[thirdparty/gcc.git] / gcc / tree-ssa-phiprop.c

/* Backward propagation of indirect loads through PHIs.
   Copyright (C) 2007-2015 Free Software Foundation, Inc.
   Contributed by Richard Guenther <rguenther@suse.de>

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 "backend.h"
#include "tree.h"
#include "gimple.h"
#include "hard-reg-set.h"
#include "ssa.h"
#include "alias.h"
#include "fold-const.h"
#include "tm_p.h"
#include "gimple-pretty-print.h"
#include "internal-fn.h"
#include "tree-eh.h"
#include "gimplify.h"
#include "gimple-iterator.h"
#include "tree-pass.h"
#include "langhooks.h"
#include "flags.h"

/* This pass propagates indirect loads through the PHI node for its
   address to make the load source possibly non-addressable and to
   allow for PHI optimization to trigger.

   For example the pass changes

     # addr_1 = PHI <&a, &b>
     tmp_1 = *addr_1;

   to

     # tmp_1 = PHI <a, b>

   but also handles more complex scenarios like

     D.2077_2 = &this_1(D)->a1;
     ...

     # b_12 = PHI <&c(2), D.2077_2(3)>
     D.2114_13 = *b_12;
     ...

     # b_15 = PHI <b_12(4), &b(5)>
     D.2080_5 = &this_1(D)->a0;
     ...

     # b_18 = PHI <D.2080_5(6), &c(7)>
     ...

     # b_21 = PHI <b_15(8), b_18(9)>
     D.2076_8 = *b_21;

   where the addresses loaded are defined by PHIs itself.
   The above happens for

     std::max(std::min(a0, c), std::min(std::max(a1, c), b))

   where this pass transforms it to a form later PHI optimization
   recognizes and transforms it to the simple

     D.2109_10 = this_1(D)->a1;
     D.2110_11 = c;
     D.2114_31 = MAX_EXPR <D.2109_10, D.2110_11>;
     D.2115_14 = b;
     D.2125_17 = MIN_EXPR <D.2115_14, D.2114_31>;
     D.2119_16 = this_1(D)->a0;
     D.2124_32 = MIN_EXPR <D.2110_11, D.2119_16>;
     D.2076_33 = MAX_EXPR <D.2125_17, D.2124_32>;

   The pass does a dominator walk processing loads using a basic-block
   local analysis and stores the result for use by transformations on
   dominated basic-blocks.  */


/* Structure to keep track of the value of a dereferenced PHI result
   and the virtual operand used for that dereference.  */

struct phiprop_d
{
  tree value;
  tree vuse;
};

/* Verify if the value recorded for NAME in PHIVN is still valid at
   the start of basic block BB.  */

static bool
phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
{
  tree vuse = phivn[SSA_NAME_VERSION (name)].vuse;
  gimple use_stmt;
  imm_use_iterator ui2;
  bool ok = true;

  /* The def stmts of the virtual uses need to be dominated by bb.  */
  gcc_assert (vuse != NULL_TREE);

  FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
    {
      /* If BB does not dominate a VDEF, the value is invalid.  */
      if ((gimple_vdef (use_stmt) != NULL_TREE
	   || gimple_code (use_stmt) == GIMPLE_PHI)
	  && !dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb))
	{
	  ok = false;
	  BREAK_FROM_IMM_USE_STMT (ui2);
	}
    }

  return ok;
}

/* Insert a new phi node for the dereference of PHI at basic_block
   BB with the virtual operands from USE_STMT.  */

static tree
phiprop_insert_phi (basic_block bb, gphi *phi, gimple use_stmt,
		    struct phiprop_d *phivn, size_t n)
{
  tree res;
  gphi *new_phi;
  edge_iterator ei;
  edge e;

  gcc_assert (is_gimple_assign (use_stmt)
	      && gimple_assign_rhs_code (use_stmt) == MEM_REF);

