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Commit 7256233c by Diego Novillo Committed by Diego Novillo
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* tree-into-ssa.c: Re-organize internal functions. 

From-SVN: r95499
parent f5e9e99c
Showing with 916 additions and 898 deletions
gcc/ChangeLog
2005-02-24 Diego Novillo <dnovillo@redhat.com>
* tree-into-ssa.c: Re-organize internal functions.
2005-02-24 Richard Henderson <rth@redhat.com> 2005-02-24 Richard Henderson <rth@redhat.com>
PR middle-end/18902 PR middle-end/18902
......
gcc/tree-into-ssa.c
...@@ -54,7 +54,6 @@ Boston, MA 02111-1307, USA. */ ...@@ -54,7 +54,6 @@ Boston, MA 02111-1307, USA. */
Graph. ACM Transactions on Programming Languages and Systems, Graph. ACM Transactions on Programming Languages and Systems,
13(4):451-490, October 1991. */ 13(4):451-490, October 1991. */
/* Structure to map a variable VAR to the set of blocks that contain /* Structure to map a variable VAR to the set of blocks that contain
definitions for VAR. */ definitions for VAR. */
struct def_blocks_d struct def_blocks_d
...@@ -66,7 +65,7 @@ struct def_blocks_d ...@@ -66,7 +65,7 @@ struct def_blocks_d
Ith block contains a definition of VAR. */ Ith block contains a definition of VAR. */
bitmap def_blocks; bitmap def_blocks;
/* Blocks that contain a phi node for VAR. */ /* Blocks that contain a PHI node for VAR. */
bitmap phi_blocks; bitmap phi_blocks;
/* Blocks where VAR is live-on-entry. Similar semantics as /* Blocks where VAR is live-on-entry. Similar semantics as
...@@ -74,6 +73,7 @@ struct def_blocks_d ...@@ -74,6 +73,7 @@ struct def_blocks_d
bitmap livein_blocks; bitmap livein_blocks;
}; };
/* Each entry in DEF_BLOCKS contains an element of type STRUCT /* Each entry in DEF_BLOCKS contains an element of type STRUCT
DEF_BLOCKS_D, mapping a variable VAR to a bitmap describing all the DEF_BLOCKS_D, mapping a variable VAR to a bitmap describing all the
basic blocks where VAR is defined (assigned a new value). It also basic blocks where VAR is defined (assigned a new value). It also
...@@ -87,19 +87,18 @@ static htab_t def_blocks; ...@@ -87,19 +87,18 @@ static htab_t def_blocks;
state after completing rewriting of a block and its dominator children. state after completing rewriting of a block and its dominator children.
This vector is used in two contexts. The first is rewriting of _DECL This vector is used in two contexts. The first is rewriting of _DECL
nodes into SSA_NAMEs. In that context it's elements have the nodes into SSA_NAMEs. In that context its elements have the
following properties: following properties:
An SSA_NAME indicates that the current definition of the underlying An SSA_NAME indicates that the current definition of the underlying
variable should be set to the given SSA_NAME. variable should be set to the given SSA_NAME.
A _DECL node indicates that the underlying variable has no current A _DECL node indicates that the underlying variable has no current
definition. definition.
A NULL node is used to mark the last node associated with the A NULL node is used to mark the last node associated with the
current block. current block.
This vector is also used when rewriting an SSA_NAME which has multiple This vector is also used when rewriting an SSA_NAME which has multiple
definition sites into multiple SSA_NAMEs. In that context entries come definition sites into multiple SSA_NAMEs. In that context entries come
in pairs. in pairs.
...@@ -127,8 +126,8 @@ struct mark_def_sites_global_data ...@@ -127,8 +126,8 @@ struct mark_def_sites_global_data
sbitmap names_to_rename; sbitmap names_to_rename;
}; };
/* Information stored for ssa names. */
/* Information stored for ssa names. */
struct ssa_name_info struct ssa_name_info
{ {
/* This field indicates whether or not the variable may need PHI nodes. /* This field indicates whether or not the variable may need PHI nodes.
...@@ -140,31 +139,6 @@ struct ssa_name_info ...@@ -140,31 +139,6 @@ struct ssa_name_info
tree current_def; tree current_def;
}; };
/* Local functions. */
static void rewrite_finalize_block (struct dom_walk_data *, basic_block);
static void rewrite_initialize_block (struct dom_walk_data *, basic_block);
static void rewrite_add_phi_arguments (struct dom_walk_data *, basic_block);
static void mark_def_sites (struct dom_walk_data *walk_data,
basic_block bb, block_stmt_iterator);
static void mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
basic_block bb);
static void set_def_block (tree, basic_block, bool, bool);
static void set_livein_block (tree, basic_block);
static bool prepare_use_operand_for_rename (use_operand_p, size_t *uid_p);
static bool prepare_def_operand_for_rename (tree def, size_t *uid_p);
static void insert_phi_nodes (bitmap *, bitmap);
static void rewrite_stmt (struct dom_walk_data *, basic_block,
block_stmt_iterator);
static inline void rewrite_operand (use_operand_p);
static void insert_phi_nodes_for (tree, bitmap *, VEC(basic_block) **);
static tree get_reaching_def (tree);
static hashval_t def_blocks_hash (const void *);
static int def_blocks_eq (const void *, const void *);
static void def_blocks_free (void *);
static int debug_def_blocks_r (void **, void *);
static inline struct def_blocks_d *get_def_blocks_for (tree);
static inline struct def_blocks_d *find_def_blocks_for (tree);
static void htab_statistics (FILE *, htab_t);
/* Use TREE_VISITED to keep track of which statements we want to /* Use TREE_VISITED to keep track of which statements we want to
rename. When renaming a subset of the variables, not all rename. When renaming a subset of the variables, not all
...@@ -183,6 +157,7 @@ get_ssa_name_ann (tree name) ...@@ -183,6 +157,7 @@ get_ssa_name_ann (tree name)
return SSA_NAME_AUX (name); return SSA_NAME_AUX (name);
} }
/* Gets phi_state field for VAR. */ /* Gets phi_state field for VAR. */
static inline enum need_phi_state static inline enum need_phi_state
...@@ -194,6 +169,7 @@ get_phi_state (tree var) ...@@ -194,6 +169,7 @@ get_phi_state (tree var)
return var_ann (var)->need_phi_state; return var_ann (var)->need_phi_state;
} }
/* Sets phi_state field for VAR to STATE. */ /* Sets phi_state field for VAR to STATE. */
static inline void static inline void
...@@ -205,6 +181,7 @@ set_phi_state (tree var, enum need_phi_state state) ...@@ -205,6 +181,7 @@ set_phi_state (tree var, enum need_phi_state state)
var_ann (var)->need_phi_state = state; var_ann (var)->need_phi_state = state;
} }
/* Return the current definition for VAR. */ /* Return the current definition for VAR. */
static inline tree static inline tree
...@@ -216,6 +193,7 @@ get_current_def (tree var) ...@@ -216,6 +193,7 @@ get_current_def (tree var)
return var_ann (var)->current_def; return var_ann (var)->current_def;
} }
/* Sets current definition of VAR to DEF. */ /* Sets current definition of VAR to DEF. */
static inline void static inline void
...@@ -227,6 +205,7 @@ set_current_def (tree var, tree def) ...@@ -227,6 +205,7 @@ set_current_def (tree var, tree def)
var_ann (var)->current_def = def; var_ann (var)->current_def = def;
} }
/* Compute global livein information given the set of blockx where /* Compute global livein information given the set of blockx where
an object is locally live at the start of the block (LIVEIN) an object is locally live at the start of the block (LIVEIN)
and the set of blocks where the object is defined (DEF_BLOCKS). and the set of blocks where the object is defined (DEF_BLOCKS).
