Initial checkin of GCC 4.9.0 from trunk (r208799).

Change-Id: I48a3c08bb98542aa215912a75f03c0890e497dba

1 files changed, 458 insertions, 0 deletions

diff --git a/gcc-4.9/gcc/tree-ssa-loop-unswitch.c b/gcc-4.9/gcc/tree-ssa-loop-unswitch.c
new file mode 100644
index 000000000..503137867
--- /dev/null
+++ b/gcc-4.9/gcc/tree-ssa-loop-unswitch.c
@@ -0,0 +1,458 @@
+/* Loop unswitching.
+   Copyright (C) 2004-2014 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 "tm_p.h"
+#include "basic-block.h"
+#include "tree-ssa-alias.h"
+#include "internal-fn.h"
+#include "gimple-expr.h"
+#include "is-a.h"
+#include "gimple.h"
+#include "gimplify.h"
+#include "gimple-ssa.h"
+#include "tree-cfg.h"
+#include "tree-phinodes.h"
+#include "ssa-iterators.h"
+#include "tree-ssa-loop-niter.h"
+#include "tree-ssa-loop.h"
+#include "tree-into-ssa.h"
+#include "cfgloop.h"
+#include "params.h"
+#include "tree-pass.h"
+#include "tree-inline.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 loop *, basic_block, tree);
+static bool tree_unswitch_single_loop (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 (void)
+{
+  struct loop *loop;
+  bool changed = false;
+  HOST_WIDE_INT iterations;
+
+  /* Go through inner loops (only original ones).  */
+  FOR_EACH_LOOP (loop, LI_ONLY_INNERMOST)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+        fprintf (dump_file, ";; Considering loop %d\n", loop->num);
+
+      /* Do not unswitch in cold regions. */
+      if (optimize_loop_for_size_p (loop))
+        {
+          if (dump_file && (dump_flags & TDF_DETAILS))
+            fprintf (dump_file, ";; Not unswitching cold loops\n");
+          continue;
+        }
+
+      /* The loop should not be too large, to limit code growth. */
+      if (tree_num_loop_insns (loop, &eni_size_weights)
+          > (unsigned) PARAM_VALUE (PARAM_MAX_UNSWITCH_INSNS))
+        {
+          if (dump_file && (dump_flags & TDF_DETAILS))
+            fprintf (dump_file, ";; Not unswitching, loop too big\n");
+          continue;
+        }
+
+      /* If the loop is not expected to iterate, there is no need
+	 for unswitching.  */
+      iterations = estimated_loop_iterations_int (loop);
+      if (iterations >= 0 && iterations <= 1)
+	{
+          if (dump_file && (dump_flags & TDF_DETAILS))
+            fprintf (dump_file, ";; Not unswitching, loop is not expected to iterate\n");
+          continue;
+	}
+
+      changed |= tree_unswitch_single_loop (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)
+{
+  gimple stmt, def;
+  tree cond, use;
+  basic_block def_bb;
+  ssa_op_iter iter;
+
+  /* BB must end in a simple conditional jump.  */
+  stmt = last_stmt (bb);
+  if (!stmt || gimple_code (stmt) != GIMPLE_COND)
+    return NULL_TREE;
+
+  /* To keep the things simple, we do not directly remove the conditions,
+     but just replace tests with 0 != 0 resp. 1 != 0.  Prevent the infinite
+     loop where we would unswitch again on such a condition.  */
+  if (gimple_cond_true_p (stmt) || gimple_cond_false_p (stmt))
+    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 = gimple_bb (def);
+      if (def_bb
+	  && flow_bb_inside_loop_p (loop, def_bb))
+	return NULL_TREE;
+    }
+
+  cond = build2 (gimple_cond_code (stmt), boolean_type_node,
+		 gimple_cond_lhs (stmt), gimple_cond_rhs (stmt));
+
+  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);
+  gimple stmt;
+
+  while (1)
+    {
+      stmt = last_stmt (e->src);
+      if (stmt
+	  && gimple_code (stmt) == GIMPLE_COND
+	  && gimple_cond_code (stmt) == TREE_CODE (cond)
+	  && operand_equal_p (gimple_cond_lhs (stmt),
+			      TREE_OPERAND (cond, 0), 0)
+	  && operand_equal_p (gimple_cond_rhs (stmt),
+			      TREE_OPERAND (cond, 1), 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_FOR_FN (cfun))
+	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 loop *loop, int num)
+{
+  basic_block *bbs;
+  struct loop *nloop;
+  unsigned i, found;
+  tree cond = NULL_TREE;
+  gimple stmt;
+  bool changed = false;
+
+  i = 0;
+  bbs = get_loop_body (loop);
+  found = loop->num_nodes;
+
+  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)
+	{
+	  if (dump_file
+	      && num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL)
+	      && (dump_flags & TDF_DETAILS))
+	    fprintf (dump_file, ";; Not unswitching anymore, hit max level\n");
+
+	  if (found == loop->num_nodes)
+	    {
+	      free (bbs);
+	      return changed;
+	    }
+	  break;
+	}
+
+      cond = simplify_using_entry_checks (loop, cond);
