--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/tree-phinodes.c	Fri Jul 17 14:47:48 2009 +0900
@@ -0,0 +1,490 @@
+/* Generic routines for manipulating PHIs
+   Copyright (C) 2003, 2005, 2007, 2008 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 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "rtl.h"
+#include "varray.h"
+#include "ggc.h"
+#include "basic-block.h"
+#include "tree-flow.h"
+#include "toplev.h"
+#include "gimple.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.
+
+   While our garbage collection mechanisms will handle this situation, it
+   is extremely wasteful to create nodes and throw them away, especially
+   when the nodes can be reused.
+
+   For PR 8361, we can significantly reduce the number of nodes allocated
+   and thus the total amount of memory allocated by managing PHIs a
+   little.  This additionally helps reduce the amount of work done by the
+   garbage collector.  Similar results have been seen on a wider variety
+   of tests (such as the compiler itself).
+
+   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.
+
+   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.
+
+   Instead we have an array of lists of free PHI nodes.  The array is
+   indexed by the number of PHI alternatives that PHI node can hold.
+   Except for the last array member, which holds all remaining PHI
+   nodes.
+
+   So to find a free PHI node, we compute its index into the free PHI
+   node array and see if there are any elements with an exact match.
+   If so, then we are done.  Otherwise, we test the next larger size
+   up and continue until we are in the last array element.
+
+   We do not actually walk members of the last array element.  While it
+   might allow us to pick up a few reusable PHI nodes, it could potentially
+   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.
+
+   Note that we can never have less than two PHI argument slots.  Thus,
+   the -2 on all the calculations below.  */
+
+#define NUM_BUCKETS 10
+static GTY ((deletable (""))) VEC(gimple,gc) *free_phinodes[NUM_BUCKETS - 2];
+static unsigned long free_phinode_count;
+
+static int ideal_phi_node_len (int);
+
+#ifdef GATHER_STATISTICS
+unsigned int phi_nodes_reused;
+unsigned int phi_nodes_created;
+#endif
+
+/* Initialize management of PHIs.  */
+
+void
+init_phinodes (void)
+{
+  int i;
+
+  for (i = 0; i < NUM_BUCKETS - 2; i++)
+    free_phinodes[i] = NULL;
+  free_phinode_count = 0;
+}
+
+/* Finalize management of PHIs.  */
+
+void
+fini_phinodes (void)
+{
+  int i;
+
+  for (i = 0; i < NUM_BUCKETS - 2; i++)
+    free_phinodes[i] = NULL;
+  free_phinode_count = 0;
+}
+
+/* Dump some simple statistics regarding the re-use of PHI nodes.  */
+
+#ifdef GATHER_STATISTICS
+void
+phinodes_print_statistics (void)
+{
+  fprintf (stderr, "PHI nodes allocated: %u\n", phi_nodes_created);
+  fprintf (stderr, "PHI nodes reused: %u\n", phi_nodes_reused);
+}
+#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 gimple
+allocate_phi_node (size_t len)
+{
+  gimple phi;
+  size_t bucket = NUM_BUCKETS - 2;
+  size_t size = sizeof (struct gimple_statement_phi)
+	        + (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
+      && gimple_phi_capacity (VEC_index (gimple, free_phinodes[bucket], 0))
+	 >= len)
+    {
+      free_phinode_count--;
+      phi = VEC_pop (gimple, free_phinodes[bucket]);
+      if (VEC_empty (gimple, free_phinodes[bucket]))
+	VEC_free (gimple, gc, free_phinodes[bucket]);
+#ifdef GATHER_STATISTICS
+      phi_nodes_reused++;
+#endif
+    }
+  else
+    {
+      phi = (gimple) ggc_alloc (size);
+#ifdef GATHER_STATISTICS
+      phi_nodes_created++;
+	{
+	  enum gimple_alloc_kind kind = gimple_alloc_kind (GIMPLE_PHI);
+          gimple_alloc_counts[(int) kind]++;
+          gimple_alloc_sizes[(int) 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.