  /* Build a new PHI node to replace the definition of
     the indirect reference lhs.  */
  res = gimple_assign_lhs (use_stmt);
  new_phi = create_phi_node (res, bb);

  if (dump_file && (dump_flags & TDF_DETAILS))
    {
      fprintf (dump_file, "Inserting PHI for result of load ");
      print_gimple_stmt (dump_file, use_stmt, 0, 0);
    }

  /* Add PHI arguments for each edge inserting loads of the
     addressable operands.  */
  FOR_EACH_EDGE (e, ei, bb->preds)
    {
      tree old_arg, new_var;
      gassign *tmp;
      source_location locus;

      old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
      locus = gimple_phi_arg_location_from_edge (phi, e);
      while (TREE_CODE (old_arg) == SSA_NAME
	     && (SSA_NAME_VERSION (old_arg) >= n
	         || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
	{
	  gimple def_stmt = SSA_NAME_DEF_STMT (old_arg);
	  old_arg = gimple_assign_rhs1 (def_stmt);
	  locus = gimple_location (def_stmt);
	}

      if (TREE_CODE (old_arg) == SSA_NAME)
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "  for edge defining ");
	      print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
	      fprintf (dump_file, " reusing PHI result ");
	      print_generic_expr (dump_file,
				  phivn[SSA_NAME_VERSION (old_arg)].value, 0);
	      fprintf (dump_file, "\n");
	    }
	  /* Reuse a formerly created dereference.  */
	  new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
	}
      else
	{
	  tree rhs = gimple_assign_rhs1 (use_stmt);
	  gcc_assert (TREE_CODE (old_arg) == ADDR_EXPR);
	  new_var = make_ssa_name (TREE_TYPE (rhs));
	  if (!is_gimple_min_invariant (old_arg))
	    old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
	  else
	    old_arg = unshare_expr (old_arg);
	  tmp = gimple_build_assign (new_var,
				     fold_build2 (MEM_REF, TREE_TYPE (rhs),
						  old_arg,
						  TREE_OPERAND (rhs, 1)));
	  gimple_set_location (tmp, locus);

	  gsi_insert_on_edge (e, tmp);
	  update_stmt (tmp);

	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "  for edge defining ");
	      print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
	      fprintf (dump_file, " inserting load ");
	      print_gimple_stmt (dump_file, tmp, 0, 0);
	    }
	}

      add_phi_arg (new_phi, new_var, e, locus);
    }

  update_stmt (new_phi);

  if (dump_file && (dump_flags & TDF_DETAILS))
    print_gimple_stmt (dump_file, new_phi, 0, 0);

  return res;
}

/* Propagate between the phi node arguments of PHI in BB and phi result
   users.  For now this matches
        # p_2 = PHI <&x, &y>
      <Lx>:;
	p_3 = p_2;
	z_2 = *p_3;
   and converts it to
	# z_2 = PHI <x, y>
      <Lx>:;
   Returns true if a transformation was done and edge insertions
   need to be committed.  Global data PHIVN and N is used to track
   past transformation results.  We need to be especially careful here
   with aliasing issues as we are moving memory reads.  */

static bool
propagate_with_phi (basic_block bb, gphi *phi, struct phiprop_d *phivn,
		    size_t n)
{
  tree ptr = PHI_RESULT (phi);
  gimple use_stmt;
  tree res = NULL_TREE;
  gimple_stmt_iterator gsi;
  imm_use_iterator ui;
  use_operand_p arg_p, use;
  ssa_op_iter i;
  bool phi_inserted;
  tree type = NULL_TREE;

  if (!POINTER_TYPE_P (TREE_TYPE (ptr))
      || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
    return false;

