You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA. */
+the Free Software Foundation, 51 Franklin Street, Fifth Floor,
+Boston, MA 02110-1301, USA. */
#include "config.h"
#include "system.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
-#include "errors.h"
#include "expr.h"
#include "function.h"
#include "diagnostic.h"
#include "cfgloop.h"
#include "domwalk.h"
#include "ggc.h"
+#include "params.h"
/* This file builds the SSA form for a function as described in:
R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
Graph. ACM Transactions on Programming Languages and Systems,
13(4):451-490, October 1991. */
+/* True if the code is in ssa form. */
+bool in_ssa_p;
+
/* Structure to map a variable VAR to the set of blocks that contain
definitions for VAR. */
struct def_blocks_d
static htab_t def_blocks;
/* Stack of trees used to restore the global currdefs to its original
- state after completing rewriting of a block and its dominator children.
-
- This vector is used in two contexts. The first is rewriting of _DECL
- nodes into SSA_NAMEs. In that context its elements have the
- following properties:
-
- An SSA_NAME indicates that the current definition of the underlying
- variable should be set to the given SSA_NAME.
-
- A _DECL node indicates that the underlying variable has no current
- definition.
-
- A NULL node is used to mark the last node associated with the
- current block.
-
- This vector is also used when rewriting an SSA_NAME which has multiple
- definition sites into multiple SSA_NAMEs. In that context entries come
- in pairs.
-
- The top entry is an SSA_NAME and the top-1 entry is the
- current value for that SSA_NAME.
-
- A NULL node at the top entry is used to mark the last node associated
- with the current block. */
-static VEC(tree_on_heap) *block_defs_stack;
+ state after completing rewriting of a block and its dominator
+ children. Its elements have the following properties:
+
+ - An SSA_NAME indicates that the current definition of the
+ underlying variable should be set to the given SSA_NAME.
+
+ - A _DECL node indicates that the underlying variable has no
+ current definition.
+
+ - A NULL node is used to mark the last node associated with the
+ current block.
+
+ - A NULL node at the top entry is used to mark the last node
+ associated with the current block. */
+static VEC(tree,heap) *block_defs_stack;
+
+/* Basic block vectors used in this file ought to be allocated in the
+ heap. We use pointer vector, because ints can be easily passed by
+ value. */
+DEF_VEC_I(int);
+DEF_VEC_ALLOC_I(int,heap);
+
+/* 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;
+
+/* Symbols whose SSA form needs to be updated or created for the first
+ time. */
+static bitmap syms_to_rename;
+
+/* 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. */
+static bitmap names_to_release;
+
+/* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
+ to grow as the callers to register_new_name_mapping will typically
+ 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))
+
+/* Tuple used to represent replacement mappings. */
+struct repl_map_d
+{
+ tree name;
+ bitmap set;
+};
-/* Basic block vectors used in this file ought to be allocated in the heap. */
-DEF_VEC_MALLOC_P(int);
+/* NEW -> OLD_SET replacement table. If we are replacing several
+ existing SSA names O_1, O_2, ..., O_j with a new name N_i,
+ then REPL_TBL[N_i] = { O_1, O_2, ..., O_j }. */
+static htab_t repl_tbl;
+
+/* true if register_new_name_mapping needs to initialize the data
+ structures needed by update_ssa. */
+static bool need_to_initialize_update_ssa_p = true;
+
+/* true if update_ssa needs to update virtual operands. */
+static bool need_to_update_vops_p = false;
+
+/* Statistics kept by update_ssa to use in the virtual mapping
+ heuristic. If the number of virtual mappings is beyond certain
+ threshold, the updater will switch from using the mappings into
+ renaming the virtual symbols from scratch. In some cases, the
+ large number of name mappings for virtual names causes significant
+ slowdowns in the PHI insertion code. */
+struct update_ssa_stats_d
+{
+ unsigned num_virtual_mappings;
+ unsigned num_total_mappings;
+ bitmap virtual_symbols;
+ unsigned num_virtual_symbols;
+};
+static struct update_ssa_stats_d update_ssa_stats;
/* Global data to attach to the main dominator walk structure. */
struct mark_def_sites_global_data
{
- /* This sbitmap contains the variables which are set before they
- are used in a basic block. We keep it as a global variable
- solely to avoid the overhead of allocating and deallocating
- the bitmap. */
+ /* This bitmap contains the variables which are set before they
+ are used in a basic block. */
bitmap kills;
/* Bitmap of names to rename. */
sbitmap names_to_rename;
+
+ /* Set of blocks that mark_def_sites deems interesting for the
+ renamer to process. */
+ sbitmap interesting_blocks;
};
-/* Information stored for ssa names. */
+/* Information stored for SSA names. */
struct ssa_name_info
{
/* This field indicates whether or not the variable may need PHI nodes.
};
+/* 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
+};
+
+
/* Use TREE_VISITED to keep track of which statements we want to
rename. When renaming a subset of the variables, not all
statements will be processed. This is decided in mark_def_sites. */
#define REWRITE_THIS_STMT(T) TREE_VISITED (T)
+/* Use the unsigned flag to keep track of which statements we want to
+ visit when marking new definition sites. This is slightly
+ different than REWRITE_THIS_STMT: 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. */
+#define REGISTER_DEFS_IN_THIS_STMT(T) (T)->common.unsigned_flag
+
+
+/* Prototypes for debugging functions. */
+extern void dump_tree_ssa (FILE *);
+extern void debug_tree_ssa (void);
+extern void debug_def_blocks (void);
+extern void dump_tree_ssa_stats (FILE *);
+extern void debug_tree_ssa_stats (void);
+void dump_update_ssa (FILE *);
+void debug_update_ssa (void);
+void dump_names_replaced_by (FILE *, tree);
+void debug_names_replaced_by (tree);
/* Get the information associated with NAME. */
if (!SSA_NAME_AUX (name))
SSA_NAME_AUX (name) = xcalloc (1, sizeof (struct ssa_name_info));
- return SSA_NAME_AUX (name);
+ return (struct ssa_name_info *) SSA_NAME_AUX (name);
}
/* Return the current definition for VAR. */
-static inline tree
+tree
get_current_def (tree var)
{
if (TREE_CODE (var) == SSA_NAME)
/* Sets current definition of VAR to DEF. */
-static inline void
+void
set_current_def (tree var, tree def)
{
if (TREE_CODE (var) == SSA_NAME)
bitmap_iterator bi;
tos = worklist
- = (basic_block *) xmalloc (sizeof (basic_block) * (n_basic_blocks + 1));
+ = (basic_block *) xmalloc (sizeof (basic_block) * (last_basic_block + 1));
EXECUTE_IF_SET_IN_BITMAP (livein, 0, i, bi)
{
slot = htab_find_slot (def_blocks, (void *) &db, INSERT);
if (*slot == NULL)
{
- db_p = xmalloc (sizeof (*db_p));
+ db_p = XNEW (struct def_blocks_d);
db_p->var = var;
db_p->def_blocks = BITMAP_ALLOC (NULL);
db_p->phi_blocks = BITMAP_ALLOC (NULL);
/* Mark block BB as the definition site for variable VAR. PHI_P is true if
- VAR is defined by a PHI node. IS_UPDATE is true if the caller is
- updating an existing SSA form. */
+ VAR is defined by a PHI node. */
static void
-set_def_block (tree var, basic_block bb, bool phi_p, bool is_update)
+set_def_block (tree var, basic_block bb, bool phi_p)
{
struct def_blocks_d *db_p;
enum need_phi_state state;
- if (!is_update && TREE_CODE (var) == SSA_NAME)
- var = SSA_NAME_VAR (var);
-
state = get_phi_state (var);
db_p = get_def_blocks_for (var);
}
-/* If the use operand pointed to by OP_P needs to be renamed, then strip away
- any SSA_NAME wrapping the operand, set *UID_P to the underlying variable's
- uid, and return true. Otherwise return false. If the operand was an
- SSA_NAME, change it to the stripped name. */
+/* Return true if symbol SYM is marked for renaming. */
-static bool
-prepare_use_operand_for_rename (use_operand_p op_p, size_t *uid_p)
+static inline bool
+symbol_marked_for_renaming (tree sym)
{
- tree use = USE_FROM_PTR (op_p);
- tree var = (TREE_CODE (use) != SSA_NAME) ? use : SSA_NAME_VAR (use);
- *uid_p = var_ann (var)->uid;
+ gcc_assert (DECL_P (sym));
+ return bitmap_bit_p (syms_to_rename, DECL_UID (sym));
+}
- /* Ignore variables that don't need to be renamed. */
- if (vars_to_rename && !bitmap_bit_p (vars_to_rename, *uid_p))
- return false;
- /* The variable needs to be renamed. If this is a use which already
- has an SSA_NAME, then strip it off.
+/* Return true if NAME is in OLD_SSA_NAMES. */
- By not throwing away SSA_NAMEs on assignments, we avoid a lot of
- useless churn of SSA_NAMEs without having to overly complicate the
- renamer. */
- if (TREE_CODE (use) == SSA_NAME)
- SET_USE (op_p, var);
+static inline bool
+is_old_name (tree name)
+{
+ unsigned ver = SSA_NAME_VERSION (name);
+ return ver < new_ssa_names->n_bits && TEST_BIT (old_ssa_names, ver);
+}
+
+
+/* Return true if NAME is in NEW_SSA_NAMES. */
- return true;
+static inline bool
+is_new_name (tree name)
+{
+ unsigned ver = SSA_NAME_VERSION (name);
+ return ver < new_ssa_names->n_bits && TEST_BIT (new_ssa_names, ver);
}
-/* If the def variable DEF needs to be renamed, then strip away any SSA_NAME
- wrapping the operand, set *UID_P to the underlying variable's uid and return
- true. Otherwise return false. */
+/* Hashing and equality functions for REPL_TBL. */
-static bool
-prepare_def_operand_for_rename (tree def, size_t *uid_p)
+static hashval_t
+repl_map_hash (const void *p)
+{
+ return htab_hash_pointer ((const void *)((const struct repl_map_d *)p)->name);
+}
+
+static int
+repl_map_eq (const void *p1, const void *p2)
{
- tree var = (TREE_CODE (def) != SSA_NAME) ? def : SSA_NAME_VAR (def);
- *uid_p = var_ann (var)->uid;
+ return ((const struct repl_map_d *)p1)->name
+ == ((const struct repl_map_d *)p2)->name;
+}
- /* Ignore variables that don't need to be renamed. */
- if (vars_to_rename && !bitmap_bit_p (vars_to_rename, *uid_p))
- return false;
+static void
+repl_map_free (void *p)
+{
+ BITMAP_FREE (((struct repl_map_d *)p)->set);
+ free (p);
+}
+
+
+/* Return the names replaced by NEW (i.e., REPL_TBL[NEW].SET). */
+
+static inline bitmap
+names_replaced_by (tree new)
+{
+ struct repl_map_d m;
+ void **slot;
+
+ m.name = new;
+ slot = htab_find_slot (repl_tbl, (void *) &m, NO_INSERT);
+
+ /* If N was not registered in the replacement table, return NULL. */
+ if (slot == NULL || *slot == NULL)
+ return NULL;
+
+ return ((struct repl_map_d *) *slot)->set;
+}
+
+
+/* Add OLD to REPL_TBL[NEW].SET. */
+
+static inline void
+add_to_repl_tbl (tree new, tree old)
+{
+ struct repl_map_d m, *mp;
+ void **slot;
+
+ m.name = new;
+ slot = htab_find_slot (repl_tbl, (void *) &m, INSERT);
+ if (*slot == NULL)
+ {
+ mp = XNEW (struct repl_map_d);
+ mp->name = new;
+ mp->set = BITMAP_ALLOC (NULL);
+ *slot = (void *) mp;
+ }
+ else
+ mp = (struct repl_map_d *) *slot;
+
+ bitmap_set_bit (mp->set, SSA_NAME_VERSION (old));
+}
+
+
+/* Add a new mapping NEW -> 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. */
- return true;
+static void
+add_new_name_mapping (tree new, tree old)
+{
+ timevar_push (TV_TREE_SSA_INCREMENTAL);
+
+ /* OLD and NEW must be different SSA names for the same symbol. */
+ gcc_assert (new != old && SSA_NAME_VAR (new) == 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 (new_ssa_names->n_bits <= 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);
+ }
+
+ /* If this mapping is for virtual names, we will need to update
+ virtual operands. */
+ if (!is_gimple_reg (new))
+ {
+ tree sym;
+ size_t uid;
+
+ need_to_update_vops_p = true;
+
+ /* Keep counts of virtual mappings and symbols to use in the
+ virtual mapping heuristic. If we have large numbers of
+ virtual mappings for a relatively low number of symbols, it
+ will make more sense to rename the symbols from scratch.
