/* Generic routines for manipulating PHIs
Copyright (C) 2003 Free Software Foundation, Inc.
-
+
This file is part of GCC.
-
+
GCC is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
-
+
GCC is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
-
+
You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING. If not, write to
the Free Software Foundation, 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
-
+
#include "config.h"
#include "system.h"
#include "coretypes.h"
/* Rewriting a function into SSA form can create a huge number of PHIs
many of which may be thrown away shortly after their creation if jumps
- were threaded through PHI nodes.
+ were threaded through PHI nodes.
While our garbage collection mechanisms will handle this situation, it
is extremely wasteful to create nodes and throw them away, especially
Right now we maintain our free list on a per-function basis. It may
or may not make sense to maintain the free list for the duration of
- a compilation unit.
+ a compilation unit.
We could also use a zone allocator for these objects since they have
a very well defined lifetime. If someone wants to experiment with that
this is the place to try it.
-
+
PHI nodes have different sizes, so we can't have a single list of all
the PHI nodes as it would be too expensive to walk down that list to
find a PHI of a suitable size.
be very expensive if the program has released a bunch of large PHI nodes,
but keeps asking for even larger PHI nodes. Experiments have shown that
walking the elements of the last array entry would result in finding less
- than .1% additional reusable PHI nodes.
+ than .1% additional reusable PHI nodes.
Note that we can never have less than two PHI argument slots. Thus,
the -2 on all the calculations below. */
}
#endif
+/* Allocate a PHI node with at least LEN arguments. If the free list
+ happens to contain a PHI node with LEN arguments or more, return
+ that one. */
+
+static inline tree
+allocate_phi_node (int len)
+{
+ tree phi;
+ int bucket = NUM_BUCKETS - 2;
+ int size = (sizeof (struct tree_phi_node)
+ + (len - 1) * sizeof (struct phi_arg_d));
+
+ if (free_phinode_count)
+ for (bucket = len - 2; bucket < NUM_BUCKETS - 2; bucket++)
+ if (free_phinodes[bucket])
+ break;
+
+ /* If our free list has an element, then use it. */
+ if (bucket < NUM_BUCKETS - 2
+ && PHI_ARG_CAPACITY (free_phinodes[bucket]) >= len)
+ {
+ free_phinode_count--;
+ phi = free_phinodes[bucket];
+ free_phinodes[bucket] = PHI_CHAIN (free_phinodes[bucket]);
+#ifdef GATHER_STATISTICS
+ phi_nodes_reused++;
+#endif
+ }
+ else
+ {
+ phi = ggc_alloc (size);
+#ifdef GATHER_STATISTICS
+ phi_nodes_created++;
+ tree_node_counts[(int) phi_kind]++;
+ tree_node_sizes[(int) phi_kind] += size;
+#endif
+ }
+
+ return phi;
+}
+
/* Given LEN, the original number of requested PHI arguments, return
a new, "ideal" length for the PHI node. The "ideal" length rounds
the total size of the PHI node up to the next power of two bytes.
/* Round it up to the next power of two. */
log2 = ceil_log2 (size);
new_size = 1 << log2;
-
- /* Now compute and return the number of PHI argument slots given an
+
+ /* Now compute and return the number of PHI argument slots given an
ideal size allocation. */
new_len = len + (new_size - size) / sizeof (struct phi_arg_d);
return new_len;
definitions created when a variable is used without a preceding
definition). */
-tree
+static tree
make_phi_node (tree var, int len)
{
tree phi;
- int size;
- int bucket = NUM_BUCKETS - 2;
+ int capacity;
- len = ideal_phi_node_len (len);
+ capacity = ideal_phi_node_len (len);
- size = sizeof (struct tree_phi_node) + (len - 1) * sizeof (struct phi_arg_d);
-