  /* Check if we can "cheaply" dereference all phi arguments.  */
  FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
    {
      tree arg = USE_FROM_PTR (arg_p);
      /* Walk the ssa chain until we reach a ssa name we already
	 created a value for or we reach a definition of the form
	 ssa_name_n = &var;  */
      while (TREE_CODE (arg) == SSA_NAME
	     && !SSA_NAME_IS_DEFAULT_DEF (arg)
	     && (SSA_NAME_VERSION (arg) >= n
	         || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
	{
	  gimple def_stmt = SSA_NAME_DEF_STMT (arg);
	  if (!gimple_assign_single_p (def_stmt))
	    return false;
	  arg = gimple_assign_rhs1 (def_stmt);
	}
      if (TREE_CODE (arg) != ADDR_EXPR
	  && !(TREE_CODE (arg) == SSA_NAME
	       && SSA_NAME_VERSION (arg) < n
	       && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
	       && (!type
		   || types_compatible_p
		       (type, TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value)))
	       && phivn_valid_p (phivn, arg, bb)))
	return false;
      if (!type
	  && TREE_CODE (arg) == SSA_NAME)
	type = TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value);
    }

  /* Find a dereferencing use.  First follow (single use) ssa
     copy chains for ptr.  */
  while (single_imm_use (ptr, &use, &use_stmt)
	 && gimple_assign_ssa_name_copy_p (use_stmt))
    ptr = gimple_assign_lhs (use_stmt);

  /* Replace the first dereference of *ptr if there is one and if we
     can move the loads to the place of the ptr phi node.  */
  phi_inserted = false;
  FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
    {
      gimple def_stmt;
      tree vuse;

      /* Only replace loads in blocks that post-dominate the PHI node.  That
         makes sure we don't end up speculating loads.  */
      if (!dominated_by_p (CDI_POST_DOMINATORS,
			   bb, gimple_bb (use_stmt)))
	continue;
         
      /* Check whether this is a load of *ptr.  */
      if (!(is_gimple_assign (use_stmt)
	    && TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME
	    && gimple_assign_rhs_code (use_stmt) == MEM_REF
	    && TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == ptr
	    && integer_zerop (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 1))
	    && (!type
		|| types_compatible_p
		     (TREE_TYPE (gimple_assign_lhs (use_stmt)), type))
	    /* We cannot replace a load that may throw or is volatile.  */
	    && !stmt_can_throw_internal (use_stmt)))
	continue;

      /* Check if we can move the loads.  The def stmt of the virtual use
	 needs to be in a different basic block dominating bb.  */
      vuse = gimple_vuse (use_stmt);
      def_stmt = SSA_NAME_DEF_STMT (vuse);
      if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
	  && (gimple_bb (def_stmt) == bb
	      || !dominated_by_p (CDI_DOMINATORS,
				  bb, gimple_bb (def_stmt))))
	goto next;

      /* Found a proper dereference.  Insert a phi node if this
	 is the first load transformation.  */
      if (!phi_inserted)
	{
	  res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
	  type = TREE_TYPE (res);

	  /* Remember the value we created for *ptr.  */
	  phivn[SSA_NAME_VERSION (ptr)].value = res;
	  phivn[SSA_NAME_VERSION (ptr)].vuse = vuse;

	  /* Remove old stmt.  The phi is taken care of by DCE, if we
	     want to delete it here we also have to delete all intermediate
	     copies.  */
	  gsi = gsi_for_stmt (use_stmt);
	  gsi_remove (&gsi, true);

	  phi_inserted = true;
	}
      else
	{
	  /* Further replacements are easy, just make a copy out of the
	     load.  */
	  gimple_assign_set_rhs1 (use_stmt, res);
	  update_stmt (use_stmt);
	}

next:;
      /* Continue searching for a proper dereference.  */
    }

  return phi_inserted;
}

/* Main entry for phiprop pass.  */

namespace {

const pass_data pass_data_phiprop =
{
  GIMPLE_PASS, /* type */
  "phiprop", /* name */
  OPTGROUP_NONE, /* optinfo_flags */
  TV_TREE_PHIPROP, /* tv_id */
  ( PROP_cfg | PROP_ssa ), /* properties_required */
  0, /* properties_provided */
  0, /* properties_destroyed */
  0, /* todo_flags_start */
  TODO_update_ssa, /* todo_flags_finish */
};

class pass_phiprop : public gimple_opt_pass
{
public:
  pass_phiprop (gcc::context *ctxt)
    : gimple_opt_pass (pass_data_phiprop, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *) { return flag_tree_phiprop; }
  virtual unsigned int execute (function *);

