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/* Rewrite a program in Normal form into SSA.
Copyright (C) 2001-2021 Free Software Foundation, Inc.
Contributed by Diego Novillo <dnovillo@redhat.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/>. */
#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "rtl.h"
#include "tree.h"
#include "gimple.h"
#include "tree-pass.h"
#include "ssa.h"
#include "gimple-pretty-print.h"
#include "diagnostic-core.h"
#include "langhooks.h"
#include "cfganal.h"
#include "gimple-iterator.h"
#include "tree-cfg.h"
#include "tree-into-ssa.h"
#include "tree-dfa.h"
#include "tree-ssa.h"
#include "domwalk.h"
#include "statistics.h"
#include "stringpool.h"
#include "attribs.h"
#include "asan.h"
#include "attr-fnspec.h"
#define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
/* This file builds the SSA form for a function as described in:
R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
Computing Static Single Assignment Form and the Control Dependence
Graph. ACM Transactions on Programming Languages and Systems,
13(4):451-490, October 1991. */
/* Structure to map a variable VAR to the set of blocks that contain
definitions for VAR. */
struct def_blocks
{
/* Blocks that contain definitions of VAR. Bit I will be set if the
Ith block contains a definition of VAR. */
bitmap def_blocks;
/* Blocks that contain a PHI node for VAR. */
bitmap phi_blocks;
/* Blocks where VAR is live-on-entry. Similar semantics as
DEF_BLOCKS. */
bitmap livein_blocks;
};
/* Stack of trees used to restore the global currdefs to its original
state after completing rewriting of a block and its dominator
children. Its elements have the following properties:
- An SSA_NAME (N) indicates that the current definition of the
underlying variable should be set to the given SSA_NAME. If the
symbol associated with the SSA_NAME is not a GIMPLE register, the
next slot in the stack must be a _DECL node (SYM). In this case,
the name N in the previous slot is the current reaching
definition for SYM.
- A _DECL node indicates that the underlying variable has no
current definition.
- A NULL node at the top entry is used to mark the last slot
associated with the current block. */
static vec<tree> block_defs_stack;
/* Set of existing SSA names being replaced by update_ssa. */
static sbitmap old_ssa_names;
/* Set of new SSA names being added by update_ssa. Note that both
NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
the operations done on them are presence tests. */
static sbitmap new_ssa_names;
static sbitmap interesting_blocks;
/* Set of SSA names that have been marked to be released after they
were registered in the replacement table. They will be finally
released after we finish updating the SSA web. */
bitmap names_to_release;
/* vec of vec of PHIs to rewrite in a basic block. Element I corresponds
the to basic block with index I. Allocated once per compilation, *not*
released between different functions. */
static vec< vec<gphi *> > phis_to_rewrite;
/* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
static bitmap blocks_with_phis_to_rewrite;
/* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
to grow as the callers to create_new_def_for will create new names on
the fly.
FIXME. Currently set to 1/3 to avoid frequent reallocations but still
need to find a reasonable growth strategy. */
#define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
/* The function the SSA updating data structures have been initialized for.
NULL if they need to be initialized by create_new_def_for. */
static struct function *update_ssa_initialized_fn = NULL;
/* Global data to attach to the main dominator walk structure. */
struct mark_def_sites_global_data
{
/* This bitmap contains the variables which are set before they
are used in a basic block. */
bitmap kills;
};
/* It is advantageous to avoid things like life analysis for variables which
do not need PHI nodes. This enum describes whether or not a particular
variable may need a PHI node. */
enum need_phi_state {
/* This is the default. If we are still in this state after finding
all the definition and use sites, then we will assume the variable
needs PHI nodes. This is probably an overly conservative assumption. */
NEED_PHI_STATE_UNKNOWN,
/* This state indicates that we have seen one or more sets of the
variable in a single basic block and that the sets dominate all
uses seen so far. If after finding all definition and use sites
we are still in this state, then the variable does not need any
PHI nodes. */
NEED_PHI_STATE_NO,
/* This state indicates that we have either seen multiple definitions of
the variable in multiple blocks, or that we encountered a use in a
block that was not dominated by the block containing the set(s) of
this variable. This variable is assumed to need PHI nodes. */
NEED_PHI_STATE_MAYBE
};
/* Information stored for both SSA names and decls. */
struct common_info
{
/* This field indicates whether or not the variable may need PHI nodes.
See the enum's definition for more detailed information about the
states. */
ENUM_BITFIELD (need_phi_state) need_phi_state : 2;
/* The current reaching definition replacing this var. */
tree current_def;
/* Definitions for this var. */
struct def_blocks def_blocks;
};
/* Information stored for decls. */
struct var_info
{
/* The variable. */
tree var;
/* Information stored for both SSA names and decls. */
common_info info;
};
/* VAR_INFOS hashtable helpers. */
struct var_info_hasher : free_ptr_hash <var_info>
{
static inline hashval_t hash (const value_type &);
static inline bool equal (const value_type &, const compare_type &);
};
inline hashval_t
var_info_hasher::hash (const value_type &p)
{
return DECL_UID (p->var);
}
inline bool
var_info_hasher::equal (const value_type &p1, const compare_type &p2)
{
return p1->var == p2->var;
}
/* Each entry in VAR_INFOS contains an element of type STRUCT
VAR_INFO_D. */
static hash_table<var_info_hasher> *var_infos;
/* Information stored for SSA names. */
struct ssa_name_info
{
/* Age of this record (so that info_for_ssa_name table can be cleared
quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
are assumed to be null. */
unsigned age;
/* Replacement mappings, allocated from update_ssa_obstack. */
bitmap repl_set;
/* Information stored for both SSA names and decls. */
common_info info;
};
static vec<ssa_name_info *> info_for_ssa_name;
static unsigned current_info_for_ssa_name_age;
static bitmap_obstack update_ssa_obstack;
/* The set of blocks affected by update_ssa. */
static bitmap blocks_to_update;
/* The main entry point to the SSA renamer (rewrite_blocks) may be
called several times to do different, but related, tasks.
Initially, we need it to rename the whole program into SSA form.
At other times, we may need it to only rename into SSA newly
exposed symbols. Finally, we can also call it to incrementally fix
an already built SSA web. */
enum rewrite_mode {
/* Convert the whole function into SSA form. */
REWRITE_ALL,
/* Incrementally update the SSA web by replacing existing SSA
names with new ones. See update_ssa for details. */
REWRITE_UPDATE
};
/* The set of symbols we ought to re-write into SSA form in update_ssa. */
static bitmap symbols_to_rename_set;
static vec<tree> symbols_to_rename;
/* Mark SYM for renaming. */
static void
mark_for_renaming (tree sym)
{
if (!symbols_to_rename_set)
symbols_to_rename_set = BITMAP_ALLOC (NULL);
if (bitmap_set_bit (symbols_to_rename_set, DECL_UID (sym)))
symbols_to_rename.safe_push (sym);
}
/* Return true if SYM is marked for renaming. */
static bool
marked_for_renaming (tree sym)
{
if (!symbols_to_rename_set || sym == NULL_TREE)
return false;
return bitmap_bit_p (symbols_to_rename_set, DECL_UID (sym));
}
/* Return true if STMT needs to be rewritten. When renaming a subset
of the variables, not all statements will be processed. This is
decided in mark_def_sites. */
static inline bool
rewrite_uses_p (gimple *stmt)
{
return gimple_visited_p (stmt);
}
/* Set the rewrite marker on STMT to the value given by REWRITE_P. */
static inline void
set_rewrite_uses (gimple *stmt, bool rewrite_p)
{
gimple_set_visited (stmt, rewrite_p);
}
/* Return true if the DEFs created by statement STMT should be
registered when marking new definition sites. This is slightly
different than rewrite_uses_p: it's used by update_ssa to
distinguish statements that need to have both uses and defs
processed from those that only need to have their defs processed.
Statements that define new SSA names only need to have their defs
registered, but they don't need to have their uses renamed. */
static inline bool
register_defs_p (gimple *stmt)
{
return gimple_plf (stmt, GF_PLF_1) != 0;
}
/* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
static inline void
set_register_defs (gimple *stmt, bool register_defs_p)
{
gimple_set_plf (stmt, GF_PLF_1, register_defs_p);
}
/* Get the information associated with NAME. */
static inline ssa_name_info *
get_ssa_name_ann (tree name)
{
unsigned ver = SSA_NAME_VERSION (name);
unsigned len = info_for_ssa_name.length ();
struct ssa_name_info *info;
/* Re-allocate the vector at most once per update/into-SSA. */
if (ver >= len)
info_for_ssa_name.safe_grow_cleared (num_ssa_names, true);
/* But allocate infos lazily. */
info = info_for_ssa_name[ver];
if (!info)
{
info = XCNEW (struct ssa_name_info);
info->age = current_info_for_ssa_name_age;
info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
info_for_ssa_name[ver] = info;
}
if (info->age < current_info_for_ssa_name_age)
{
info->age = current_info_for_ssa_name_age;
info->repl_set = NULL;
info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
info->info.current_def = NULL_TREE;
info->info.def_blocks.def_blocks = NULL;
info->info.def_blocks.phi_blocks = NULL;
info->info.def_blocks.livein_blocks = NULL;
}
return info;
}
/* Return and allocate the auxiliar information for DECL. */
static inline var_info *
get_var_info (tree decl)
{
var_info vi;
var_info **slot;
vi.var = decl;
slot = var_infos->find_slot_with_hash (&vi, DECL_UID (decl), INSERT);
if (*slot == NULL)
{
var_info *v = XCNEW (var_info);
v->var = decl;
*slot = v;
return v;
}
return *slot;
}
/* Clears info for SSA names. */
static void
clear_ssa_name_info (void)
{
current_info_for_ssa_name_age++;
/* If current_info_for_ssa_name_age wraps we use stale information.