...@@ -280,215 +259,45 @@ compute_global_livein (bitmap livein, bitmap def_blocks) ...@@ -280,215 +259,45 @@ compute_global_livein (bitmap livein, bitmap def_blocks)
} }
/* Block initialization routine for mark_def_sites. Clear the /* Return the set of blocks where variable VAR is defined and the blocks
KILLS bitmap at the start of each block. */ where VAR is live on entry (livein). If no entry is found in
DEF_BLOCKS, a new one is created and returned. */
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 = walk_data->global_data;
bitmap kills = gd->kills;
bitmap_clear (kills);
}
/* Block initialization routine for mark_def_sites. Clear the
KILLS bitmap at the start of each block. */
static void
ssa_mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
basic_block bb)
{
struct mark_def_sites_global_data *gd = walk_data->global_data;
bitmap kills = gd->kills;
tree phi, def;
unsigned def_uid;
bitmap_clear (kills);
for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
def = PHI_RESULT (phi);
def_uid = SSA_NAME_VERSION (def);
if (!TEST_BIT (gd->names_to_rename, def_uid))
continue;
set_def_block (def, bb, true, true);
bitmap_set_bit (kills, def_uid);
}
}
/* 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)
{
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;
FOR_EACH_EDGE (e, ei, bb->succs)
{
if (e->dest == EXIT_BLOCK_PTR)
continue;
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;
uid = SSA_NAME_VERSION (use);
if (TEST_BIT (gd->names_to_rename, uid)
&& !bitmap_bit_p (kills, uid))
set_livein_block (use, bb);
}
}
}
/* Call back for walk_dominator_tree used to collect definition sites
for every variable in the function. For every statement S in block
BB:
1- Variables defined by S in DEF_OPS(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.
This information is used to determine which variables are live
across block boundaries to reduce the number of PHI nodes
we create. */
static void static inline struct def_blocks_d *
mark_def_sites (struct dom_walk_data *walk_data, get_def_blocks_for (tree var)
basic_block bb,
block_stmt_iterator bsi)
{ {
struct mark_def_sites_global_data *gd = walk_data->global_data; struct def_blocks_d db, *db_p;
bitmap kills = gd->kills; void **slot;
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);
get_stmt_operands (stmt);
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, db.var = var;
SSA_OP_USE | SSA_OP_VUSE | SSA_OP_VMUSTDEFKILL) slot = htab_find_slot (def_blocks, (void *) &db, INSERT);
{ if (*slot == NULL)
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);
}
}
/* Note that virtual definitions are irrelevant for computing KILLS
because a V_MAY_DEF does not constitute a killing definition of the
variable. However, the operand of a virtual definitions is a use
of the variable, so it may cause the variable to be considered
live-on-entry. */
FOR_EACH_SSA_MAYDEF_OPERAND (def_p, use_p, stmt, iter)
{ {
if (prepare_use_operand_for_rename (use_p, &uid)) db_p = xmalloc (sizeof (*db_p));
{ db_p->var = var;
/* If we do not already have an SSA_NAME for our destination, db_p->def_blocks = BITMAP_ALLOC (NULL);
then set the destination to the source. */ db_p->phi_blocks = BITMAP_ALLOC (NULL);
if (TREE_CODE (DEF_FROM_PTR (def_p)) != SSA_NAME) db_p->livein_blocks = BITMAP_ALLOC (NULL);
SET_DEF (def_p, USE_FROM_PTR (use_p)); *slot = (void *) db_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;
}
} }
else
db_p = (struct def_blocks_d *) *slot;
/* Now process the defs and must-defs made by this statement. */ return db_p;
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;
}
}
} }
/* Same as mark_def_sites, but works over SSA names. */
static void
ssa_mark_def_sites (struct dom_walk_data *walk_data,
basic_block bb,
block_stmt_iterator bsi)
{
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;
/* Mark all the blocks that have definitions for each variable in the
names_to_rename bitmap. */
stmt = bsi_stmt (bsi);
get_stmt_operands (stmt);
/* 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)
{
uid = SSA_NAME_VERSION (use);
if (TEST_BIT (gd->names_to_rename, uid)
&& !bitmap_bit_p (kills, uid))
set_livein_block (use, bb);
}
/* 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)
{
def_uid = SSA_NAME_VERSION (def);
if (TEST_BIT (gd->names_to_rename, def_uid))
{
set_def_block (def, bb, false, true);
bitmap_set_bit (kills, def_uid);
}
}
}
/* Mark block BB as the definition site for variable VAR. PHI_P is true if /* Mark block BB as the definition site for variable VAR. PHI_P is true if
VAR is defined by a phi node. SSA_P is true if we are called from VAR is defined by a PHI node. IS_UPDATE is true if the caller is
rewrite_ssa_into_ssa. */ updating an existing SSA form. */
static void static void
set_def_block (tree var, basic_block bb, bool phi_p, bool ssa_p) set_def_block (tree var, basic_block bb, bool phi_p, bool is_update)
{ {
struct def_blocks_d *db_p; struct def_blocks_d *db_p;
enum need_phi_state state; enum need_phi_state state;
if (!ssa_p if (!is_update && TREE_CODE (var) == SSA_NAME)
&& TREE_CODE (var) == SSA_NAME)
var = SSA_NAME_VAR (var); var = SSA_NAME_VAR (var);
state = get_phi_state (var); state = get_phi_state (var);
...@@ -499,11 +308,11 @@ set_def_block (tree var, basic_block bb, bool phi_p, bool ssa_p) ...@@ -499,11 +308,11 @@ set_def_block (tree var, basic_block bb, bool phi_p, bool ssa_p)
if (phi_p) if (phi_p)
bitmap_set_bit (db_p->phi_blocks, bb->index); bitmap_set_bit (db_p->phi_blocks, bb->index);
/* Keep track of whether or not we may need to insert phi nodes. /* Keep track of whether or not we may need to insert PHI nodes.
If we are in the UNKNOWN state, then this is the first definition If we are in the UNKNOWN state, then this is the first definition
of VAR. Additionally, we have not seen any uses of VAR yet, so of VAR. Additionally, we have not seen any uses of VAR yet, so
we do not need a phi node for this variable at this time (i.e., we do not need a PHI node for this variable at this time (i.e.,
transition to NEED_PHI_STATE_NO). transition to NEED_PHI_STATE_NO).
If we are in any other state, then we either have multiple definitions If we are in any other state, then we either have multiple definitions
...@@ -531,7 +340,7 @@ set_livein_block (tree var, basic_block bb) ...@@ -531,7 +340,7 @@ set_livein_block (tree var, basic_block bb)
/* Set the bit corresponding to the block where VAR is live in. */ /* Set the bit corresponding to the block where VAR is live in. */
bitmap_set_bit (db_p->livein_blocks, bb->index); bitmap_set_bit (db_p->livein_blocks, bb->index);
/* Keep track of whether or not we may need to insert phi nodes. /* Keep track of whether or not we may need to insert PHI nodes.