+ Otherwise, the insertion of PHI nodes for each of the old
+ names in these mappings will be very slow. */
+ sym = SSA_NAME_VAR (new);
+ uid = DECL_UID (sym);
+ update_ssa_stats.num_virtual_mappings++;
+ if (!bitmap_bit_p (update_ssa_stats.virtual_symbols, uid))
+ {
+ bitmap_set_bit (update_ssa_stats.virtual_symbols, uid);
+ update_ssa_stats.num_virtual_symbols++;
+ }
+ }
+
+ /* Update the REPL_TBL table. */
+ add_to_repl_tbl (new, old);
+
+ /* If OLD had already been registered as a new name, then all the
+ names that OLD replaces should also be replaced by NEW. */
+ if (is_new_name (old))
+ bitmap_ior_into (names_replaced_by (new), names_replaced_by (old));
+
+ /* Register NEW and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
+ respectively. */
+ SET_BIT (new_ssa_names, SSA_NAME_VERSION (new));
+ SET_BIT (old_ssa_names, SSA_NAME_VERSION (old));
+
+ /* Update mapping counter to use in the virtual mapping heuristic. */
+ update_ssa_stats.num_total_mappings++;
+
+ timevar_pop (TV_TREE_SSA_INCREMENTAL);
}
for every variable in the function. For every statement S in block
BB:
- 1- Variables defined by S in DEF_OPS(S) are marked in the bitmap
+ 1- Variables defined by S in the DEFS of S are marked in the bitmap
WALK_DATA->GLOBAL_DATA->KILLS.
2- If S uses a variable VAR and there is no preceding kill of VAR,
- then it is marked in marked in the LIVEIN_BLOCKS bitmap
- associated with 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
basic_block bb,
block_stmt_iterator bsi)
{
- struct mark_def_sites_global_data *gd = walk_data->global_data;
+ struct mark_def_sites_global_data *gd =
+ (struct mark_def_sites_global_data *) walk_data->global_data;
bitmap kills = gd->kills;
- size_t uid;
tree stmt, def;
use_operand_p use_p;
def_operand_p def_p;
ssa_op_iter iter;
- /* Mark all the blocks that have definitions for each variable in the
- VARS_TO_RENAME bitmap. */
stmt = bsi_stmt (bsi);
update_stmt_if_modified (stmt);
+ REGISTER_DEFS_IN_THIS_STMT (stmt) = 0;
REWRITE_THIS_STMT (stmt) = 0;
/* 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_USE | SSA_OP_VUSE | SSA_OP_VMUSTDEFKILL)
+ SSA_OP_USE | SSA_OP_VUSE | SSA_OP_VMUSTKILL)
{
- if (prepare_use_operand_for_rename (use_p, &uid))
- {
- REWRITE_THIS_STMT (stmt) = 1;
- if (!bitmap_bit_p (kills, uid))
- set_livein_block (USE_FROM_PTR (use_p), bb);
- }
+ tree sym = USE_FROM_PTR (use_p);
+ gcc_assert (DECL_P (sym));
+ if (!bitmap_bit_p (kills, DECL_UID (sym)))
+ set_livein_block (sym, bb);
+ REWRITE_THIS_STMT (stmt) = 1;
}
/* Note that virtual definitions are irrelevant for computing KILLS
live-on-entry. */
FOR_EACH_SSA_MAYDEF_OPERAND (def_p, use_p, stmt, iter)
{
- if (prepare_use_operand_for_rename (use_p, &uid))
- {
- /* If we do not already have an SSA_NAME for our destination,
- then set the destination to the source. */
- if (TREE_CODE (DEF_FROM_PTR (def_p)) != SSA_NAME)
- SET_DEF (def_p, USE_FROM_PTR (use_p));
-
- set_livein_block (USE_FROM_PTR (use_p), bb);
- set_def_block (DEF_FROM_PTR (def_p), bb, false, false);
- REWRITE_THIS_STMT (stmt) = 1;
- }
+ tree sym = USE_FROM_PTR (use_p);
+ gcc_assert (DECL_P (sym));
+ set_livein_block (sym, bb);
+ set_def_block (sym, bb, false);
+ REGISTER_DEFS_IN_THIS_STMT (stmt) = 1;
+ REWRITE_THIS_STMT (stmt) = 1;
}
/* Now process the defs and must-defs made by this statement. */
FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF | SSA_OP_VMUSTDEF)
{
- if (prepare_def_operand_for_rename (def, &uid))
- {
- set_def_block (def, bb, false, false);
- bitmap_set_bit (kills, uid);
- REWRITE_THIS_STMT (stmt) = 1;
- }
+ gcc_assert (DECL_P (def));
+ set_def_block (def, bb, false);
+ bitmap_set_bit (kills, DECL_UID (def));
+ REGISTER_DEFS_IN_THIS_STMT (stmt) = 1;
}
+
+ /* If we found the statement interesting then also mark the block BB
+ as interesting. */
+ if (REWRITE_THIS_STMT (stmt) || REGISTER_DEFS_IN_THIS_STMT (stmt))
+ SET_BIT (gd->interesting_blocks, bb->index);
}
{
bitmap_iterator bi;
unsigned bb_index;
- VEC(int) *work_stack;
+ VEC(int,heap) *work_stack;
bitmap phi_insertion_points;
- work_stack = VEC_alloc (int, n_basic_blocks);
+ work_stack = VEC_alloc (int, heap, n_basic_blocks);
phi_insertion_points = BITMAP_ALLOC (NULL);
/* Seed the work list with all the blocks in DEF_BLOCKS. */
while (VEC_length (int, work_stack) > 0)
{
bb_index = VEC_pop (int, work_stack);
-
+
+ /* Since the registration of NEW -> OLD name mappings is done
+ separately from the call to update_ssa, when updating the SSA
+ form, the basic blocks where new and/or old names are defined
+ may have disappeared by CFG cleanup calls. In this case,
+ we may pull a non-existing block from the work stack. */
+ gcc_assert (bb_index < (unsigned) last_basic_block);
+
EXECUTE_IF_AND_COMPL_IN_BITMAP (dfs[bb_index], phi_insertion_points,
- 0, bb_index, bi)
+ 0, bb_index, bi)
{
/* Use a safe push because if there is a definition of VAR
in every basic block, then WORK_STACK may eventually have
more than N_BASIC_BLOCK entries. */
- VEC_safe_push (int, work_stack, bb_index);
+ VEC_safe_push (int, heap, work_stack, bb_index);
bitmap_set_bit (phi_insertion_points, bb_index);
}
}
- VEC_free (int, work_stack);
+ VEC_free (int, heap, work_stack);
return phi_insertion_points;
}
}
+/* Retrieve or create a default definition for symbol SYM. */
+
+static inline tree
+get_default_def_for (tree sym)
+{
+ tree ddef = default_def (sym);
+
+ if (ddef == NULL_TREE)
+ {
+ ddef = make_ssa_name (sym, build_empty_stmt ());
+ set_default_def (sym, ddef);
+ }
+
+ return ddef;
+}
+
+
/* Insert PHI nodes for variable VAR using the iterated dominance
- frontier given in PHI_INSERTION_POINTS. */
+ frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
+ function assumes that the caller is incrementally updating the SSA
+ form, in which case (1) VAR is assumed to be an SSA name, (2) a new
+ SSA name is created for VAR's symbol, and, (3) all the arguments
+ for the newly created PHI node are set to VAR.