+      stmt = last_stmt (bbs[i]);
+      if (integer_nonzerop (cond))
+	{
+	  /* Remove false path.  */
+	  gimple_cond_set_condition_from_tree (stmt, boolean_true_node);
+	  changed = true;
+	}
+      else if (integer_zerop (cond))
+	{
+	  /* Remove true path.  */
+	  gimple_cond_set_condition_from_tree (stmt, boolean_false_node);
+	  changed = true;
+	}
+      /* Do not unswitch too much.  */
+      else if (num > PARAM_VALUE (PARAM_MAX_UNSWITCH_LEVEL))
+	{
+	  i++;
+	  continue;
+	}
+      /* In nested tree_unswitch_single_loop first optimize all conditions
+	 using entry checks, then discover still reachable blocks in the
+	 loop and find the condition only among those still reachable bbs.  */
+      else if (num != 0)
+	{
+	  if (found == loop->num_nodes)
+	    found = i;
+	  i++;
+	  continue;
+	}
+      else
+	{
+	  found = i;
+	  break;
+	}
+
+      update_stmt (stmt);
+      i++;
+    }
+
+  if (num != 0)
+    {
+      basic_block *tos, *worklist;
+
+      /* When called recursively, first do a quick discovery
+	 of reachable bbs after the above changes and only
+	 consider conditions in still reachable bbs.  */
+      tos = worklist = XNEWVEC (basic_block, loop->num_nodes);
+
+      for (i = 0; i < loop->num_nodes; i++)
+	bbs[i]->flags &= ~BB_REACHABLE;
+
+      /* Start with marking header.  */
+      *tos++ = bbs[0];
+      bbs[0]->flags |= BB_REACHABLE;
+
+      /* Iterate: find everything reachable from what we've already seen
+	 within the same innermost loop.  Don't look through false edges
+	 if condition is always true or true edges if condition is
+	 always false.  */
+      while (tos != worklist)
+	{
+	  basic_block b = *--tos;
+	  edge e;
+	  edge_iterator ei;
+	  int flags = 0;
+
+	  if (EDGE_COUNT (b->succs) == 2)
+	    {
+	      gimple stmt = last_stmt (b);
+	      if (stmt
+		  && gimple_code (stmt) == GIMPLE_COND)
+		{
+		  if (gimple_cond_true_p (stmt))
+		    flags = EDGE_FALSE_VALUE;
+		  else if (gimple_cond_false_p (stmt))
+		    flags = EDGE_TRUE_VALUE;
+		}
+	    }
+
+	  FOR_EACH_EDGE (e, ei, b->succs)
+	    {
+	      basic_block dest = e->dest;
+
+	      if (dest->loop_father == loop
+		  && !(dest->flags & BB_REACHABLE)
+		  && !(e->flags & flags))
+		{
+		  *tos++ = dest;
+		  dest->flags |= BB_REACHABLE;
+		}
+	    }
+	}
+
+      free (worklist);
+
+      /* Find a bb to unswitch on.  */
+      for (; found < loop->num_nodes; found++)
+	if ((bbs[found]->flags & BB_REACHABLE)
+	    && (cond = tree_may_unswitch_on (bbs[found], loop)))
+	  break;
+
+      if (found == loop->num_nodes)
+	{
+	  free (bbs);
+	  return changed;
+	}
+    }
+
+  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 (loop, bbs[found], 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 (nloop, num + 1);
+  tree_unswitch_single_loop (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 loop *loop,
+		    basic_block unswitch_on, tree cond)
+{
+  unsigned prob_true;
+  edge edge_true, edge_false;
+
+  /* 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);
+
+  extract_true_false_edges_from_block (unswitch_on, &edge_true, &edge_false);
+  prob_true = edge_true->probability;
+  return loop_version (loop, unshare_expr (cond),
+		       NULL, prob_true, prob_true,
+		       REG_BR_PROB_BASE - prob_true, false);
+}
+
+/* Loop unswitching pass.  */
+
+static unsigned int
+tree_ssa_loop_unswitch (void)
+{
+  if (number_of_loops (cfun) <= 1)
+    return 0;
+
+  return tree_ssa_unswitch_loops ();
+}
+
+static bool
+gate_tree_ssa_loop_unswitch (void)
+{
+  return flag_unswitch_loops != 0;
+}
+
+namespace {
+
+const pass_data pass_data_tree_unswitch =
+{
+  GIMPLE_PASS, /* type */
+  "unswitch", /* name */
+  OPTGROUP_LOOP, /* optinfo_flags */
+  true, /* has_gate */
+  true, /* has_execute */
+  TV_TREE_LOOP_UNSWITCH, /* tv_id */
+  PROP_cfg, /* properties_required */
+  0, /* properties_provided */
+  0, /* properties_destroyed */
+  0, /* todo_flags_start */
+  0, /* todo_flags_finish */
+};
+
+class pass_tree_unswitch : public gimple_opt_pass
+{
+public:
+  pass_tree_unswitch (gcc::context *ctxt)
+    : gimple_opt_pass (pass_data_tree_unswitch, ctxt)
+  {}
+
+  /* opt_pass methods: */
+  bool gate () { return gate_tree_ssa_loop_unswitch (); }
+  unsigned int execute () { return tree_ssa_loop_unswitch (); }
+
+}; // class pass_tree_unswitch
+
+} // anon namespace
+
+gimple_opt_pass *
+make_pass_tree_unswitch (gcc::context *ctxt)
+{
+  return new pass_tree_unswitch (ctxt);
+}
+
+