}; // class pass_phiprop

unsigned int
pass_phiprop::execute (function *fun)
{
  vec<basic_block> bbs;
  struct phiprop_d *phivn;
  bool did_something = false;
  basic_block bb;
  gphi_iterator gsi;
  unsigned i;
  size_t n;

  calculate_dominance_info (CDI_DOMINATORS);
  calculate_dominance_info (CDI_POST_DOMINATORS);

  n = num_ssa_names;
  phivn = XCNEWVEC (struct phiprop_d, n);

  /* Walk the dominator tree in preorder.  */
  bbs = get_all_dominated_blocks (CDI_DOMINATORS,
				  single_succ (ENTRY_BLOCK_PTR_FOR_FN (fun)));
  FOR_EACH_VEC_ELT (bbs, i, bb)
    for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
      did_something |= propagate_with_phi (bb, gsi.phi (), phivn, n);

  if (did_something)
    gsi_commit_edge_inserts ();

  bbs.release ();
  free (phivn);

  free_dominance_info (CDI_POST_DOMINATORS);

  return 0;
}

} // anon namespace

gimple_opt_pass *
make_pass_phiprop (gcc::context *ctxt)
{
  return new pass_phiprop (ctxt);
}
Commit	Line	Data
a2fd87ad	1	/* Backward propagation of indirect loads through PHIs.
d353bf18	2	Copyright (C) 2007-2015 Free Software Foundation, Inc.
a2fd87ad	3	Contributed by Richard Guenther <rguenther@suse.de>
	4
	5	This file is part of GCC.
	6
	7	GCC is free software; you can redistribute it and/or modify
	8	it under the terms of the GNU General Public License as published by
	9	the Free Software Foundation; either version 3, or (at your option)
	10	any later version.
	11
	12	GCC is distributed in the hope that it will be useful,
	13	but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	15	GNU General Public License for more details.
	16
	17	You should have received a copy of the GNU General Public License
	18	along with GCC; see the file COPYING3. If not see
	19	<http://www.gnu.org/licenses/>. */
	20
	21	#include "config.h"
	22	#include "system.h"
	23	#include "coretypes.h"
9ef16211	24	#include "backend.h"
a2fd87ad	25	#include "tree.h"
9ef16211	26	#include "gimple.h"
	27	#include "hard-reg-set.h"
	28	#include "ssa.h"
	29	#include "alias.h"
b20a8bb4	30	#include "fold-const.h"
a2fd87ad	31	#include "tm_p.h"
ce084dfc	32	#include "gimple-pretty-print.h"
bc61cadb	33	#include "internal-fn.h"
bc61cadb	34	#include "tree-eh.h"
a8783bee	35	#include "gimplify.h"
dcf1a1ec	36	#include "gimple-iterator.h"
a2fd87ad	37	#include "tree-pass.h"
a2fd87ad	38	#include "langhooks.h"
	39	#include "flags.h"
	40
	41	/* This pass propagates indirect loads through the PHI node for its
f0b5f617	42	address to make the load source possibly non-addressable and to
a2fd87ad	43	allow for PHI optimization to trigger.
	44
	45	For example the pass changes
	46
	47	# addr_1 = PHI <&a, &b>
	48	tmp_1 = *addr_1;
	49
	50	to
	51
	52	# tmp_1 = PHI <a, b>
	53
f0b5f617	54	but also handles more complex scenarios like
a2fd87ad	55
	56	D.2077_2 = &this_1(D)->a1;
	57	...
	58
	59	# b_12 = PHI <&c(2), D.2077_2(3)>
	60	D.2114_13 = *b_12;
	61	...
	62
	63	# b_15 = PHI <b_12(4), &b(5)>
	64	D.2080_5 = &this_1(D)->a0;
	65	...
	66
	67	# b_18 = PHI <D.2080_5(6), &c(7)>
	68	...
	69
	70	# b_21 = PHI <b_15(8), b_18(9)>
