#include "except.h"
#include "cfgloop.h"
#include "cfglayout.h"
+#include "hashtab.h"
/* This file contains functions for building the Control Flow Graph (CFG)
for a function tree. */
building of the CFG in code with lots of gotos. */
static GTY(()) varray_type label_to_block_map;
+/* This hash table allows us to efficiently lookup the one and only one
+ CASE_LABEL_EXPR which contains the LABEL_DECL for the target block
+ of one or more case statements. Efficient access to this node
+ allows us to efficiently update the case vector in response to
+ edge redirections and similar operations.
+
+ Right now this is only used to set up case label leaders. In the
+ future we hope to make this table more persistent and use it to
+ more efficiently update case labels. */
+
+struct edge_to_case_leader_elt
+{
+ /* The edge itself. Necessary for hashing and equality tests. */
+ edge e;
+
+ /* The "leader" for all the CASE_LABEL_EXPRs which transfer control
+ to E->dest. When we change the destination of E, we will need to
+ update the CASE_LEADER_OR_LABEL of this CASE_LABEL_EXPR (and no
+ others). */
+ tree case_label;
+};
+
+static htab_t edge_to_case_leader;
+
/* CFG statistics. */
struct cfg_stats_d
{
static void tree_make_forwarder_block (edge);
static bool thread_jumps (void);
static bool tree_forwarder_block_p (basic_block);
-static void bsi_commit_edge_inserts_1 (edge e);
static void tree_cfg2vcg (FILE *);
/* Flowgraph optimization and cleanup. */
if (found_computed_goto)
factor_computed_gotos ();
- /* Make sure there is always at least one block, even if its empty. */
+ /* Make sure there is always at least one block, even if it's empty. */
if (n_basic_blocks == 0)
create_empty_bb (ENTRY_BLOCK_PTR);
gcc_assert (!e);
- /* Create and initialize a new basic block. */
+ /* Create and initialize a new basic block. Since alloc_block uses
+ ggc_alloc_cleared to allocate a basic block, we do not have to
+ clear the newly allocated basic block here. */
bb = alloc_block ();
- memset (bb, 0, sizeof (*bb));
bb->index = last_basic_block;
bb->flags = BB_NEW;
make_edge (bb, else_bb, EDGE_FALSE_VALUE);
}
+/* Hashing routine for EDGE_TO_CASE_LEADER. */
+
+static hashval_t
+edge_to_case_leader_hash (const void *p)
+{
+ edge e = ((struct edge_to_case_leader_elt *)p)->e;
+
+ /* Hash on the edge itself (which is a pointer). */
+ return htab_hash_pointer (e);
+}
+
+/* Equality routine for EDGE_TO_CASE_LEADER, edges are unique, so testing
+ for equality is just a pointer comparison. */
+
+static int
+edge_to_case_leader_eq (const void *p1, const void *p2)
+{
+ edge e1 = ((struct edge_to_case_leader_elt *)p1)->e;
+ edge e2 = ((struct edge_to_case_leader_elt *)p2)->e;
+
+ return e1 == e2;
+}
+
+/* Record that CASE_LABEL (a CASE_LABEL_EXPR) references edge E. */
+
+static void
+record_switch_edge (edge e, tree case_label)
+{
+ struct edge_to_case_leader_elt *elt;
+ void **slot;
+
+ /* Build a hash table element so we can see if E is already
+ in the table. */
+ elt = xmalloc (sizeof (struct edge_to_case_leader_elt));
+ elt->e = e;
+ elt->case_label = case_label;
+
+ slot = htab_find_slot (edge_to_case_leader, elt, INSERT);
+
+ if (*slot == NULL)
+ {
+ /* E was not in the hash table. Install E into the hash table. */
+ *slot = (void *)elt;
+ }
+ else
+ {
+ /* E was already in the hash table. Free ELT as we do not need it
+ anymore. */
+ free (elt);
+
+ /* Get the entry stored in the hash table. */
+ elt = (struct edge_to_case_leader_elt *) *slot;
+
+ /* Make ELT->case_label the leader for CASE_LABEL. */
+ CASE_LEADER_OR_LABEL (case_label) = elt->case_label;
+ }
+}
+
+/* Subroutine of get_case_leader_for_edge; returns the case leader for the
+ chain of CASE_LABEL_EXPRs associated with E using a hash table lookup. */
+
+static tree
+get_case_leader_for_edge_hash (edge e)
+{
+ struct edge_to_case_leader_elt elt, *elt_p;
+ void **slot;
+
+ elt.e = e;
+ elt.case_label = NULL;
+ slot = htab_find_slot (edge_to_case_leader, &elt, NO_INSERT);
+
+ if (slot)
+ {
+ tree t;
+
+ elt_p = (struct edge_to_case_leader_elt *)*slot;
+ t = elt_p->case_label;
+
+ while (TREE_CODE (CASE_LEADER_OR_LABEL (t)) == CASE_LABEL_EXPR)
+ t = CASE_LEADER_OR_LABEL (t);
+ return t;
+ }
+
+ return NULL;
+}
+
+/* Given an edge E, return the case leader for the chain of CASE_LABEL_EXPRs
+ which use E. */
+
+static tree
+get_case_leader_for_edge (edge e)
+{
+ tree vec, stmt;
+ size_t i, n;
+
+ /* If we have a hash table, then use it as it's significantly faster. */
+ if (edge_to_case_leader)
+ return get_case_leader_for_edge_hash (e);
+
+ /* No hash table. We have to walk the case vector. */
+ stmt = bsi_stmt (bsi_last (e->src));
+ vec = SWITCH_LABELS (stmt);
+ n = TREE_VEC_LENGTH (vec);
+
+ for (i = 0; i < n; i++)
+ {
+ tree elt = TREE_VEC_ELT (vec, i);
+ tree t = CASE_LEADER_OR_LABEL (elt);
+
+ if (TREE_CODE (t) == LABEL_DECL
+ && label_to_block (t) == e->dest)
+ return elt;
+ }
+
+ abort ();
+}
/* Create the edges for a SWITCH_EXPR starting at block BB.
