GCC 4.2.0 release.

1 files changed, 292 insertions, 0 deletions

diff --git a/contrib/gcc/tree-ssa-loop-unswitch.c b/contrib/gcc/tree-ssa-loop-unswitch.c
new file mode 100644
index 0000000..d9102b2
--- /dev/null
+++ b/contrib/gcc/tree-ssa-loop-unswitch.c
@@ -0,0 +1,292 @@
+/* Loop unswitching.
+   Copyright (C) 2004, 2005 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, 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301, USA.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "rtl.h"
+#include "tm_p.h"
+#include "hard-reg-set.h"
+#include "basic-block.h"
+#include "output.h"
+#include "diagnostic.h"
+#include "tree-flow.h"
+#include "tree-dump.h"
+#include "timevar.h"
+#include "cfgloop.h"
+#include "domwalk.h"
+#include "params.h"
+#include "tree-pass.h"
+
+/* This file implements the loop unswitching, i.e. transformation of loops like
+
+   while (A)
+     {
+       if (inv)
+         B;
+
+       X;
+
+       if (!inv)
+	 C;
+     }
+
+   where inv is the loop invariant, into
+
+   if (inv)
+     {
+       while (A)
+	 {
+           B;
+	   X;
+	 }
+     }
+   else
+     {
+       while (A)
+	 {
+	   X;
+	   C;
+	 }
+     }
+
+   Inv is considered invariant iff the values it compares are both invariant;
+   tree-ssa-loop-im.c ensures that all the suitable conditions are in this
+   shape.  */
+
+static struct loop *tree_unswitch_loop (struct loops *, struct loop *, basic_block,
+				   tree);
+static bool tree_unswitch_single_loop (struct loops *, struct loop *, int);
+static tree tree_may_unswitch_on (basic_block, struct loop *);
+
+/* Main entry point.  Perform loop unswitching on all suitable LOOPS.  */
+
+unsigned int
+tree_ssa_unswitch_loops (struct loops *loops)
+{
+  int i, num;
+  struct loop *loop;
+  bool changed = false;
+
+  /* Go through inner loops (only original ones).  */
+  num = loops->num;
+
+  for (i = 1; i < num; i++)
+    {
+      /* Removed loop?  */
+      loop = loops->parray[i];
+      if (!loop)
+	continue;
+
+      if (loop->inner)
+	continue;
+
+      changed |= tree_unswitch_single_loop (loops, loop, 0);
+    }
+
+  if (changed)
+    return TODO_cleanup_cfg;
+  return 0;
+}
+
+/* Checks whether we can unswitch LOOP on condition at end of BB -- one of its
+   basic blocks (for what it means see comments below).  */
+
+static tree
+tree_may_unswitch_on (basic_block bb, struct loop *loop)
+{
+  tree stmt, def, cond, use;
+  basic_block def_bb;
+  ssa_op_iter iter;
+
+  /* BB must end in a simple conditional jump.  */
+  stmt = last_stmt (bb);
+  if (!stmt || TREE_CODE (stmt) != COND_EXPR)
+    return NULL_TREE;
+
+  /* Condition must be invariant.  */
+  FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_USE)
+    {
+      def = SSA_NAME_DEF_STMT (use);
+      def_bb = bb_for_stmt (def);
+      if (def_bb
+	  && flow_bb_inside_loop_p (loop, def_bb))
+	return NULL_TREE;
+    }
+
+  cond = COND_EXPR_COND (stmt);
+  /* To keep the things simple, we do not directly remove the conditions,
+     but just replace tests with 0/1.  Prevent the infinite loop where we
+     would unswitch again on such a condition.  */
+  if (integer_zerop (cond) || integer_nonzerop (cond))
+    return NULL_TREE;
+
+  return cond;
+}
+
+/* Simplifies COND using checks in front of the entry of the LOOP.  Just very
+   simplish (sufficient to prevent us from duplicating loop in unswitching
+   unnecessarily).  */
+
+static tree
+simplify_using_entry_checks (struct loop *loop, tree cond)
+{
+  edge e = loop_preheader_edge (loop);