	71	D.2076_8 = *b_21;
	72
	73	where the addresses loaded are defined by PHIs itself.
	74	The above happens for
	75
	76	std::max(std::min(a0, c), std::min(std::max(a1, c), b))
	77
	78	where this pass transforms it to a form later PHI optimization
	79	recognizes and transforms it to the simple
	80
	81	D.2109_10 = this_1(D)->a1;
	82	D.2110_11 = c;
	83	D.2114_31 = MAX_EXPR <D.2109_10, D.2110_11>;
	84	D.2115_14 = b;
	85	D.2125_17 = MIN_EXPR <D.2115_14, D.2114_31>;
	86	D.2119_16 = this_1(D)->a0;
	87	D.2124_32 = MIN_EXPR <D.2110_11, D.2119_16>;
	88	D.2076_33 = MAX_EXPR <D.2125_17, D.2124_32>;
	89
	90	The pass does a dominator walk processing loads using a basic-block
	91	local analysis and stores the result for use by transformations on
	92	dominated basic-blocks. */
	93
	94
	95	/* Structure to keep track of the value of a dereferenced PHI result
d977f485	96	and the virtual operand used for that dereference. */
a2fd87ad	97
	98	struct phiprop_d
	99	{
	100	tree value;
d977f485	101	tree vuse;
a2fd87ad	102	};
	103
	104	/* Verify if the value recorded for NAME in PHIVN is still valid at
	105	the start of basic block BB. */
	106
	107	static bool
	108	phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
	109	{
d977f485	110	tree vuse = phivn[SSA_NAME_VERSION (name)].vuse;
	111	gimple use_stmt;
	112	imm_use_iterator ui2;
	113	bool ok = true;
a2fd87ad	114
d977f485	115	/* The def stmts of the virtual uses need to be dominated by bb. */
d977f485	116	gcc_assert (vuse != NULL_TREE);
a2fd87ad	117
d977f485	118	FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
	119	{
	120	/* If BB does not dominate a VDEF, the value is invalid. */
	121	if ((gimple_vdef (use_stmt) != NULL_TREE
	122	\|\| gimple_code (use_stmt) == GIMPLE_PHI)
	123	&& !dominated_by_p (CDI_DOMINATORS, gimple_bb (use_stmt), bb))
a2fd87ad	124	{
d977f485	125	ok = false;
d977f485	126	BREAK_FROM_IMM_USE_STMT (ui2);
a2fd87ad	127	}
a2fd87ad	128	}
a2fd87ad	129
d977f485	130	return ok;
a2fd87ad	131	}
	132
	133	/* Insert a new phi node for the dereference of PHI at basic_block
	134	BB with the virtual operands from USE_STMT. */
	135
	136	static tree
1a91d914	137	phiprop_insert_phi (basic_block bb, gphi *phi, gimple use_stmt,
a2fd87ad	138	struct phiprop_d *phivn, size_t n)
a2fd87ad	139	{
75a70cf9	140	tree res;
1a91d914	141	gphi *new_phi;
a2fd87ad	142	edge_iterator ei;
	143	edge e;
	144
75a70cf9	145	gcc_assert (is_gimple_assign (use_stmt)
182cf5a9	146	&& gimple_assign_rhs_code (use_stmt) == MEM_REF);
75a70cf9	147
a2fd87ad	148	/* Build a new PHI node to replace the definition of
a2fd87ad	149	the indirect reference lhs. */
75a70cf9	150	res = gimple_assign_lhs (use_stmt);
9c06f260	151	new_phi = create_phi_node (res, bb);
a2fd87ad	152
d977f485	153	if (dump_file && (dump_flags & TDF_DETAILS))
	154	{
	155	fprintf (dump_file, "Inserting PHI for result of load ");
	156	print_gimple_stmt (dump_file, use_stmt, 0, 0);
	157	}
	158
a2fd87ad	159	/* Add PHI arguments for each edge inserting loads of the
	160	addressable operands. */
	161	FOR_EACH_EDGE (e, ei, bb->preds)
	162	{