At this point, the switch body has been lowered and the
vec = SWITCH_LABELS (entry);
n = TREE_VEC_LENGTH (vec);
+ edge_to_case_leader
+ = htab_create (n, edge_to_case_leader_hash, edge_to_case_leader_eq, free);
+
for (i = 0; i < n; ++i)
{
tree lab = CASE_LABEL (TREE_VEC_ELT (vec, i));
basic_block label_bb = label_to_block (lab);
- make_edge (bb, label_bb, 0);
+ edge e = make_edge (bb, label_bb, 0);
+
+ if (!e)
+ e = find_edge (bb, label_bb);
+
+ record_switch_edge (e, TREE_VEC_ELT (vec, i));
}
+ htab_delete (edge_to_case_leader);
+ edge_to_case_leader = NULL;
}
{
int uid = LABEL_DECL_UID (dest);
- /* We would die hard when faced by undefined label. Emit label to
- very first basic block. This will hopefully make even the dataflow
+ /* We would die hard when faced by an undefined label. Emit a label to
+ the very first basic block. This will hopefully make even the dataflow
and undefined variable warnings quite right. */
if ((errorcount || sorrycount) && uid < 0)
{
bool
cleanup_tree_cfg (void)
{
- bool something_changed = true;
bool retval = false;
timevar_push (TV_TREE_CLEANUP_CFG);
- /* These three transformations can cascade, so we iterate on them until
- nothing changes. */
- while (something_changed)
+ retval = cleanup_control_flow ();
+ retval |= delete_unreachable_blocks ();
+ retval |= thread_jumps ();
+
+#ifdef ENABLE_CHECKING
+ if (retval)
{
- something_changed = cleanup_control_flow ();
- something_changed |= delete_unreachable_blocks ();
- something_changed |= thread_jumps ();
- retval |= something_changed;
+ gcc_assert (!cleanup_control_flow ());
+ gcc_assert (!delete_unreachable_blocks ());
+ gcc_assert (!thread_jumps ());
}
+#endif
/* Merging the blocks creates no new opportunities for the other
optimizations, so do it here. */
return label_for_bb[bb->index];
}
-/* Cleanup redundant labels. This is a three-steo process:
+/* Cleanup redundant labels. This is a three-step process:
1) Find the leading label for each block.
2) Redirect all references to labels to the leading labels.
3) Cleanup all useless labels. */
label_for_bb = xcalloc (last_basic_block, sizeof (tree));
/* Find a suitable label for each block. We use the first user-defined
- label is there is one, or otherwise just the first label we see. */
+ label if there is one, or otherwise just the first label we see. */
FOR_EACH_BB (bb)
{
block_stmt_iterator i;
/* Replace all destination labels. */
for (i = 0; i < n; ++i)
- CASE_LABEL (TREE_VEC_ELT (vec, i))
- = main_block_label (CASE_LABEL (TREE_VEC_ELT (vec, i)));
-
+ {
+ tree elt = TREE_VEC_ELT (vec, i);
+ tree label = main_block_label (CASE_LABEL (elt));
+ CASE_LEADER_OR_LABEL (elt) = label;
+ }
break;
}
tree labels = SWITCH_LABELS (stmt);
int old_size = TREE_VEC_LENGTH (labels);
int i, j, new_size = old_size;
- tree default_label = TREE_VEC_ELT (labels, old_size - 1);
+ tree default_case = TREE_VEC_ELT (labels, old_size - 1);
+ tree default_label;
+
+ /* The default label is always the last case in a switch
+ statement after gimplification. */
+ default_label = CASE_LABEL (default_case);
/* Look for possible opportunities to merge cases.
Ignore the last element of the label vector because it
must be the default case. */
i = 0;
- while (i < old_size - 2)
+ while (i < old_size - 1)
{
tree base_case, base_label, base_high, type;
base_case = TREE_VEC_ELT (labels, i);
{
TREE_VEC_ELT (labels, i) = NULL_TREE;
i++;
+ new_size--;
continue;
}
type = TREE_TYPE (CASE_LOW (base_case));
base_high = CASE_HIGH (base_case) ?