Asser that this does not happen. */
gcc_assert (current_info_for_ssa_name_age != 0);
}
/* Get access to the auxiliar information stored per SSA name or decl. */
static inline common_info *
get_common_info (tree var)
{
if (TREE_CODE (var) == SSA_NAME)
return &get_ssa_name_ann (var)->info;
else
return &get_var_info (var)->info;
}
/* Return the current definition for VAR. */
tree
get_current_def (tree var)
{
return get_common_info (var)->current_def;
}
/* Sets current definition of VAR to DEF. */
void
set_current_def (tree var, tree def)
{
get_common_info (var)->current_def = def;
}
/* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
all statements in basic block BB. */
static void
initialize_flags_in_bb (basic_block bb)
{
gimple *stmt;
gimple_stmt_iterator gsi;
for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
gimple *phi = gsi_stmt (gsi);
set_rewrite_uses (phi, false);
set_register_defs (phi, false);
}
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
{
stmt = gsi_stmt (gsi);
/* We are going to use the operand cache API, such as
SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
cache for each statement should be up-to-date. */
gcc_checking_assert (!gimple_modified_p (stmt));
set_rewrite_uses (stmt, false);
set_register_defs (stmt, false);
}
}
/* Mark block BB as interesting for update_ssa. */
static void
mark_block_for_update (basic_block bb)
{
gcc_checking_assert (blocks_to_update != NULL);
if (!bitmap_set_bit (blocks_to_update, bb->index))
return;
initialize_flags_in_bb (bb);
}
/* Return the set of blocks where variable VAR is defined and the blocks
where VAR is live on entry (livein). If no entry is found in
DEF_BLOCKS, a new one is created and returned. */
static inline def_blocks *
get_def_blocks_for (common_info *info)
{
def_blocks *db_p = &info->def_blocks;
if (!db_p->def_blocks)
{
db_p->def_blocks = BITMAP_ALLOC (&update_ssa_obstack);
db_p->phi_blocks = BITMAP_ALLOC (&update_ssa_obstack);
db_p->livein_blocks = BITMAP_ALLOC (&update_ssa_obstack);
}
return db_p;
}
/* Mark block BB as the definition site for variable VAR. PHI_P is true if
VAR is defined by a PHI node. */
static void
set_def_block (tree var, basic_block bb, bool phi_p)
{
def_blocks *db_p;
common_info *info;
info = get_common_info (var);
db_p = get_def_blocks_for (info);
/* Set the bit corresponding to the block where VAR is defined. */
bitmap_set_bit (db_p->def_blocks, bb->index);
if (phi_p)
bitmap_set_bit (db_p->phi_blocks, bb->index);
/* Keep track of whether or not we may need to insert PHI nodes.
If we are in the UNKNOWN state, then this is the first definition
of VAR. Additionally, we have not seen any uses of VAR yet, so
we do not need a PHI node for this variable at this time (i.e.,
transition to NEED_PHI_STATE_NO).
If we are in any other state, then we either have multiple definitions
of this variable occurring in different blocks or we saw a use of the
variable which was not dominated by the block containing the
definition(s). In this case we may need a PHI node, so enter
state NEED_PHI_STATE_MAYBE. */
if (info->need_phi_state == NEED_PHI_STATE_UNKNOWN)
info->need_phi_state = NEED_PHI_STATE_NO;
else
info->need_phi_state = NEED_PHI_STATE_MAYBE;
}
/* Mark block BB as having VAR live at the entry to BB. */
static void
set_livein_block (tree var, basic_block bb)
{
common_info *info;
def_blocks *db_p;
info = get_common_info (var);
db_p = get_def_blocks_for (info);
/* Set the bit corresponding to the block where VAR is live in. */
bitmap_set_bit (db_p->livein_blocks, bb->index);
/* Keep track of whether or not we may need to insert PHI nodes.
If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
by the single block containing the definition(s) of this variable. If
it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
NEED_PHI_STATE_MAYBE. */
if (info->need_phi_state == NEED_PHI_STATE_NO)
{
int def_block_index = bitmap_first_set_bit (db_p->def_blocks);
if (def_block_index == -1
|| ! dominated_by_p (CDI_DOMINATORS, bb,
BASIC_BLOCK_FOR_FN (cfun, def_block_index)))
info->need_phi_state = NEED_PHI_STATE_MAYBE;
}
else
info->need_phi_state = NEED_PHI_STATE_MAYBE;
}
/* Return true if NAME is in OLD_SSA_NAMES. */
static inline bool
is_old_name (tree name)
{
unsigned ver = SSA_NAME_VERSION (name);
if (!old_ssa_names)
return false;
return (ver < SBITMAP_SIZE (old_ssa_names)
&& bitmap_bit_p (old_ssa_names, ver));
}
/* Return true if NAME is in NEW_SSA_NAMES. */
static inline bool
is_new_name (tree name)
{
unsigned ver = SSA_NAME_VERSION (name);
if (!new_ssa_names)
return false;
return (ver < SBITMAP_SIZE (new_ssa_names)
&& bitmap_bit_p (new_ssa_names, ver));
}
/* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
static inline bitmap
names_replaced_by (tree new_tree)
{
return get_ssa_name_ann (new_tree)->repl_set;
}
/* Add OLD to REPL_TBL[NEW_TREE].SET. */
static inline void
add_to_repl_tbl (tree new_tree, tree old)
{
bitmap *set = &get_ssa_name_ann (new_tree)->repl_set;
if (!*set)
*set = BITMAP_ALLOC (&update_ssa_obstack);
bitmap_set_bit (*set, SSA_NAME_VERSION (old));
}
/* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
represents the set of names O_1 ... O_j replaced by N_i. This is
used by update_ssa and its helpers to introduce new SSA names in an
already formed SSA web. */
static void
add_new_name_mapping (tree new_tree, tree old)
{
/* OLD and NEW_TREE must be different SSA names for the same symbol. */
gcc_checking_assert (new_tree != old
&& SSA_NAME_VAR (new_tree) == SSA_NAME_VAR (old));
/* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
caller may have created new names since the set was created. */
if (SBITMAP_SIZE (new_ssa_names) <= num_ssa_names - 1)
{
unsigned int new_sz = num_ssa_names + NAME_SETS_GROWTH_FACTOR;
new_ssa_names = sbitmap_resize (new_ssa_names, new_sz, 0);
old_ssa_names = sbitmap_resize (old_ssa_names, new_sz, 0);
}
/* Update the REPL_TBL table. */
add_to_repl_tbl (new_tree, old);
/* If OLD had already been registered as a new name, then all the
names that OLD replaces should also be replaced by NEW_TREE. */
if (is_new_name (old))
bitmap_ior_into (names_replaced_by (new_tree), names_replaced_by (old));
/* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
respectively. */
bitmap_set_bit (new_ssa_names, SSA_NAME_VERSION (new_tree));
bitmap_set_bit (old_ssa_names, SSA_NAME_VERSION (old));
}
/* Call back for walk_dominator_tree used to collect definition sites
for every variable in the function. For every statement S in block
BB:
1- Variables defined by S in the DEFS of S are marked in the bitmap
KILLS.
2- If S uses a variable VAR and there is no preceding kill of VAR,
then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
This information is used to determine which variables are live
across block boundaries to reduce the number of PHI nodes
we create. */
static void
mark_def_sites (basic_block bb, gimple *stmt, bitmap kills)
{
tree def;
use_operand_p use_p;
ssa_op_iter iter;
/* Since this is the first time that we rewrite the program into SSA
form, force an operand scan on every statement. */
update_stmt (stmt);
gcc_checking_assert (blocks_to_update == NULL);
set_register_defs (stmt, false);
set_rewrite_uses (stmt, false);
if (is_gimple_debug (stmt))
{
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
{
tree sym = USE_FROM_PTR (use_p);
gcc_checking_assert (DECL_P (sym));
set_rewrite_uses (stmt, true);
}
if (rewrite_uses_p (stmt))
bitmap_set_bit (interesting_blocks, bb->index);
return;
}
/* If a variable is used before being set, then the variable is live
across a block boundary, so mark it live-on-entry to BB. */
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
{
tree sym = USE_FROM_PTR (use_p);
if (TREE_CODE (sym) == SSA_NAME)
continue;
gcc_checking_assert (DECL_P (sym));
if (!bitmap_bit_p (kills, DECL_UID (sym)))
set_livein_block (sym, bb);
set_rewrite_uses (stmt, true);
}
/* Now process the defs. Mark BB as the definition block and add
each def to the set of killed symbols. */
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
{
if (TREE_CODE (def) == SSA_NAME)
continue;
gcc_checking_assert (DECL_P (def));
set_def_block (def, bb, false);
bitmap_set_bit (kills, DECL_UID (def));
set_register_defs (stmt, true);
}
/* If we found the statement interesting then also mark the block BB
as interesting. */
if (rewrite_uses_p (stmt) || register_defs_p (stmt))
bitmap_set_bit (interesting_blocks, bb->index);
}
/* Structure used by prune_unused_phi_nodes to record bounds of the intervals
in the dfs numbering of the dominance tree. */
struct dom_dfsnum
{
/* Basic block whose index this entry corresponds to. */
unsigned bb_index;
/* The dfs number of this node. */
unsigned dfs_num;
};
/* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
for qsort. */
static int
cmp_dfsnum (const void *a, const void *b)
{
const struct dom_dfsnum *const da = (const struct dom_dfsnum *) a;
const struct dom_dfsnum *const db = (const struct dom_dfsnum *) b;
return (int) da->dfs_num - (int) db->dfs_num;
}
/* Among the intervals starting at the N points specified in DEFS, find
the one that contains S, and return its bb_index. */
static unsigned
find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s)
{
unsigned f = 0, t = n, m;
while (t > f + 1)
{
m = (f + t) / 2;
if (defs[m].dfs_num <= s)
f = m;
else
t = m;
}
return defs[f].bb_index;
}
/* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
KILLS is a bitmap of blocks where the value is defined before any use. */
static void
prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses)
{
bitmap_iterator bi;
unsigned i, b, p, u, top;
bitmap live_phis;
basic_block def_bb, use_bb;
edge e;
edge_iterator ei;
bitmap to_remove;
struct dom_dfsnum *defs;
unsigned n_defs, adef;
if (bitmap_empty_p (uses))
{
bitmap_clear (phis);
return;
}
/* The phi must dominate a use, or an argument of a live phi. Also, we
do not create any phi nodes in def blocks, unless they are also livein. */
to_remove = BITMAP_ALLOC (NULL);
bitmap_and_compl (to_remove, kills, uses);
bitmap_and_compl_into (phis, to_remove);
if (bitmap_empty_p (phis))
{
BITMAP_FREE (to_remove);
return;
}
/* We want to remove the unnecessary phi nodes, but we do not want to compute
liveness information, as that may be linear in the size of CFG, and if
there are lot of different variables to rewrite, this may lead to quadratic
behavior.