+
+ 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)
+insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
{
unsigned bb_index;
edge e;
struct def_blocks_d *def_map;
def_map = find_def_blocks_for (var);
+ gcc_assert (def_map);
/* Remove the blocks where we already have PHI nodes for VAR. */
bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
0, bb_index, bi)
{
bb = BASIC_BLOCK (bb_index);
- phi = create_phi_node (var, bb);
- /* If we are rewriting SSA names, add also the PHI arguments. */
- if (TREE_CODE (var) == SSA_NAME)
+ if (update_p && 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;
+
+ phi = create_phi_node (var, bb);
+ new_lhs = duplicate_ssa_name (var, phi);
+ SET_PHI_RESULT (phi, new_lhs);
+ 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);
}
- }
-}
-
-
-/* Helper for insert_phi_nodes. If VAR needs PHI nodes, insert them
- at the dominance frontier (DFS) of blocks defining VAR. */
-
-static inline void
-insert_phi_nodes_1 (tree var, bitmap *dfs)
-{
- struct def_blocks_d *def_map;
- bitmap idf;
-
- def_map = find_def_blocks_for (var);
- if (def_map == NULL)
- return;
-
- idf = find_idf (def_map->def_blocks, dfs);
-
- if (get_phi_state (var) != NEED_PHI_STATE_NO)
- insert_phi_nodes_for (var, idf);
+ else
+ {
+ tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var);
+ phi = create_phi_node (sym, bb);
+ }
- BITMAP_FREE (idf);
+ /* Mark this PHI node as interesting for update_ssa. */
+ REGISTER_DEFS_IN_THIS_STMT (phi) = 1;
+ REWRITE_THIS_STMT (phi) = 1;
+ }
}
the flowgraph. PHI nodes will only be inserted at the dominance
frontier of definition blocks for variables whose NEED_PHI_STATE
annotation is marked as ``maybe'' or ``unknown'' (computed by
- mark_def_sites). If NAMES_TO_RENAME is not NULL, do the same but
- for ssa name rewriting. */
+ mark_def_sites). */
static void
-insert_phi_nodes (bitmap *dfs, bitmap names_to_rename)
+insert_phi_nodes (bitmap *dfs)
{
- unsigned i;
- bitmap_iterator bi;
+ referenced_var_iterator rvi;
+ tree var;
timevar_push (TV_TREE_INSERT_PHI_NODES);
-
- /* Iterate over all variables in VARS_TO_RENAME. For each variable, add
- to the work list all the blocks that have a definition for the
- variable. PHI nodes will be added to the dominance frontier blocks of
- each definition block. */
- if (names_to_rename)
- {
- EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi)
- if (ssa_name (i))
- insert_phi_nodes_1 (ssa_name (i), dfs);
- }
- else if (vars_to_rename)
- {
- EXECUTE_IF_SET_IN_BITMAP (vars_to_rename, 0, i, bi)
- insert_phi_nodes_1 (referenced_var (i), dfs);
- }
- else
+
+ FOR_EACH_REFERENCED_VAR (var, rvi)
{
- for (i = 0; i < num_referenced_vars; i++)
- insert_phi_nodes_1 (referenced_var (i), dfs);
+ struct def_blocks_d *def_map;
+ bitmap idf;
+
+ def_map = find_def_blocks_for (var);
+ if (def_map == NULL)
+ continue;
+
+ if (get_phi_state (var) != NEED_PHI_STATE_NO)
+ {
+ idf = find_idf (def_map->def_blocks, dfs);
+ insert_phi_nodes_for (var, idf, false);
+ BITMAP_FREE (idf);
+ }
}
timevar_pop (TV_TREE_INSERT_PHI_NODES);
/* Register DEF (an SSA_NAME) to be a new definition for its underlying
variable (SSA_NAME_VAR (DEF)) and push VAR's current reaching definition
- into the stack pointed by BLOCK_DEFS_P. */
+ into the stack pointed to by BLOCK_DEFS_P. */
void
-register_new_def (tree def, VEC (tree_on_heap) **block_defs_p)
+register_new_def (tree def, VEC(tree,heap) **block_defs_p)
{
tree var = SSA_NAME_VAR (def);
tree currdef;
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. */
- VEC_safe_push (tree_on_heap, *block_defs_p, currdef ? currdef : var);
+ VEC_safe_push (tree, heap, *block_defs_p, currdef ? currdef : var);
/* Set the current reaching definition for VAR to be DEF. */
set_current_def (var, def);
fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
/* Mark the unwind point for this block. */
- VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
+ VEC_safe_push (tree, heap, block_defs_stack, 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
static tree
get_reaching_def (tree var)
{
- tree default_d, currdef_var, avar;
+ tree currdef_var, avar;
/* Lookup the current reaching definition for VAR. */
- default_d = NULL_TREE;
currdef_var = get_current_def (var);
/* If there is no reaching definition for VAR, create and register a
default definition for it (if needed). */
if (currdef_var == NULL_TREE)
{
- if (TREE_CODE (var) == SSA_NAME)
- avar = SSA_NAME_VAR (var);
- else
- avar = var;
-
- default_d = default_def (avar);
- if (default_d == NULL_TREE)
- {
- default_d = make_ssa_name (avar, build_empty_stmt ());
- set_default_def (avar, default_d);
- }
- set_current_def (var, default_d);
+ avar = DECL_P (var) ? var : SSA_NAME_VAR (var);
+ currdef_var = get_default_def_for (avar);
+ set_current_def (var, currdef_var);
}
/* Return the current reaching definition for VAR, or the default
definition, if we had to create one. */
- return (currdef_var) ? currdef_var : default_d;
-}
-
-
-/* Replace the operand pointed by OP_P with its immediate reaching
- definition. */
-
-static inline void
-rewrite_operand (use_operand_p op_p)
-{
- tree var = USE_FROM_PTR (op_p);
- if (TREE_CODE (var) != SSA_NAME)
- SET_USE (op_p, get_reaching_def (var));
- else
- {
-#if defined ENABLE_CHECKING
- /* If we get to this point, VAR is an SSA_NAME. If VAR's symbol
- was marked for renaming, make sure that its reaching
- definition is VAR itself. Otherwise, something has gone
- wrong. */
- tree sym = SSA_NAME_VAR (var);
- if (bitmap_bit_p (vars_to_rename, var_ann (sym)->uid))
- gcc_assert (var == get_reaching_def (SSA_NAME_VAR (var)));
-#endif
- }
+ return currdef_var;
}
/* If mark_def_sites decided that we don't need to rewrite this
statement, ignore it. */
- if (!REWRITE_THIS_STMT (stmt))
+ if (!REWRITE_THIS_STMT (stmt) && !REGISTER_DEFS_IN_THIS_STMT (stmt))
return;
if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\n");
}
- get_stmt_operands (stmt);
-
/* Step 1. Rewrite USES and VUSES in the statement. */
- FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
- rewrite_operand (use_p);
+ if (REWRITE_THIS_STMT (stmt))
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
+ SSA_OP_ALL_USES|SSA_OP_ALL_KILLS)
+ {
+ tree var = USE_FROM_PTR (use_p);
+ gcc_assert (DECL_P (var));
+ SET_USE (use_p, get_reaching_def (var));
+ }
/* Step 2. Register the statement's DEF and VDEF operands. */
- FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
- {
- if (TREE_CODE (DEF_FROM_PTR (def_p)) != SSA_NAME)
- SET_DEF (def_p, make_ssa_name (DEF_FROM_PTR (def_p), stmt));
-
- /* FIXME: We shouldn't be registering new defs if the variable
- doesn't need to be renamed. */
- register_new_def (DEF_FROM_PTR (def_p), &block_defs_stack);
- }
+ if (REGISTER_DEFS_IN_THIS_STMT (stmt))
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
+ {
+ tree var = DEF_FROM_PTR (def_p);
+ gcc_assert (DECL_P (var));
+ SET_DEF (def_p, make_ssa_name (var, stmt));
+ register_new_def (DEF_FROM_PTR (def_p), &block_defs_stack);
+ }
}
for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
{
tree currdef;
-
- /* If this PHI node has already been rewritten, then there is
- nothing to do for this PHI or any following PHIs since we
- always add new PHI nodes at the start of the PHI chain. */
- if (PHI_REWRITTEN (phi))
- break;
-
currdef = get_reaching_def (SSA_NAME_VAR (PHI_RESULT (phi)));
add_phi_arg (phi, currdef, e);
}
}
-/* Rewrite existing virtual PHI arguments so that they have the correct
- reaching definitions. BB is the basic block whose successors contain the
- PHI nodes we want to add arguments for. */
-
-static void
-rewrite_virtual_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
- basic_block bb)
-{
- edge e;
- use_operand_p op;
- edge_iterator ei;
-
- FOR_EACH_EDGE (e, ei, bb->succs)
- {
- tree phi;
-
- if (e->dest == EXIT_BLOCK_PTR)
- continue;
-
- for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
- {
- tree result = PHI_RESULT (phi);
- op = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
-
- if (is_gimple_reg (result)
- || !bitmap_bit_p (vars_to_rename,
- var_ann (SSA_NAME_VAR (result))->uid))
- continue;
-
- SET_USE (op, get_reaching_def (SSA_NAME_VAR (result)));
- if (e->flags & EDGE_ABNORMAL)
- SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (op)) = 1;
- }
- }
-}
-
-
/* Called after visiting basic block BB. Restore CURRDEFS to its
original value. */
basic_block bb ATTRIBUTE_UNUSED)
{
/* Restore CURRDEFS to its original state. */
- while (VEC_length (tree_on_heap, block_defs_stack) > 0)
+ while (VEC_length (tree, block_defs_stack) > 0)
{
- tree tmp = VEC_pop (tree_on_heap, block_defs_stack);
+ tree tmp = VEC_pop (tree, block_defs_stack);
tree saved_def, var;
if (tmp == NULL_TREE)
static void
def_blocks_free (void *p)
{
- struct def_blocks_d *entry = p;
+ struct def_blocks_d *entry = (struct def_blocks_d *) p;
BITMAP_FREE (entry->def_blocks);
BITMAP_FREE (entry->phi_blocks);
BITMAP_FREE (entry->livein_blocks);
}
-/* If a variable V in VARS_TO_RENAME is a pointer, the renaming
- process will cause us to lose the name memory tags that may have
- been associated with the various SSA_NAMEs of V. This means that
- the variables aliased to those name tags also need to be renamed
- again.
+/* 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)
+{
+ tree currdef = get_current_def (old_name);
+
+ /* Push the current reaching definition into *BLOCK_DEFS_P.
+ 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. */
+ VEC_reserve (tree, heap, block_defs_stack, 2);
+ VEC_quick_push (tree, block_defs_stack, currdef);
+ VEC_quick_push (tree, block_defs_stack, old_name);
+
+ /* Set the current reaching definition for OLD_NAME to be
+ NEW_NAME. */
+ set_current_def (old_name, new_name);
+}
- FIXME 1- We should either have a better scheme for renaming
- pointers that doesn't lose name tags or re-run alias
- analysis to recover points-to information.