75a70cf9	163	tree old_arg, new_var;
1a91d914	164	gassign *tmp;
efbcb6de	165	source_location locus;
a2fd87ad	166
a2fd87ad	167	old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
efbcb6de	168	locus = gimple_phi_arg_location_from_edge (phi, e);
a2fd87ad	169	while (TREE_CODE (old_arg) == SSA_NAME
	170	&& (SSA_NAME_VERSION (old_arg) >= n
	171	\|\| phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
	172	{
75a70cf9	173	gimple def_stmt = SSA_NAME_DEF_STMT (old_arg);
75a70cf9	174	old_arg = gimple_assign_rhs1 (def_stmt);
efbcb6de	175	locus = gimple_location (def_stmt);
a2fd87ad	176	}
	177
	178	if (TREE_CODE (old_arg) == SSA_NAME)
d977f485	179	{
	180	if (dump_file && (dump_flags & TDF_DETAILS))
	181	{
	182	fprintf (dump_file, " for edge defining ");
	183	print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
	184	fprintf (dump_file, " reusing PHI result ");
	185	print_generic_expr (dump_file,
	186	phivn[SSA_NAME_VERSION (old_arg)].value, 0);
	187	fprintf (dump_file, "\n");
	188	}
	189	/* Reuse a formerly created dereference. */
	190	new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
	191	}
a2fd87ad	192	else
a2fd87ad	193	{
16952c2c	194	tree rhs = gimple_assign_rhs1 (use_stmt);
75a70cf9	195	gcc_assert (TREE_CODE (old_arg) == ADDR_EXPR);
f9e245b2	196	new_var = make_ssa_name (TREE_TYPE (rhs));
16952c2c	197	if (!is_gimple_min_invariant (old_arg))
	198	old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
	199	else
	200	old_arg = unshare_expr (old_arg);
	201	tmp = gimple_build_assign (new_var,
	202	fold_build2 (MEM_REF, TREE_TYPE (rhs),
	203	old_arg,
	204	TREE_OPERAND (rhs, 1)));
efbcb6de	205	gimple_set_location (tmp, locus);
a2fd87ad	206
75a70cf9	207	gsi_insert_on_edge (e, tmp);
a2fd87ad	208	update_stmt (tmp);
d977f485	209
	210	if (dump_file && (dump_flags & TDF_DETAILS))
	211	{
	212	fprintf (dump_file, " for edge defining ");
	213	print_generic_expr (dump_file, PHI_ARG_DEF_FROM_EDGE (phi, e), 0);
	214	fprintf (dump_file, " inserting load ");
	215	print_gimple_stmt (dump_file, tmp, 0, 0);
	216	}
a2fd87ad	217	}
a2fd87ad	218
60d535d2	219	add_phi_arg (new_phi, new_var, e, locus);
a2fd87ad	220	}
	221
	222	update_stmt (new_phi);
	223
d977f485	224	if (dump_file && (dump_flags & TDF_DETAILS))
	225	print_gimple_stmt (dump_file, new_phi, 0, 0);
	226
a2fd87ad	227	return res;
	228	}
	229
	230	/* Propagate between the phi node arguments of PHI in BB and phi result
	231	users. For now this matches
	232	# p_2 = PHI <&x, &y>
	233	<Lx>:;
	234	p_3 = p_2;
	235	z_2 = *p_3;
	236	and converts it to
	237	# z_2 = PHI <x, y>
	238	<Lx>:;
	239	Returns true if a transformation was done and edge insertions
	240	need to be committed. Global data PHIVN and N is used to track
	241	past transformation results. We need to be especially careful here
	242	with aliasing issues as we are moving memory reads. */
	243
	244	static bool
1a91d914	245	propagate_with_phi (basic_block bb, gphi phi, struct phiprop_d phivn,
75a70cf9	246	size_t n)
a2fd87ad	247	{
a2fd87ad	248	tree ptr = PHI_RESULT (phi);
75a70cf9	249	gimple use_stmt;