Instead, we basically emulate standard dce. We put all uses to worklist,
then for each of them find the nearest def that dominates them. If this
def is a phi node, we mark it live, and if it was not live before, we
add the predecessors of its basic block to the worklist.
To quickly locate the nearest def that dominates use, we use dfs numbering
of the dominance tree (that is already available in order to speed up
queries). For each def, we have the interval given by the dfs number on
entry to and on exit from the corresponding subtree in the dominance tree.
The nearest dominator for a given use is the smallest of these intervals
that contains entry and exit dfs numbers for the basic block with the use.
If we store the bounds for all the uses to an array and sort it, we can
locate the nearest dominating def in logarithmic time by binary search.*/
bitmap_ior (to_remove, kills, phis);
n_defs = bitmap_count_bits (to_remove);
defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1);
defs[0].bb_index = 1;
defs[0].dfs_num = 0;
adef = 1;
EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi)
{
def_bb = BASIC_BLOCK_FOR_FN (cfun, i);
defs[adef].bb_index = i;
defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb);
defs[adef + 1].bb_index = i;
defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb);
adef += 2;
}
BITMAP_FREE (to_remove);
gcc_assert (adef == 2 * n_defs + 1);
qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum);
gcc_assert (defs[0].bb_index == 1);
/* Now each DEFS entry contains the number of the basic block to that the
dfs number corresponds. Change them to the number of basic block that
corresponds to the interval following the dfs number. Also, for the
dfs_out numbers, increase the dfs number by one (so that it corresponds
to the start of the following interval, not to the end of the current
one). We use WORKLIST as a stack. */
auto_vec<int> worklist (n_defs + 1);
worklist.quick_push (1);
top = 1;
n_defs = 1;
for (i = 1; i < adef; i++)
{
b = defs[i].bb_index;
if (b == top)
{
/* This is a closing element. Interval corresponding to the top
of the stack after removing it follows. */
worklist.pop ();
top = worklist[worklist.length () - 1];
defs[n_defs].bb_index = top;
defs[n_defs].dfs_num = defs[i].dfs_num + 1;
}
else
{
/* Opening element. Nothing to do, just push it to the stack and move
it to the correct position. */
defs[n_defs].bb_index = defs[i].bb_index;
defs[n_defs].dfs_num = defs[i].dfs_num;
worklist.quick_push (b);
top = b;
}
/* If this interval starts at the same point as the previous one, cancel
the previous one. */
if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num)
defs[n_defs - 1].bb_index = defs[n_defs].bb_index;
else
n_defs++;
}
worklist.pop ();
gcc_assert (worklist.is_empty ());
/* Now process the uses. */
live_phis = BITMAP_ALLOC (NULL);
EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi)
{
worklist.safe_push (i);
}
while (!worklist.is_empty ())
{
b = worklist.pop ();
if (b == ENTRY_BLOCK)
continue;
/* If there is a phi node in USE_BB, it is made live. Otherwise,
find the def that dominates the immediate dominator of USE_BB
(the kill in USE_BB does not dominate the use). */
if (bitmap_bit_p (phis, b))
p = b;
else
{
use_bb = get_immediate_dominator (CDI_DOMINATORS,
BASIC_BLOCK_FOR_FN (cfun, b));
p = find_dfsnum_interval (defs, n_defs,
bb_dom_dfs_in (CDI_DOMINATORS, use_bb));
if (!bitmap_bit_p (phis, p))
continue;
}
/* If the phi node is already live, there is nothing to do. */
if (!bitmap_set_bit (live_phis, p))
continue;
/* Add the new uses to the worklist. */
def_bb = BASIC_BLOCK_FOR_FN (cfun, p);
FOR_EACH_EDGE (e, ei, def_bb->preds)
{
u = e->src->index;
if (bitmap_bit_p (uses, u))
continue;
/* In case there is a kill directly in the use block, do not record
the use (this is also necessary for correctness, as we assume that
uses dominated by a def directly in their block have been filtered
out before). */
if (bitmap_bit_p (kills, u))
continue;
bitmap_set_bit (uses, u);
worklist.safe_push (u);
}
}
bitmap_copy (phis, live_phis);
BITMAP_FREE (live_phis);
free (defs);
}
/* Return the set of blocks where variable VAR is defined and the blocks
where VAR is live on entry (livein). Return NULL, if no entry is
found in DEF_BLOCKS. */
static inline def_blocks *
find_def_blocks_for (tree var)
{
def_blocks *p = &get_common_info (var)->def_blocks;
if (!p->def_blocks)
return NULL;
return p;
}
/* Marks phi node PHI in basic block BB for rewrite. */
static void
mark_phi_for_rewrite (basic_block bb, gphi *phi)
{
vec<gphi *> phis;
unsigned n, idx = bb->index;
if (rewrite_uses_p (phi))
return;
set_rewrite_uses (phi, true);
if (!blocks_with_phis_to_rewrite)
return;
if (bitmap_set_bit (blocks_with_phis_to_rewrite, idx))
{
n = (unsigned) last_basic_block_for_fn (cfun) + 1;
if (phis_to_rewrite.length () < n)
phis_to_rewrite.safe_grow_cleared (n, true);
phis = phis_to_rewrite[idx];
gcc_assert (!phis.exists ());
phis.create (10);
}
else
phis = phis_to_rewrite[idx];
phis.safe_push (phi);
phis_to_rewrite[idx] = phis;
}
/* Insert PHI nodes for variable VAR using the iterated dominance
frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
function assumes that the caller is incrementally updating the
existing SSA form, in which case VAR may be an SSA name instead of
a symbol.
PHI_INSERTION_POINTS is updated to reflect nodes that already had a
PHI node for VAR. On exit, only the nodes that received a PHI node
for VAR will be present in PHI_INSERTION_POINTS. */
static void
insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
{
unsigned bb_index;
edge e;
gphi *phi;
basic_block bb;
bitmap_iterator bi;
def_blocks *def_map = find_def_blocks_for (var);
/* Remove the blocks where we already have PHI nodes for VAR. */
bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
/* Remove obviously useless phi nodes. */
prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks,
def_map->livein_blocks);
/* And insert the PHI nodes. */
EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi)
{
bb = BASIC_BLOCK_FOR_FN (cfun, bb_index);
if (update_p)
mark_block_for_update (bb);
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "creating PHI node in block #%d for ", bb_index);
print_generic_expr (dump_file, var, TDF_SLIM);
fprintf (dump_file, "\n");
}
phi = NULL;
if (TREE_CODE (var) == SSA_NAME)
{
/* If we are rewriting SSA names, create the LHS of the PHI
node by duplicating VAR. This is useful in the case of
pointers, to also duplicate pointer attributes (alias
information, in particular). */
edge_iterator ei;
tree new_lhs;
gcc_checking_assert (update_p);
new_lhs = duplicate_ssa_name (var, NULL);
phi = create_phi_node (new_lhs, bb);
add_new_name_mapping (new_lhs, var);
/* Add VAR to every argument slot of PHI. We need VAR in
every argument so that rewrite_update_phi_arguments knows
which name is this PHI node replacing. If VAR is a
symbol marked for renaming, this is not necessary, the
renamer will use the symbol on the LHS to get its
reaching definition. */
FOR_EACH_EDGE (e, ei, bb->preds)
add_phi_arg (phi, var, e, UNKNOWN_LOCATION);
}
else
{
tree tracked_var;
gcc_checking_assert (DECL_P (var));
phi = create_phi_node (var, bb);
tracked_var = target_for_debug_bind (var);
if (tracked_var)
{
gimple *note = gimple_build_debug_bind (tracked_var,
PHI_RESULT (phi),
phi);
gimple_stmt_iterator si = gsi_after_labels (bb);
gsi_insert_before (&si, note, GSI_SAME_STMT);
}
}
/* Mark this PHI node as interesting for update_ssa. */
set_register_defs (phi, true);
mark_phi_for_rewrite (bb, phi);
}
}
/* Sort var_infos after DECL_UID of their var. */
static int
insert_phi_nodes_compare_var_infos (const void *a, const void *b)
{
const var_info *defa = *(var_info * const *)a;
const var_info *defb = *(var_info * const *)b;
if (DECL_UID (defa->var) < DECL_UID (defb->var))
return -1;
else
return 1;
}
/* Insert PHI nodes at the dominance frontier of blocks with variable
definitions. DFS contains the dominance frontier information for
the flowgraph. */
static void
insert_phi_nodes (bitmap_head *dfs)
{
hash_table<var_info_hasher>::iterator hi;
unsigned i;
var_info *info;
/* When the gimplifier introduces SSA names it cannot easily avoid
situations where abnormal edges added by CFG construction break
the use-def dominance requirement. For this case rewrite SSA
names with broken use-def dominance out-of-SSA and register them
for PHI insertion. We only need to do this if abnormal edges
can appear in the function. */
tree name;
if (cfun->calls_setjmp
|| cfun->has_nonlocal_label)
FOR_EACH_SSA_NAME (i, name, cfun)
{
gimple *def_stmt = SSA_NAME_DEF_STMT (name);
if (SSA_NAME_IS_DEFAULT_DEF (name))
continue;
basic_block def_bb = gimple_bb (def_stmt);
imm_use_iterator it;
gimple *use_stmt;
bool need_phis = false;
FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
{
basic_block use_bb = gimple_bb (use_stmt);
if (use_bb != def_bb
&& ! dominated_by_p (CDI_DOMINATORS, use_bb, def_bb))
need_phis = true;
}
if (need_phis)
{
tree var = create_tmp_reg (TREE_TYPE (name));
use_operand_p use_p;
FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
{
basic_block use_bb = gimple_bb (use_stmt);
FOR_EACH_IMM_USE_ON_STMT (use_p, it)
SET_USE (use_p, var);
update_stmt (use_stmt);
set_livein_block (var, use_bb);
set_rewrite_uses (use_stmt, true);
bitmap_set_bit (interesting_blocks, use_bb->index);
}
def_operand_p def_p;
ssa_op_iter dit;
FOR_EACH_SSA_DEF_OPERAND (def_p, def_stmt, dit, SSA_OP_DEF)
if (DEF_FROM_PTR (def_p) == name)
SET_DEF (def_p, var);
update_stmt (def_stmt);
set_def_block (var, def_bb, false);
set_register_defs (def_stmt, true);
bitmap_set_bit (interesting_blocks, def_bb->index);
release_ssa_name (name);
}
}
auto_vec<var_info *> vars (var_infos->elements ());
FOR_EACH_HASH_TABLE_ELEMENT (*var_infos, info, var_info_p, hi)
if (info->info.need_phi_state != NEED_PHI_STATE_NO)
vars.quick_push (info);
/* Do two stages to avoid code generation differences for UID
differences but no UID ordering differences. */
vars.qsort (insert_phi_nodes_compare_var_infos);
FOR_EACH_VEC_ELT (vars, i, info)
{
bitmap idf = compute_idf (info->info.def_blocks.def_blocks, dfs);
insert_phi_nodes_for (info->var, idf, false);
BITMAP_FREE (idf);
}
}
/* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
register DEF (an SSA_NAME) to be a new definition for SYM. */
static void
register_new_def (tree def, tree sym)
{
common_info *info = get_common_info (sym);
tree currdef;
/* If this variable is set in a single basic block and all uses are
dominated by the set(s) in that single basic block, then there is
no reason to record anything for this variable in the block local
definition stacks. Doing so just wastes time and memory.