- 2- Currently we just invalidate *all* the name tags. This
- should be more selective. */
+/* 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 void
-invalidate_name_tags (bitmap vars_to_rename)
+static inline void
+register_new_update_set (tree new_name, bitmap old_names)
{
- unsigned i;
- bool rename_name_tags_p;
bitmap_iterator bi;
+ unsigned i;
- rename_name_tags_p = false;
- EXECUTE_IF_SET_IN_BITMAP (vars_to_rename, 0, i, bi)
- {
- if (POINTER_TYPE_P (TREE_TYPE (referenced_var (i))))
- {
- rename_name_tags_p = true;
- break;
- }
- }
-
- if (rename_name_tags_p)
- for (i = 0; i < num_referenced_vars; i++)
- {
- var_ann_t ann = var_ann (referenced_var (i));
-
- if (ann->mem_tag_kind == NAME_TAG)
- {
- size_t j;
- varray_type may_aliases = ann->may_aliases;
-
- bitmap_set_bit (vars_to_rename, ann->uid);
- if (ann->may_aliases)
- for (j = 0; j < VARRAY_ACTIVE_SIZE (may_aliases); j++)
- {
- tree var = VARRAY_TREE (may_aliases, j);
- bitmap_set_bit (vars_to_rename, var_ann (var)->uid);
- }
- }
- }
+ EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi)
+ register_new_update_single (new_name, ssa_name (i));
}
-/* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
- form. FIX_VIRTUAL_PHIS is true if we should only be fixing up virtual
- PHI arguments, instead of adding new PHI arguments for just added PHI
- nodes. */
+/* 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. */
static void
-rewrite_blocks (bool fix_virtual_phis)
+rewrite_update_init_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
+ basic_block bb)
{
- struct dom_walk_data walk_data;
-
- /* Rewrite all the basic blocks in the program. */
- timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
-
- /* Setup callbacks for the generic dominator tree walker. */
- walk_data.walk_stmts_backward = false;
- walk_data.dom_direction = CDI_DOMINATORS;
- walk_data.initialize_block_local_data = NULL;
- walk_data.before_dom_children_before_stmts = rewrite_initialize_block;
- walk_data.before_dom_children_walk_stmts = rewrite_stmt;
- walk_data.before_dom_children_after_stmts = NULL;
- if (!fix_virtual_phis)
- walk_data.before_dom_children_after_stmts = rewrite_add_phi_arguments;
- else
- walk_data.before_dom_children_after_stmts = rewrite_virtual_phi_arguments;
-
- walk_data.after_dom_children_before_stmts = NULL;
- walk_data.after_dom_children_walk_stmts = NULL;
- walk_data.after_dom_children_after_stmts = rewrite_finalize_block;
- walk_data.global_data = NULL;
- walk_data.block_local_data_size = 0;
-
- block_defs_stack = VEC_alloc (tree_on_heap, 10);
+ edge e;
+ edge_iterator ei;
+ tree phi;
+ bool is_abnormal_phi;
- /* Initialize the dominator walker. */
- init_walk_dominator_tree (&walk_data);
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ fprintf (dump_file, "\n\nRegistering new PHI nodes in block #%d\n\n",
+ bb->index);
- /* Recursively walk the dominator tree rewriting each statement in
- each basic block. */
- walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
+ /* Mark the unwind point for this block. */
+ VEC_safe_push (tree, heap, block_defs_stack, NULL_TREE);
- /* Finalize the dominator walker. */
- fini_walk_dominator_tree (&walk_data);
+ /* Mark the LHS if any of the arguments flows through an abnormal
+ edge. */
+ is_abnormal_phi = false;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (e->flags & EDGE_ABNORMAL)
+ {
+ is_abnormal_phi = true;
+ break;
+ }
- /* Debugging dumps. */
- if (dump_file && (dump_flags & TDF_STATS))
+ /* 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 (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
- dump_dfa_stats (dump_file);
- dump_tree_ssa_stats (dump_file);
- }
+ tree lhs, lhs_sym;
- htab_delete (def_blocks);
- def_blocks = NULL;
-
- VEC_free (tree_on_heap, block_defs_stack);
- block_defs_stack = NULL;
+ if (!REGISTER_DEFS_IN_THIS_STMT (phi))
+ continue;
+
+ lhs = PHI_RESULT (phi);
+ lhs_sym = SSA_NAME_VAR (lhs);
- timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
+ if (symbol_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;
+ }
}
-/* Block initialization routine for mark_def_sites. Clear the
- KILLS bitmap at the start of each block. */
+/* 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. */
static void
-mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
- basic_block bb ATTRIBUTE_UNUSED)
+rewrite_update_fini_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
+ basic_block bb ATTRIBUTE_UNUSED)
{
- struct mark_def_sites_global_data *gd = walk_data->global_data;
+ while (VEC_length (tree, block_defs_stack) > 0)
+ {
+ tree var = VEC_pop (tree, block_defs_stack);
+ tree saved_def;
+
+ /* NULL indicates the unwind stop point for this block (see
+ rewrite_update_init_block). */
+ if (var == NULL)
+ return;
+
+ saved_def = VEC_pop (tree, block_defs_stack);
+ set_current_def (var, saved_def);
+ }
+}
+
+
+/* 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 (symbol_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);
+}
+
+
+/* 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. */
+
+static inline void
+maybe_register_def (def_operand_p def_p, tree stmt)
+{
+ tree def = DEF_FROM_PTR (def_p);
+ tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
+
+ /* If DEF is a naked symbol that needs renaming, create a
+ new name for it. */
+ if (symbol_marked_for_renaming (sym))
+ {
+ if (DECL_P (def))
+ {
+ def = make_ssa_name (def, stmt);
+ SET_DEF (def_p, def);
+ }
+
+ 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);
+ }
+}
+
+
+/* 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. */
+
+static void
+rewrite_update_stmt (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
+ basic_block bb ATTRIBUTE_UNUSED,
+ block_stmt_iterator si)
+{
+ stmt_ann_t ann;
+ tree stmt;
+ use_operand_p use_p;
+ def_operand_p def_p;
+ ssa_op_iter iter;
+
+ stmt = bsi_stmt (si);
+ ann = stmt_ann (stmt);
+
+ /* Only update marked statements. */
+ if (!REWRITE_THIS_STMT (stmt) && !REGISTER_DEFS_IN_THIS_STMT (stmt))
+ return;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Updating SSA information for statement ");
+ print_generic_stmt (dump_file, stmt, TDF_SLIM);
+ fprintf (dump_file, "\n");
+ }
+
+ /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
+ symbol is marked for renaming. */
+ if (REWRITE_THIS_STMT (stmt))
+ {
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
+ maybe_replace_use (use_p);
+
+ if (need_to_update_vops_p)
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter,
+ SSA_OP_VIRTUAL_USES | SSA_OP_VIRTUAL_KILLS)
+ 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. */
+ if (REGISTER_DEFS_IN_THIS_STMT (stmt))
+ {
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF)
+ maybe_register_def (def_p, stmt);
+
+ if (need_to_update_vops_p)
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_VIRTUAL_DEFS)
+ maybe_register_def (def_p, stmt);
+ }
+}
+
+
+/* Replace the operand pointed to by USE_P with USE's current reaching
+ definition. */
+
+static inline void
+replace_use (use_operand_p use_p, tree use)
+{
+ tree rdef = get_reaching_def (use);
+ if (rdef != use)
+ SET_USE (use_p, rdef);
+}
+
+
+/* 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 (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
+ basic_block bb)
+{
+ edge e;
+ edge_iterator ei;
+
+ FOR_EACH_EDGE (e, ei, bb->succs)
+ {
+ tree phi;
+
+ for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
+ {
+ tree arg;
+ use_operand_p arg_p;
+
+ /* Skip PHI nodes that are not marked for rewrite. */
+ if (!REWRITE_THIS_STMT (phi))
+ continue;
+
+ 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;
+
+ 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. */
+ replace_use (arg_p, SSA_NAME_VAR (PHI_RESULT (phi)));
+ }
+ else
+ {
+ tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg);
+
+ if (symbol_marked_for_renaming (sym))
+ replace_use (arg_p, sym);
+ else if (is_old_name (arg))
+ replace_use (arg_p, arg);
+ }
+
+ if (e->flags & EDGE_ABNORMAL)
+ SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1;
+ }
+ }
+}
+
+
+/* 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, sbitmap blocks)
+{
+ struct dom_walk_data walk_data;
+
+ /* Rewrite all the basic blocks in the program. */
+ timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
+
+ /* Setup callbacks for the generic dominator tree walker. */
+ memset (&walk_data, 0, sizeof (walk_data));
+
+ walk_data.dom_direction = CDI_DOMINATORS;
+ walk_data.interesting_blocks = blocks;
+
+ if (what == REWRITE_UPDATE)
+ walk_data.before_dom_children_before_stmts = rewrite_update_init_block;
+ else
+ walk_data.before_dom_children_before_stmts = rewrite_initialize_block;
+
+ if (what == REWRITE_ALL)
+ walk_data.before_dom_children_walk_stmts = rewrite_stmt;
+ else if (what == REWRITE_UPDATE)
+ walk_data.before_dom_children_walk_stmts = rewrite_update_stmt;
+ else
+ gcc_unreachable ();
+
+ if (what == REWRITE_ALL)
+ walk_data.before_dom_children_after_stmts = rewrite_add_phi_arguments;
+ else if (what == REWRITE_UPDATE)
+ walk_data.before_dom_children_after_stmts = rewrite_update_phi_arguments;
+ else
+ gcc_unreachable ();
+
+ if (what == REWRITE_ALL)
+ walk_data.after_dom_children_after_stmts = rewrite_finalize_block;
+ else if (what == REWRITE_UPDATE)
+ walk_data.after_dom_children_after_stmts = rewrite_update_fini_block;
+ else
+ gcc_unreachable ();
+
+ block_defs_stack = VEC_alloc (tree, heap, 10);
+
+ /* Initialize the dominator walker. */
+ init_walk_dominator_tree (&walk_data);
+
+ /* Recursively walk the dominator tree rewriting each statement in
+ each basic block. */
+ walk_dominator_tree (&walk_data, entry);
+
+ /* Finalize the dominator walker. */
+ fini_walk_dominator_tree (&walk_data);
+
+ /* Debugging dumps. */
+ if (dump_file && (dump_flags & TDF_STATS))
+ {
+ dump_dfa_stats (dump_file);
+ if (def_blocks)
+ dump_tree_ssa_stats (dump_file);
+ }
+
+ if (def_blocks)
+ {
+ htab_delete (def_blocks);
+ def_blocks = NULL;
+ }
+
+ VEC_free (tree, heap, block_defs_stack);
+
+ timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
+}
+
+
+/* Block initialization routine for mark_def_sites. Clear the
+ KILLS bitmap at the start of each block. */
+
+static void
+mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
+ basic_block bb ATTRIBUTE_UNUSED)
+{
+ struct mark_def_sites_global_data *gd =
+ (struct mark_def_sites_global_data *) walk_data->global_data;
bitmap kills = gd->kills;
bitmap_clear (kills);
}
-/* Mark the definition site blocks for each variable, so that we know where
- the variable is actually live. */
+/* Mark the definition site blocks for each variable, so that we know
+ where the variable is actually live.
-static void
-mark_def_site_blocks (void)
+ INTERESTING_BLOCKS will be filled in with all the blocks that
+ should be processed by the renamer. It is assumed to be
+ initialized and zeroed by the caller. */
+
+static void
+mark_def_site_blocks (sbitmap interesting_blocks)
{
- size_t i;
struct dom_walk_data walk_data;
struct mark_def_sites_global_data mark_def_sites_global_data;
+ referenced_var_iterator rvi;
+ tree var;
/* Allocate memory for the DEF_BLOCKS hash table. */
- def_blocks = htab_create (VARRAY_ACTIVE_SIZE (referenced_vars),
+ def_blocks = htab_create (num_referenced_vars,
def_blocks_hash, def_blocks_eq, def_blocks_free);
-
- for (i = 0; i < num_referenced_vars; i++)
- set_current_def (referenced_var (i), NULL_TREE);
-
- /* Ensure that the dominance information is OK. */
- calculate_dominance_info (CDI_DOMINATORS);
+ FOR_EACH_REFERENCED_VAR(var, rvi)
+ set_current_def (var, NULL_TREE);
/* Setup callbacks for the generic dominator tree walker to find and
mark definition sites. */
walk_data.after_dom_children_before_stmts = NULL;
walk_data.after_dom_children_walk_stmts = NULL;
walk_data.after_dom_children_after_stmts = NULL;
+ walk_data.interesting_blocks = NULL;
/* 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. */
mark_def_sites_global_data.kills = BITMAP_ALLOC (NULL);
+
+ /* Create the set of interesting blocks that will be filled by
+ mark_def_sites. */
+ mark_def_sites_global_data.interesting_blocks = interesting_blocks;
walk_data.global_data = &mark_def_sites_global_data;
/* We do not have any local data. */
/* Main entry point into the SSA builder. The renaming process
- proceeds in five main phases:
+ proceeds in four main phases:
- 1- If VARS_TO_RENAME has any entries, any existing PHI nodes for
- those variables are removed from the flow graph so that they can
- be computed again.
+ 1- Compute dominance frontier and immediate dominators, needed to
+ insert PHI nodes and rename the function in dominator tree
+ order.
- 2- Compute dominance frontier, needed to insert PHI nodes and
- rename the function in dominator tree order.
-
- 3- Find and mark all the blocks that define variables
+ 2- Find and mark all the blocks that define variables
(mark_def_site_blocks).
- 4- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
-
- 5- Rename all the blocks (rewrite_blocks) and statements in the program.
+ 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
- Steps 3 and 5 are done using the dominator tree walker
- (walk_dominator_tree).
+ 4- Rename all the blocks (rewrite_blocks) and statements in the program.