CASE_HIGH (base_case) : CASE_LOW (base_case);
-
+ i++;
/* Try to merge case labels. Break out when we reach the end
of the label vector or when we cannot merge the next case
label with the current one. */
- while (i < old_size - 2)
+ while (i < old_size - 1)
{
- tree merge_case = TREE_VEC_ELT (labels, ++i);
+ tree merge_case = TREE_VEC_ELT (labels, i);
tree merge_label = CASE_LABEL (merge_case);
tree t = int_const_binop (PLUS_EXPR, base_high,
integer_one_node, 1);
CASE_HIGH (base_case) = base_high;
TREE_VEC_ELT (labels, i) = NULL_TREE;
new_size--;
+ i++;
}
else
break;
else_has_label = data->has_label;
data->has_label = save_has_label | then_has_label | else_has_label;
- fold_stmt (stmt_p);
then_clause = COND_EXPR_THEN (*stmt_p);
else_clause = COND_EXPR_ELSE (*stmt_p);
cond = COND_EXPR_COND (*stmt_p);
}
}
break;
- case SWITCH_EXPR:
+ case ASM_EXPR:
fold_stmt (tp);
data->last_goto = NULL;
break;
}
/* Remove all the instructions in the block. */
- for (i = bsi_start (bb); !bsi_end_p (i); bsi_remove (&i))
+ for (i = bsi_start (bb); !bsi_end_p (i);)
{
tree stmt = bsi_stmt (i);
- release_defs (stmt);
+ if (TREE_CODE (stmt) == LABEL_EXPR
+ && FORCED_LABEL (LABEL_EXPR_LABEL (stmt)))
+ {
+ basic_block new_bb = bb->prev_bb;
+ block_stmt_iterator new_bsi = bsi_after_labels (new_bb);
+
+ bsi_remove (&i);
+ bsi_insert_after (&new_bsi, stmt, BSI_NEW_STMT);
+ }
+ else
+ {
+ release_defs (stmt);
- set_bb_for_stmt (stmt, NULL);
+ set_bb_for_stmt (stmt, NULL);
+ bsi_remove (&i);
+ }
/* Don't warn for removed gotos. Gotos are often removed due to
jump threading, thus resulting in bogus warnings. Not great,
remove_phi_nodes_and_edges_for_unreachable_block (bb);
}
-
-/* Examine BB to determine if it is a forwarding block (a block which only
- transfers control to a new destination). If BB is a forwarding block,
- then return the edge leading to the ultimate destination. */
-
-edge
-tree_block_forwards_to (basic_block bb)
-{
- block_stmt_iterator bsi;
- bb_ann_t ann = bb_ann (bb);
- tree stmt;
-
- /* If this block is not forwardable, then avoid useless work. */
- if (! ann->forwardable)
- return NULL;
-
- /* Set this block to not be forwardable. This prevents infinite loops since
- any block currently under examination is considered non-forwardable. */
- ann->forwardable = 0;
-
- /* No forwarding is possible if this block is a special block (ENTRY/EXIT),
- this block has more than one successor, this block's single successor is
- reached via an abnormal edge, this block has phi nodes, or this block's
- single successor has phi nodes. */
- if (bb == EXIT_BLOCK_PTR
- || bb == ENTRY_BLOCK_PTR
- || EDGE_COUNT (bb->succs) != 1
- || EDGE_SUCC (bb, 0)->dest == EXIT_BLOCK_PTR
- || (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL) != 0
- || phi_nodes (bb)
- || phi_nodes (EDGE_SUCC (bb, 0)->dest))
- return NULL;
-
- /* Walk past any labels at the start of this block. */
- for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
- {
- stmt = bsi_stmt (bsi);
- if (TREE_CODE (stmt) != LABEL_EXPR)
- break;
- }
-
- /* If we reached the end of this block we may be able to optimize this
- case. */
- if (bsi_end_p (bsi))
- {
- edge dest;
-
- /* Recursive call to pick up chains of forwarding blocks. */
- dest = tree_block_forwards_to (EDGE_SUCC (bb, 0)->dest);
-
- /* If none found, we forward to bb->succs[0] at minimum. */
- if (!dest)
- dest = EDGE_SUCC (bb, 0);
-
- ann->forwardable = 1;
- return dest;
- }
-
- /* No forwarding possible. */
- return NULL;
-}
-
-
/* Try to remove superfluous control structures. */
static bool
taken_edge->flags = EDGE_FALLTHRU;
/* We removed some paths from the cfg. */
- if (dom_computed[CDI_DOMINATORS] >= DOM_CONS_OK)
- dom_computed[CDI_DOMINATORS] = DOM_CONS_OK;
+ free_dominance_info (CDI_DOMINATORS);
return retval;
}
-/* Given a control block BB and a predicate VAL, return the edge that
- will be taken out of the block. If VAL does not match a unique
- edge, NULL is returned. */
+/* Given a basic block BB ending with COND_EXPR or SWITCH_EXPR, and a
+ predicate VAL, return the edge that will be taken out of the block.
+ If VAL does not match a unique edge, NULL is returned. */
edge
find_taken_edge (basic_block bb, tree val)
gcc_assert (stmt);
gcc_assert (is_ctrl_stmt (stmt));
+ gcc_assert (val);
/* If VAL is a predicate of the form N RELOP N, where N is an
SSA_NAME, we can usually determine its truth value. */
- if (val && COMPARISON_CLASS_P (val))
+ if (COMPARISON_CLASS_P (val))
val = fold (val);
/* If VAL is not a constant, we can't determine which edge might
be taken. */
- if (val == NULL || !really_constant_p (val))
+ if (!really_constant_p (val))
return NULL;
if (TREE_CODE (stmt) == COND_EXPR)
if (TREE_CODE (stmt) == SWITCH_EXPR)
return find_taken_edge_switch_expr (bb, val);
- return EDGE_SUCC (bb, 0);
+ gcc_unreachable ();
}
extract_true_false_edges_from_block (bb, &true_edge, &false_edge);
- /* If both edges of the branch lead to the same basic block, it doesn't
- matter which edge is taken. */
- if (true_edge->dest == false_edge->dest)
- return true_edge;
-
/* Otherwise, try to determine which branch of the if() will be taken.