If we reach here in NEED_PHI_STATE_NO, see if this use is dominated If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
by the single block containing the definition(s) of this variable. If by the single block containing the definition(s) of this variable. If
...@@ -579,6 +388,7 @@ prepare_use_operand_for_rename (use_operand_p op_p, size_t *uid_p) ...@@ -579,6 +388,7 @@ prepare_use_operand_for_rename (use_operand_p op_p, size_t *uid_p)
return true; return true;
} }
/* If the def variable DEF needs to be renamed, then strip away any SSA_NAME /* 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 wrapping the operand, set *UID_P to the underlying variable's uid and return
true. Otherwise return false. */ true. Otherwise return false. */
...@@ -596,66 +406,299 @@ prepare_def_operand_for_rename (tree def, size_t *uid_p) ...@@ -596,66 +406,299 @@ prepare_def_operand_for_rename (tree def, size_t *uid_p)
return true; return true;
} }
/* Helper for insert_phi_nodes. If VAR needs PHI nodes, insert them
at the dominance frontier (DFS) of blocks defining VAR.
WORK_STACK is the vector used to implement the worklist of basic
blocks. */
static inline void
insert_phi_nodes_1 (tree var, bitmap *dfs, VEC(basic_block) **work_stack)
{
if (get_phi_state (var) != NEED_PHI_STATE_NO)
insert_phi_nodes_for (var, dfs, work_stack);
}
/* Insert PHI nodes at the dominance frontier of blocks with variable /* Call back for walk_dominator_tree used to collect definition sites
definitions. DFS contains the dominance frontier information for for every variable in the function. For every statement S in block
the flowgraph. PHI nodes will only be inserted at the dominance BB:
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. */
static void 1- Variables defined by S in DEF_OPS(S) are marked in the bitmap
insert_phi_nodes (bitmap *dfs, bitmap names_to_rename) WALK_DATA->GLOBAL_DATA->KILLS.
{
unsigned i;
VEC(basic_block) *work_stack;
bitmap_iterator bi;
timevar_push (TV_TREE_INSERT_PHI_NODES); 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.
/* Vector WORK_STACK is a stack of CFG blocks. Each block that contains This information is used to determine which variables are live
an assignment or PHI node will be pushed to this stack. */ across block boundaries to reduce the number of PHI nodes
work_stack = VEC_alloc (basic_block, n_basic_blocks); we create. */
/* Iterate over all variables in VARS_TO_RENAME. For each variable, add static void
to the work list all the blocks that have a definition for the mark_def_sites (struct dom_walk_data *walk_data,
basic_block bb,
block_stmt_iterator bsi)
{
struct mark_def_sites_global_data *gd = 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);
get_stmt_operands (stmt);
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)
{
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);
}
}
/* Note that virtual definitions are irrelevant for computing KILLS
because a V_MAY_DEF does not constitute a killing definition of the
variable. However, the operand of a virtual definitions is a use
of the variable, so it may cause the variable to be considered
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;
}
}
/* 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;
}
}
}
/* Given a set of blocks with variable definitions (DEF_BLOCKS),
return a bitmap with all the blocks in the iterated dominance
frontier of the blocks in DEF_BLOCKS. DFS contains dominance
frontier information as returned by compute_dominance_frontiers.
The resulting set of blocks are the potential sites where PHI nodes
are needed. The caller is responsible from freeing the memory
allocated for the return value. */
static bitmap
find_idf (bitmap def_blocks, bitmap *dfs)
{
bitmap_iterator bi;
unsigned bb_index;
VEC(basic_block) *work_stack;
bitmap phi_insertion_points;
work_stack = VEC_alloc (basic_block, n_basic_blocks);
phi_insertion_points = BITMAP_ALLOC (NULL);
/* Seed the work list with all the blocks in DEF_BLOCKS. */
EXECUTE_IF_SET_IN_BITMAP (def_blocks, 0, bb_index, bi)
VEC_safe_push (basic_block, work_stack, BASIC_BLOCK (bb_index));
/* Pop a block off the worklist, add every block that appears in
the original block's DF that we have not already processed to
the worklist. Iterate until the worklist is empty. Blocks
which are added to the worklist are potential sites for
PHI nodes. */
while (VEC_length (basic_block, work_stack) > 0)
{
basic_block bb = VEC_pop (basic_block, work_stack);
bb_index = bb->index;
EXECUTE_IF_AND_COMPL_IN_BITMAP (dfs[bb_index], phi_insertion_points,
0, bb_index, bi)
{
bb = BASIC_BLOCK (bb_index);
/* 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 (basic_block, work_stack, bb);
bitmap_set_bit (phi_insertion_points, bb_index);
}
}
VEC_free (basic_block, work_stack);
return phi_insertion_points;
}
/* Return the set of blocks where variable VAR is defined and the blocks
where VAR is live on entry (livein). Return NULL, if no entry is
found in DEF_BLOCKS. */
static inline struct def_blocks_d *
find_def_blocks_for (tree var)
{
struct def_blocks_d dm;
dm.var = var;
return (struct def_blocks_d *) htab_find (def_blocks, &dm);
}
/* Insert PHI nodes for variable VAR using the iterated dominance
frontier given in PHI_INSERTION_POINTS. */
static void
insert_phi_nodes_for (tree var, bitmap phi_insertion_points)
{
unsigned bb_index;
edge e;
tree phi;
basic_block bb;
bitmap_iterator bi;
struct def_blocks_d *def_map;
def_map = find_def_blocks_for (var);
/* Remove the blocks where we already have PHI nodes for VAR. */
bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
/* Now compute global livein for this variable. Note this modifies
def_map->livein_blocks. */
compute_global_livein (def_map->livein_blocks, def_map->def_blocks);
/* And insert the PHI nodes. */
EXECUTE_IF_AND_IN_BITMAP (phi_insertion_points, def_map->livein_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)
{
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->preds)
add_phi_arg (phi, var, e);
}
/* Mark this PHI node as interesting for the rename process. */
REWRITE_THIS_STMT (phi) = 1;
}
}
/* 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);
BITMAP_FREE (idf);
}
/* Insert PHI nodes at the dominance frontier of blocks with variable
definitions. DFS contains the dominance frontier information for
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. */
static void
insert_phi_nodes (bitmap *dfs, bitmap names_to_rename)
{
unsigned i;
bitmap_iterator bi;
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 variable. PHI nodes will be added to the dominance frontier blocks of
each definition block. */ each definition block. */
if (names_to_rename) if (names_to_rename)
{ {
EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi) EXECUTE_IF_SET_IN_BITMAP (names_to_rename, 0, i, bi)
{ if (ssa_name (i))
if (ssa_name (i)) insert_phi_nodes_1 (ssa_name (i), dfs);
insert_phi_nodes_1 (ssa_name (i), dfs, &work_stack);
}
} }
else if (vars_to_rename) else if (vars_to_rename)
EXECUTE_IF_SET_IN_BITMAP (vars_to_rename, 0, i, bi) {
{ EXECUTE_IF_SET_IN_BITMAP (vars_to_rename, 0, i, bi)
insert_phi_nodes_1 (referenced_var (i), dfs, &work_stack); insert_phi_nodes_1 (referenced_var (i), dfs);
} }
else else
for (i = 0; i < num_referenced_vars; i++) {
insert_phi_nodes_1 (referenced_var (i), dfs, &work_stack); for (i = 0; i < num_referenced_vars; i++)
insert_phi_nodes_1 (referenced_var (i), dfs);
VEC_free (basic_block, work_stack); }
timevar_pop (TV_TREE_INSERT_PHI_NODES); 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. */
void
register_new_def (tree def, VEC (tree_on_heap) **block_defs_p)
{
tree var = SSA_NAME_VAR (def);
tree currdef;
/* If this variable is set in a single basic block and all uses are
dominated by the set(s) in that single basic block, then there is
no reason to record anything for this variable in the block local
definition stacks. Doing so just wastes time and memory.
