cannot delete
them. */
if ((GET_CODE (PATTERN (insn)) == CLOBBER)
|| volatile_refs_p (PATTERN (insn))
|| (!cfun->can_delete_dead_exceptions && !insn_nothrow_p (insn))
|| (RTX_FRAME_RELATED_P (insn))
|| find_reg_note (insn, REG_FRAME_RELATED_EXPR, NULL_RTX))
insn_info->cannot_delete = true;
body = PATTERN (insn);
if (GET_CODE (body) == PARALLEL)
{
int i;
for (i = 0; i < XVECLEN (body, 0); i++)
mems_found += record_store (XVECEXP (body, 0, i), bb_info);
}
else
mems_found += record_store (body, bb_info);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "mems_found = %d, cannot_delete = %s\n",
mems_found, insn_info->cannot_delete ? "true" : "false");
/* If we found some sets of mems, add it into the active_local_stores so
that it can be locally deleted if found dead or used for
replace_read and redundant constant store elimination. Otherwise mark
it as cannot delete. This simplifies the processing later. */
if (mems_found == 1)
{
if (active_local_stores_len++ >= max_active_local_stores)
{
active_local_stores_len = 1;
active_local_stores = NULL;
}
insn_info->fixed_regs_live = copy_fixed_regs (bb_info->regs_live);
insn_info->next_local_store = active_local_stores;
active_local_stores = insn_info;
}
else
insn_info->cannot_delete = true;
}
/* Remove BASE from the set of active_local_stores. This is a
callback from cselib that is used to get rid of the stores in
active_local_stores. */
static void
remove_useless_values (cselib_val *base)
{
insn_info_t insn_info = active_local_stores;
insn_info_t last = NULL;
while (insn_info)
{
store_info *store_info = insn_info->store_rec;
bool del = false;
/* If ANY of the store_infos match the cselib group that is
being deleted, then the insn cannot be deleted. */
while (store_info)
{
if ((store_info->group_id == -1)
&& (store_info->cse_base == base))
{
del = true;
break;
}
store_info = store_info->next;
}
if (del)
{
active_local_stores_len--;
if (last)
last->next_local_store = insn_info->next_local_store;
else
active_local_stores = insn_info->next_local_store;
free_store_info (insn_info);
}
else
last = insn_info;
insn_info = insn_info->next_local_store;
}
}
/* Do all of step 1. */
static void
dse_step1 (void)
{
basic_block bb;
bitmap regs_live = BITMAP_ALLOC (&reg_obstack);
cselib_init (0);
all_blocks = BITMAP_ALLOC (NULL);
bitmap_set_bit (all_blocks, ENTRY_BLOCK);
bitmap_set_bit (all_blocks, EXIT_BLOCK);
/* For -O1 reduce the maximum number of active local stores for RTL DSE
since this can consume huge amounts of memory (PR89115). */
int max_active_local_stores = param_max_dse_active_local_stores;
if (optimize < 2)
max_active_local_stores /= 10;
FOR_ALL_BB_FN (bb, cfun)
{
insn_info_t ptr;
bb_info_t bb_info = dse_bb_info_type_pool.allocate ();
memset (bb_info, 0, sizeof (dse_bb_info_type));
bitmap_set_bit (all_blocks, bb->index);
bb_info->regs_live = regs_live;
bitmap_copy (regs_live, DF_LR_IN (bb));
df_simulate_initialize_forwards (bb, regs_live);
bb_table[bb->index] = bb_info;
cselib_discard_hook = remove_useless_values;
if (bb->index >= NUM_FIXED_BLOCKS)
{
rtx_insn *insn;
active_local_stores = NULL;
active_local_stores_len = 0;
cselib_clear_table ();
/* Scan the insns. */
FOR_BB_INSNS (bb, insn)
{
if (INSN_P (insn))
scan_insn (bb_info, insn, max_active_local_stores);
cselib_process_insn (insn);
if (INSN_P (insn))
df_simulate_one_insn_forwards (bb, insn, regs_live);
}
/* This is something of a hack, because the global algorithm
is supposed to take care of the case where stores go dead
at the end of the function. However, the global
algorithm must take a more conservative view of block
mode reads than the local alg does. So to get the case
where you have a store to the frame followed by a non
overlapping block more read, we look at the active local
stores at the end of the function and delete all of the
frame and spill based ones. */
if (stores_off_frame_dead_at_return
&& (EDGE_COUNT (bb->succs) == 0
|| (single_succ_p (bb)
&& single_succ (bb) == EXIT_BLOCK_PTR_FOR_FN (cfun)
&& ! crtl->calls_eh_return)))
{
insn_info_t i_ptr = active_local_stores;
while (i_ptr)
{
store_info *store_info = i_ptr->store_rec;
/* Skip the clobbers. */
while (!store_info->is_set)
store_info = store_info->next;
if (store_info->group_id >= 0)
{
group_info *group = rtx_group_vec[store_info->group_id];
if (group->frame_related && !i_ptr->cannot_delete)
delete_dead_store_insn (i_ptr);
}
i_ptr = i_ptr->next_local_store;