If VAL is a constant but it can't be reduced to a 0 or a 1, then
we don't really know which edge will be taken at runtime. This
/* Finds iterator for STMT. */
extern block_stmt_iterator
-stmt_for_bsi (tree stmt)
+bsi_for_stmt (tree stmt)
{
block_stmt_iterator bsi;
The requirement for no PHI nodes could be relaxed. Basically we
would have to examine the PHIs to prove that none of them used
- the value set by the statement we want to insert on E. That
+ the value set by the statement we want to insert on E. That
hardly seems worth the effort. */
if (EDGE_COUNT (dest->preds) == 1
&& ! phi_nodes (dest)
/* This routine will commit all pending edge insertions, creating any new
- basic blocks which are necessary.
-
- If specified, NEW_BLOCKS returns a count of the number of new basic
- blocks which were created. */
+ basic blocks which are necessary. */
void
-bsi_commit_edge_inserts (int *new_blocks)
+bsi_commit_edge_inserts (void)
{
basic_block bb;
edge e;
- int blocks;
edge_iterator ei;
- blocks = n_basic_blocks;
-
- bsi_commit_edge_inserts_1 (EDGE_SUCC (ENTRY_BLOCK_PTR, 0));
+ bsi_commit_one_edge_insert (EDGE_SUCC (ENTRY_BLOCK_PTR, 0), NULL);
FOR_EACH_BB (bb)
FOR_EACH_EDGE (e, ei, bb->succs)
- bsi_commit_edge_inserts_1 (e);
-
- if (new_blocks)
- *new_blocks = n_basic_blocks - blocks;
+ bsi_commit_one_edge_insert (e, NULL);
}
-/* Commit insertions pending at edge E. */
+/* Commit insertions pending at edge E. If a new block is created, set NEW_BB
+ to this block, otherwise set it to NULL. */
-static void
-bsi_commit_edge_inserts_1 (edge e)
+void
+bsi_commit_one_edge_insert (edge e, basic_block *new_bb)
{
+ if (new_bb)
+ *new_bb = NULL;
if (PENDING_STMT (e))
{
block_stmt_iterator bsi;
PENDING_STMT (e) = NULL_TREE;
- if (tree_find_edge_insert_loc (e, &bsi, NULL))
+ if (tree_find_edge_insert_loc (e, &bsi, new_bb))
bsi_insert_after (&bsi, stmt, BSI_NEW_STMT);
else
bsi_insert_before (&bsi, stmt, BSI_NEW_STMT);
break;
case COND_EXPR:
- x = TREE_OPERAND (t, 0);
+ x = COND_EXPR_COND (t);
if (TREE_CODE (TREE_TYPE (x)) != BOOLEAN_TYPE)
{
error ("non-boolean used in condition");
|| TREE_CODE (t) == SSA_NAME)
return true;
+ if (TREE_CODE (t) == CASE_LABEL_EXPR)
+ return true;
+
while (((TREE_CODE (t) == ARRAY_REF || TREE_CODE (t) == ARRAY_RANGE_REF)
/* We check for constants explicitly since they are not considered
gimple invariants if they overflowed. */
if (label_to_block (LABEL_EXPR_LABEL (bsi_stmt (bsi))) != bb)
{
+ tree stmt = bsi_stmt (bsi);
error ("Label %s to block does not match in bb %d\n",
- IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))),
+ IDENTIFIER_POINTER (DECL_NAME (LABEL_EXPR_LABEL (stmt))),
bb->index);
err = 1;
}
if (decl_function_context (LABEL_EXPR_LABEL (bsi_stmt (bsi)))
!= current_function_decl)
{
+ tree stmt = bsi_stmt (bsi);
error ("Label %s has incorrect context in bb %d\n",
- IDENTIFIER_POINTER (DECL_NAME (bsi_stmt (bsi))),
+ IDENTIFIER_POINTER (DECL_NAME (LABEL_EXPR_LABEL (stmt))),
bb->index);
err = 1;
}
}
-/* Updates phi nodes after creating forwarder block joined
+/* Updates phi nodes after creating a forwarder block joined
by edge FALLTHRU. */
static void
edge e;
edge_iterator ei;
basic_block dummy, bb;
- tree phi, new_phi, var, prev, next;
+ tree phi, new_phi, var;
dummy = fallthru->src;
bb = fallthru->dest;
}
/* Ensure that the PHI node chain is in the same order. */
- prev = NULL;
- for (phi = phi_nodes (bb); phi; phi = next)
- {
- next = PHI_CHAIN (phi);
- PHI_CHAIN (phi) = prev;
- prev = phi;
- }
- set_phi_nodes (bb, prev);
+ set_phi_nodes (bb, phi_reverse (phi_nodes (bb)));
/* Add the arguments we have stored on edges. */
FOR_EACH_EDGE (e, ei, bb->preds)
if (e == fallthru)
continue;
- for (phi = phi_nodes (bb), var = PENDING_STMT (e);
- phi;
- phi = PHI_CHAIN (phi), var = TREE_CHAIN (var))
- add_phi_arg (&phi, TREE_VALUE (var), e);
-
- PENDING_STMT (e) = NULL;
+ flush_pending_stmts (e);
}
}
/* Return true if basic block BB does nothing except pass control
flow to another block and that we can safely insert a label at
- the start of the successor block. */
+ the start of the successor block.