This is the same test to prune the set of variables which may
need PHI nodes. So we just use that information since it's already
computed and available for us to use. */
if (info->need_phi_state == NEED_PHI_STATE_NO)
{
info->current_def = def;
return;
}
currdef = info->current_def;
/* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
in the stack so that we know which symbol is being defined by
this SSA name when we unwind the stack. */
if (currdef && !is_gimple_reg (sym))
block_defs_stack.safe_push (sym);
/* Push the current reaching definition into BLOCK_DEFS_STACK. This
stack is later used by the dominator tree callbacks to restore
the reaching definitions for all the variables defined in the
block after a recursive visit to all its immediately dominated
blocks. If there is no current reaching definition, then just
record the underlying _DECL node. */
block_defs_stack.safe_push (currdef ? currdef : sym);
/* Set the current reaching definition for SYM to be DEF. */
info->current_def = def;
}
/* Perform a depth-first traversal of the dominator tree looking for
variables to rename. BB is the block where to start searching.
Renaming is a five step process:
1- Every definition made by PHI nodes at the start of the blocks is
registered as the current definition for the corresponding variable.
2- Every statement in BB is rewritten. USE and VUSE operands are
rewritten with their corresponding reaching definition. DEF and
VDEF targets are registered as new definitions.
3- All the PHI nodes in successor blocks of BB are visited. The
argument corresponding to BB is replaced with its current reaching
definition.
4- Recursively rewrite every dominator child block of BB.
5- Restore (in reverse order) the current reaching definition for every
new definition introduced in this block. This is done so that when
we return from the recursive call, all the current reaching
definitions are restored to the names that were valid in the
dominator parent of BB. */
/* Return the current definition for variable VAR. If none is found,
create a new SSA name to act as the zeroth definition for VAR. */
static tree
get_reaching_def (tree var)
{
common_info *info = get_common_info (var);
tree currdef;
/* Lookup the current reaching definition for VAR. */
currdef = info->current_def;
/* If there is no reaching definition for VAR, create and register a
default definition for it (if needed). */
if (currdef == NULL_TREE)
{
tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var);
if (! sym)
sym = create_tmp_reg (TREE_TYPE (var));
currdef = get_or_create_ssa_default_def (cfun, sym);
}
/* Return the current reaching definition for VAR, or the default
definition, if we had to create one. */
return currdef;
}
/* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
static void
rewrite_debug_stmt_uses (gimple *stmt)
{
use_operand_p use_p;
ssa_op_iter iter;
bool update = false;
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
{
tree var = USE_FROM_PTR (use_p), def;
common_info *info = get_common_info (var);
gcc_checking_assert (DECL_P (var));
def = info->current_def;
if (!def)
{
if (TREE_CODE (var) == PARM_DECL
&& single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun)))
{
gimple_stmt_iterator gsi
=
gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
int lim;
/* Search a few source bind stmts at the start of first bb to
see if a DEBUG_EXPR_DECL can't be reused. */
for (lim = 32;
!gsi_end_p (gsi) && lim > 0;
gsi_next (&gsi), lim--)
{
gimple *gstmt = gsi_stmt (gsi);
if (!gimple_debug_source_bind_p (gstmt))
break;
if (gimple_debug_source_bind_get_value (gstmt) == var)
{
def = gimple_debug_source_bind_get_var (gstmt);
if (TREE_CODE (def) == DEBUG_EXPR_DECL)
break;
else
def = NULL_TREE;
}
}
/* If not, add a new source bind stmt. */
if (def == NULL_TREE)
{
gimple *def_temp;
def = make_node (DEBUG_EXPR_DECL);
def_temp = gimple_build_debug_source_bind (def, var, NULL);
DECL_ARTIFICIAL (def) = 1;
TREE_TYPE (def) = TREE_TYPE (var);
SET_DECL_MODE (def, DECL_MODE (var));
gsi =
gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
gsi_insert_before (&gsi, def_temp, GSI_SAME_STMT);
}
update = true;
}
}
else
{
/* Check if info->current_def can be trusted. */
basic_block bb = gimple_bb (stmt);
basic_block def_bb
= SSA_NAME_IS_DEFAULT_DEF (def)
? NULL : gimple_bb (SSA_NAME_DEF_STMT (def));
/* If definition is in current bb, it is fine. */
if (bb == def_bb)
;
/* If definition bb doesn't dominate the current bb,
it can't be used. */
else if (def_bb && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
def = NULL;
/* If there is just one definition and dominates the current
bb, it is fine. */
else if (info->need_phi_state == NEED_PHI_STATE_NO)
;
else
{
def_blocks *db_p = get_def_blocks_for (info);
/* If there are some non-debug uses in the current bb,
it is fine. */
if (bitmap_bit_p (db_p->livein_blocks, bb->index))
;
/* Otherwise give up for now. */
else
def = NULL;
}
}
if (def == NULL)
{
gimple_debug_bind_reset_value (stmt);
update_stmt (stmt);
return;
}
SET_USE (use_p, def);
}
if (update)
update_stmt (stmt);
}
/* SSA Rewriting Step 2. Rewrite every variable used in each statement in
the block with its immediate reaching definitions. Update the current
definition of a variable when a new real or virtual definition is found. */
static void
rewrite_stmt (gimple_stmt_iterator *si)
{
use_operand_p use_p;
def_operand_p def_p;
ssa_op_iter iter;
gimple *stmt = gsi_stmt (*si);
/* If mark_def_sites decided that we don't need to rewrite this
statement, ignore it. */
gcc_assert (blocks_to_update == NULL);
if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Renaming statement ");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}
/* Step 1. Rewrite USES in the statement. */
if (rewrite_uses_p (stmt))
{
if (is_gimple_debug (stmt))
rewrite_debug_stmt_uses (stmt);
else
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
{
tree var = USE_FROM_PTR (use_p);
if (TREE_CODE (var) == SSA_NAME)
continue;
gcc_checking_assert (DECL_P (var));
SET_USE (use_p, get_reaching_def (var));
}
}
/* Step 2. Register the statement's DEF operands. */
if (register_defs_p (stmt))
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
{
tree var = DEF_FROM_PTR (def_p);
tree name;
tree tracked_var;
if (TREE_CODE (var) == SSA_NAME)
continue;
gcc_checking_assert (DECL_P (var));
if (gimple_clobber_p (stmt)
&& is_gimple_reg (var))
{
/* If we rewrite a DECL into SSA form then drop its
clobber stmts and replace uses with a new default def. */
gcc_checking_assert (VAR_P (var) && !gimple_vdef (stmt));
gsi_replace (si, gimple_build_nop (), true);
register_new_def (get_or_create_ssa_default_def (cfun, var), var);
break;
}
name = make_ssa_name (var, stmt);
SET_DEF (def_p, name);
register_new_def (DEF_FROM_PTR (def_p), var);
/* Do not insert debug stmts if the stmt ends the BB. */
if (stmt_ends_bb_p (stmt))
continue;
tracked_var = target_for_debug_bind (var);
if (tracked_var)
{
gimple *note = gimple_build_debug_bind (tracked_var, name, stmt);
gsi_insert_after (si, note, GSI_SAME_STMT);
}
}
}
/* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
PHI nodes. For every PHI node found, add a new argument containing the
current reaching definition for the variable and the edge through which
that definition is reaching the PHI node. */
static void
rewrite_add_phi_arguments (basic_block bb)
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
{
gphi *phi;
gphi_iterator gsi;
for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);
gsi_next (&gsi))
{
tree currdef, res;
location_t loc;
phi = gsi.phi ();
res = gimple_phi_result (phi);
currdef = get_reaching_def (SSA_NAME_VAR (res));
/* Virtual operand PHI args do not need a location. */
if (virtual_operand_p (res))
loc = UNKNOWN_LOCATION;
else
loc = gimple_location (SSA_NAME_DEF_STMT (currdef));
add_phi_arg (phi, currdef, e, loc);
}
}
}
class rewrite_dom_walker : public dom_walker
{
public:
rewrite_dom_walker (cdi_direction direction)
: dom_walker (direction, ALL_BLOCKS, NULL) {}
virtual edge before_dom_children (basic_block);
virtual void after_dom_children (basic_block);
};
/* SSA Rewriting Step 1. Initialization, create a block local stack
of reaching definitions for new SSA names produced in this block
(BLOCK_DEFS). Register new definitions for every PHI node in the
block. */
edge
rewrite_dom_walker::before_dom_children (basic_block bb)
{
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
/* Mark the unwind point for this block. */
block_defs_stack.safe_push (NULL_TREE);
/* Step 1. Register new definitions for every PHI node in the block.