- if (free_phinode_count)
- for (bucket = len - 2; bucket < NUM_BUCKETS - 2; bucket++)
- if (free_phinodes[bucket])
- break;
+ phi = allocate_phi_node (capacity);
- /* If our free list has an element, then use it. */
- if (bucket < NUM_BUCKETS - 2
- && PHI_ARG_CAPACITY (free_phinodes[bucket]) >= len)
- {
- free_phinode_count--;
- phi = free_phinodes[bucket];
- free_phinodes[bucket] = TREE_CHAIN (free_phinodes[bucket]);
-#ifdef GATHER_STATISTICS
- phi_nodes_reused++;
-#endif
- }
- else
- {
- phi = ggc_alloc (size);
-#ifdef GATHER_STATISTICS
- phi_nodes_created++;
- tree_node_counts[(int) phi_kind]++;
- tree_node_sizes[(int) phi_kind] += size;
-#endif
-
- }
-
- memset (phi, 0, size);
+ /* We need to clear the entire PHI node, including the argument
+ portion, because we represent a "missing PHI argument" by placing
+ NULL_TREE in PHI_ARG_DEF. */
+ memset (phi, 0, (sizeof (struct tree_phi_node) - sizeof (struct phi_arg_d)
+ + sizeof (struct phi_arg_d) * len));
TREE_SET_CODE (phi, PHI_NODE);
- PHI_ARG_CAPACITY (phi) = len;
+ PHI_NUM_ARGS (phi) = len;
+ PHI_ARG_CAPACITY (phi) = capacity;
+ TREE_TYPE (phi) = TREE_TYPE (var);
if (TREE_CODE (var) == SSA_NAME)
- PHI_RESULT (phi) = var;
+ SET_PHI_RESULT (phi, var);
else
- PHI_RESULT (phi) = make_ssa_name (var, phi);
+ SET_PHI_RESULT (phi, make_ssa_name (var, phi));
return phi;
}
bucket = len > NUM_BUCKETS - 1 ? NUM_BUCKETS - 1 : len;
bucket -= 2;
- TREE_CHAIN (phi) = free_phinodes[bucket];
+ PHI_CHAIN (phi) = free_phinodes[bucket];
free_phinodes[bucket] = phi;
free_phinode_count++;
}
/* Resize an existing PHI node. The only way is up. Return the
possibly relocated phi. */
-
+
static void
resize_phi_node (tree *phi, int len)
{
- int size, old_size;
+ int old_size;
tree new_phi;
- int i, old_len, bucket = NUM_BUCKETS - 2;
-
-#ifdef ENABLE_CHECKING
- if (len < PHI_ARG_CAPACITY (*phi))
- abort ();
-#endif
-
- /* Note that OLD_SIZE is guaranteed to be smaller than SIZE. */
- old_size = (sizeof (struct tree_phi_node)
- + (PHI_ARG_CAPACITY (*phi) - 1) * sizeof (struct phi_arg_d));
- size = sizeof (struct tree_phi_node) + (len - 1) * sizeof (struct phi_arg_d);
- if (free_phinode_count)
- for (bucket = len - 2; bucket < NUM_BUCKETS - 2; bucket++)
- if (free_phinodes[bucket])
- break;
+ gcc_assert (len > PHI_ARG_CAPACITY (*phi));
- /* If our free list has an element, then use it. */
- if (bucket < NUM_BUCKETS - 2
- && PHI_ARG_CAPACITY (free_phinodes[bucket]) >= len)
- {
- free_phinode_count--;
- new_phi = free_phinodes[bucket];
- free_phinodes[bucket] = TREE_CHAIN (free_phinodes[bucket]);
-#ifdef GATHER_STATISTICS
- phi_nodes_reused++;
-#endif
- }
- else
- {
- new_phi = ggc_alloc (size);
-#ifdef GATHER_STATISTICS
- phi_nodes_created++;
- tree_node_counts[(int) phi_kind]++;
- tree_node_sizes[(int) phi_kind] += size;
-#endif
- }
+ /* The garbage collector will not look at the PHI node beyond the
+ first PHI_NUM_ARGS elements. Therefore, all we have to copy is a
+ portion of the PHI node currently in use. */
+ old_size = (sizeof (struct tree_phi_node)
+ + (PHI_NUM_ARGS (*phi) - 1) * sizeof (struct phi_arg_d));
+
+ new_phi = allocate_phi_node (len);
memcpy (new_phi, *phi, old_size);
- old_len = PHI_ARG_CAPACITY (new_phi);
PHI_ARG_CAPACITY (new_phi) = len;
-
- for (i = old_len; i < len; i++)
- {
- PHI_ARG_DEF (new_phi, i) = NULL_TREE;
- PHI_ARG_EDGE (new_phi, i) = NULL;
- }
*phi = new_phi;
}
+/* Reserve PHI arguments for a new edge to basic block BB. */
+
+void
+reserve_phi_args_for_new_edge (basic_block bb)
+{
+ tree *loc;
+ int len = EDGE_COUNT (bb->preds);
+ int cap = ideal_phi_node_len (len + 4);
+
+ for (loc = &(bb_ann (bb)->phi_nodes);
+ *loc;
+ loc = &PHI_CHAIN (*loc))
+ {