+
+ As a precondition, we require that BB be not equal to
+ ENTRY_BLOCK_PTR. */
static bool
tree_forwarder_block_p (basic_block bb)
edge e;
edge_iterator ei;
- /* If we have already determined that this block is not forwardable,
- then no further checks are necessary. */
- if (! bb_ann (bb)->forwardable)
- return false;
-
- /* BB must have a single outgoing normal edge. Otherwise it can not be
- a forwarder block. */
+ /* BB must have a single outgoing edge. */
if (EDGE_COUNT (bb->succs) != 1
+ /* BB can not have any PHI nodes. This could potentially be
+ relaxed early in compilation if we re-rewrote the variables
+ appearing in any PHI nodes in forwarder blocks. */
+ || phi_nodes (bb)
+ /* BB may not be a predecessor of EXIT_BLOCK_PTR. */
|| EDGE_SUCC (bb, 0)->dest == EXIT_BLOCK_PTR
- || (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL)
- || bb == ENTRY_BLOCK_PTR)
- {
- bb_ann (bb)->forwardable = 0;
- return false;
- }
+ /* BB may not have an abnormal outgoing edge. */
+ || (EDGE_SUCC (bb, 0)->flags & EDGE_ABNORMAL))
+ return false;
+
+#if ENABLE_CHECKING
+ gcc_assert (bb != ENTRY_BLOCK_PTR);
+#endif
/* Successors of the entry block are not forwarders. */
FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
if (e->dest == bb)
- {
- bb_ann (bb)->forwardable = 0;
- return false;
- }
-
- /* BB can not have any PHI nodes. This could potentially be relaxed
- early in compilation if we re-rewrote the variables appearing in
- any PHI nodes in forwarder blocks. */
- if (phi_nodes (bb))
- {
- bb_ann (bb)->forwardable = 0;
- return false;
- }
+ return false;
/* Now walk through the statements. We can ignore labels, anything else
means this is not a forwarder block. */
break;
default:
- bb_ann (bb)->forwardable = 0;
return false;
}
}
return true;
}
+/* Thread jumps from BB. */
-/* Thread jumps over empty statements.
-
- This code should _not_ thread over obviously equivalent conditions
- as that requires nontrivial updates to the SSA graph. */
-
static bool
-thread_jumps (void)
+thread_jumps_from_bb (basic_block bb)
{
- edge e, last, old;
- basic_block bb, dest, tmp, old_dest, curr, dom;
- tree phi;
- int arg;
+ edge_iterator ei;
+ edge e;
bool retval = false;
- FOR_EACH_BB (bb)
- bb_ann (bb)->forwardable = 1;
-
- FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
+ /* Examine each of our block's successors to see if it is
+ forwardable. */
+ for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
{
- edge_iterator ei;
-
- /* Don't waste time on unreachable blocks. */
- if (EDGE_COUNT (bb->preds) == 0)
- continue;
+ int freq;
+ gcov_type count;
+ edge last, old;
+ basic_block dest, tmp, curr, old_dest;
+ tree phi;
+ int arg;
- /* Nor on forwarders. */
- if (tree_forwarder_block_p (bb))
- continue;
-
- /* This block is now part of a forwarding path, mark it as not
- forwardable so that we can detect loops. This bit will be
- reset below. */
- bb_ann (bb)->forwardable = 0;
+ /* If the edge is abnormal or its destination is not
+ forwardable, then there's nothing to do. */
+ if ((e->flags & EDGE_ABNORMAL)
+ || !bb_ann (e->dest)->forwardable)
+ {
+ ei_next (&ei);
+ continue;
+ }
- /* Examine each of our block's successors to see if it is
- forwardable. */
- for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
+ /* Now walk through as many forwarder blocks as possible to find
+ the ultimate destination we want to thread our jump to. */
+ last = EDGE_SUCC (e->dest, 0);
+ bb_ann (e->dest)->forwardable = 0;
+ for (dest = EDGE_SUCC (e->dest, 0)->dest;
+ bb_ann (dest)->forwardable;
+ last = EDGE_SUCC (dest, 0),
+ dest = EDGE_SUCC (dest, 0)->dest)
+ bb_ann (dest)->forwardable = 0;
+
+ /* Reset the forwardable marks to 1. */
+ for (tmp = e->dest;
+ tmp != dest;
+ tmp = EDGE_SUCC (tmp, 0)->dest)
+ bb_ann (tmp)->forwardable = 1;
+
+ if (dest == e->dest)
{
- int freq;
- gcov_type count;
+ ei_next (&ei);
+ continue;
+ }
- /* If the edge is abnormal or its destination is not
- forwardable, then there's nothing to do. */
- if ((e->flags & EDGE_ABNORMAL)
- || !tree_forwarder_block_p (e->dest))
+ old = find_edge (bb, dest);
+ if (old)
+ {
+ /* If there already is an edge, check whether the values in
+ phi nodes differ. */
+ if (!phi_alternatives_equal (dest, last, old))
{
- ei_next (&ei);
- continue;
+ /* The previous block is forwarder. Redirect our jump
+ to that target instead since we know it has no PHI
+ nodes that will need updating. */
+ dest = last->src;
+
+ /* That might mean that no forwarding at all is
+ possible. */
+ if (dest == e->dest)
+ {
+ ei_next (&ei);
+ continue;
+ }
+
+ old = find_edge (bb, dest);
}
+ }
+
+ /* Perform the redirection. */
+ retval = true;
+ count = e->count;
+ freq = EDGE_FREQUENCY (e);
+ old_dest = e->dest;
+ e = redirect_edge_and_branch (e, dest);
+
+ /* Update the profile. */
+ if (profile_status != PROFILE_ABSENT)
+ for (curr = old_dest;
+ curr != dest;
+ curr = EDGE_SUCC (curr, 0)->dest)
+ {
+ curr->frequency -= freq;
+ if (curr->frequency < 0)
+ curr->frequency = 0;
+ curr->count -= count;
+ if (curr->count < 0)
+ curr->count = 0;
+ EDGE_SUCC (curr, 0)->count -= count;
+ if (EDGE_SUCC (curr, 0)->count < 0)
+ EDGE_SUCC (curr, 0)->count = 0;
+ }
- count = e->count;
- freq = EDGE_FREQUENCY (e);
-
- /* Now walk through as many forwarder block as possible to
- find the ultimate destination we want to thread our jump
- to. */
- last = EDGE_SUCC (e->dest, 0);
- bb_ann (e->dest)->forwardable = 0;
- for (dest = EDGE_SUCC (e->dest, 0)->dest;
- tree_forwarder_block_p (dest);
- last = EDGE_SUCC (dest, 0),
- dest = EDGE_SUCC (dest, 0)->dest)
+ if (!old)
+ {
+ /* Update PHI nodes. We know that the new argument should
+ have the same value as the argument associated with LAST.