This is the same test to prune the set of variables which may
need PHI nodes. So we just use that information since it's already
computed and available for us to use. */
if (get_phi_state (var) == NEED_PHI_STATE_NO)
{
set_current_def (var, def);
return;
}
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. 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);
/* Set the current reaching definition for VAR to be DEF. */
set_current_def (var, def);
}
/* Perform a depth-first traversal of the dominator tree looking for /* Perform a depth-first traversal of the dominator tree looking for
variables to rename. BB is the block where to start searching. variables to rename. BB is the block where to start searching.
Renaming is a five step process: Renaming is a five step process:
...@@ -702,84 +745,124 @@ rewrite_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, ...@@ -702,84 +745,124 @@ rewrite_initialize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi)) for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{ {
tree result = PHI_RESULT (phi); tree result = PHI_RESULT (phi);
if (REWRITE_THIS_STMT (phi))
register_new_def (result, &block_defs_stack); register_new_def (result, &block_defs_stack);
} }
} }
/* 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. */
static void
ssa_register_new_def (tree var, tree def)
{
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)
{
set_current_def (var, def);
return;
}
currdef = get_current_def (var); /* Return the current definition for variable VAR. If none is found,
create a new SSA name to act as the zeroth definition for VAR. If VAR
is call clobbered and there exists a more recent definition of
GLOBAL_VAR, return the definition for GLOBAL_VAR. This means that VAR
has been clobbered by a function call since its last assignment. */
/* Push the current reaching definition into *BLOCK_DEFS_P. This stack is static tree
later used by the dominator tree callbacks to restore the reaching get_reaching_def (tree var)
definitions for all the variables defined in the block after a recursive {
visit to all its immediately dominated blocks. */ tree default_d, currdef_var, avar;
VEC_safe_push (tree_on_heap, block_defs_stack, currdef);
VEC_safe_push (tree_on_heap, block_defs_stack, var); /* Lookup the current reaching definition for VAR. */
default_d = NULL_TREE;
currdef_var = get_current_def (var);
/* Set the current reaching definition for VAR to be DEF. */ /* If there is no reaching definition for VAR, create and register a
set_current_def (var, def); 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);
}
/* Return the current reaching definition for VAR, or the default
definition, if we had to create one. */
return (currdef_var) ? currdef_var : default_d;
} }
/* Ditto, for rewriting ssa names. */
/* 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
}
}
/* SSA Rewriting Step 2. Rewrite every variable used in each statement in
the block with its immediate reaching definitions. Update the current
definition of a variable when a new real or virtual definition is found. */
static void static void
ssa_rewrite_initialize_block (struct dom_walk_data *walk_data, basic_block bb) rewrite_stmt (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
basic_block bb ATTRIBUTE_UNUSED,
block_stmt_iterator si)
{ {
tree phi, new_name; stmt_ann_t ann;
sbitmap names_to_rename = walk_data->global_data; tree stmt;
edge e; use_operand_p use_p;
bool abnormal_phi; def_operand_p def_p;
edge_iterator ei; ssa_op_iter iter;
stmt = bsi_stmt (si);
ann = stmt_ann (stmt);
/* If mark_def_sites decided that we don't need to rewrite this
statement, ignore it. */
if (!REWRITE_THIS_STMT (stmt))
return;
if (dump_file && (dump_flags & TDF_DETAILS)) if (dump_file && (dump_flags & TDF_DETAILS))
fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index); {
fprintf (dump_file, "Renaming statement ");
print_generic_stmt (dump_file, stmt, TDF_SLIM);
fprintf (dump_file, "\n");
}
/* Mark the unwind point for this block. */ get_stmt_operands (stmt);
VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
FOR_EACH_EDGE (e, ei, bb->preds) /* Step 1. Rewrite USES and VUSES in the statement. */
if (e->flags & EDGE_ABNORMAL) FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
break; rewrite_operand (use_p);
abnormal_phi = (e != NULL);
/* Step 1. Register new definitions for every PHI node in the block. /* Step 2. Register the statement's DEF and VDEF operands. */
Conceptually, all the PHI nodes are executed in parallel and each PHI FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
node introduces a new version for the associated variable. */
for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{ {
tree result = PHI_RESULT (phi); if (TREE_CODE (DEF_FROM_PTR (def_p)) != SSA_NAME)
SET_DEF (def_p, make_ssa_name (DEF_FROM_PTR (def_p), stmt));
if (TEST_BIT (names_to_rename, SSA_NAME_VERSION (result)))
{
new_name = duplicate_ssa_name (result, phi);
SET_PHI_RESULT (phi, new_name);
if (abnormal_phi) /* FIXME: We shouldn't be registering new defs if the variable
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1; doesn't need to be renamed. */
ssa_register_new_def (result, new_name); register_new_def (DEF_FROM_PTR (def_p), &block_defs_stack);
}
} }
} }
/* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
PHI nodes. For every PHI node found, add a new argument containing the PHI nodes. For every PHI node found, add a new argument containing the
current reaching definition for the variable and the edge through which current reaching definition for the variable and the edge through which
...@@ -812,9 +895,10 @@ rewrite_add_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, ...@@ -812,9 +895,10 @@ rewrite_add_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
} }
} }
/* Rewrite existing virtual PHI arguments so that they have the correct /* Rewrite existing virtual PHI arguments so that they have the correct
reaching definitions. BB is the basic block whose successors contain the reaching definitions. BB is the basic block whose successors contain the
phi nodes we want to add arguments for. */ PHI nodes we want to add arguments for. */
static void static void
rewrite_virtual_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, rewrite_virtual_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
...@@ -848,42 +932,10 @@ rewrite_virtual_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, ...@@ -848,42 +932,10 @@ rewrite_virtual_phi_arguments (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
} }
} }
/* Ditto, for ssa name rewriting. */
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_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))
{
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;
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;
}
}
}
/* Called after visiting basic block BB. Restore CURRDEFS to its
original value. */
/* Similar to restore_vars_to_original_value, except that it restores
CURRDEFS to its original value. */
static void static void
rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
basic_block bb ATTRIBUTE_UNUSED) basic_block bb ATTRIBUTE_UNUSED)
...@@ -916,28 +968,6 @@ rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, ...@@ -916,28 +968,6 @@ rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
} }
} }
/* Ditto, for rewriting ssa names. */
static void
ssa_rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
basic_block bb ATTRIBUTE_UNUSED)
{
/* 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)
{
tree var = VEC_pop (tree_on_heap, block_defs_stack);
tree saved_def;
if (var == NULL)
break;
saved_def = VEC_pop (tree_on_heap, block_defs_stack);
set_current_def (var, saved_def);
}
}
/* Dump SSA information to FILE. */ /* Dump SSA information to FILE. */
...@@ -969,6 +999,18 @@ debug_tree_ssa (void) ...@@ -969,6 +999,18 @@ debug_tree_ssa (void)
} }
/* Dump statistics for the hash table HTAB. */
static void
htab_statistics (FILE *file, htab_t htab)
{
fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
(long) htab_size (htab),
(long) htab_elements (htab),
htab_collisions (htab));
}
/* Dump SSA statistics on FILE. */ /* Dump SSA statistics on FILE. */
void void
...@@ -992,656 +1034,653 @@ debug_tree_ssa_stats (void) ...@@ -992,656 +1034,653 @@ debug_tree_ssa_stats (void)
} }
/* Dump statistics for the hash table HTAB. */ /* Hashing and equality functions for DEF_BLOCKS. */
static void static hashval_t
htab_statistics (FILE *file, htab_t htab) def_blocks_hash (const void *p)
{ {
fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n", return htab_hash_pointer
(long) htab_size (htab), ((const void *)((const struct def_blocks_d *)p)->var);
(long) htab_elements (htab), }
htab_collisions (htab));
static int
def_blocks_eq (const void *p1, const void *p2)
{
return ((const struct def_blocks_d *)p1)->var
== ((const struct def_blocks_d *)p2)->var;
} }
/* Insert PHI nodes for variable VAR using the dominance frontier /* Free memory allocated by one entry in DEF_BLOCKS. */
information given in DFS. WORK_STACK is the vector used to
implement the worklist of basic blocks. */
static void static void
insert_phi_nodes_for (tree var, bitmap *dfs, VEC(basic_block) **work_stack) def_blocks_free (void *p)
{ {
struct def_blocks_d *def_map; struct def_blocks_d *entry = p;
bitmap phi_insertion_points; BITMAP_FREE (entry->def_blocks);
unsigned bb_index; BITMAP_FREE (entry->phi_blocks);
edge e; BITMAP_FREE (entry->livein_blocks);
tree phi; free (entry);
basic_block bb; }
bitmap_iterator bi;
def_map = find_def_blocks_for (var);
if (def_map == NULL)
return;
phi_insertion_points = BITMAP_ALLOC (NULL);
EXECUTE_IF_SET_IN_BITMAP (def_map->def_blocks, 0, bb_index, bi) /* Callback for htab_traverse to dump the DEF_BLOCKS hash table. */
{
VEC_safe_push (basic_block, *work_stack, BASIC_BLOCK (bb_index));
}
/* Pop a block off the worklist, add every block that appears in static int
the original block's dfs that we have not already processed to debug_def_blocks_r (void **slot, void *data ATTRIBUTE_UNUSED)
the worklist. Iterate until the worklist is empty. Blocks {
which are added to the worklist are potential sites for struct def_blocks_d *db_p = (struct def_blocks_d *) *slot;
PHI nodes.