Conceptually, all the PHI nodes are executed in parallel and each PHI
node introduces a new version for the associated variable. */
for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
gsi_next (&gsi))
{
tree result = gimple_phi_result (gsi_stmt (gsi));
register_new_def (result, SSA_NAME_VAR (result));
}
/* Step 2. Rewrite every variable used in each statement in the block
with its immediate reaching definitions. Update the current definition
of a variable when a new real or virtual definition is found. */
if (bitmap_bit_p (interesting_blocks, bb->index))
for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
gsi_next (&gsi))
rewrite_stmt (&gsi);
/* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
For every PHI node found, add a new argument containing the current
reaching definition for the variable and the edge through which that
definition is reaching the PHI node. */
rewrite_add_phi_arguments (bb);
return NULL;
}
/* Called after visiting all the statements in basic block BB and all
of its dominator children. Restore CURRDEFS to its original value. */
void
rewrite_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
{
/* Restore CURRDEFS to its original state. */
while (block_defs_stack.length () > 0)
{
tree tmp = block_defs_stack.pop ();
tree saved_def, var;
if (tmp == NULL_TREE)
break;
if (TREE_CODE (tmp) == SSA_NAME)
{
/* If we recorded an SSA_NAME, then make the SSA_NAME the
current definition of its underlying variable. Note that
if the SSA_NAME is not for a GIMPLE register, the symbol
being defined is stored in the next slot in the stack.
This mechanism is needed because an SSA name for a
non-register symbol may be the definition for more than
one symbol (e.g., SFTs, aliased variables, etc). */
saved_def = tmp;
var = SSA_NAME_VAR (saved_def);
if (!is_gimple_reg (var))
var = block_defs_stack.pop ();
}
else
{
/* If we recorded anything else, it must have been a _DECL
node and its current reaching definition must have been
NULL. */
saved_def = NULL;
var = tmp;
}
get_common_info (var)->current_def = saved_def;
}
}
/* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
DEBUG_FUNCTION void
debug_decl_set (bitmap set)
{
dump_decl_set (stderr, set);
fprintf (stderr, "\n");
}
/* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
stack up to a maximum of N levels. If N is -1, the whole stack is
dumped. New levels are created when the dominator tree traversal
used for renaming enters a new sub-tree. */
void
dump_defs_stack (FILE *file, int n)
{
int i, j;
fprintf (file, "\n\nRenaming stack");
if (n > 0)
fprintf (file, " (up to %d levels)", n);
fprintf (file, "\n\n");
i = 1;
fprintf (file, "Level %d (current level)\n", i);
for (j = (int) block_defs_stack.length () - 1; j >= 0; j--)
{
tree name, var;
name = block_defs_stack[j];
if (name == NULL_TREE)
{
i++;
if (n > 0 && i > n)
break;
fprintf (file, "\nLevel %d\n", i);
continue;
}
if (DECL_P (name))
{
var = name;
name = NULL_TREE;
}
else
{
var = SSA_NAME_VAR (name);
if (!is_gimple_reg (var))
{
j--;
var = block_defs_stack[j];
}
}
fprintf (file, " Previous CURRDEF (");
print_generic_expr (file, var);
fprintf (file, ") = ");
if (name)
print_generic_expr (file, name);
else
fprintf (file, "<NIL>");
fprintf (file, "\n");
}
}
/* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
stack up to a maximum of N levels. If N is -1, the whole stack is
dumped. New levels are created when the dominator tree traversal
used for renaming enters a new sub-tree. */
DEBUG_FUNCTION void
debug_defs_stack (int n)
{
dump_defs_stack (stderr, n);
}
/* Dump the current reaching definition of every symbol to FILE. */
void
dump_currdefs (FILE *file)
{
if (symbols_to_rename.is_empty ())
return;
fprintf (file, "\n\nCurrent reaching definitions\n\n");
for (tree var : symbols_to_rename)
{
common_info *info = get_common_info (var);
fprintf (file, "CURRDEF (");
print_generic_expr (file, var);
fprintf (file, ") = ");
if (info->current_def)
print_generic_expr (file, info->current_def);
else
fprintf (file, "<NIL>");
fprintf (file, "\n");
}
}
/* Dump the current reaching definition of every symbol to stderr. */
DEBUG_FUNCTION void
debug_currdefs (void)
{
dump_currdefs (stderr);
}
/* Dump SSA information to FILE. */
void
dump_tree_ssa (FILE *file)
{
const char *funcname
= lang_hooks.decl_printable_name (current_function_decl, 2);
fprintf (file, "SSA renaming information for %s\n\n", funcname);
dump_var_infos (file);
dump_defs_stack (file, -1);
dump_currdefs (file);
dump_tree_ssa_stats (file);
}
/* Dump SSA information to stderr. */
DEBUG_FUNCTION void
debug_tree_ssa (void)
{
dump_tree_ssa (stderr);
}
/* Dump statistics for the hash table HTAB. */
static void
htab_statistics (FILE *file, const hash_table<var_info_hasher> &htab)
{
fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
(long) htab.size (),
(long) htab.elements (),
htab.collisions ());
}
/* Dump SSA statistics on FILE. */
void
dump_tree_ssa_stats (FILE *file)
{
if (var_infos)
{
fprintf (file, "\nHash table statistics:\n");
fprintf (file, " var_infos: ");
htab_statistics (file, *var_infos);
fprintf (file, "\n");
}
}
/* Dump SSA statistics on stderr. */
DEBUG_FUNCTION void
debug_tree_ssa_stats (void)
{
dump_tree_ssa_stats (stderr);
}
/* Callback for htab_traverse to dump the VAR_INFOS hash table. */
int
debug_var_infos_r (var_info **slot, FILE *file)
{
var_info *info = *slot;
fprintf (file, "VAR: ");
print_generic_expr (file, info->var, dump_flags);
bitmap_print (file, info->info.def_blocks.def_blocks,
", DEF_BLOCKS: { ", "}");
bitmap_print (file, info->info.def_blocks.livein_blocks,
", LIVEIN_BLOCKS: { ", "}");
bitmap_print (file, info->info.def_blocks.phi_blocks,
", PHI_BLOCKS: { ", "}\n");
return 1;
}
/* Dump the VAR_INFOS hash table on FILE. */
void
dump_var_infos (FILE *file)
{
fprintf (file, "\n\nDefinition and live-in blocks:\n\n");
if (var_infos)
var_infos->traverse <FILE *, debug_var_infos_r> (file);
}
/* Dump the VAR_INFOS hash table on stderr. */
DEBUG_FUNCTION void
debug_var_infos (void)
{
dump_var_infos (stderr);
}
/* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
static inline void
register_new_update_single (tree new_name, tree old_name)
{
common_info *info = get_common_info (old_name);
tree currdef = info->current_def;
/* Push the current reaching definition into BLOCK_DEFS_STACK.
This stack is later used by the dominator tree callbacks to
restore the reaching definitions for all the variables
defined in the block after a recursive visit to all its
immediately dominated blocks. */
block_defs_stack.reserve (2);
block_defs_stack.quick_push (currdef);
block_defs_stack.quick_push (old_name);
/* Set the current reaching definition for OLD_NAME to be
NEW_NAME. */
info->current_def = new_name;
}
/* Register NEW_NAME to be the new reaching definition for all the
names in OLD_NAMES. Used by the incremental SSA update routines to
replace old SSA names with new ones. */
static inline void
register_new_update_set (tree new_name, bitmap old_names)
{
bitmap_iterator bi;
unsigned i;
EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi)
register_new_update_single (new_name, ssa_name (i));
}
/* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
it is a symbol marked for renaming, replace it with USE_P's current
reaching definition. */
static inline void
maybe_replace_use (use_operand_p use_p)
{
tree rdef = NULL_TREE;
tree use = USE_FROM_PTR (use_p);
tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
if (marked_for_renaming (sym))
rdef = get_reaching_def (sym);
else if (is_old_name (use))
rdef = get_reaching_def (use);
if (rdef && rdef != use)
SET_USE (use_p, rdef);
}
/* Same as maybe_replace_use, but without introducing default stmts,
returning false to indicate a need to do so. */
static inline bool
maybe_replace_use_in_debug_stmt (use_operand_p use_p)
{
tree rdef = NULL_TREE;
tree use = USE_FROM_PTR (use_p);
tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
if (marked_for_renaming (sym))
rdef = get_var_info (sym)->info.current_def;
else if (is_old_name (use))
{
rdef = get_ssa_name_ann (use)->info.current_def;
/* We can't assume that, if there's no current definition, the
default one should be used. It could be the case that we've
rearranged blocks so that the earlier definition no longer
dominates the use. */
if (!rdef && SSA_NAME_IS_DEFAULT_DEF (use))
rdef = use;
}
else
rdef = use;
if (rdef && rdef != use)
SET_USE (use_p, rdef);
return rdef != NULL_TREE;
}
/* If DEF has x_5 = ASAN_POISON () as its current def, add
ASAN_POISON_USE (x_5) stmt before GSI to denote the stmt writes into
a poisoned (out of scope) variable. */
static void
maybe_add_asan_poison_write (tree def, gimple_stmt_iterator *gsi)
{
tree cdef = get_current_def (def);
if (cdef != NULL
&& TREE_CODE (cdef) == SSA_NAME
&& gimple_call_internal_p (SSA_NAME_DEF_STMT (cdef), IFN_ASAN_POISON))
{
gcall *call
= gimple_build_call_internal (IFN_ASAN_POISON_USE, 1, cdef);
gimple_set_location (call, gimple_location (gsi_stmt (*gsi)));
gsi_insert_before (gsi, call, GSI_SAME_STMT);
}
}
/* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
register it as the current definition for the names replaced by
DEF_P. Returns whether the statement should be removed. */
static inline bool
maybe_register_def (def_operand_p def_p, gimple *stmt,
gimple_stmt_iterator gsi)
{
tree def = DEF_FROM_PTR (def_p);
tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
bool to_delete = false;
/* If DEF is a naked symbol that needs renaming, create a new
name for it. */
if (marked_for_renaming (sym))
{
if (DECL_P (def))
{
if (gimple_clobber_p (stmt) && is_gimple_reg (sym))
{
gcc_checking_assert (VAR_P (sym));
/* Replace clobber stmts with a default def. This new use of a
default definition may make it look like SSA_NAMEs have
conflicting lifetimes, so we need special code to let them
coalesce properly. */
to_delete = true;
def = get_or_create_ssa_default_def (cfun, sym);
}
else
{
if (asan_sanitize_use_after_scope ())
maybe_add_asan_poison_write (def, &gsi);
def = make_ssa_name (def, stmt);
}
SET_DEF (def_p, def);
tree tracked_var = target_for_debug_bind (sym);
if (tracked_var)
{
gimple *note = gimple_build_debug_bind (tracked_var, def, stmt);
/* If stmt ends the bb, insert the debug stmt on the single
non-EH edge from the stmt. */
if (gsi_one_before_end_p (gsi) && stmt_ends_bb_p (stmt))
{
basic_block bb = gsi_bb (gsi);
edge_iterator ei;
edge e, ef = NULL;
FOR_EACH_EDGE (e, ei, bb->succs)
if (!(e->flags & EDGE_EH))
{
gcc_checking_assert (!ef);
ef = e;
}
/* If there are other predecessors to ef->dest, then
there must be PHI nodes for the modified
variable, and therefore there will be debug bind
stmts after the PHI nodes. The debug bind notes
we'd insert would force the creation of a new
block (diverging codegen) and be redundant with
the post-PHI bind stmts, so don't add them.