}
}
/* Get rid of the loads that were discovered in
replace_read. Cselib is finished with this block. */
while (deferred_change_list)
{
deferred_change *next = deferred_change_list->next;
/* There is no reason to validate this change. That was
done earlier. */
*deferred_change_list->loc = deferred_change_list->reg;
deferred_change_pool.remove (deferred_change_list);
deferred_change_list = next;
}
/* Get rid of all of the cselib based store_infos in this
block and mark the containing insns as not being
deletable. */
ptr = bb_info->last_insn;
while (ptr)
{
if (ptr->contains_cselib_groups)
{
store_info *s_info = ptr->store_rec;
while (s_info && !s_info->is_set)
s_info = s_info->next;
if (s_info
&& s_info->redundant_reason
&& s_info->redundant_reason->insn
&& !ptr->cannot_delete)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Locally deleting insn %d "
"because insn %d stores the "
"same value and couldn't be "
"eliminated\n",
INSN_UID (ptr->insn),
INSN_UID (s_info->redundant_reason->insn));
delete_dead_store_insn (ptr);
}
free_store_info (ptr);
}
else
{
store_info *s_info;
/* Free at least positions_needed bitmaps. */
for (s_info = ptr->store_rec; s_info; s_info = s_info->next)
if (s_info->is_large)
{
BITMAP_FREE (s_info->positions_needed.large.bmap);
s_info->is_large = false;
}
}
ptr = ptr->prev_insn;
}
cse_store_info_pool.release ();
}
bb_info->regs_live = NULL;
}
BITMAP_FREE (regs_live);
cselib_finish ();
rtx_group_table->empty ();
}
/*----------------------------------------------------------------------------
Second step.
Assign each byte position in the stores that we are going to
analyze globally to a position in the bitmaps. Returns true if
there are any bit positions assigned.
----------------------------------------------------------------------------*/
static void
dse_step2_init (void)
{
unsigned int i;
group_info *group;
FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
{
/* For all non stack related bases, we only consider a store to
be deletable if there are two or more stores for that
position. This is because it takes one store to make the
other store redundant. However, for the stores that are
stack related, we consider them if there is only one store
for the position. We do this because the stack related
stores can be deleted if their is no read between them and
the end of the function.
To make this work in the current framework, we take the stack
related bases add all of the bits from store1 into store2.
This has the effect of making the eligible even if there is
only one store. */
if (stores_off_frame_dead_at_return && group->frame_related)
{
bitmap_ior_into (group->store2_n, group->store1_n);
bitmap_ior_into (group->store2_p, group->store1_p);
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "group %d is frame related ", i);
}
group->offset_map_size_n++;
group->offset_map_n = XOBNEWVEC (&dse_obstack, int,
group->offset_map_size_n);
group->offset_map_size_p++;
group->offset_map_p = XOBNEWVEC (&dse_obstack, int,
group->offset_map_size_p);
group->process_globally = false;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "group %d(%d+%d): ", i,
(int)bitmap_count_bits (group->store2_n),
(int)bitmap_count_bits (group->store2_p));
bitmap_print (dump_file, group->store2_n, "n ", " ");
bitmap_print (dump_file, group->store2_p, "p ", "\n");
}
}
}
/* Init the offset tables. */
static bool
dse_step2 (void)
{
unsigned int i;
group_info *group;
/* Position 0 is unused because 0 is used in the maps to mean
unused. */
current_position = 1;
FOR_EACH_VEC_ELT (rtx_group_vec, i, group)
{
bitmap_iterator bi;
unsigned int j;
memset (group->offset_map_n, 0, sizeof (int) * group->offset_map_size_n);
memset (group->offset_map_p, 0, sizeof (int) * group->offset_map_size_p);
bitmap_clear (group->group_kill);
EXECUTE_IF_SET_IN_BITMAP (group->store2_n, 0, j, bi)
{
bitmap_set_bit (group->group_kill, current_position);
if (bitmap_bit_p (group->escaped_n, j))
bitmap_set_bit (kill_on_calls, current_position);
group->offset_map_n[j] = current_position++;
group->process_globally = true;
}
EXECUTE_IF_SET_IN_BITMAP (group->store2_p, 0, j, bi)
{
bitmap_set_bit (group->group_kill, current_position);
if (bitmap_bit_p (group->escaped_p, j))
bitmap_set_bit (kill_on_calls, current_position);
group->offset_map_p[j] = current_position++;
group->process_globally = true;
}
}
return current_position != 1;