- ALL is true if all variables should be renamed (otherwise just those
- mentioned in vars_to_rename are taken into account). */
+ Steps 3 and 4 are done using the dominator tree walker
+ (walk_dominator_tree). */
-void
-rewrite_into_ssa (bool all)
+static void
+rewrite_into_ssa (void)
{
bitmap *dfs;
basic_block bb;
- bitmap old_vars_to_rename = vars_to_rename;
+ sbitmap interesting_blocks;
timevar_push (TV_TREE_SSA_OTHER);
- if (all)
- vars_to_rename = NULL;
- else
- {
- /* Initialize the array of variables to rename. */
- gcc_assert (vars_to_rename);
-
- if (bitmap_empty_p (vars_to_rename))
- {
- timevar_pop (TV_TREE_SSA_OTHER);
- return;
- }
-
- invalidate_name_tags (vars_to_rename);
-
- /* Now remove all the existing PHI nodes (if any) for the variables
- that we are about to rename into SSA. */
- remove_all_phi_nodes_for (vars_to_rename);
- }
+ /* Initialize operand data structures. */
+ init_ssa_operands ();
- mark_def_site_blocks ();
+ /* 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);
+ sbitmap_zero (interesting_blocks);
/* Initialize dominance frontier. */
- dfs = (bitmap *) xmalloc (last_basic_block * sizeof (bitmap *));
+ dfs = (bitmap *) xmalloc (last_basic_block * sizeof (bitmap));
FOR_EACH_BB (bb)
dfs[bb->index] = BITMAP_ALLOC (NULL);
- /* Compute dominance frontiers. */
+ /* 1- Compute dominance frontiers. */
+ calculate_dominance_info (CDI_DOMINATORS);
compute_dominance_frontiers (dfs);
- /* Insert PHI nodes at dominance frontiers of definition blocks. */
- insert_phi_nodes (dfs, NULL);
+ /* 2- Find and mark definition sites. */
+ mark_def_site_blocks (interesting_blocks);
- rewrite_blocks (false);
+ /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
+ insert_phi_nodes (dfs);
+
+ /* 4- Rename all the blocks. */
+ rewrite_blocks (ENTRY_BLOCK_PTR, REWRITE_ALL, interesting_blocks);
/* Free allocated memory. */
FOR_EACH_BB (bb)
BITMAP_FREE (dfs[bb->index]);
free (dfs);
+ sbitmap_free (interesting_blocks);
- vars_to_rename = old_vars_to_rename;
timevar_pop (TV_TREE_SSA_OTHER);
+ in_ssa_p = true;
}
-/* Rewrites all variables into SSA. */
-
-static void
-rewrite_all_into_ssa (void)
-{
- init_ssa_operands ();
- rewrite_into_ssa (true);
-}
-
struct tree_opt_pass pass_build_ssa =
{
"ssa", /* name */
NULL, /* gate */
- rewrite_all_into_ssa, /* execute */
+ rewrite_into_ssa, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
PROP_ssa, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
- TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */
+ TODO_dump_func
+ | TODO_verify_ssa
+ | TODO_remove_unused_locals, /* todo_flags_finish */
0 /* letter */
};
-/* Rewrite the def-def chains of virtual operands so that they have
- the correct reaching definitions. */
-
-void
-rewrite_def_def_chains (void)
-{
- /* Ensure that the dominance information is OK. */
- calculate_dominance_info (CDI_DOMINATORS);
- mark_def_site_blocks ();
- rewrite_blocks (true);
-}
-
-
-
-/*---------------------------------------------------------------------------
- Functions to fix a program in invalid SSA form into valid SSA
- form. The main entry point here is rewrite_ssa_into_ssa.
----------------------------------------------------------------------------*/
-
-/* Called after visiting basic block BB. Restore CURRDEFS to its
- original value. */
+/* 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
-ssa_rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
- basic_block bb ATTRIBUTE_UNUSED)
+mark_def_interesting (tree var, tree stmt, basic_block bb, bitmap blocks,
+ bool insert_phi_p)
{
+ REGISTER_DEFS_IN_THIS_STMT (stmt) = 1;
+ bitmap_set_bit (blocks, bb->index);
- /* Step 5. Restore the current reaching definition for each variable
- referenced in the block (in reverse order). */
- while (VEC_length (tree_on_heap, block_defs_stack) > 0)
+ if (insert_phi_p)
{
- tree var = VEC_pop (tree_on_heap, block_defs_stack);
- tree saved_def;
-
- if (var == NULL)
- break;
+ bool is_phi_p = TREE_CODE (stmt) == PHI_NODE;
- saved_def = VEC_pop (tree_on_heap, block_defs_stack);
- set_current_def (var, saved_def);
+ 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);
+ }
}
}
-/* Register DEF (an SSA_NAME) to be a new definition for the original
- ssa name VAR and push VAR's current reaching definition
- into the stack pointed by BLOCK_DEFS_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. BLOCKS is the set of blocks that need updating. */
-static void
-ssa_register_new_def (tree var, tree def)
+static inline void
+mark_use_interesting (tree var, tree stmt, basic_block bb, bitmap blocks,
+ bool insert_phi_p)
{
- 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
- nothing to do. TODO we should not be called at all, and just
- keep the original name. */
- if (get_phi_state (var) == NEED_PHI_STATE_NO)
+ REWRITE_THIS_STMT (stmt) = 1;
+ bitmap_set_bit (blocks, bb->index);
+
+ /* 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)
{
- set_current_def (var, def);
- return;
+ struct def_blocks_d *db_p = get_def_blocks_for (var);
+ if (!bitmap_bit_p (db_p->def_blocks, bb->index))
+ set_livein_block (var, bb);
}
-
- currdef = get_current_def (var);
-
- /* Push the current reaching definition into *BLOCK_DEFS_P. 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. */
- VEC_safe_push (tree_on_heap, block_defs_stack, currdef);
- VEC_safe_push (tree_on_heap, block_defs_stack, var);
-
- /* Set the current reaching definition for VAR to be DEF. */
- set_current_def (var, def);
}
-/* Same as rewrite_stmt, for rewriting ssa names. */
+/* Do a dominator walk starting at BB processing statements that
+ reference symbols in SYMS_TO_RENAME. This is very similar to
+ mark_def_sites, but the scan handles statements whose operands may
+ already be SSA names. Blocks that contain defs or uses of symbols
+ in SYMS_TO_RENAME are added to BLOCKS.
+
+ 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. */
static void
-ssa_rewrite_stmt (struct dom_walk_data *walk_data,
- basic_block bb ATTRIBUTE_UNUSED,
- block_stmt_iterator si)
+prepare_block_for_update (basic_block bb, bitmap blocks, bool insert_phi_p)
{
- stmt_ann_t ann;
- tree stmt, var;
- ssa_op_iter iter;
- use_operand_p use_p;
- def_operand_p def_p;
- sbitmap names_to_rename = walk_data->global_data;
-
- stmt = bsi_stmt (si);
- ann = stmt_ann (stmt);
+ basic_block son;
+ block_stmt_iterator si;
+ tree phi;
- if (dump_file && (dump_flags & TDF_DETAILS))
+ /* Process PHI nodes marking interesting those that define or use
+ the symbols that we are interested in. */
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
- fprintf (dump_file, "Renaming statement ");
- print_generic_stmt (dump_file, stmt, TDF_SLIM);
- fprintf (dump_file, "\n");
- }
+ tree lhs_sym, lhs = PHI_RESULT (phi);
- /* We have just scanned the code for operands. No statement should
- be modified. */
- gcc_assert (!ann->modified);
+ lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
- /* Step 1. Rewrite USES and VUSES in the statement. */
- FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
- {
- if (TEST_BIT (names_to_rename, SSA_NAME_VERSION (USE_FROM_PTR (use_p))))
- SET_USE (use_p, get_reaching_def (USE_FROM_PTR (use_p)));
+ if (symbol_marked_for_renaming (lhs_sym))
+ {
+ mark_use_interesting (lhs_sym, phi, bb, blocks, insert_phi_p);
+ mark_def_interesting (lhs_sym, phi, bb, blocks, insert_phi_p);
+ }
}
- /* Step 2. Register the statement's DEF and VDEF operands. */
- FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
+ /* Process the statements. */
+ for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
{
- var = DEF_FROM_PTR (def_p);
-
- if (!TEST_BIT (names_to_rename, SSA_NAME_VERSION (var)))
- continue;
+ tree stmt;
+ ssa_op_iter i;
+ use_operand_p use_p;
+ def_operand_p def_p;
+
+ stmt = bsi_stmt (si);
- SET_DEF (def_p, duplicate_ssa_name (var, stmt));
- ssa_register_new_def (var, DEF_FROM_PTR (def_p));
- }
-}
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_USE)
+ {
+ tree use = USE_FROM_PTR (use_p);
+ tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
+ if (symbol_marked_for_renaming (sym))
+ mark_use_interesting (use, stmt, bb, blocks, insert_phi_p);
+ }
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_DEF)
+ {
+ tree def = DEF_FROM_PTR (def_p);
+ tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
-/* Ditto, for ssa name rewriting. */
+ if (symbol_marked_for_renaming (sym))
+ mark_def_interesting (def, stmt, bb, blocks, insert_phi_p);
+ }
-static void
-ssa_rewrite_phi_arguments (struct dom_walk_data *walk_data, basic_block bb)
-{
- edge e;
- sbitmap names_to_rename = walk_data->global_data;
- use_operand_p op;
- edge_iterator ei;
+ FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_VIRTUAL_DEFS)
+ {
+ tree def = DEF_FROM_PTR (def_p);
+ tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
- FOR_EACH_EDGE (e, ei, bb->succs)
- {
- tree phi;
-
- if (e->dest == EXIT_BLOCK_PTR)
- continue;
+ if (symbol_marked_for_renaming (sym))
+ {
+ mark_use_interesting (sym, stmt, bb, blocks, insert_phi_p);
+ mark_def_interesting (sym, stmt, bb, blocks, insert_phi_p);
+ }
+ }
- for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
+ FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_VUSE)
{
- op = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
- if (TREE_CODE (USE_FROM_PTR (op)) != SSA_NAME)
- continue;
-
- if (!TEST_BIT (names_to_rename, SSA_NAME_VERSION (USE_FROM_PTR (op))))
- continue;
+ tree use = USE_FROM_PTR (use_p);
+ tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
- SET_USE (op, get_reaching_def (USE_FROM_PTR (op)));
- if (e->flags & EDGE_ABNORMAL)
- SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (op)) = 1;
+ if (symbol_marked_for_renaming (sym))
+ mark_use_interesting (sym, stmt, bb, blocks, insert_phi_p);
}
}
+
+ /* Now visit all the blocks dominated by BB. */
+ for (son = first_dom_son (CDI_DOMINATORS, bb);
+ son;
+ son = next_dom_son (CDI_DOMINATORS, son))
+ prepare_block_for_update (son, blocks, insert_phi_p);
}
-/* Ditto, for rewriting ssa names. */
+
+/* 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
-ssa_rewrite_initialize_block (struct dom_walk_data *walk_data, basic_block bb)
+prepare_use_sites_for (tree name, bitmap blocks, bool insert_phi_p)
{
- tree phi, new_name;
- sbitmap names_to_rename = walk_data->global_data;
- edge e;
- bool abnormal_phi;
- edge_iterator ei;
-
- 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. */
- VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
-
- FOR_EACH_EDGE (e, ei, bb->preds)
- if (e->flags & EDGE_ABNORMAL)
- break;
- abnormal_phi = (e != NULL);
+ use_operand_p use_p;
+ imm_use_iterator iter;
- /* 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 (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ FOR_EACH_IMM_USE_FAST (use_p, iter, name)
{
- tree result = PHI_RESULT (phi);
+ tree stmt = USE_STMT (use_p);
+ basic_block bb = bb_for_stmt (stmt);
- if (TEST_BIT (names_to_rename, SSA_NAME_VERSION (result)))
+ if (TREE_CODE (stmt) == PHI_NODE)
{
- new_name = duplicate_ssa_name (result, phi);
- SET_PHI_RESULT (phi, new_name);
+ /* Mark this use of NAME interesting for the renamer.