As for the exit edge, there wouldn't be redundant
bind stmts, but there wouldn't be a PC to bind
them to either, so avoid diverging the CFG. */
if (ef && single_pred_p (ef->dest)
&& ef->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
{
/* If there were PHI nodes in the node, we'd
have to make sure the value we're binding
doesn't need rewriting. But there shouldn't
be PHI nodes in a single-predecessor block,
so we just add the note. */
gsi_insert_on_edge_immediate (ef, note);
}
}
else
gsi_insert_after (&gsi, note, GSI_SAME_STMT);
}
}
register_new_update_single (def, sym);
}
else
{
/* If DEF is a new name, register it as a new definition
for all the names replaced by DEF. */
if (is_new_name (def))
register_new_update_set (def, names_replaced_by (def));
/* If DEF is an old name, register DEF as a new
definition for itself. */
if (is_old_name (def))
register_new_update_single (def, def);
}
return to_delete;
}
/* Update every variable used in the statement pointed-to by SI. The
statement is assumed to be in SSA form already. Names in
OLD_SSA_NAMES used by SI will be updated to their current reaching
definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
will be registered as a new definition for their corresponding name
in OLD_SSA_NAMES. Returns whether STMT should be removed. */
static bool
rewrite_update_stmt (gimple *stmt, gimple_stmt_iterator gsi)
{
use_operand_p use_p;
def_operand_p def_p;
ssa_op_iter iter;
/* Only update marked statements. */
if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
return false;
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Updating SSA information for statement ");
print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
}
/* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
symbol is marked for renaming. */
if (rewrite_uses_p (stmt))
{
if (is_gimple_debug (stmt))
{
bool failed = false;
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
if (!maybe_replace_use_in_debug_stmt (use_p))
{
failed = true;
break;
}
if (failed)
{
/* DOM sometimes threads jumps in such a way that a
debug stmt ends up referencing a SSA variable that no
longer dominates the debug stmt, but such that all
incoming definitions refer to the same definition in
an earlier dominator. We could try to recover that
definition somehow, but this will have to do for now.
Introducing a default definition, which is what
maybe_replace_use() would do in such cases, may
modify code generation, for the otherwise-unused
default definition would never go away, modifying SSA
version numbers all over. */
gimple_debug_bind_reset_value (stmt);
update_stmt (stmt);
}
}
else
{
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
maybe_replace_use (use_p);
}
}
/* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
Also register definitions for names whose underlying symbol is
marked for renaming. */
bool to_delete = false;
if (register_defs_p (stmt))
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
to_delete |= maybe_register_def (def_p, stmt, gsi);
return to_delete;
}
/* Visit all the successor blocks of BB looking for PHI nodes. For
every PHI node found, check if any of its arguments is in
OLD_SSA_NAMES. If so, and if the argument has a current reaching
definition, replace it. */
static void
rewrite_update_phi_arguments (basic_block bb)
{
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
{
vec<gphi *> phis;
if (!bitmap_bit_p (blocks_with_phis_to_rewrite, e->dest->index))
continue;
phis = phis_to_rewrite[e->dest->index];
for (gphi *phi : phis)
{
tree arg, lhs_sym, reaching_def = NULL;
use_operand_p arg_p;
gcc_checking_assert (rewrite_uses_p (phi));
arg_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
arg = USE_FROM_PTR (arg_p);
if (arg && !DECL_P (arg) && TREE_CODE (arg) != SSA_NAME)
continue;
lhs_sym = SSA_NAME_VAR (gimple_phi_result (phi));
if (arg == NULL_TREE)
{
/* When updating a PHI node for a recently introduced
symbol we may find NULL arguments. That's why we
take the symbol from the LHS of the PHI node. */
reaching_def = get_reaching_def (lhs_sym);
}
else
{
tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg);
if (marked_for_renaming (sym))
reaching_def = get_reaching_def (sym);
else if (is_old_name (arg))
reaching_def = get_reaching_def (arg);
}
/* Update the argument if there is a reaching def. */
if (reaching_def)
{
location_t locus;
int arg_i = PHI_ARG_INDEX_FROM_USE (arg_p);
SET_USE (arg_p, reaching_def);
/* Virtual operands do not need a location. */
if (virtual_operand_p (reaching_def))
locus = UNKNOWN_LOCATION;
else
{
gimple *stmt = SSA_NAME_DEF_STMT (reaching_def);
gphi *other_phi = dyn_cast <gphi *> (stmt);
/* Single element PHI nodes behave like copies, so get the
location from the phi argument. */
if (other_phi
&& gimple_phi_num_args (other_phi) == 1)
locus = gimple_phi_arg_location (other_phi, 0);
else
locus = gimple_location (stmt);
}
gimple_phi_arg_set_location (phi, arg_i, locus);
}
if (e->flags & EDGE_ABNORMAL)
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1;
}
}
}
class rewrite_update_dom_walker : public dom_walker
{
public:
rewrite_update_dom_walker (cdi_direction direction)
: dom_walker (direction, ALL_BLOCKS, NULL) {}
virtual edge before_dom_children (basic_block);
virtual void after_dom_children (basic_block);
};
/* Initialization of block data structures for the incremental SSA
update pass. Create a block local stack of reaching definitions
for new SSA names produced in this block (BLOCK_DEFS). Register
new definitions for every PHI node in the block. */
edge
rewrite_update_dom_walker::before_dom_children (basic_block bb)
{
bool is_abnormal_phi;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "Registering new PHI nodes in block #%d\n",
bb->index);
/* Mark the unwind point for this block. */
block_defs_stack.safe_push (NULL_TREE);
if (!bitmap_bit_p (blocks_to_update, bb->index))
return NULL;
/* Mark the LHS if any of the arguments flows through an abnormal
edge. */
is_abnormal_phi = bb_has_abnormal_pred (bb);
/* If any of the PHI nodes is a replacement for a name in
OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
register it as a new definition for its corresponding name. Also
register definitions for names whose underlying symbols are
marked for renaming. */
for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
gsi_next (&gsi))
{
tree lhs, lhs_sym;
gphi *phi = gsi.phi ();
if (!register_defs_p (phi))
continue;
lhs = gimple_phi_result (phi);
lhs_sym = SSA_NAME_VAR (lhs);
if (marked_for_renaming (lhs_sym))
register_new_update_single (lhs, lhs_sym);
else
{
/* If LHS is a new name, register a new definition for all
the names replaced by LHS. */
if (is_new_name (lhs))
register_new_update_set (lhs, names_replaced_by (lhs));
/* If LHS is an OLD name, register it as a new definition
for itself. */
if (is_old_name (lhs))
register_new_update_single (lhs, lhs);
}
if (is_abnormal_phi)
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) = 1;
}
/* Step 2. Rewrite every variable used in each statement in the block. */
if (bitmap_bit_p (interesting_blocks, bb->index))
{
gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
if (rewrite_update_stmt (gsi_stmt (gsi), gsi))
gsi_remove (&gsi, true);
else
gsi_next (&gsi);
}
/* Step 3. Update PHI nodes. */
rewrite_update_phi_arguments (bb);
return NULL;
}
/* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
the current reaching definition of every name re-written in BB to
the original reaching definition before visiting BB. This
unwinding must be done in the opposite order to what is done in
register_new_update_set. */
void
rewrite_update_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
{
while (block_defs_stack.length () > 0)
{
tree var = block_defs_stack.pop ();
tree saved_def;
/* NULL indicates the unwind stop point for this block (see
rewrite_update_enter_block). */
if (var == NULL)
return;
saved_def = block_defs_stack.pop ();
get_common_info (var)->current_def = saved_def;
}
}
/* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
form.
ENTRY indicates the block where to start. Every block dominated by
ENTRY will be rewritten.
WHAT indicates what actions will be taken by the renamer (see enum
rewrite_mode).