fprintf (stderr, "VAR: ");
print_generic_expr (stderr, db_p->var, dump_flags);
bitmap_print (stderr, db_p->def_blocks, ", DEF_BLOCKS: { ", "}");
bitmap_print (stderr, db_p->livein_blocks, ", LIVEIN_BLOCKS: { ", "}\n");
The iteration step could be done during PHI insertion just as return 1;
easily. We do it here for historical reasons -- we used to have }
a heuristic which used the potential PHI insertion points to
determine if fully pruned or semi pruned SSA form was appropriate.
We now always use fully pruned SSA form. */
while (VEC_length (basic_block, *work_stack) > 0)
{
unsigned dfs_index;
bitmap_iterator bi;
bb = VEC_pop (basic_block, *work_stack); /* Dump the DEF_BLOCKS hash table on stderr. */
bb_index = bb->index;
EXECUTE_IF_AND_COMPL_IN_BITMAP (dfs[bb_index],
phi_insertion_points,
0, dfs_index, bi)
{
basic_block bb = BASIC_BLOCK (dfs_index);
/* Use a safe push because if there is a definition of VAR void
in every basic block, then WORK_STACK may eventually have debug_def_blocks (void)
more than N_BASIC_BLOCK entries. */ {
VEC_safe_push (basic_block, *work_stack, bb); htab_traverse (def_blocks, debug_def_blocks_r, NULL);
bitmap_set_bit (phi_insertion_points, dfs_index); }
}
}
/* Remove the blocks where we already have the phis. */
bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
/* Now compute global livein for this variable. Note this modifies /* If a variable V in VARS_TO_RENAME is a pointer, the renaming
def_map->livein_blocks. */ process will cause us to lose the name memory tags that may have
compute_global_livein (def_map->livein_blocks, def_map->def_blocks); 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.
/* And insert the PHI nodes. */ FIXME 1- We should either have a better scheme for renaming
EXECUTE_IF_AND_IN_BITMAP (phi_insertion_points, def_map->livein_blocks, pointers that doesn't lose name tags or re-run alias
0, bb_index, bi) analysis to recover points-to information.
{
bb = BASIC_BLOCK (bb_index);
phi = create_phi_node (var, bb); 2- Currently we just invalidate *all* the name tags. This
should be more selective. */
/* If we are rewriting ssa names, add also the phi arguments. */ static void
if (TREE_CODE (var) == SSA_NAME) invalidate_name_tags (bitmap vars_to_rename)
{
unsigned i;
bool rename_name_tags_p;
bitmap_iterator bi;
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))))
{ {
edge_iterator ei; rename_name_tags_p = true;
FOR_EACH_EDGE (e, ei, bb->preds) break;
add_phi_arg (phi, var, e);
} }
} }
BITMAP_FREE (phi_insertion_points); 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);
}
}
}
} }
/* SSA Rewriting Step 2. Rewrite every variable used in each statement in
the block with its immediate reaching definitions. Update the current /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
definition of a variable when a new real or virtual definition is found. */ 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. */
static void static void
rewrite_stmt (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, rewrite_blocks (bool fix_virtual_phis)
basic_block bb ATTRIBUTE_UNUSED,
block_stmt_iterator si)
{ {
stmt_ann_t ann; struct dom_walk_data walk_data;
tree stmt;
use_operand_p use_p; /* Rewrite all the basic blocks in the program. */
def_operand_p def_p; timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
ssa_op_iter iter;
stmt = bsi_stmt (si); /* Setup callbacks for the generic dominator tree walker. */
ann = stmt_ann (stmt); 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;
/* If mark_def_sites decided that we don't need to rewrite this block_defs_stack = VEC_alloc (tree_on_heap, 10);
statement, ignore it. */
if (!REWRITE_THIS_STMT (stmt))
return;
if (dump_file && (dump_flags & TDF_DETAILS)) /* Initialize the dominator walker. */
{ init_walk_dominator_tree (&walk_data);
fprintf (dump_file, "Renaming statement ");
print_generic_stmt (dump_file, stmt, TDF_SLIM);
fprintf (dump_file, "\n");
}
/* We have just scanned the code for operands. No statement should /* Recursively walk the dominator tree rewriting each statement in
be modified. */ each basic block. */
gcc_assert (!ann->modified); walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
/* Step 1. Rewrite USES and VUSES in the statement. */ /* Finalize the dominator walker. */
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS) fini_walk_dominator_tree (&walk_data);
rewrite_operand (use_p);
/* Step 2. Register the statement's DEF and VDEF operands. */ /* Debugging dumps. */
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS) if (dump_file && (dump_flags & TDF_STATS))
{ {
if (TREE_CODE (DEF_FROM_PTR (def_p)) != SSA_NAME) dump_dfa_stats (dump_file);
SET_DEF (def_p, make_ssa_name (DEF_FROM_PTR (def_p), stmt)); dump_tree_ssa_stats (dump_file);
/* 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);
} }
htab_delete (def_blocks);
def_blocks = NULL;
VEC_free (tree_on_heap, block_defs_stack);
block_defs_stack = NULL;
timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
} }
/* Same as rewrite_stmt, for rewriting ssa names. */ /* Block initialization routine for mark_def_sites. Clear the
KILLS bitmap at the start of each block. */
static void static void
ssa_rewrite_stmt (struct dom_walk_data *walk_data, mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
basic_block bb ATTRIBUTE_UNUSED, basic_block bb ATTRIBUTE_UNUSED)
block_stmt_iterator si)
{ {
stmt_ann_t ann; struct mark_def_sites_global_data *gd = walk_data->global_data;
tree stmt, var; bitmap kills = gd->kills;
ssa_op_iter iter; bitmap_clear (kills);
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);
if (dump_file && (dump_flags & TDF_DETAILS)) /* Mark the definition site blocks for each variable, so that we know where
{ the variable is actually live. */
fprintf (dump_file, "Renaming statement ");
print_generic_stmt (dump_file, stmt, TDF_SLIM);
fprintf (dump_file, "\n");
}
/* We have just scanned the code for operands. No statement should static void
be modified. */ mark_def_site_blocks (void)
gcc_assert (!ann->modified); {
size_t i;
struct dom_walk_data walk_data;
struct mark_def_sites_global_data mark_def_sites_global_data;
/* Step 1. Rewrite USES and VUSES in the statement. */ /* Allocate memory for the DEF_BLOCKS hash table. */
FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS) def_blocks = htab_create (VARRAY_ACTIVE_SIZE (referenced_vars),
{ def_blocks_hash, def_blocks_eq, def_blocks_free);
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)));
}
/* Step 2. Register the statement's DEF and VDEF operands. */ for (i = 0; i < num_referenced_vars; i++)
FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS) set_current_def (referenced_var (i), NULL_TREE);
{
var = DEF_FROM_PTR (def_p);
if (!TEST_BIT (names_to_rename, SSA_NAME_VERSION (var))) /* Ensure that the dominance information is OK. */
continue; calculate_dominance_info (CDI_DOMINATORS);
SET_DEF (def_p, duplicate_ssa_name (var, stmt)); /* Setup callbacks for the generic dominator tree walker to find and
ssa_register_new_def (var, DEF_FROM_PTR (def_p)); 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 = mark_def_sites_initialize_block;
walk_data.before_dom_children_walk_stmts = mark_def_sites;
walk_data.before_dom_children_after_stmts = NULL;
walk_data.after_dom_children_before_stmts = NULL;