+ Notice that we explicitly call mark_use_interesting with
+ INSERT_PHI_P == false.
+
+ This is to avoid marking NAME as live-in in this block
+ BB. If we were to mark NAME live-in to BB, then NAME
+ would be considered live-in through ALL incoming edges to
+ BB which is not what we want. Since we are updating the
+ SSA form for NAME, we don't really know what other names
+ of NAME are coming in through other edges into BB.
+
+ If we considered NAME live-in at BB, then the PHI
+ placement algorithm may try to insert PHI nodes in blocks
+ that are not only unnecessary but also the renamer would
+ not know how to fill in. */
+ mark_use_interesting (name, stmt, bb, blocks, false);
+
+ /* As discussed above, we only want to mark NAME live-in
+ through the edge corresponding to its slot inside the PHI
+ argument list. So, we look for the block BB1 where NAME
+ is flowing through. If BB1 does not contain a definition
+ of NAME, then consider NAME live-in at BB1. */
+ if (insert_phi_p)
+ {
+ int ix = PHI_ARG_INDEX_FROM_USE (use_p);
+ edge e = PHI_ARG_EDGE (stmt, ix);
+ basic_block bb1 = e->src;
+ struct def_blocks_d *db = get_def_blocks_for (name);
- if (abnormal_phi)
- SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1;
- ssa_register_new_def (result, new_name);
+ if (!bitmap_bit_p (db->def_blocks, bb1->index))
+ set_livein_block (name, bb1);
+ }
+ }
+ else
+ {
+ /* For regular statements, mark this as an interesting use
+ for NAME. */
+ mark_use_interesting (name, stmt, bb, blocks, insert_phi_p);
}
}
}
-/* Same as mark_def_sites, but works over SSA names. */
+/* 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
-ssa_mark_def_sites (struct dom_walk_data *walk_data,
- basic_block bb,
- block_stmt_iterator bsi)
+prepare_def_site_for (tree name, bitmap blocks, bool insert_phi_p)
{
- struct mark_def_sites_global_data *gd = walk_data->global_data;
- bitmap kills = gd->kills;
- size_t uid, def_uid;
- tree stmt, use, def;
- ssa_op_iter iter;
+ tree stmt;
+ basic_block bb;
- /* Mark all the blocks that have definitions for each variable in the
- names_to_rename bitmap. */
- stmt = bsi_stmt (bsi);
- update_stmt_if_modified (stmt);
+ gcc_assert (names_to_release == NULL
+ || !bitmap_bit_p (names_to_release, SSA_NAME_VERSION (name)));
- /* 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_TREE_OPERAND (use, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
+ stmt = SSA_NAME_DEF_STMT (name);
+ bb = bb_for_stmt (stmt);
+ if (bb)
{
- uid = SSA_NAME_VERSION (use);
+ gcc_assert (bb->index < last_basic_block);
+ mark_def_interesting (name, stmt, bb, blocks, insert_phi_p);
+ }
+}
+
+
+/* Mark definition and use sites of names in NEW_SSA_NAMES and
+ OLD_SSA_NAMES. Add each definition block to BLOCKS. INSERT_PHI_P
+ is true if the caller wants to insert PHI nodes for newly created
+ names. */
- if (TEST_BIT (gd->names_to_rename, uid)
- && !bitmap_bit_p (kills, uid))
- set_livein_block (use, bb);
+static void
+prepare_names_to_update (bitmap blocks, 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)
+ RESET_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_SBITMAP (new_ssa_names, 0, i, sbi)
+ prepare_def_site_for (ssa_name (i), blocks, 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_SBITMAP (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), blocks, insert_phi_p);
+ prepare_use_sites_for (ssa_name (i), blocks, insert_phi_p);
}
-
- /* Now process the definition made by this statement. Mark the
- variables in KILLS. */
- FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
+}
+
+
+/* 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, 0);
+ 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), 0);
+ fprintf (file, " ");
+ }
+
+ fprintf (file, "}\n");
+}
+
+
+/* Dump all the names replaced by NAME to stderr. */
+
+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 ())
+ return;
+
+ if (new_ssa_names && sbitmap_first_set_bit (new_ssa_names) >= 0)
{
- def_uid = SSA_NAME_VERSION (def);
+ 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_SBITMAP (new_ssa_names, 0, i, sbi)
+ dump_names_replaced_by (file, ssa_name (i));
+
+ fprintf (file, "\n");
+ fprintf (file, "Number of virtual NEW -> OLD mappings: %7u\n",
+ update_ssa_stats.num_virtual_mappings);
+ fprintf (file, "Number of real NEW -> OLD mappings: %7u\n",
+ update_ssa_stats.num_total_mappings
+ - update_ssa_stats.num_virtual_mappings);
+ fprintf (file, "Number of total NEW -> OLD mappings: %7u\n",
+ update_ssa_stats.num_total_mappings);
+
+ fprintf (file, "\nNumber of virtual symbols: %u\n",
+ update_ssa_stats.num_virtual_symbols);
+ }
- if (TEST_BIT (gd->names_to_rename, def_uid))
+ if (syms_to_rename && !bitmap_empty_p (syms_to_rename))
+ {
+ fprintf (file, "\n\nSymbols to be put in SSA form\n\n");
+ EXECUTE_IF_SET_IN_BITMAP (syms_to_rename, 0, i, bi)
+ {
+ print_generic_expr (file, referenced_var (i), 0);
+ fprintf (file, " ");
+ }
+ }
+
+ if (names_to_release && !bitmap_empty_p (names_to_release))
+ {
+ fprintf (file, "\n\nSSA names to release after updating the SSA web\n\n");
+ EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
{
- set_def_block (def, bb, false, true);
- bitmap_set_bit (kills, def_uid);
+ print_generic_expr (file, ssa_name (i), 0);
+ fprintf (file, " ");
}
}
+
+ fprintf (file, "\n\n");
}
-/* Block initialization routine for mark_def_sites. Clear the
- KILLS bitmap at the start of each block. */
+/* Dump SSA update information to stderr. */
+
+void
+debug_update_ssa (void)
+{
+ dump_update_ssa (stderr);
+}
+
+
+/* Initialize data structures used for incremental SSA updates. */
static void
-ssa_mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
- basic_block bb)
+init_update_ssa (void)
{
- struct mark_def_sites_global_data *gd = walk_data->global_data;
- bitmap kills = gd->kills;
- tree phi, def;
- unsigned def_uid;
+ /* 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);
+ sbitmap_zero (old_ssa_names);
+
+ new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
+ sbitmap_zero (new_ssa_names);
+
+ repl_tbl = htab_create (20, repl_map_hash, repl_map_eq, repl_map_free);
+ need_to_initialize_update_ssa_p = false;
+ need_to_update_vops_p = false;
+ syms_to_rename = BITMAP_ALLOC (NULL);
+ names_to_release = NULL;
+ memset (&update_ssa_stats, 0, sizeof (update_ssa_stats));
+ update_ssa_stats.virtual_symbols = BITMAP_ALLOC (NULL);
+}
- bitmap_clear (kills);
- for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+/* 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;
+
+ htab_delete (repl_tbl);
+ repl_tbl = NULL;
+
+ need_to_initialize_update_ssa_p = true;
+ need_to_update_vops_p = false;
+ BITMAP_FREE (syms_to_rename);
+ BITMAP_FREE (update_ssa_stats.virtual_symbols);
+
+ if (names_to_release)
{
- def = PHI_RESULT (phi);
- def_uid = SSA_NAME_VERSION (def);
+ EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
+ release_ssa_name (ssa_name (i));
+ BITMAP_FREE (names_to_release);
+ }
- if (!TEST_BIT (gd->names_to_rename, def_uid))
- continue;
+ for (i = 1; i < num_ssa_names; i++)
+ {
+ tree n = ssa_name (i);
- set_def_block (def, bb, true, true);
- bitmap_set_bit (kills, def_uid);
+ if (n)
+ {
+ free (SSA_NAME_AUX (n));
+ SSA_NAME_AUX (n) = NULL;
+ }
}
}
-/* Marks ssa names used as arguments of phis at the end of BB. */
-static void
-ssa_mark_phi_uses (struct dom_walk_data *walk_data, basic_block bb)
+/* Create a new name for OLD_NAME in statement STMT and replace the
+ operand pointed to by DEF_P with the newly created name. Return
+ the new name and register the replacement mapping <NEW, OLD> in
+ update_ssa's tables. */
+
+tree
+create_new_def_for (tree old_name, tree stmt, def_operand_p def)
{
- struct mark_def_sites_global_data *gd = walk_data->global_data;
- bitmap kills = gd->kills;
- edge e;
- tree phi, use;
- unsigned uid;
- edge_iterator ei;
+ tree new_name = duplicate_ssa_name (old_name, stmt);
- FOR_EACH_EDGE (e, ei, bb->succs)
+ SET_DEF (def, new_name);
+
+ if (TREE_CODE (stmt) == PHI_NODE)
{
- if (e->dest == EXIT_BLOCK_PTR)
- continue;
+ edge e;
+ edge_iterator ei;
+ basic_block bb = bb_for_stmt (stmt);
- for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
- {
- use = PHI_ARG_DEF_FROM_EDGE (phi, e);
- if (TREE_CODE (use) != SSA_NAME)
- continue;
+ /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (e->flags & EDGE_ABNORMAL)
+ {
+ SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1;
+ break;
+ }
+ }
- uid = SSA_NAME_VERSION (use);
+ register_new_name_mapping (new_name, old_name);
- if (TEST_BIT (gd->names_to_rename, uid)
- && !bitmap_bit_p (kills, uid))
- set_livein_block (use, bb);
- }
- }
+ /* 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. */
+ set_current_def (old_name, new_name);
+
+ return new_name;
}
-
-
-/* The marked ssa names may have more than one definition;
- add PHI nodes and rewrite them to fix this. */
+
+
+/* Register name NEW to be a replacement for name OLD. This function
+ must be called for every replacement that should be performed by
+ update_ssa. */
void
-rewrite_ssa_into_ssa (void)
+register_new_name_mapping (tree new, tree old)
+{
+ if (need_to_initialize_update_ssa_p)
+ init_update_ssa ();
+
+ add_new_name_mapping (new, old);
+}
+
+
+/* Register symbol SYM to be renamed by update_ssa. */
+
+void
+mark_sym_for_renaming (tree sym)
+{
+ if (need_to_initialize_update_ssa_p)
+ init_update_ssa ();
+
+ bitmap_set_bit (syms_to_rename, DECL_UID (sym));
+
+ if (!is_gimple_reg (sym))
+ need_to_update_vops_p = true;
+}
+
+
+/* Register all the symbols in SET to be renamed by update_ssa. */
+
+void
+mark_set_for_renaming (bitmap set)
{
- bitmap *dfs;
- basic_block bb;
- struct dom_walk_data walk_data;
- struct mark_def_sites_global_data mark_def_sites_global_data;
- unsigned i;
- sbitmap snames_to_rename;
- bitmap to_rename;
bitmap_iterator bi;
+ unsigned i;
+
+ if (bitmap_empty_p (set))
+ return;
+
+ if (need_to_initialize_update_ssa_p)
+ init_update_ssa ();
+
+ bitmap_ior_into (syms_to_rename, set);
+
+ EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
+ if (!is_gimple_reg (referenced_var (i)))
+ {
+ need_to_update_vops_p = true;
+ break;
+ }
+}
+
+
+/* Return true if there is any work to be done by update_ssa. */
+
+bool
+need_ssa_update_p (void)
+{
+ return syms_to_rename || old_ssa_names || new_ssa_names;
+}
+
+
+/* Return true if name N has been registered in the replacement table. */
+
+bool
+name_registered_for_update_p (tree n)
+{
+ if (!need_ssa_update_p ())
+ return false;
+
+ return is_new_name (n)
+ || is_old_name (n)
+ || symbol_marked_for_renaming (SSA_NAME_VAR (n));
+}
+
+
+/* Return the set of all the SSA names marked to be replaced. */
+
+bitmap
+ssa_names_to_replace (void)
+{
+ unsigned i = 0;
+ bitmap ret;
+ sbitmap_iterator sbi;
- if (!any_marked_for_rewrite_p ())
+ ret = BITMAP_ALLOC (NULL);
+ EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
+ bitmap_set_bit (ret, i);
+
+ return ret;
+}
+
+
+/* Mark NAME to be released after update_ssa has finished. */
+
+void
+release_ssa_name_after_update_ssa (tree name)
+{
+ gcc_assert (!need_to_initialize_update_ssa_p);
+
+ if (names_to_release == NULL)
+ names_to_release = BITMAP_ALLOC (NULL);
+
+ bitmap_set_bit (names_to_release, SSA_NAME_VERSION (name));
+}
+
+
+/* Insert new PHI nodes to replace VAR. DFS contains dominance
+ frontier information. BLOCKS is the set of blocks to be updated.