BLOCKS are the set of interesting blocks for the dominator walker
to process. If this set is NULL, then all the nodes dominated
by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
are not present in BLOCKS are ignored. */
static void
rewrite_blocks (basic_block entry, enum rewrite_mode what)
{
block_defs_stack.create (10);
/* Recursively walk the dominator tree rewriting each statement in
each basic block. */
if (what == REWRITE_ALL)
rewrite_dom_walker (CDI_DOMINATORS).walk (entry);
else if (what == REWRITE_UPDATE)
rewrite_update_dom_walker (CDI_DOMINATORS).walk (entry);
else
gcc_unreachable ();
/* Debugging dumps. */
if (dump_file && (dump_flags & TDF_STATS))
{
dump_dfa_stats (dump_file);
if (var_infos)
dump_tree_ssa_stats (dump_file);
}
block_defs_stack.release ();
}
class mark_def_dom_walker : public dom_walker
{
public:
mark_def_dom_walker (cdi_direction direction);
~mark_def_dom_walker ();
virtual edge before_dom_children (basic_block);
private:
/* Notice that this bitmap is indexed using variable UIDs, so it must be
large enough to accommodate all the variables referenced in the
function, not just the ones we are renaming. */
bitmap m_kills;
};
mark_def_dom_walker::mark_def_dom_walker (cdi_direction direction)
: dom_walker (direction, ALL_BLOCKS, NULL), m_kills (BITMAP_ALLOC (NULL))
{
}
mark_def_dom_walker::~mark_def_dom_walker ()
{
BITMAP_FREE (m_kills);
}
/* Block processing routine for mark_def_sites. Clear the KILLS bitmap
at the start of each block, and call mark_def_sites for each statement. */
edge
mark_def_dom_walker::before_dom_children (basic_block bb)
{
gimple_stmt_iterator gsi;
bitmap_clear (m_kills);
for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
mark_def_sites (bb, gsi_stmt (gsi), m_kills);
return NULL;
}
/* Initialize internal data needed during renaming. */
static void
init_ssa_renamer (void)
{
cfun->gimple_df->in_ssa_p = false;
/* Allocate memory for the DEF_BLOCKS hash table. */
gcc_assert (!var_infos);
var_infos = new hash_table<var_info_hasher>
(vec_safe_length (cfun->local_decls));
bitmap_obstack_initialize (&update_ssa_obstack);
}
/* Deallocate internal data structures used by the renamer. */
static void
fini_ssa_renamer (void)
{
delete var_infos;
var_infos = NULL;
bitmap_obstack_release (&update_ssa_obstack);
cfun->gimple_df->ssa_renaming_needed = 0;
cfun->gimple_df->rename_vops = 0;
cfun->gimple_df->in_ssa_p = true;
}
/* Main entry point into the SSA builder. The renaming process
proceeds in four main phases:
1- Compute dominance frontier and immediate dominators, needed to
insert PHI nodes and rename the function in dominator tree
order.
2- Find and mark all the blocks that define variables.
3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
4- Rename all the blocks (rewrite_blocks) and statements in the program.
Steps 3 and 4 are done using the dominator tree walker
(walk_dominator_tree). */
namespace {
const pass_data pass_data_build_ssa =
{
GIMPLE_PASS, /* type */
"ssa", /* name */
OPTGROUP_NONE, /* optinfo_flags */
TV_TREE_INTO_SSA, /* tv_id */
PROP_cfg, /* properties_required */
PROP_ssa, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_remove_unused_locals, /* todo_flags_finish */
};
class pass_build_ssa : public gimple_opt_pass
{
public:
pass_build_ssa (gcc::context *ctxt)
: gimple_opt_pass (pass_data_build_ssa, ctxt)
{}
/* opt_pass methods: */
virtual bool gate (function *fun)
{
/* Do nothing for funcions that was produced already in SSA form. */
return !(fun->curr_properties & PROP_ssa);
}
virtual unsigned int execute (function *);
}; // class pass_build_ssa
unsigned int
pass_build_ssa::execute (function *fun)
{
bitmap_head *dfs;
basic_block bb;
/* Increase the set of variables we can rewrite into SSA form
by clearing TREE_ADDRESSABLE and transform the IL to support this. */
if (optimize)
execute_update_addresses_taken ();
/* Initialize operand data structures. */
init_ssa_operands (fun);
/* Initialize internal data needed by the renamer. */
init_ssa_renamer ();
/* Initialize the set of interesting blocks. The callback
mark_def_sites will add to this set those blocks that the renamer
should process. */
interesting_blocks = sbitmap_alloc (last_basic_block_for_fn (fun));
bitmap_clear (interesting_blocks);
/* Initialize dominance frontier. */
dfs = XNEWVEC (bitmap_head, last_basic_block_for_fn (fun));
FOR_EACH_BB_FN (bb, fun)
bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
/* 1- Compute dominance frontiers. */
calculate_dominance_info (CDI_DOMINATORS);
compute_dominance_frontiers (dfs);
/* 2- Find and mark definition sites. */
mark_def_dom_walker (CDI_DOMINATORS).walk (fun->cfg->x_entry_block_ptr);
/* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
insert_phi_nodes (dfs);
/* 4- Rename all the blocks. */
rewrite_blocks (ENTRY_BLOCK_PTR_FOR_FN (fun), REWRITE_ALL);
/* Free allocated memory. */
FOR_EACH_BB_FN (bb, fun)
bitmap_clear (&dfs[bb->index]);
free (dfs);
sbitmap_free (interesting_blocks);
fini_ssa_renamer ();
/* Try to get rid of all gimplifier generated temporaries by making
its SSA names anonymous. This way we can garbage collect them
all after removing unused locals which we do in our TODO. */
unsigned i;
tree name;
FOR_EACH_SSA_NAME (i, name, cfun)
{
if (SSA_NAME_IS_DEFAULT_DEF (name))
continue;
tree decl = SSA_NAME_VAR (name);
if (decl
&& VAR_P (decl)
&& !VAR_DECL_IS_VIRTUAL_OPERAND (decl)
&& DECL_IGNORED_P (decl))
SET_SSA_NAME_VAR_OR_IDENTIFIER (name, DECL_NAME (decl));
}
/* Initialize SSA_NAME_POINTS_TO_READONLY_MEMORY. */
tree fnspec_tree
= lookup_attribute ("fn spec",
TYPE_ATTRIBUTES (TREE_TYPE (fun->decl)));
if (fnspec_tree)
{
attr_fnspec fnspec (TREE_VALUE (TREE_VALUE (fnspec_tree)));
unsigned i = 0;
for (tree arg = DECL_ARGUMENTS (cfun->decl);
arg; arg = DECL_CHAIN (arg), ++i)
{
if (!fnspec.arg_specified_p (i))
break;
if (fnspec.arg_readonly_p (i))
{
tree name = ssa_default_def (fun, arg);
if (name)
SSA_NAME_POINTS_TO_READONLY_MEMORY (name) = 1;
}
}
}
return 0;
}
} // anon namespace
gimple_opt_pass *
make_pass_build_ssa (gcc::context *ctxt)
{
return new pass_build_ssa (ctxt);
}
/* Mark the definition of VAR at STMT and BB as interesting for the
renamer. BLOCKS is the set of blocks that need updating. */
static void
mark_def_interesting (tree var, gimple *stmt, basic_block bb,
bool insert_phi_p)
{
gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
set_register_defs (stmt, true);
if (insert_phi_p)
{
bool is_phi_p = gimple_code (stmt) == GIMPLE_PHI;
set_def_block (var, bb, is_phi_p);
/* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
site for both itself and all the old names replaced by it. */
if (TREE_CODE (var) == SSA_NAME && is_new_name (var))
{
bitmap_iterator bi;
unsigned i;
bitmap set = names_replaced_by (var);
if (set)
EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
set_def_block (ssa_name (i), bb, is_phi_p);
}
}
}
/* Mark the use of VAR at STMT and BB as interesting for the
renamer. INSERT_PHI_P is true if we are going to insert new PHI
nodes. */
static inline void
mark_use_interesting (tree var, gimple *stmt, basic_block bb,
bool insert_phi_p)
{
basic_block def_bb = gimple_bb (stmt);
mark_block_for_update (def_bb);
mark_block_for_update (bb);
if (gimple_code (stmt) == GIMPLE_PHI)
mark_phi_for_rewrite (def_bb, as_a <gphi *> (stmt));
else
{
set_rewrite_uses (stmt, true);
if (is_gimple_debug (stmt))
return;
}
/* If VAR has not been defined in BB, then it is live-on-entry
to BB. Note that we cannot just use the block holding VAR's
definition because if VAR is one of the names in OLD_SSA_NAMES,
it will have several definitions (itself and all the names that
replace it). */
if (insert_phi_p)
{
def_blocks *db_p = get_def_blocks_for (get_common_info (var));
if (!bitmap_bit_p (db_p->def_blocks, bb->index))
set_livein_block (var, bb);
}
}
/* Processing statements in BB that reference symbols in SSA operands.
This is very similar to mark_def_sites, but the scan handles
statements whose operands may already be SSA names.
If INSERT_PHI_P is true, mark those uses as live in the
corresponding block. This is later used by the PHI placement
algorithm to make PHI pruning decisions.
FIXME. Most of this would be unnecessary if we could associate a
symbol to all the SSA names that reference it. But that
sounds like it would be expensive to maintain. Still, it
would be interesting to see if it makes better sense to do
that. */
static void
prepare_block_for_update_1 (basic_block bb, bool insert_phi_p)
{
edge e;
edge_iterator ei;
mark_block_for_update (bb);
/* Process PHI nodes marking interesting those that define or use
the symbols that we are interested in. */
for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si);
gsi_next (&si))
{
gphi *phi = si.phi ();
tree lhs_sym, lhs = gimple_phi_result (phi);
if (TREE_CODE (lhs) == SSA_NAME
&& (! virtual_operand_p (lhs)
|| ! cfun->gimple_df->rename_vops))
continue;
lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
mark_for_renaming (lhs_sym);
mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
/* Mark the uses in phi nodes as interesting. It would be more correct
to process the arguments of the phi nodes of the successor edges of
BB at the end of prepare_block_for_update, however, that turns out
to be significantly more expensive. Doing it here is conservatively
correct -- it may only cause us to believe a value to be live in a
block that also contains its definition, and thus insert a few more
phi nodes for it. */
FOR_EACH_EDGE (e, ei, bb->preds)
mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p);
}
/* Process the statements. */
for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si);
gsi_next (&si))
{
gimple *stmt;
ssa_op_iter i;
use_operand_p use_p;
def_operand_p def_p;
stmt = gsi_stmt (si);
if (cfun->gimple_df->rename_vops
&& gimple_vuse (stmt))
{
tree use = gimple_vuse (stmt);
tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
mark_for_renaming (sym);
mark_use_interesting (sym, stmt, bb, insert_phi_p);
}
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_USE)
{
tree use = USE_FROM_PTR (use_p);
if (!DECL_P (use))
continue;
mark_for_renaming (use);
mark_use_interesting (use, stmt, bb, insert_phi_p);
}
if (cfun->gimple_df->rename_vops
&& gimple_vdef (stmt))
{
tree def = gimple_vdef (stmt);
tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
mark_for_renaming (sym);
mark_def_interesting (sym, stmt, bb, insert_phi_p);
}
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_DEF)
{
tree def = DEF_FROM_PTR (def_p);
if (!DECL_P (def))
continue;
mark_for_renaming (def);
mark_def_interesting (def, stmt, bb, insert_phi_p);
}
}
}
/* Do a dominator walk starting at BB processing statements that
reference symbols in SSA operands. This is very similar to
mark_def_sites, but the scan handles statements whose operands may
already be SSA names.