+  tree stmt;
+
+  while (1)
+    {
+      stmt = last_stmt (e->src);
+      if (stmt
+	  && TREE_CODE (stmt) == COND_EXPR
+	  && operand_equal_p (COND_EXPR_COND (stmt), cond, 0))
+	return (e->flags & EDGE_TRUE_VALUE
+		? boolean_true_node
+		: boolean_false_node);
+
+      if (!single_pred_p (e->src))
+	return cond;
+
+      e = single_pred_edge (e->src);
+      if (e->src == ENTRY_BLOCK_PTR)
+	return cond;
+    }
+}
+
+/* Unswitch single LOOP.  NUM is number of unswitchings done; we do not allow
+   it to grow too much, it is too easy to create example on that the code would
+   grow exponentially.  */
+
+static bool
+tree_unswitch_single_loop (struct loops *loops, struct loop *loop, int num)
+{
+  basic_block *bbs;
+  struct loop *nloop;
+  unsigned i;
+  tree cond = NULL_TREE, stmt;
+  bool changed = false;
+
+  /* Do not unswitch too much.  */
+  if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
+      return false;
+    }
+
+  /* Only unswitch innermost loops.  */
+  if (loop->inner)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, ";; Not unswitching, not innermost loop\n");
+      return false;
+    }
+
+  /* The loop should not be too large, to limit code growth.  */
+  if (tree_num_loop_insns (loop)
+      > (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, ";; Not unswitching, loop too big\n");
+      return false;
+    }
+
+  i = 0;
+  bbs = get_loop_body (loop);
+  
+  while (1)
+    {
+      /* Find a bb to unswitch on.  */
+      for (; i < loop->num_nodes; i++)
+	if ((cond = tree_may_unswitch_on (bbs[i], loop)))
+	  break;
+
+      if (i == loop->num_nodes)
+	{
+	  free (bbs);
+	  return changed;
+	}
+
+      cond = simplify_using_entry_checks (loop, cond);
+      stmt = last_stmt (bbs[i]);
+      if (integer_nonzerop (cond))
+	{
+	  /* Remove false path.  */
+	  COND_EXPR_COND (stmt) = boolean_true_node;
+	  changed = true;
+	}
+      else if (integer_zerop (cond))
+	{
+	  /* Remove true path.  */
+	  COND_EXPR_COND (stmt) = boolean_false_node;
+	  changed = true;
+	}
+      else
+	break;
+
+      update_stmt (stmt);
+      i++;
+    }
+
+  if (dump_file && (dump_flags & TDF_DETAILS))
+    fprintf (dump_file, ";; Unswitching loop\n");
+
+  initialize_original_copy_tables ();
+  /* Unswitch the loop on this condition.  */
+  nloop = tree_unswitch_loop (loops, loop, bbs[i], cond);
+  if (!nloop)
+    {
+      free_original_copy_tables ();
+      free (bbs);
+      return changed;
+    }
+
+  /* Update the SSA form after unswitching.  */
+  update_ssa (TODO_update_ssa);
+  free_original_copy_tables ();
+
+  /* Invoke itself on modified loops.  */
+  tree_unswitch_single_loop (loops, nloop, num + 1);
+  tree_unswitch_single_loop (loops, loop, num + 1);
+  free (bbs);
+  return true;
+}
+
+/* Unswitch a LOOP w.r. to given basic block UNSWITCH_ON.  We only support
+   unswitching of innermost loops.  COND is the condition determining which
+   loop is entered -- the new loop is entered if COND is true.  Returns NULL
+   if impossible, new loop otherwise.  */
+
+static struct loop *
+tree_unswitch_loop (struct loops *loops, struct loop *loop,
+		    basic_block unswitch_on, tree cond)
+{
+  basic_block condition_bb;
+
+  /* Some sanity checking.  */
+  gcc_assert (flow_bb_inside_loop_p (loop, unswitch_on));
+  gcc_assert (EDGE_COUNT (unswitch_on->succs) == 2);
+  gcc_assert (loop->inner == NULL);
+
+  return loop_version (loops, loop, unshare_expr (cond), 
+		       &condition_bb, false);
+}