walk_data.after_dom_children_walk_stmts = NULL;
walk_data.after_dom_children_after_stmts = NULL;
/* Replace the operand pointed by OP_P with its immediate reaching /* Notice that this bitmap is indexed using variable UIDs, so it must be
definition. */ 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);
walk_data.global_data = &mark_def_sites_global_data;
static inline void /* We do not have any local data. */
rewrite_operand (use_operand_p op_p) walk_data.block_local_data_size = 0;
{
tree var = USE_FROM_PTR (op_p); /* Initialize the dominator walker. */
if (TREE_CODE (var) != SSA_NAME) init_walk_dominator_tree (&walk_data);
SET_USE (op_p, get_reaching_def (var));
else /* Recursively walk the dominator tree. */
{ walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
#if defined ENABLE_CHECKING
/* If we get to this point, VAR is an SSA_NAME. If VAR's symbol /* Finalize the dominator walker. */
was marked for renaming, make sure that its reaching fini_walk_dominator_tree (&walk_data);
definition is VAR itself. Otherwise, something has gone
wrong. */ /* We no longer need this bitmap, clear and free it. */
tree sym = SSA_NAME_VAR (var); BITMAP_FREE (mark_def_sites_global_data.kills);
if (bitmap_bit_p (vars_to_rename, var_ann (sym)->uid))
gcc_assert (var == get_reaching_def (SSA_NAME_VAR (var)));
#endif
}
} }
/* 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. */
void /* Main entry point into the SSA builder. The renaming process
register_new_def (tree def, VEC (tree_on_heap) **block_defs_p) proceeds in five main phases:
{
tree var = SSA_NAME_VAR (def);
tree currdef;
/* If this variable is set in a single basic block and all uses are
dominated by the set(s) in that single basic block, then there is
no reason to record anything for this variable in the block local
definition stacks. Doing so just wastes time and memory.
This is the same test to prune the set of variables which may 1- If VARS_TO_RENAME has any entries, any existing PHI nodes for
need PHI nodes. So we just use that information since it's already those variables are removed from the flow graph so that they can
computed and available for us to use. */ be computed again.
if (get_phi_state (var) == NEED_PHI_STATE_NO)
{
set_current_def (var, def);
return;
}
currdef = get_current_def (var); 2- Compute dominance frontier and immediate dominators, needed to
insert PHI nodes and rename the function in dominator tree
order.
/* Push the current reaching definition into *BLOCK_DEFS_P. This stack is 3- Find and mark all the blocks that define variables
later used by the dominator tree callbacks to restore the reaching (mark_def_site_blocks).
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);
/* Set the current reaching definition for VAR to be DEF. */ 4- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
set_current_def (var, def);
}
/* Return the current definition for variable VAR. If none is found, 5- Rename all the blocks (rewrite_blocks) and statements in the program.
create a new SSA name to act as the zeroth definition for VAR. If VAR
is call clobbered and there exists a more recent definition of
GLOBAL_VAR, return the definition for GLOBAL_VAR. This means that VAR
has been clobbered by a function call since its last assignment. */
static tree Steps 3 and 5 are done using the dominator tree walker
get_reaching_def (tree var) (walk_dominator_tree).
ALL is true if all variables should be renamed (otherwise just those
mentioned in vars_to_rename are taken into account). */
void
rewrite_into_ssa (bool all)
{ {
tree default_d, currdef_var, avar; bitmap *dfs;
basic_block bb;
bitmap old_vars_to_rename = vars_to_rename;
/* Lookup the current reaching definition for VAR. */ timevar_push (TV_TREE_SSA_OTHER);
default_d = NULL_TREE;
currdef_var = get_current_def (var);
/* If there is no reaching definition for VAR, create and register a if (all)
default definition for it (if needed). */ vars_to_rename = NULL;
if (currdef_var == NULL_TREE) else
{ {
if (TREE_CODE (var) == SSA_NAME) /* Initialize the array of variables to rename. */
avar = SSA_NAME_VAR (var); gcc_assert (vars_to_rename);
else
avar = var;
default_d = default_def (avar); if (bitmap_empty_p (vars_to_rename))
if (default_d == NULL_TREE)
{ {
default_d = make_ssa_name (avar, build_empty_stmt ()); timevar_pop (TV_TREE_SSA_OTHER);
set_default_def (avar, default_d); return;
} }
set_current_def (var, default_d);
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);
} }
/* Return the current reaching definition for VAR, or the default mark_def_site_blocks ();
definition, if we had to create one. */
return (currdef_var) ? currdef_var : default_d;
}
/* 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);
/* Hashing and equality functions for DEF_BLOCKS. */ /* Compute dominance frontiers. */
compute_dominance_frontiers (dfs);
static hashval_t /* Insert PHI nodes at dominance frontiers of definition blocks. */
def_blocks_hash (const void *p) insert_phi_nodes (dfs, NULL);
{
return htab_hash_pointer
((const void *)((const struct def_blocks_d *)p)->var);
}
static int rewrite_blocks (false);
def_blocks_eq (const void *p1, const void *p2)
{
return ((const struct def_blocks_d *)p1)->var
== ((const struct def_blocks_d *)p2)->var;
}
/* Free memory allocated by one entry in DEF_BLOCKS. */ /* Free allocated memory. */
FOR_EACH_BB (bb)
BITMAP_FREE (dfs[bb->index]);
free (dfs);
static void vars_to_rename = old_vars_to_rename;
def_blocks_free (void *p) timevar_pop (TV_TREE_SSA_OTHER);
{
struct def_blocks_d *entry = p;
BITMAP_FREE (entry->def_blocks);
BITMAP_FREE (entry->phi_blocks);
BITMAP_FREE (entry->livein_blocks);
free (entry);
} }
/* Dump the DEF_BLOCKS hash table on stderr. */ /* Rewrites all variables into SSA. */
void static void
debug_def_blocks (void) rewrite_all_into_ssa (void)
{ {
htab_traverse (def_blocks, debug_def_blocks_r, NULL); rewrite_into_ssa (true);
} }
/* Callback for htab_traverse to dump the DEF_BLOCKS hash table. */ struct tree_opt_pass pass_build_ssa =
static int
debug_def_blocks_r (void **slot, void *data ATTRIBUTE_UNUSED)
{ {
struct def_blocks_d *db_p = (struct def_blocks_d *) *slot; "ssa", /* name */
NULL, /* gate */
fprintf (stderr, "VAR: "); rewrite_all_into_ssa, /* execute */
print_generic_expr (stderr, db_p->var, dump_flags); NULL, /* sub */
bitmap_print (stderr, db_p->def_blocks, ", DEF_BLOCKS: { ", "}"); NULL, /* next */
bitmap_print (stderr, db_p->livein_blocks, ", LIVEIN_BLOCKS: { ", "}\n"); 0, /* static_pass_number */
0, /* tv_id */
return 1; PROP_cfg | PROP_referenced_vars, /* properties_required */
} PROP_ssa, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */
0 /* letter */
};
/* Return the set of blocks where variable VAR is defined and the blocks /* Rewrite the def-def chains of virtual operands so that they have
where VAR is live on entry (livein). Return NULL, if no entry is the correct reaching definitions. */
found in DEF_BLOCKS. */
static inline struct def_blocks_d * void
find_def_blocks_for (tree var) rewrite_def_def_chains (void)
{ {
struct def_blocks_d dm; /* Ensure that the dominance information is OK. */
dm.var = var; calculate_dominance_info (CDI_DOMINATORS);
return (struct def_blocks_d *) htab_find (def_blocks, &dm); mark_def_site_blocks ();
rewrite_blocks (true);
} }
/* Return the set of blocks where variable VAR is defined and the blocks