+
+ This is slightly different than the regular PHI insertion
+ algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
+ real names (i.e., GIMPLE registers) are inserted:
+
+ - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
+ nodes inside the region affected by the block that defines VAR
+ and the blocks that define all its replacements. All these
+ definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
+
+ First, we compute the entry point to the region (ENTRY). This is
+ given by the nearest common dominator to all the definition
+ blocks. When computing the iterated dominance frontier (IDF), any
+ block not strictly dominated by ENTRY is ignored.
+
+ We then call the standard PHI insertion algorithm with the pruned
+ IDF.
+
+ - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
+ names is not pruned. PHI nodes are inserted at every IDF block. */
+
+static void
+insert_updated_phi_nodes_for (tree var, bitmap *dfs, bitmap blocks,
+ unsigned update_flags)
+{
+ basic_block entry;
+ struct def_blocks_d *db;
+ bitmap idf, pruned_idf;
+ bitmap_iterator bi;
+ unsigned i;
+
+#if defined ENABLE_CHECKING
+ if (TREE_CODE (var) == SSA_NAME)
+ gcc_assert (is_old_name (var));
+ else
+ gcc_assert (symbol_marked_for_renaming (var));
+#endif
+
+ /* Get all the definition sites for VAR. */
+ db = find_def_blocks_for (var);
+
+ /* No need to do anything if there were no definitions to VAR. */
+ if (db == NULL || bitmap_empty_p (db->def_blocks))
return;
- to_rename = marked_ssa_names ();
- timevar_push (TV_TREE_SSA_OTHER);
+ /* Compute the initial iterated dominance frontier. */
+ idf = find_idf (db->def_blocks, dfs);
+ pruned_idf = BITMAP_ALLOC (NULL);
- /* Allocate memory for the DEF_BLOCKS hash table. */
- def_blocks = htab_create (num_ssa_names,
- def_blocks_hash, def_blocks_eq, def_blocks_free);
+ if (TREE_CODE (var) == SSA_NAME)
+ {
+ if (update_flags == TODO_update_ssa)
+ {
+ /* If doing regular SSA updates for GIMPLE registers, we are
+ only interested in IDF blocks dominated by the nearest
+ common dominator of all the definition blocks. */
+ entry = nearest_common_dominator_for_set (CDI_DOMINATORS,
+ db->def_blocks);
+
+ if (entry != ENTRY_BLOCK_PTR)
+ EXECUTE_IF_SET_IN_BITMAP (idf, 0, i, bi)
+ if (BASIC_BLOCK (i) != entry
+ && dominated_by_p (CDI_DOMINATORS, BASIC_BLOCK (i), entry))
+ bitmap_set_bit (pruned_idf, i);
+ }
+ else
+ {
+ /* Otherwise, do not prune the IDF for VAR. */
+ gcc_assert (update_flags == TODO_update_ssa_full_phi);
+ bitmap_copy (pruned_idf, idf);
+ }
+ }
+ else
+ {
+ /* Otherwise, VAR is a symbol that needs to be put into SSA form
+ for the first time, so we need to compute the full IDF for
+ it. */
+ bitmap_copy (pruned_idf, idf);
+ }
- /* Initialize dominance frontier and immediate dominator bitmaps.
- Also count the number of predecessors for each block. Doing so
- can save significant time during PHI insertion for large graphs. */
- dfs = (bitmap *) xmalloc (last_basic_block * sizeof (bitmap *));
- FOR_EACH_BB (bb)
- dfs[bb->index] = BITMAP_ALLOC (NULL);
+ if (!bitmap_empty_p (pruned_idf))
+ {
+ /* Make sure that PRUNED_IDF blocks and all their feeding blocks
+ are included in the region to be updated. The feeding blocks
+ are important to guarantee that the PHI arguments are renamed
+ properly. */
+ bitmap_ior_into (blocks, pruned_idf);
+ EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi)
+ {
+ edge e;
+ edge_iterator ei;
+ basic_block bb = BASIC_BLOCK (i);
- /* Ensure that the dominance information is OK. */
- calculate_dominance_info (CDI_DOMINATORS);
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (e->src->index >= 0)
+ bitmap_set_bit (blocks, e->src->index);
+ }
- /* Compute dominance frontiers. */
- compute_dominance_frontiers (dfs);
+ insert_phi_nodes_for (var, pruned_idf, true);
+ }
- /* Setup callbacks for the generic dominator tree walker to find and
- mark definition sites. */
- walk_data.walk_stmts_backward = false;
- walk_data.dom_direction = CDI_DOMINATORS;
- walk_data.initialize_block_local_data = NULL;
- walk_data.before_dom_children_before_stmts
- = ssa_mark_def_sites_initialize_block;
- walk_data.before_dom_children_walk_stmts = ssa_mark_def_sites;
- walk_data.before_dom_children_after_stmts = ssa_mark_phi_uses;
- walk_data.after_dom_children_before_stmts = NULL;
- walk_data.after_dom_children_walk_stmts = NULL;
- walk_data.after_dom_children_after_stmts = NULL;
+ BITMAP_FREE (pruned_idf);
+ BITMAP_FREE (idf);
+}
+
+
+/* Heuristic to determine whether SSA name mappings for virtual names
+ should be discarded and their symbols rewritten from scratch. When
+ there is a large number of mappings for virtual names, the
+ insertion of PHI nodes for the old names in the mappings takes
+ considerable more time than if we inserted PHI nodes for the
+ symbols instead.
+
+ Currently the heuristic takes these stats into account:
+
+ - Number of mappings for virtual SSA names.
+ - Number of distinct virtual symbols involved in those mappings.
+
+ If the number of virtual mappings is much larger than the number of
+ virtual symbols, then it will be faster to compute PHI insertion
+ spots for the symbols. Even if this involves traversing the whole
+ CFG, which is what happens when symbols are renamed from scratch. */
+
+static bool
+switch_virtuals_to_full_rewrite_p (void)
+{
+ if (update_ssa_stats.num_virtual_mappings < (unsigned) MIN_VIRTUAL_MAPPINGS)
+ return false;
+
+ if (update_ssa_stats.num_virtual_mappings
+ > (unsigned) VIRTUAL_MAPPINGS_TO_SYMS_RATIO
+ * update_ssa_stats.num_virtual_symbols)
+ return true;
+
+ return false;
+}
+
+
+/* Remove every virtual mapping and mark all the affected virtual
+ symbols for renaming. */
+
+static void
+switch_virtuals_to_full_rewrite (void)
+{
+ unsigned i = 0;
+ sbitmap_iterator sbi;
- snames_to_rename = sbitmap_alloc (num_ssa_names);
- sbitmap_zero (snames_to_rename);
- EXECUTE_IF_SET_IN_BITMAP (to_rename, 0, i, bi)
+ if (dump_file)
{
- SET_BIT (snames_to_rename, i);
- set_current_def (ssa_name (i), NULL_TREE);
+ fprintf (dump_file, "\nEnabled virtual name mapping heuristic.\n");
+ fprintf (dump_file, "\tNumber of virtual mappings: %7u\n",
+ update_ssa_stats.num_virtual_mappings);
+ fprintf (dump_file, "\tNumber of unique virtual symbols: %7u\n",
+ update_ssa_stats.num_virtual_symbols);
+ fprintf (dump_file, "Updating FUD-chains from top of CFG will be "
+ "faster than processing\nthe name mappings.\n\n");
}
- mark_def_sites_global_data.kills = BITMAP_ALLOC (NULL);
- mark_def_sites_global_data.names_to_rename = snames_to_rename;
- walk_data.global_data = &mark_def_sites_global_data;
+ /* Remove all virtual names from NEW_SSA_NAMES and OLD_SSA_NAMES.
+ Note that it is not really necessary to remove the mappings from
+ REPL_TBL, that would only waste time. */
+ EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi)
+ if (!is_gimple_reg (ssa_name (i)))
+ RESET_BIT (new_ssa_names, i);
- block_defs_stack = VEC_alloc (tree_on_heap, 10);
+ EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
+ if (!is_gimple_reg (ssa_name (i)))
+ RESET_BIT (old_ssa_names, i);
- /* We do not have any local data. */
- walk_data.block_local_data_size = 0;
+ bitmap_ior_into (syms_to_rename, update_ssa_stats.virtual_symbols);
+}
- /* Initialize the dominator walker. */
- init_walk_dominator_tree (&walk_data);
- /* Recursively walk the dominator tree. */
- walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
+/* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
+ existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
+
+ 1- The names in OLD_SSA_NAMES dominated by the definitions of
+ NEW_SSA_NAMES are all re-written to be reached by the
+ appropriate definition from NEW_SSA_NAMES.
+
+ 2- If needed, new PHI nodes are added to the iterated dominance
+ frontier of the blocks where each of NEW_SSA_NAMES are defined.
+
+ The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
+ calling register_new_name_mapping for every pair of names that the
+ caller wants to replace.
+
+ The caller identifies the new names that have been inserted and the
+ names that need to be replaced by calling register_new_name_mapping
+ for every pair <NEW, OLD>. Note that the function assumes that the
+ new names have already been inserted in the IL.
+
+ For instance, given the following code:
+
+ 1 L0:
+ 2 x_1 = PHI (0, x_5)
+ 3 if (x_1 < 10)
+ 4 if (x_1 > 7)
+ 5 y_2 = 0
+ 6 else
+ 7 y_3 = x_1 + x_7
+ 8 endif
+ 9 x_5 = x_1 + 1
+ 10 goto L0;
+ 11 endif
+
+ Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
+
+ 1 L0:
+ 2 x_1 = PHI (0, x_5)
+ 3 if (x_1 < 10)
+ 4 x_10 = ...
+ 5 if (x_1 > 7)
+ 6 y_2 = 0
+ 7 else
+ 8 x_11 = ...