If INSERT_PHI_P is true, mark those uses as live in the
corresponding block. This is later used by the PHI placement
algorithm to make PHI pruning decisions.
FIXME. Most of this would be unnecessary if we could associate a
symbol to all the SSA names that reference it. But that
sounds like it would be expensive to maintain. Still, it
would be interesting to see if it makes better sense to do
that. */
static void
prepare_block_for_update (basic_block bb, bool insert_phi_p)
{
size_t sp = 0;
basic_block *worklist;
/* Allocate the worklist. */
worklist = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
/* Add the BB to the worklist. */
worklist[sp++] = bb;
while (sp)
{
basic_block bb;
basic_block son;
/* Pick a block from the worklist. */
bb = worklist[--sp];
prepare_block_for_update_1 (bb, insert_phi_p);
/* Now add all the blocks dominated by BB to the worklist. */
for (son = first_dom_son (CDI_DOMINATORS, bb);
son;
son = next_dom_son (CDI_DOMINATORS, son))
worklist[sp++] = son;
}
free (worklist);
}
/* Helper for prepare_names_to_update. Mark all the use sites for
NAME as interesting. BLOCKS and INSERT_PHI_P are as in
prepare_names_to_update. */
static void
prepare_use_sites_for (tree name, bool insert_phi_p)
{
use_operand_p use_p;
imm_use_iterator iter;
/* If we rename virtual operands do not update them. */
if (virtual_operand_p (name)
&& cfun->gimple_df->rename_vops)
return;
FOR_EACH_IMM_USE_FAST (use_p, iter, name)
{
gimple *stmt = USE_STMT (use_p);
basic_block bb = gimple_bb (stmt);
if (gimple_code (stmt) == GIMPLE_PHI)
{
int ix = PHI_ARG_INDEX_FROM_USE (use_p);
edge e = gimple_phi_arg_edge (as_a <gphi *> (stmt), ix);
mark_use_interesting (name, stmt, e->src, insert_phi_p);
}
else
{
/* For regular statements, mark this as an interesting use
for NAME. */
mark_use_interesting (name, stmt, bb, insert_phi_p);
}
}
}
/* Helper for prepare_names_to_update. Mark the definition site for
NAME as interesting. BLOCKS and INSERT_PHI_P are as in
prepare_names_to_update. */
static void
prepare_def_site_for (tree name, bool insert_phi_p)
{
gimple *stmt;
basic_block bb;
gcc_checking_assert (names_to_release == NULL
|| !bitmap_bit_p (names_to_release,
SSA_NAME_VERSION (name)));
/* If we rename virtual operands do not update them. */
if (virtual_operand_p (name)
&& cfun->gimple_df->rename_vops)
return;
stmt = SSA_NAME_DEF_STMT (name);
bb = gimple_bb (stmt);
if (bb)
{
gcc_checking_assert (bb->index < last_basic_block_for_fn (cfun));
mark_block_for_update (bb);
mark_def_interesting (name, stmt, bb, insert_phi_p);
}
}
/* Mark definition and use sites of names in NEW_SSA_NAMES and
OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
PHI nodes for newly created names. */
static void
prepare_names_to_update (bool insert_phi_p)
{
unsigned i = 0;
bitmap_iterator bi;
sbitmap_iterator sbi;
/* If a name N from NEW_SSA_NAMES is also marked to be released,
remove it from NEW_SSA_NAMES so that we don't try to visit its
defining basic block (which most likely doesn't exist). Notice
that we cannot do the same with names in OLD_SSA_NAMES because we
want to replace existing instances. */
if (names_to_release)
EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
bitmap_clear_bit (new_ssa_names, i);
/* First process names in NEW_SSA_NAMES. Otherwise, uses of old
names may be considered to be live-in on blocks that contain
definitions for their replacements. */
EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
prepare_def_site_for (ssa_name (i), insert_phi_p);
/* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
OLD_SSA_NAMES, but we have to ignore its definition site. */
EXECUTE_IF_SET_IN_BITMAP (old_ssa_names, 0, i, sbi)
{
if (names_to_release == NULL || !bitmap_bit_p (names_to_release, i))
prepare_def_site_for (ssa_name (i), insert_phi_p);
prepare_use_sites_for (ssa_name (i), insert_phi_p);
}
}
/* Dump all the names replaced by NAME to FILE. */
void
dump_names_replaced_by (FILE *file, tree name)
{
unsigned i;
bitmap old_set;
bitmap_iterator bi;
print_generic_expr (file, name);
fprintf (file, " -> { ");
old_set = names_replaced_by (name);
EXECUTE_IF_SET_IN_BITMAP (old_set, 0, i, bi)
{
print_generic_expr (file, ssa_name (i));
fprintf (file, " ");
}
fprintf (file, "}\n");
}
/* Dump all the names replaced by NAME to stderr. */
DEBUG_FUNCTION void
debug_names_replaced_by (tree name)
{
dump_names_replaced_by (stderr, name);
}
/* Dump SSA update information to FILE. */
void
dump_update_ssa (FILE *file)
{
unsigned i = 0;
bitmap_iterator bi;
if (!need_ssa_update_p (cfun))
return;
if (new_ssa_names && bitmap_first_set_bit (new_ssa_names) >= 0)
{
sbitmap_iterator sbi;
fprintf (file, "\nSSA replacement table\n");
fprintf (file, "N_i -> { O_1 ... O_j } means that N_i replaces "
"O_1, ..., O_j\n\n");
EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
dump_names_replaced_by (file, ssa_name (i));
}
if (symbols_to_rename_set && !bitmap_empty_p (symbols_to_rename_set))
{
fprintf (file, "\nSymbols to be put in SSA form\n");
dump_decl_set (file, symbols_to_rename_set);
fprintf (file, "\n");
}
if (names_to_release && !bitmap_empty_p (names_to_release))
{
fprintf (file, "\nSSA names to release after updating the SSA web\n\n");
EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
{
print_generic_expr (file, ssa_name (i));
fprintf (file, " ");
}
fprintf (file, "\n");
}
}
/* Dump SSA update information to stderr. */
DEBUG_FUNCTION void
debug_update_ssa (void)
{
dump_update_ssa (stderr);
}
/* Initialize data structures used for incremental SSA updates. */
static void
init_update_ssa (struct function *fn)
{
/* Reserve more space than the current number of names. The calls to
add_new_name_mapping are typically done after creating new SSA
names, so we'll need to reallocate these arrays. */
old_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
bitmap_clear (old_ssa_names);
new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
bitmap_clear (new_ssa_names);
bitmap_obstack_initialize (&update_ssa_obstack);
names_to_release = NULL;
update_ssa_initialized_fn = fn;
}
/* Deallocate data structures used for incremental SSA updates. */
void
delete_update_ssa (void)
{
unsigned i;
bitmap_iterator bi;
sbitmap_free (old_ssa_names);
old_ssa_names = NULL;
sbitmap_free (new_ssa_names);
new_ssa_names = NULL;
BITMAP_FREE (symbols_to_rename_set);
symbols_to_rename_set = NULL;
symbols_to_rename.release ();
if (names_to_release)
{
EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
release_ssa_name (ssa_name (i));
BITMAP_FREE (names_to_release);
}
clear_ssa_name_info ();
fini_ssa_renamer ();
if (blocks_with_phis_to_rewrite)
EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite, 0, i, bi)
phis_to_rewrite[i].release ();
BITMAP_FREE (blocks_with_phis_to_rewrite);
BITMAP_FREE (blocks_to_update);
update_ssa_initialized_fn = NULL;
}
/* Create a new name for OLD_NAME in statement STMT and replace the
operand pointed to by DEF_P with the newly created name. If DEF_P
is NULL then STMT should be a GIMPLE assignment.
Return the new name and register the replacement mapping <NEW, OLD> in
update_ssa's tables. */
tree
create_new_def_for (tree old_name, gimple *stmt, def_operand_p def)
{
tree new_name;
timevar_push (TV_TREE_SSA_INCREMENTAL);
if (!update_ssa_initialized_fn)
init_update_ssa (cfun);
gcc_assert (update_ssa_initialized_fn == cfun);
new_name = duplicate_ssa_name (old_name, stmt);
if (def)
SET_DEF (def, new_name);
else
gimple_assign_set_lhs (stmt, new_name);
if (gimple_code (stmt) == GIMPLE_PHI)
{
basic_block bb = gimple_bb (stmt);
/* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = bb_has_abnormal_pred (bb);
}
add_new_name_mapping (new_name, old_name);
/* For the benefit of passes that will be updating the SSA form on
their own, set the current reaching definition of OLD_NAME to be
NEW_NAME. */
get_ssa_name_ann (old_name)->info.current_def = new_name;
timevar_pop (TV_TREE_SSA_INCREMENTAL);
return new_name;
}
/* Mark virtual operands of FN for renaming by update_ssa. */
void
mark_virtual_operands_for_renaming (struct function *fn)
{
fn->gimple_df->ssa_renaming_needed = 1;
fn->gimple_df->rename_vops = 1;
}
/* Replace all uses of NAME by underlying variable and mark it
for renaming. This assumes the defining statement of NAME is
going to be removed. */
void
mark_virtual_operand_for_renaming (tree name)
{
tree name_var = SSA_NAME_VAR (name);
bool used = false;
imm_use_iterator iter;
use_operand_p use_p;
gimple *stmt;
gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var));
FOR_EACH_IMM_USE_STMT (stmt, iter, name)
{
FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
SET_USE (use_p, name_var);
used = true;
}
if (used)
mark_virtual_operands_for_renaming (cfun);
}
/* Replace all uses of the virtual PHI result by its underlying variable
and mark it for renaming. This assumes the PHI node is going to be
removed. */
void
mark_virtual_phi_result_for_renaming (gphi *phi)
{
if (dump_file && (dump_flags & TDF_DETAILS))
{
fprintf (dump_file, "Marking result for renaming : ");
print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
fprintf (dump_file, "\n");
}