+ Otherwise we would have changed our target block
+ above. */
+ for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
{
- /* An infinite loop detected. We redirect the edge anyway, so
- that the loop is shrunk into single basic block. */
- if (!bb_ann (dest)->forwardable)
- break;
+ arg = phi_arg_from_edge (phi, last);
+ gcc_assert (arg >= 0);
+ add_phi_arg (&phi, PHI_ARG_DEF (phi, arg), e);
+ }
+ }
- if (EDGE_SUCC (dest, 0)->dest == EXIT_BLOCK_PTR)
- break;
+ /* Remove the unreachable blocks (observe that if all blocks
+ were reachable before, only those in the path we threaded
+ over and did not have any predecessor outside of the path
+ become unreachable). */
+ for (; old_dest != dest; old_dest = tmp)
+ {
+ tmp = EDGE_SUCC (old_dest, 0)->dest;
- bb_ann (dest)->forwardable = 0;
- }
+ if (EDGE_COUNT (old_dest->preds) > 0)
+ break;
- /* Reset the forwardable marks to 1. */
- for (tmp = e->dest;
- tmp != dest;
- tmp = EDGE_SUCC (tmp, 0)->dest)
- bb_ann (tmp)->forwardable = 1;
+ delete_basic_block (old_dest);
+ }
- if (dest == e->dest)
- {
- ei_next (&ei);
- continue;
- }
-
- old = find_edge (bb, dest);
- if (old)
+ /* Update the dominators. */
+ if (dom_info_available_p (CDI_DOMINATORS))
+ {
+ /* If the dominator of the destination was in the
+ path, set its dominator to the start of the
+ redirected edge. */
+ if (get_immediate_dominator (CDI_DOMINATORS, old_dest) == NULL)
+ set_immediate_dominator (CDI_DOMINATORS, old_dest, bb);
+
+ /* Now proceed like if we forwarded just over one edge at a
+ time. Algorithm for forwarding edge S --> A over
+ edge A --> B then is
+
+ if (idom (B) == A
+ && !dominated_by (S, B))
+ idom (B) = idom (A);
+ recount_idom (A); */
+
+ for (; old_dest != dest; old_dest = tmp)
{
- /* If there already is an edge, check whether the values
- in phi nodes differ. */
- if (!phi_alternatives_equal (dest, last, old))
- {
- /* The previous block is forwarder. Redirect our jump
- to that target instead since we know it has no PHI
- nodes that will need updating. */
- dest = last->src;
-
- /* That might mean that no forwarding at all is possible. */
- if (dest == e->dest)
- {
- ei_next (&ei);
- continue;
- }
+ basic_block dom;
+
+ tmp = EDGE_SUCC (old_dest, 0)->dest;
- old = find_edge (bb, dest);
+ if (get_immediate_dominator (CDI_DOMINATORS, tmp) == old_dest
+ && !dominated_by_p (CDI_DOMINATORS, bb, tmp))
+ {
+ dom = get_immediate_dominator (CDI_DOMINATORS, old_dest);
+ set_immediate_dominator (CDI_DOMINATORS, tmp, dom);
}
+
+ dom = recount_dominator (CDI_DOMINATORS, old_dest);
+ set_immediate_dominator (CDI_DOMINATORS, old_dest, dom);
}
+ }
+ }
- /* Perform the redirection. */
- retval = true;
- old_dest = e->dest;
- e = redirect_edge_and_branch (e, dest);
+ return retval;
+}
- /* Update the profile. */
- if (profile_status != PROFILE_ABSENT)
- for (curr = old_dest; curr != dest; curr = EDGE_SUCC (curr, 0)->dest)
- {
- curr->frequency -= freq;
- if (curr->frequency < 0)
- curr->frequency = 0;
- curr->count -= count;
- if (curr->count < 0)
- curr->count = 0;
- EDGE_SUCC (curr, 0)->count -= count;
- if (EDGE_SUCC (curr, 0)->count < 0)
- EDGE_SUCC (curr, 0)->count = 0;
- }
- if (!old)
+/* Thread jumps over empty statements.
+
+ This code should _not_ thread over obviously equivalent conditions
+ as that requires nontrivial updates to the SSA graph.