where VAR is live on entry (livein). If no entry is found in
DEF_BLOCKS, a new one is created and returned. */
static inline struct def_blocks_d * /*---------------------------------------------------------------------------
get_def_blocks_for (tree var) 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. */
static void
ssa_rewrite_finalize_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
basic_block bb ATTRIBUTE_UNUSED)
{ {
struct def_blocks_d db, *db_p;
void **slot;
db.var = var; /* Step 5. Restore the current reaching definition for each variable
slot = htab_find_slot (def_blocks, (void *) &db, INSERT); referenced in the block (in reverse order). */
if (*slot == NULL) while (VEC_length (tree_on_heap, block_defs_stack) > 0)
{ {
db_p = xmalloc (sizeof (*db_p)); tree var = VEC_pop (tree_on_heap, block_defs_stack);
db_p->var = var; tree saved_def;
db_p->def_blocks = BITMAP_ALLOC (NULL);
db_p->phi_blocks = BITMAP_ALLOC (NULL); if (var == NULL)
db_p->livein_blocks = BITMAP_ALLOC (NULL); break;
*slot = (void *) db_p;
}
else
db_p = (struct def_blocks_d *) *slot;
return db_p; saved_def = VEC_pop (tree_on_heap, block_defs_stack);
set_current_def (var, saved_def);
}
} }
/* 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.
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 /* Register DEF (an SSA_NAME) to be a new definition for the original
should be more selective. */ ssa name VAR and push VAR's current reaching definition
into the stack pointed by BLOCK_DEFS_P. */
static void static void
invalidate_name_tags (bitmap vars_to_rename) ssa_register_new_def (tree var, tree def)
{ {
unsigned i; tree currdef;
bool rename_name_tags_p;
bitmap_iterator bi; /* 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
rename_name_tags_p = false; nothing to do. TODO we should not be called at all, and just
EXECUTE_IF_SET_IN_BITMAP (vars_to_rename, 0, i, bi) keep the original name. */
if (get_phi_state (var) == NEED_PHI_STATE_NO)
{ {
if (POINTER_TYPE_P (TREE_TYPE (referenced_var (i)))) set_current_def (var, def);
{ return;
rename_name_tags_p = true;
break;
}
} }
if (rename_name_tags_p) currdef = get_current_def (var);
for (i = 0; i < num_referenced_vars; i++)
{
var_ann_t ann = var_ann (referenced_var (i));
if (ann->mem_tag_kind == NAME_TAG) /* Push the current reaching definition into *BLOCK_DEFS_P. This stack is
{ later used by the dominator tree callbacks to restore the reaching
size_t j; definitions for all the variables defined in the block after a recursive
varray_type may_aliases = ann->may_aliases; 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);
bitmap_set_bit (vars_to_rename, ann->uid); /* Set the current reaching definition for VAR to be DEF. */
if (ann->may_aliases) set_current_def (var, def);
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);
}
}
}
} }
/* 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. */
/* Same as rewrite_stmt, for rewriting ssa names. */
static void static void
rewrite_blocks (bool fix_virtual_phis) ssa_rewrite_stmt (struct dom_walk_data *walk_data,
basic_block bb ATTRIBUTE_UNUSED,
block_stmt_iterator si)
{ {
struct dom_walk_data walk_data; stmt_ann_t ann;
tree stmt, var;
/* Rewrite all the basic blocks in the program. */ ssa_op_iter iter;
timevar_push (TV_TREE_SSA_REWRITE_BLOCKS); use_operand_p use_p;
def_operand_p def_p;
/* Setup callbacks for the generic dominator tree walker. */ sbitmap names_to_rename = walk_data->global_data;
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);
/* 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_BLOCK_PTR);
/* Finalize the dominator walker. */ stmt = bsi_stmt (si);
fini_walk_dominator_tree (&walk_data); ann = stmt_ann (stmt);
/* Debugging dumps. */ if (dump_file && (dump_flags & TDF_DETAILS))
if (dump_file && (dump_flags & TDF_STATS))
{ {
dump_dfa_stats (dump_file); fprintf (dump_file, "Renaming statement ");
dump_tree_ssa_stats (dump_file); print_generic_stmt (dump_file, stmt, TDF_SLIM);
fprintf (dump_file, "\n");
} }
htab_delete (def_blocks); /* We have just scanned the code for operands. No statement should
def_blocks = NULL; be modified. */
gcc_assert (!ann->modified);
VEC_free (tree_on_heap, block_defs_stack);
block_defs_stack = NULL;
timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
}
/* 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)
{
size_t i;
struct dom_walk_data walk_data;
struct mark_def_sites_global_data mark_def_sites_global_data;
/* Allocate memory for the DEF_BLOCKS hash table. */ /* Step 1. Rewrite USES and VUSES in the statement. */
def_blocks = htab_create (VARRAY_ACTIVE_SIZE (referenced_vars), FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES | SSA_OP_ALL_KILLS)
def_blocks_hash, def_blocks_eq, def_blocks_free); {
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)));
}
for (i = 0; i < num_referenced_vars; i++) /* Step 2. Register the statement's DEF and VDEF operands. */
set_current_def (referenced_var (i), NULL_TREE); FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
{
var = DEF_FROM_PTR (def_p);
/* Ensure that the dominance information is OK. */ if (!TEST_BIT (names_to_rename, SSA_NAME_VERSION (var)))
calculate_dominance_info (CDI_DOMINATORS); continue;
SET_DEF (def_p, duplicate_ssa_name (var, stmt));
ssa_register_new_def (var, DEF_FROM_PTR (def_p));
}
}
/* 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 = mark_def_sites_initialize_block;
walk_data.before_dom_children_walk_stmts = mark_def_sites;
walk_data.before_dom_children_after_stmts = NULL;
walk_data.after_dom_children_before_stmts = NULL;
walk_data.after_dom_children_walk_stmts = NULL;
walk_data.after_dom_children_after_stmts = NULL;
/* Notice that this bitmap is indexed using variable UIDs, so it must be /* Ditto, for ssa name rewriting. */
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);
walk_data.global_data = &mark_def_sites_global_data;
/* We do not have any local data. */ static void
walk_data.block_local_data_size = 0; 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;
/* Initialize the dominator walker. */ FOR_EACH_EDGE (e, ei, bb->succs)
init_walk_dominator_tree (&walk_data); {
tree phi;
/* Recursively walk the dominator tree. */ if (e->dest == EXIT_BLOCK_PTR)
walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR); continue;
/* Finalize the dominator walker. */ for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
fini_walk_dominator_tree (&walk_data); {
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;
/* We no longer need this bitmap, clear and free it. */ SET_USE (op, get_reaching_def (USE_FROM_PTR (op)));
BITMAP_FREE (mark_def_sites_global_data.kills); if (e->flags & EDGE_ABNORMAL)
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (op)) = 1;
}
}
} }
/* Ditto, for rewriting ssa names. */
/* Main entry point into the SSA builder. The renaming process static void
proceeds in five main phases: ssa_rewrite_initialize_block (struct dom_walk_data *walk_data, basic_block bb)
{
tree phi, new_name;
sbitmap names_to_rename = walk_data->global_data;
edge e;
bool abnormal_phi;
edge_iterator ei;
1- If VARS_TO_RENAME has any entries, any existing PHI nodes for if (dump_file && (dump_flags & TDF_DETAILS))
those variables are removed from the flow graph so that they can fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
be computed again.