+
+   Rounding up will not result in wasting any memory since the size request
+   will be rounded up by the GC system anyway.  [ Note this is not entirely
+   true since the original length might have fit on one of the special
+   GC pages. ]  By rounding up, we may avoid the need to reallocate the
+   PHI node later if we increase the number of arguments for the PHI.  */
+
+static int
+ideal_phi_node_len (int len)
+{
+  size_t size, new_size;
+  int log2, new_len;
+
+  /* We do not support allocations of less than two PHI argument slots.  */
+  if (len < 2)
+    len = 2;
+
+  /* Compute the number of bytes of the original request.  */
+  size = sizeof (struct gimple_statement_phi)
+	 + (len - 1) * sizeof (struct phi_arg_d);
+
+  /* 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
+     ideal size allocation.  */
+  new_len = len + (new_size - size) / sizeof (struct phi_arg_d);
+  return new_len;
+}
+
+/* Return a PHI node with LEN argument slots for variable VAR.  */
+
+gimple
+make_phi_node (tree var, int len)
+{
+  gimple phi;
+  int capacity, i;
+
+  capacity = ideal_phi_node_len (len);
+
+  phi = allocate_phi_node (capacity);
+
+  /* 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 gimple_statement_phi)
+		   - sizeof (struct phi_arg_d)
+		   + sizeof (struct phi_arg_d) * len));
+  phi->gsbase.code = GIMPLE_PHI;
+  phi->gimple_phi.nargs = len;
+  phi->gimple_phi.capacity = capacity;
+  if (TREE_CODE (var) == SSA_NAME)
+    gimple_phi_set_result (phi, var);
+  else
+    gimple_phi_set_result (phi, make_ssa_name (var, phi));
+
+  for (i = 0; i < capacity; i++)
+    {
+      use_operand_p  imm;
+      imm = gimple_phi_arg_imm_use_ptr (phi, i);
+      imm->use = gimple_phi_arg_def_ptr (phi, i);
+      imm->prev = NULL;
+      imm->next = NULL;
+      imm->loc.stmt = phi;
+    }
+
+  return phi;
+}
+
+/* We no longer need PHI, release it so that it may be reused.  */
+
+void
+release_phi_node (gimple phi)
+{
+  size_t bucket;
+  size_t len = gimple_phi_capacity (phi);
+  size_t x;
+
+  for (x = 0; x < gimple_phi_num_args (phi); x++)
+    {
+      use_operand_p  imm;
+      imm = gimple_phi_arg_imm_use_ptr (phi, x);
+      delink_imm_use (imm);
+    }
+
+  bucket = len > NUM_BUCKETS - 1 ? NUM_BUCKETS - 1 : len;
+  bucket -= 2;
+  VEC_safe_push (gimple, gc, 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 (gimple *phi, size_t len)
+{
+  size_t old_size, i;
+  gimple new_phi;
+
+  gcc_assert (len > gimple_phi_capacity (*phi));
+
+  /* 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 gimple_statement_phi)
+	     + (gimple_phi_num_args (*phi) - 1) * sizeof (struct phi_arg_d);
+
+  new_phi = allocate_phi_node (len);
+
+  memcpy (new_phi, *phi, old_size);
+
+  for (i = 0; i < gimple_phi_num_args (new_phi); i++)
+    {
+      use_operand_p imm, old_imm;
+      imm = gimple_phi_arg_imm_use_ptr (new_phi, i);
+      old_imm = gimple_phi_arg_imm_use_ptr (*phi, i);
+      imm->use = gimple_phi_arg_def_ptr (new_phi, i);
+      relink_imm_use_stmt (imm, old_imm, new_phi);
+    }
+
+  new_phi->gimple_phi.capacity = len;
+
+  for (i = gimple_phi_num_args (new_phi); i < len; i++)
+    {
+      use_operand_p imm;
+      imm = gimple_phi_arg_imm_use_ptr (new_phi, i);
+      imm->use = gimple_phi_arg_def_ptr (new_phi, i);
+      imm->prev = NULL;
+      imm->next = NULL;
+      imm->loc.stmt = new_phi;
+    }
+
+  *phi = new_phi;
+}
+
+/* Reserve PHI arguments for a new edge to basic block BB.  */
+
+void
+reserve_phi_args_for_new_edge (basic_block bb)
+{
+  size_t len = EDGE_COUNT (bb->preds);
+  size_t cap = ideal_phi_node_len (len + 4);
+  gimple_stmt_iterator gsi;
+
+  for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+    {
+      gimple *loc = gsi_stmt_ptr (&gsi);
+
+      if (len > gimple_phi_capacity (*loc))
+	{
+	  gimple old_phi = *loc;
+
+	  resize_phi_node (loc, cap);
+
+	  /* The result of the PHI is defined by this PHI node.  */
+	  SSA_NAME_DEF_STMT (gimple_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);
+
+      (*loc)->gimple_phi.nargs++;
+    }
+}
+
+/* Adds PHI to BB.  */
+
+void 
+add_phi_node_to_bb (gimple phi, basic_block bb)
+{
+  gimple_stmt_iterator gsi;
+  /* Add the new PHI node to the list of PHI nodes for block BB.  */
+  if (phi_nodes (bb) == NULL)
+    set_phi_nodes (bb, gimple_seq_alloc ());
+
+  gsi = gsi_last (phi_nodes (bb));
+  gsi_insert_after (&gsi, phi, GSI_NEW_STMT);
+
+  /* Associate BB to the PHI node.  */
+  gimple_set_bb (phi, bb);
+
+}
+
+/* Create a new PHI node for variable VAR at basic block BB.  */
+
+gimple
+create_phi_node (tree var, basic_block bb)
+{
+  gimple phi = make_phi_node (var, EDGE_COUNT (bb->preds));
+
+  add_phi_node_to_bb (phi, bb);
+  return phi;
+}
+
+
+/* Add a new argument to PHI node PHI.  DEF is the incoming reaching
+   definition and E is the edge through which DEF reaches PHI.  The new
+   argument is added at the end of the argument list.