+
+ As a precondition, we require that all basic blocks be reachable.
+ That is, there should be no opportunities left for
+ delete_unreachable_blocks. */
+
+static bool
+thread_jumps (void)
+{
+ basic_block bb;
+ bool retval = false;
+ basic_block *worklist = xmalloc (sizeof (basic_block) * last_basic_block);
+ basic_block *current = worklist;
+
+ FOR_EACH_BB (bb)
+ {
+ bb_ann (bb)->forwardable = tree_forwarder_block_p (bb);
+ bb->flags &= ~BB_VISITED;
+ }
+
+ /* We pretend to have ENTRY_BLOCK_PTR in WORKLIST. This way,
+ ENTRY_BLOCK_PTR will never be entered into WORKLIST. */
+ ENTRY_BLOCK_PTR->flags |= BB_VISITED;
+
+ /* Initialize WORKLIST by putting non-forwarder blocks that
+ immediately precede forwarder blocks because those are the ones
+ that we know we can thread jumps from. We use BB_VISITED to
+ indicate whether a given basic block is in WORKLIST or not,
+ thereby avoiding duplicates in WORKLIST. */
+ FOR_EACH_BB (bb)
+ {
+ edge_iterator ei;
+ edge e;
+
+ /* We are not interested in finding non-forwarder blocks
+ directly. We want to find non-forwarder blocks as
+ predecessors of a forwarder block. */
+ if (!bb_ann (bb)->forwardable)
+ continue;
+
+ /* Now we know BB is a forwarder block. Visit each of its
+ incoming edges and add to WORKLIST all non-forwarder blocks
+ among BB's predecessors. */
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ /* We don't want to put a duplicate into WORKLIST. */
+ if ((e->src->flags & BB_VISITED) == 0
+ /* We are not interested in threading jumps from a forwarder
+ block. */
+ && !bb_ann (e->src)->forwardable)
{
- /* Update PHI nodes. We know that the new argument should
- have the same value as the argument associated with LAST.
- Otherwise we would have changed our target block above. */
- for (phi = phi_nodes (dest); phi; phi = PHI_CHAIN (phi))
- {
- arg = phi_arg_from_edge (phi, last);
- gcc_assert (arg >= 0);
- add_phi_arg (&phi, PHI_ARG_DEF (phi, arg), e);
- }
+ e->src->flags |= BB_VISITED;
+ *current++ = e->src;
}
+ }
+ }
- /* Update the dominators. */
- if (dom_computed[CDI_DOMINATORS] >= DOM_CONS_OK)
- {
- /* Remove the unreachable blocks (observe that if all blocks
- were reachable before, only those in the path we threaded
- over and did not have any predecessor outside of the path
- become unreachable). */
- for (; old_dest != dest; old_dest = tmp)
- {
- tmp = EDGE_SUCC (old_dest, 0)->dest;
+ /* Now let's drain WORKLIST. */
+ while (worklist != current)
+ {
+ bb = *--current;
- if (EDGE_COUNT (old_dest->preds) > 0)
- break;
+ /* BB is no longer in WORKLIST, so clear BB_VISITED. */
+ bb->flags &= ~BB_VISITED;
- delete_basic_block (old_dest);
- }
- /* If the dominator of the destination was in the path, set its
- dominator to the start of the redirected edge. */
- if (get_immediate_dominator (CDI_DOMINATORS, old_dest) == NULL)
- set_immediate_dominator (CDI_DOMINATORS, old_dest, bb);
+ if (thread_jumps_from_bb (bb))
+ {
+ retval = true;
- /* Now proceed like if we forwarded just over one edge at a time.
- Algorithm for forwarding edge S --> A over edge A --> B then
- is
+ if (tree_forwarder_block_p (bb))
+ {
+ edge_iterator ej;
+ edge f;
- if (idom (B) == A
- && !dominated_by (S, B))
- idom (B) = idom (A);
- recount_idom (A); */
+ bb_ann (bb)->forwardable = true;
- for (; old_dest != dest; old_dest = tmp)
+ /* Attempts to thread through BB may have been blocked
+ because BB was not a forwarder block before. Now
+ that BB is a forwarder block, we should revisit BB's
+ predecessors. */
+ FOR_EACH_EDGE (f, ej, bb->preds)
{
- tmp = EDGE_SUCC (old_dest, 0)->dest;
-
- if (get_immediate_dominator (CDI_DOMINATORS, tmp) == old_dest
- && !dominated_by_p (CDI_DOMINATORS, bb, tmp))
+ /* We don't want to put a duplicate into WORKLIST. */
+ if ((f->src->flags & BB_VISITED) == 0
+ /* We are not interested in threading jumps from a
+ forwarder block. */
+ && !bb_ann (f->src)->forwardable)
{
- dom = get_immediate_dominator (CDI_DOMINATORS, old_dest);
- set_immediate_dominator (CDI_DOMINATORS, tmp, dom);
+ f->src->flags |= BB_VISITED;
+ *current++ = f->src;
}
-
- dom = recount_dominator (CDI_DOMINATORS, old_dest);
- set_immediate_dominator (CDI_DOMINATORS, old_dest, dom);
}
}
}
-
- /* Reset the forwardable bit on our block since it's no longer in
- a forwarding chain path. */
- bb_ann (bb)->forwardable = 1;
}
+ ENTRY_BLOCK_PTR->flags &= ~BB_VISITED;
+
+ free (worklist);
+
return retval;
}
case SWITCH_EXPR:
{
- tree vec = SWITCH_LABELS (stmt);
- size_t i, n = TREE_VEC_LENGTH (vec);
+ edge e2;
+
+ /* We need to update the LABEL_DECL in the switch vector to
+ reflect the edge redirection.