+ 9 y_3 = x_1 + x_7
+ 10 endif
+ 11 x_5 = x_1 + 1
+ 12 goto L0;
+ 13 endif
+
+ We want to replace all the uses of x_1 with the new definitions of
+ x_10 and x_11. Note that the only uses that should be replaced are
+ those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
+ *not* be replaced (this is why we cannot just mark symbol 'x' for
+ renaming).
+
+ Additionally, we may need to insert a PHI node at line 11 because
+ that is a merge point for x_10 and x_11. So the use of x_1 at line
+ 11 will be replaced with the new PHI node. The insertion of PHI
+ nodes is optional. They are not strictly necessary to preserve the
+ SSA form, and depending on what the caller inserted, they may not
+ even be useful for the optimizers. UPDATE_FLAGS controls various
+ aspects of how update_ssa operates, see the documentation for
+ TODO_update_ssa*. */
- /* Finalize the dominator walker. */
- fini_walk_dominator_tree (&walk_data);
+void
+update_ssa (unsigned update_flags)
+{
+ bitmap blocks;
+ basic_block bb, start_bb;
+ bitmap_iterator bi;
+ unsigned i = 0;
+ sbitmap tmp;
+ bool insert_phi_p;
+ sbitmap_iterator sbi;
- /* We no longer need this bitmap, clear and free it. */
- BITMAP_FREE (mark_def_sites_global_data.kills);
+ if (!need_ssa_update_p ())
+ return;
- /* Insert PHI nodes at dominance frontiers of definition blocks. */
- insert_phi_nodes (dfs, to_rename);
+ timevar_push (TV_TREE_SSA_INCREMENTAL);
- /* Rewrite all the basic blocks in the program. */
- timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
+ /* Ensure that the dominance information is up-to-date. */
+ calculate_dominance_info (CDI_DOMINATORS);
- /* Setup callbacks for the generic dominator tree walker. */
- walk_data.walk_stmts_backward = false;
- walk_data.dom_direction = CDI_DOMINATORS;
- walk_data.initialize_block_local_data = NULL;
- walk_data.before_dom_children_before_stmts = ssa_rewrite_initialize_block;
- walk_data.before_dom_children_walk_stmts = ssa_rewrite_stmt;
- walk_data.before_dom_children_after_stmts = ssa_rewrite_phi_arguments;
- walk_data.after_dom_children_before_stmts = NULL;
- walk_data.after_dom_children_walk_stmts = NULL;
- walk_data.after_dom_children_after_stmts = ssa_rewrite_finalize_block;
- walk_data.global_data = snames_to_rename;
- walk_data.block_local_data_size = 0;
+ /* Only one update flag should be set. */
+ gcc_assert (update_flags == TODO_update_ssa
+ || update_flags == TODO_update_ssa_no_phi
+ || update_flags == TODO_update_ssa_full_phi
+ || update_flags == TODO_update_ssa_only_virtuals);
- /* Initialize the dominator walker. */
- init_walk_dominator_tree (&walk_data);
+ /* If we only need to update virtuals, remove all the mappings for
+ real names before proceeding. The caller is responsible for
+ having dealt with the name mappings before calling update_ssa. */
+ if (update_flags == TODO_update_ssa_only_virtuals)
+ {
+ sbitmap_zero (old_ssa_names);
+ sbitmap_zero (new_ssa_names);
+ htab_empty (repl_tbl);
+ }
- /* Recursively walk the dominator tree rewriting each statement in
- each basic block. */
- walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
+ insert_phi_p = (update_flags != TODO_update_ssa_no_phi);
- /* Finalize the dominator walker. */
- fini_walk_dominator_tree (&walk_data);
+ if (insert_phi_p)
+ {
+ /* If the caller requested PHI nodes to be added, initialize
+ live-in information data structures (DEF_BLOCKS). */
+
+ /* For each SSA name N, the DEF_BLOCKS table describes where the
+ name is defined, which blocks have PHI nodes for N, and which
+ blocks have uses of N (i.e., N is live-on-entry in those
+ blocks). */
+ def_blocks = htab_create (num_ssa_names, def_blocks_hash,
+ def_blocks_eq, def_blocks_free);
+ }
+ else
+ {
+ def_blocks = NULL;
+ }
- unmark_all_for_rewrite ();
+ blocks = BITMAP_ALLOC (NULL);
- EXECUTE_IF_SET_IN_BITMAP (to_rename, 0, i, bi)
+ /* Clear the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags
+ for every statement and PHI node. */
+ FOR_EACH_BB (bb)
{
- /* Free SSA_NAME_AUX. We don't have to zero it because
- release_ssa_name will. */
- if (SSA_NAME_AUX (ssa_name (i)))
- free (SSA_NAME_AUX (ssa_name (i)));
+ block_stmt_iterator si;
+ tree phi;
- release_ssa_name (ssa_name (i));
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+ {
+ REWRITE_THIS_STMT (phi) = 0;
+ REGISTER_DEFS_IN_THIS_STMT (phi) = 0;
+ }
+
+ for (si = bsi_start (bb); !bsi_end_p (si); bsi_next (&si))
+ {
+ tree stmt = bsi_stmt (si);
+ /* 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_assert (!stmt_modified_p (stmt));
+ REWRITE_THIS_STMT (stmt) = 0;
+ REGISTER_DEFS_IN_THIS_STMT (stmt) = 0;
+ }
}
- sbitmap_free (snames_to_rename);
+ /* Heuristic to avoid massive slow downs when the replacement
+ mappings include lots of virtual names. */
+ if (insert_phi_p && switch_virtuals_to_full_rewrite_p ())
+ switch_virtuals_to_full_rewrite ();
- timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
+ /* If there are names defined in the replacement table, prepare
+ definition and use sites for all the names in NEW_SSA_NAMES and
+ OLD_SSA_NAMES. */
+ if (sbitmap_first_set_bit (new_ssa_names) >= 0)
+ {
+ prepare_names_to_update (blocks, insert_phi_p);
+
+ /* If all the names in NEW_SSA_NAMES had been marked for
+ removal, and there are no symbols to rename, then there's
+ nothing else to do. */
+ if (sbitmap_first_set_bit (new_ssa_names) < 0
+ && bitmap_empty_p (syms_to_rename))
+ goto done;
+ }
- /* Debugging dumps. */
- if (dump_file && (dump_flags & TDF_STATS))
+ /* Next, determine the block at which to start the renaming process. */
+ if (!bitmap_empty_p (syms_to_rename))
{
- dump_dfa_stats (dump_file);
- dump_tree_ssa_stats (dump_file);
+ /* If we have to rename some symbols from scratch, we need to
+ start the process at the root of the CFG. FIXME, it should
+ be possible to determine the nearest block that had a
+ definition for each of the symbols that are marked for
+ updating. For now this seems more work than it's worth. */
+ start_bb = ENTRY_BLOCK_PTR;
+
+ /* Traverse the CFG looking for definitions and uses of symbols
+ in SYMS_TO_RENAME. Mark interesting blocks and statements
+ and set local live-in information for the PHI placement
+ heuristics. */
+ prepare_block_for_update (start_bb, blocks, insert_phi_p);
+ }
+ else
+ {
+ /* Otherwise, the entry block to the region is the nearest
+ common dominator for the blocks in BLOCKS. */
+ start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS, blocks);
}
- /* Free allocated memory. */
- FOR_EACH_BB (bb)
- BITMAP_FREE (dfs[bb->index]);
- free (dfs);
+ /* If requested, insert PHI nodes at the iterated dominance frontier
+ of every block, creating new definitions for names in OLD_SSA_NAMES
+ and for symbols in SYMS_TO_RENAME. */
+ if (insert_phi_p)
+ {
+ bitmap *dfs;
- htab_delete (def_blocks);
+ /* If the caller requested PHI nodes to be added, compute
+ dominance frontiers. */
+ dfs = XNEWVEC (bitmap, last_basic_block);
+ FOR_EACH_BB (bb)
+ dfs[bb->index] = BITMAP_ALLOC (NULL);
+ compute_dominance_frontiers (dfs);
-#ifdef ENABLE_CHECKING
- for (i = 1; i < num_ssa_names; i++)
+ if (sbitmap_first_set_bit (old_ssa_names) >= 0)
+ {
+ sbitmap_iterator sbi;
+
+ /* insert_update_phi_nodes_for will call add_new_name_mapping
+ when inserting new PHI nodes, so the set OLD_SSA_NAMES
+ will grow while we are traversing it (but it will not
+ gain any new members). Copy OLD_SSA_NAMES to a temporary
+ for traversal. */
+ sbitmap tmp = sbitmap_alloc (old_ssa_names->n_bits);
+ sbitmap_copy (tmp, old_ssa_names);
+ EXECUTE_IF_SET_IN_SBITMAP (tmp, 0, i, sbi)
+ insert_updated_phi_nodes_for (ssa_name (i), dfs, blocks,
+ update_flags);
+ sbitmap_free (tmp);
+ }
+
+ EXECUTE_IF_SET_IN_BITMAP (syms_to_rename, 0, i, bi)
+ insert_updated_phi_nodes_for (referenced_var (i), dfs, blocks,
+ update_flags);
+
+ FOR_EACH_BB (bb)
+ BITMAP_FREE (dfs[bb->index]);
+ free (dfs);
+
+ /* Insertion of PHI nodes may have added blocks to the region.
+ We need to re-compute START_BB to include the newly added
+ blocks. */
+ if (start_bb != ENTRY_BLOCK_PTR)
+ start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS, blocks);
+ }
+
+ /* Reset the current definition for name and symbol before renaming
+ the sub-graph. */
+ EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
+ set_current_def (ssa_name (i), NULL_TREE);
+
+ EXECUTE_IF_SET_IN_BITMAP (syms_to_rename, 0, i, bi)
+ set_current_def (referenced_var (i), NULL_TREE);
+
+ /* Now start the renaming process at START_BB. */
+ tmp = sbitmap_alloc (last_basic_block);
+ sbitmap_zero (tmp);
+ EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
+ SET_BIT (tmp, i);
+
+ rewrite_blocks (start_bb, REWRITE_UPDATE, tmp);
+
+ sbitmap_free (tmp);
+
+ /* Debugging dumps. */
+ if (dump_file)
{
- tree name = ssa_name (i);
- if (!name)
- continue;
+ int c;
+ unsigned i;
- gcc_assert (SSA_NAME_AUX (name) == NULL);
+ dump_update_ssa (dump_file);
+
+ fprintf (dump_file, "Incremental SSA update started at block: %d\n\n",
+ start_bb->index);
+
+ c = 0;
+ EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
+ c++;
+ fprintf (dump_file, "Number of blocks in CFG: %d\n", last_basic_block);
+ fprintf (dump_file, "Number of blocks to update: %d (%3.0f%%)\n\n",
+ c, PERCENT (c, last_basic_block));
+
+ if (dump_flags & TDF_DETAILS)
+ {
+ fprintf (dump_file, "Affected blocks: ");
+ EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
+ fprintf (dump_file, "%u ", i);
+ fprintf (dump_file, "\n");
+ }
+
+ fprintf (dump_file, "\n\n");
}
-#endif
- BITMAP_FREE (to_rename);
-
- VEC_free (tree_on_heap, block_defs_stack);
- block_defs_stack = NULL;
- timevar_pop (TV_TREE_SSA_OTHER);
+ /* Free allocated memory. */
+done:
+ BITMAP_FREE (blocks);
+ delete_update_ssa ();
+
+ timevar_pop (TV_TREE_SSA_INCREMENTAL);
}
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