2- Compute dominance frontier and immediate dominators, needed to /* Mark the unwind point for this block. */
insert PHI nodes and rename the function in dominator tree VEC_safe_push (tree_on_heap, block_defs_stack, NULL_TREE);
order.
3- Find and mark all the blocks that define variables FOR_EACH_EDGE (e, ei, bb->preds)
(mark_def_site_blocks). if (e->flags & EDGE_ABNORMAL)
break;
abnormal_phi = (e != NULL);
4- Insert PHI nodes at dominance frontiers (insert_phi_nodes). /* 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))
{
tree result = PHI_RESULT (phi);
5- Rename all the blocks (rewrite_blocks) and statements in the program. if (TEST_BIT (names_to_rename, SSA_NAME_VERSION (result)))
{
new_name = duplicate_ssa_name (result, phi);
SET_PHI_RESULT (phi, new_name);
Steps 3 and 5 are done using the dominator tree walker if (abnormal_phi)
(walk_dominator_tree). SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1;
ssa_register_new_def (result, new_name);
}
}
}
ALL is true if all variables should be renamed (otherwise just those
mentioned in vars_to_rename are taken into account). */
void /* Same as mark_def_sites, but works over SSA names. */
rewrite_into_ssa (bool all)
static void
ssa_mark_def_sites (struct dom_walk_data *walk_data,
basic_block bb,
block_stmt_iterator bsi)
{ {
bitmap *dfs; struct mark_def_sites_global_data *gd = walk_data->global_data;
basic_block bb; bitmap kills = gd->kills;
bitmap old_vars_to_rename = vars_to_rename; size_t uid, def_uid;
tree stmt, use, def;
timevar_push (TV_TREE_SSA_OTHER); ssa_op_iter iter;
if (all) /* Mark all the blocks that have definitions for each variable in the
vars_to_rename = NULL; names_to_rename bitmap. */
else stmt = bsi_stmt (bsi);
get_stmt_operands (stmt);
/* 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)
{ {
/* Initialize the array of variables to rename. */ uid = SSA_NAME_VERSION (use);
gcc_assert (vars_to_rename);
if (bitmap_empty_p (vars_to_rename)) if (TEST_BIT (gd->names_to_rename, uid)
&& !bitmap_bit_p (kills, uid))
set_livein_block (use, bb);
}
/* 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)
{
def_uid = SSA_NAME_VERSION (def);
if (TEST_BIT (gd->names_to_rename, def_uid))
{ {
timevar_pop (TV_TREE_SSA_OTHER); set_def_block (def, bb, false, true);
return; bitmap_set_bit (kills, def_uid);
} }
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);
} }
}
mark_def_site_blocks ();
/* Initialize dominance frontier and immediate dominator bitmaps. /* Block initialization routine for mark_def_sites. Clear the
Also count the number of predecessors for each block. Doing so KILLS bitmap at the start of each block. */
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);
/* Compute dominance frontiers. */ static void
compute_dominance_frontiers (dfs); ssa_mark_def_sites_initialize_block (struct dom_walk_data *walk_data,
basic_block bb)
{
struct mark_def_sites_global_data *gd = walk_data->global_data;
bitmap kills = gd->kills;
tree phi, def;
unsigned def_uid;
/* Insert PHI nodes at dominance frontiers of definition blocks. */ bitmap_clear (kills);
insert_phi_nodes (dfs, NULL);
rewrite_blocks (false); for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
def = PHI_RESULT (phi);
def_uid = SSA_NAME_VERSION (def);
/* Free allocated memory. */ if (!TEST_BIT (gd->names_to_rename, def_uid))
FOR_EACH_BB (bb) continue;
BITMAP_FREE (dfs[bb->index]);
free (dfs);
vars_to_rename = old_vars_to_rename; set_def_block (def, bb, true, true);
timevar_pop (TV_TREE_SSA_OTHER); bitmap_set_bit (kills, def_uid);
}
} }
/* Rewrite the def-def chains so that they have the correct reaching /* Marks ssa names used as arguments of phis at the end of BB. */
definitions. */
void static void
rewrite_def_def_chains (void) ssa_mark_phi_uses (struct dom_walk_data *walk_data, basic_block bb)
{ {
/* Ensure that the dominance information is OK. */ struct mark_def_sites_global_data *gd = walk_data->global_data;
calculate_dominance_info (CDI_DOMINATORS); bitmap kills = gd->kills;
mark_def_site_blocks (); edge e;
rewrite_blocks (true); tree phi, use;
unsigned uid;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->succs)
{
if (e->dest == EXIT_BLOCK_PTR)
continue;
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;
uid = SSA_NAME_VERSION (use);
if (TEST_BIT (gd->names_to_rename, uid)
&& !bitmap_bit_p (kills, uid))
set_livein_block (use, bb);
}
}
} }
/* The marked ssa names may have more than one definition; /* The marked ssa names may have more than one definition;
add phi nodes and rewrite them to fix this. */ add PHI nodes and rewrite them to fix this. */
void void
rewrite_ssa_into_ssa (void) rewrite_ssa_into_ssa (void)
...@@ -1796,28 +1835,3 @@ rewrite_ssa_into_ssa (void) ...@@ -1796,28 +1835,3 @@ rewrite_ssa_into_ssa (void)
block_defs_stack = NULL; block_defs_stack = NULL;
timevar_pop (TV_TREE_SSA_OTHER); timevar_pop (TV_TREE_SSA_OTHER);
} }
/* Rewrites all variables into ssa. */
static void
rewrite_all_into_ssa (void)
{
rewrite_into_ssa (true);
}
struct tree_opt_pass pass_build_ssa =
{
"ssa", /* name */
NULL, /* gate */
rewrite_all_into_ssa, /* execute */
NULL, /* sub */
NULL, /* next */
0, /* static_pass_number */
0, /* tv_id */
PROP_cfg | PROP_referenced_vars, /* properties_required */
PROP_ssa, /* properties_provided */
0, /* properties_destroyed */
0, /* todo_flags_start */
TODO_dump_func | TODO_verify_ssa, /* todo_flags_finish */
0 /* letter */
};
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