+   If PHI has reached its maximum capacity, add a few slots.  In this case,
+   PHI points to the reallocated phi node when we return.  */
+
+void
+add_phi_arg (gimple phi, tree def, edge e)
+{
+  basic_block bb = e->dest;
+
+  gcc_assert (bb == gimple_bb (phi));
+
+  /* We resize PHI nodes upon edge creation.  We should always have
+     enough room at this point.  */
+  gcc_assert (gimple_phi_num_args (phi) <= gimple_phi_capacity (phi));
+
+  /* We resize PHI nodes upon edge creation.  We should always have
+     enough room at this point.  */
+  gcc_assert (e->dest_idx < gimple_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.  */
+  if (e->flags & EDGE_ABNORMAL)
+    {
+      SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def) = 1;
+      SSA_NAME_OCCURS_IN_ABNORMAL_PHI (PHI_RESULT (phi)) = 1;
+    }
+
+  SET_PHI_ARG_DEF (phi, e->dest_idx, def);
+}
+
+
+/* Remove the Ith argument from PHI's argument list.  This routine
+   implements removal by swapping the last alternative with the
+   alternative we want to delete and then shrinking the vector, which
+   is consistent with how we remove an edge from the edge vector.  */
+
+static void
+remove_phi_arg_num (gimple phi, int i)
+{
+  int num_elem = gimple_phi_num_args (phi);
+
+  gcc_assert (i < num_elem);
+
+  /* Delink the item which is being removed.  */
+  delink_imm_use (gimple_phi_arg_imm_use_ptr (phi, i));
+
+  /* If it is not the last element, move the last element
+     to the element we want to delete, resetting all the links. */
+  if (i != num_elem - 1)
+    {
+      use_operand_p old_p, new_p;
+      old_p = gimple_phi_arg_imm_use_ptr (phi, num_elem - 1);
+      new_p = gimple_phi_arg_imm_use_ptr (phi, i);
+      /* Set use on new node, and link into last element's place.  */
+      *(new_p->use) = *(old_p->use);
+      relink_imm_use (new_p, old_p);
+    }
+
+  /* Shrink the vector and return.  Note that we do not have to clear
+     PHI_ARG_DEF because the garbage collector will not look at those
+     elements beyond the first PHI_NUM_ARGS elements of the array.  */
+  phi->gimple_phi.nargs--;
+}
+
+
+/* Remove all PHI arguments associated with edge E.  */
+
+void
+remove_phi_args (edge e)
+{
+  gimple_stmt_iterator gsi;
+
+  for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); gsi_next (&gsi))
+    remove_phi_arg_num (gsi_stmt (gsi), e->dest_idx);
+}
+
+
+/* Remove the PHI node pointed-to by iterator GSI from basic block BB.  After
+   removal, iterator GSI is updated to point to the next PHI node in the
+   sequence. If RELEASE_LHS_P is true, the LHS of this PHI node is released
+   into the free pool of SSA names.  */
+
+void
+remove_phi_node (gimple_stmt_iterator *gsi, bool release_lhs_p)
+{
+  gimple phi = gsi_stmt (*gsi);
+  gsi_remove (gsi, false);
+
+  /* If we are deleting the PHI node, then we should release the
+     SSA_NAME node so that it can be reused.  */
+  release_phi_node (phi);
+  if (release_lhs_p)
+    release_ssa_name (gimple_phi_result (phi));
+}
+
+/* Remove all the phi nodes from BB.  */
+
+void
+remove_phi_nodes (basic_block bb)
+{
+  gimple_stmt_iterator gsi;
+
+  for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); )
+    remove_phi_node (&gsi, true);
+
+  set_phi_nodes (bb, NULL);
+}
+
+#include "gt-tree-phinodes.h"