- for (i = 0; i < n; ++i)
+ There is precisely one CASE_LABEL_EXPR in the switch vector
+ which needs updating. Either its label needs to be updated
+ or it needs to be directed to a new case leader. */
+ e2 = find_edge (e->src, dest);
+ if (e2)
{
- tree elt = TREE_VEC_ELT (vec, i);
- if (label_to_block (CASE_LABEL (elt)) == e->dest)
- CASE_LABEL (elt) = label;
+ /* In this case we need to change the case leader for the
+ current leader of E to be the case leader for E2. */
+ tree e_leader = get_case_leader_for_edge (e);
+ tree e2_leader = get_case_leader_for_edge (e2);
+ CASE_LEADER_OR_LABEL (e_leader) = e2_leader;
}
+ else
+ {
+ /* No edge exists from E->src to DEST, so we will simply
+ change E->dest. The case leader does not change, but
+ the LABEL_DECL for the leader does change. */
+ CASE_LEADER_OR_LABEL (get_case_leader_for_edge (e)) = label;
+ }
+ break;
}
- break;
case RETURN_EXPR:
bsi_remove (&bsi);
/* First copy the phi nodes. We do not copy phi node arguments here,
since the edges are not ready yet. Keep the chain of phi nodes in
the same order, so that we can add them later. */
- for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
mark_for_rewrite (PHI_RESULT (phi));
create_phi_node (PHI_RESULT (phi), new_bb);
}
- set_phi_nodes (new_bb, nreverse (phi_nodes (new_bb)));
+ set_phi_nodes (new_bb, phi_reverse (phi_nodes (new_bb)));
bsi_tgt = bsi_start (new_bb);
for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
for (phi = phi_nodes (e->dest), phi_copy = phi_nodes (e_copy->dest);
phi;
- phi = phi_next, phi_copy = TREE_CHAIN (phi_copy))
+ phi = phi_next, phi_copy = PHI_CHAIN (phi_copy))
{
- phi_next = TREE_CHAIN (phi);
+ phi_next = PHI_CHAIN (phi);
gcc_assert (PHI_RESULT (phi) == PHI_RESULT (phi_copy));
def = PHI_ARG_DEF_FROM_EDGE (phi, e);
if (e->flags & EDGE_ABNORMAL)
break;
- for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
rewrite_to_new_ssa_names_def (PHI_RESULT_PTR (phi), phi, map);
if (e)
v_must_defs = V_MUST_DEF_OPS (ann);
for (i = 0; i < NUM_V_MUST_DEFS (v_must_defs); i++)
- rewrite_to_new_ssa_names_def
- (V_MUST_DEF_OP_PTR (v_must_defs, i), stmt, map);
+ {
+ rewrite_to_new_ssa_names_def
+ (V_MUST_DEF_RESULT_PTR (v_must_defs, i), stmt, map);
+ rewrite_to_new_ssa_names_use
+ (V_MUST_DEF_KILL_PTR (v_must_defs, i), map);
+ }
}
FOR_EACH_EDGE (e, ei, bb->succs)
- for (phi = phi_nodes (e->dest); phi; phi = TREE_CHAIN (phi))
+ for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
{
rewrite_to_new_ssa_names_use
(PHI_ARG_DEF_PTR_FROM_EDGE (phi, e), map);
struct loop *loop = entry->dest->loop_father;
edge exit_copy;
bitmap definitions;
- tree phi, var;
+ tree phi;
basic_block *doms;
htab_t ssa_name_map = NULL;
edge redirected;
/* Redirect the entry and add the phi node arguments. */
redirected = redirect_edge_and_branch (entry, entry->dest->rbi->copy);
gcc_assert (redirected != NULL);
- for (phi = phi_nodes (entry->dest), var = PENDING_STMT (entry);
- phi;
- phi = TREE_CHAIN (phi), var = TREE_CHAIN (var))
- add_phi_arg (&phi, TREE_VALUE (var), entry);
- PENDING_STMT (entry) = NULL;
+ flush_pending_stmts (entry);
/* Concerning updating of dominators: We must recount dominators
for entry block and its copy. Anything that is outside of the region, but
if (e->dest == EXIT_BLOCK_PTR)
{
bsi_insert_on_edge (e, build_empty_stmt ());
- bsi_commit_edge_inserts ((int *)NULL);
+ bsi_commit_edge_inserts ();
break;
}
}
ei_next (&ei);
}
+ /* Removal of dead EH edges might change dominators of not
+ just immediate successors. E.g. when bb1 is changed so that
+ it no longer can throw and bb1->bb3 and bb1->bb4 are dead
+ eh edges purged by this function in:
+ 0
+ / \
+ v v
+ 1-->2
+ / \ |
+ v v |
+ 3-->4 |
+ \ v
+ --->5
+ |
+ -
+ idom(bb5) must be recomputed. For now just free the dominance
+ info. */
+ if (changed)
+ free_dominance_info (CDI_DOMINATORS);
+
return changed;
}
tree_purge_all_dead_eh_edges (bitmap blocks)
{
bool changed = false;
- size_t i;
+ unsigned i;
bitmap_iterator bi;
EXECUTE_IF_SET_IN_BITMAP (blocks, 0, i, bi)
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