+ if (len > PHI_ARG_CAPACITY (*loc))
+ {
+ tree old_phi = *loc;
+
+ resize_phi_node (loc, cap);
+
+ /* The result of the phi is defined by this phi node. */
+ SSA_NAME_DEF_STMT (PHI_RESULT (*loc)) = *loc;
+
+ release_phi_node (old_phi);
+ }
+
+ /* We represent a "missing PHI argument" by placing NULL_TREE in
+ the corresponding slot. If PHI arguments were added
+ immediately after an edge is created, this zeroing would not
+ be necessary, but unfortunately this is not the case. For
+ example, the loop optimizer duplicates several basic blocks,
+ redirects edges, and then fixes up PHI arguments later in
+ batch. */
+ SET_PHI_ARG_DEF (*loc, len - 1, NULL_TREE);
+
+ PHI_NUM_ARGS (*loc)++;
+ }
+}
+
/* Create a new PHI node for variable VAR at basic block BB. */
tree
{
tree phi;
- phi = make_phi_node (var, bb_ann (bb)->num_preds);
-
- /* This is a new phi node, so note that is has not yet been
- rewritten. */
- PHI_REWRITTEN (phi) = 0;
+ phi = make_phi_node (var, EDGE_COUNT (bb->preds));
/* Add the new PHI node to the list of PHI nodes for block BB. */
- TREE_CHAIN (phi) = phi_nodes (bb);
+ PHI_CHAIN (phi) = phi_nodes (bb);
bb_ann (bb)->phi_nodes = phi;
/* Associate BB to the PHI node. */
void
add_phi_arg (tree *phi, tree def, edge e)
{
- int i = PHI_NUM_ARGS (*phi);
-
- if (i >= PHI_ARG_CAPACITY (*phi))
- {
- tree old_phi = *phi;
+ basic_block bb = e->dest;
- /* Resize the phi. Unfortunately, this may also relocate it. */
- resize_phi_node (phi, ideal_phi_node_len (i + 4));
+ gcc_assert (bb == bb_for_stmt (*phi));
- /* The result of the phi is defined by this phi node. */
- SSA_NAME_DEF_STMT (PHI_RESULT (*phi)) = *phi;
+ /* We resize PHI nodes upon edge creation. We should always have
+ enough room at this point. */
+ gcc_assert (PHI_NUM_ARGS (*phi) <= PHI_ARG_CAPACITY (*phi));
- /* If the PHI was relocated, update the PHI chains appropriately and
- release the old PHI node. */
- if (*phi != old_phi)
- {
- release_phi_node (old_phi);
-
- /* Update the list head if replacing the first listed phi. */
- if (phi_nodes (e->dest) == old_phi)
- bb_ann (e->dest)->phi_nodes = *phi;
- else
- {
- /* Traverse the list looking for the phi node to chain to. */
- tree p;
-
- for (p = phi_nodes (e->dest);
- p && TREE_CHAIN (p) != old_phi;
- p = TREE_CHAIN (p))
- ;
-
- if (!p)
- abort ();
-
- TREE_CHAIN (p) = *phi;
- }
- }
- }
+ /* We resize PHI nodes upon edge creation. We should always have
+ enough room at this point. */
+ gcc_assert (e->dest_idx < (unsigned int) PHI_NUM_ARGS (*phi));
/* Copy propagation needs to know what object occur in abnormal
PHI nodes. This is a convenient place to record such information. */
SSA_NAME_OCCURS_IN_ABNORMAL_PHI (PHI_RESULT (*phi)) = 1;
}
- PHI_ARG_DEF (*phi, i) = def;
- PHI_ARG_EDGE (*phi, i) = e;
- PHI_NUM_ARGS (*phi)++;
+ SET_PHI_ARG_DEF (*phi, e->dest_idx, def);
+ PHI_ARG_NONZERO (*phi, e->dest_idx) = false;
}
-/* Remove a PHI argument from PHI. BLOCK is the predecessor block where
- the PHI argument is coming from. */
-
-void
-remove_phi_arg (tree phi, basic_block block)
-{
- int i, num_elem = PHI_NUM_ARGS (phi);
-
- for (i = 0; i < num_elem; i++)
- {
- basic_block src_bb;
-
- src_bb = PHI_ARG_EDGE (phi, i)->src;
-
- if (src_bb == block)
- {
- remove_phi_arg_num (phi, i);
- return;
- }
- }
-}
-
-
/* Remove the Ith argument from PHI's argument list. This routine assumes
ordering of alternatives in the vector is not important and implements
removal by swapping the last alternative with the alternative we want to
delete, then shrinking the vector. */
-void
+static void
remove_phi_arg_num (tree phi, int i)
{
int num_elem = PHI_NUM_ARGS (phi);
+ gcc_assert (i < num_elem);
+
/* If we are not at the last element, switch the last element
with the element we want to delete. */
if (i != num_elem - 1)
{
- PHI_ARG_DEF (phi, i) = PHI_ARG_DEF (phi, num_elem - 1);
- PHI_ARG_EDGE (phi, i) = PHI_ARG_EDGE (phi, num_elem - 1);
+ SET_PHI_ARG_DEF (phi, i, PHI_ARG_DEF (phi, num_elem - 1));
+ PHI_ARG_NONZERO (phi, i) = PHI_ARG_NONZERO (phi, num_elem - 1);
}
- /* Shrink the vector and return. */
- PHI_ARG_DEF (phi, num_elem - 1) = NULL_TREE;
- PHI_ARG_EDGE (phi, num_elem - 1) = NULL;
+ /* Shrink the vector and return. Note that we do not have to clear
+ PHI_ARG_DEF or PHI_ARG_NONZERO because the garbage collector will
+ not look at those elements beyond the first PHI_NUM_ARGS elements
+ of the array. */
PHI_NUM_ARGS (phi)--;
+}
+
+/* Remove all PHI arguments associated with edge E. */
- /* If we removed the last PHI argument, then go ahead and
- remove the PHI node. */
- if (PHI_NUM_ARGS (phi) == 0)
- remove_phi_node (phi, NULL, bb_for_stmt (phi));
+void
+remove_phi_args (edge e)
+{
+ tree phi;
+
+ for (phi = phi_nodes (e->dest); phi; phi = PHI_CHAIN (phi))
+ {
+ int index = phi_arg_from_edge (phi, e);
+ if (index >= 0)
+ remove_phi_arg_num (phi, index);
+ }
}
/* Remove PHI node PHI from basic block BB. If PREV is non-NULL, it is
if (prev)
{
/* Rewire the list if we are given a PREV pointer. */
- TREE_CHAIN (prev) = TREE_CHAIN (phi);
+ PHI_CHAIN (prev) = PHI_CHAIN (phi);
/* If we are deleting the PHI node, then we should release the
SSA_NAME node so that it can be reused. */
else if (phi == phi_nodes (bb))
{
/* Update the list head if removing the first element. */
- bb_ann (bb)->phi_nodes = TREE_CHAIN (phi);
+ bb_ann (bb)->phi_nodes = PHI_CHAIN (phi);
/* If we are deleting the PHI node, then we should release the
SSA_NAME node so that it can be reused. */
/* Traverse the list looking for the node to remove. */
tree prev, t;
prev = NULL_TREE;
- for (t = phi_nodes (bb); t && t != phi; t = TREE_CHAIN (t))
+ for (t = phi_nodes (bb); t && t != phi; t = PHI_CHAIN (t))
prev = t;
if (t)
remove_phi_node (t, prev, bb);
FOR_EACH_BB (bb)
{
/* Build a new PHI list for BB without variables in VARS. */
- tree phi, new_phi_list, last_phi, next;
+ tree phi, new_phi_list, next;
+ tree *lastp = &new_phi_list;
- last_phi = new_phi_list = NULL_TREE;
- for (phi = phi_nodes (bb), next = NULL; phi; phi = next)
+ for (phi = phi_nodes (bb); phi; phi = next)
{
tree var = SSA_NAME_VAR (PHI_RESULT (phi));
- next = TREE_CHAIN (phi);
+ next = PHI_CHAIN (phi);
/* Only add PHI nodes for variables not in VARS. */
if (!bitmap_bit_p (vars, var_ann (var)->uid))
{
Note that fact in PHI_REWRITTEN. */
PHI_REWRITTEN (phi) = 1;
- if (new_phi_list == NULL_TREE)
- new_phi_list = last_phi = phi;
- else
- {
- TREE_CHAIN (last_phi) = phi;
- last_phi = phi;
- }
+ *lastp = phi;
+ lastp = &PHI_CHAIN (phi);
}
else
{
}
/* Make sure the last node in the new list has no successors. */
- if (last_phi)
- TREE_CHAIN (last_phi) = NULL_TREE;
+ *lastp = NULL;
bb_ann (bb)->phi_nodes = new_phi_list;
#if defined ENABLE_CHECKING
- for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
+ for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
{
tree var = SSA_NAME_VAR (PHI_RESULT (phi));
- if (bitmap_bit_p (vars, var_ann (var)->uid))
- abort ();
+ gcc_assert (!bitmap_bit_p (vars, var_ann (var)->uid));
}
#endif
}
}
+/* Reverse the order of PHI nodes in the chain PHI.
+ Return the new head of the chain (old last PHI node). */
+
+tree
+phi_reverse (tree phi)
+{
+ tree prev = NULL_TREE, next;
+ for (; phi; phi = next)
+ {
+ next = PHI_CHAIN (phi);
+ PHI_CHAIN (phi) = prev;
+ prev = phi;
+ }
+ return prev;
+}
#include "gt-tree-phinodes.h"
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