	250	tree res = NULL_TREE;
	251	gimple_stmt_iterator gsi;
a2fd87ad	252	imm_use_iterator ui;
	253	use_operand_p arg_p, use;
	254	ssa_op_iter i;
	255	bool phi_inserted;
16952c2c	256	tree type = NULL_TREE;
a2fd87ad	257
dd277d48	258	if (!POINTER_TYPE_P (TREE_TYPE (ptr))
a2fd87ad	259	\|\| !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
	260	return false;
	261
	262	/* Check if we can "cheaply" dereference all phi arguments. */
	263	FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)
	264	{
	265	tree arg = USE_FROM_PTR (arg_p);
	266	/* Walk the ssa chain until we reach a ssa name we already
	267	created a value for or we reach a definition of the form
	268	ssa_name_n = &var; */
	269	while (TREE_CODE (arg) == SSA_NAME
	270	&& !SSA_NAME_IS_DEFAULT_DEF (arg)
	271	&& (SSA_NAME_VERSION (arg) >= n
	272	\|\| phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
	273	{
75a70cf9	274	gimple def_stmt = SSA_NAME_DEF_STMT (arg);
024e445d	275	if (!gimple_assign_single_p (def_stmt))
a2fd87ad	276	return false;
75a70cf9	277	arg = gimple_assign_rhs1 (def_stmt);
a2fd87ad	278	}
16952c2c	279	if (TREE_CODE (arg) != ADDR_EXPR
a2fd87ad	280	&& !(TREE_CODE (arg) == SSA_NAME
80a26b8b	281	&& SSA_NAME_VERSION (arg) < n
a2fd87ad	282	&& phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
16952c2c	283	&& (!type
	284	\|\| types_compatible_p
	285	(type, TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value)))
a2fd87ad	286	&& phivn_valid_p (phivn, arg, bb)))
a2fd87ad	287	return false;
16952c2c	288	if (!type
	289	&& TREE_CODE (arg) == SSA_NAME)
	290	type = TREE_TYPE (phivn[SSA_NAME_VERSION (arg)].value);
a2fd87ad	291	}
	292
	293	/* Find a dereferencing use. First follow (single use) ssa
	294	copy chains for ptr. */
	295	while (single_imm_use (ptr, &use, &use_stmt)
75a70cf9	296	&& gimple_assign_ssa_name_copy_p (use_stmt))
75a70cf9	297	ptr = gimple_assign_lhs (use_stmt);
a2fd87ad	298
	299	/* Replace the first dereference of *ptr if there is one and if we
	300	can move the loads to the place of the ptr phi node. */
	301	phi_inserted = false;
	302	FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)
	303	{
d977f485	304	gimple def_stmt;
a2fd87ad	305	tree vuse;
a2fd87ad	306
335252cb	307	/* Only replace loads in blocks that post-dominate the PHI node. That
	308	makes sure we don't end up speculating loads. */
	309	if (!dominated_by_p (CDI_POST_DOMINATORS,
	310	bb, gimple_bb (use_stmt)))
	311	continue;
	312
a2fd87ad	313	/* Check whether this is a load of ptr. /
75a70cf9	314	if (!(is_gimple_assign (use_stmt)
48e1416a	315	&& TREE_CODE (gimple_assign_lhs (use_stmt)) == SSA_NAME
182cf5a9	316	&& gimple_assign_rhs_code (use_stmt) == MEM_REF
75a70cf9	317	&& TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 0) == ptr
182cf5a9	318	&& integer_zerop (TREE_OPERAND (gimple_assign_rhs1 (use_stmt), 1))
16952c2c	319	&& (!type
	320	\|\| types_compatible_p
	321	(TREE_TYPE (gimple_assign_lhs (use_stmt)), type))
a2fd87ad	322	/* We cannot replace a load that may throw or is volatile. */
75a70cf9	323	&& !stmt_can_throw_internal (use_stmt)))
a2fd87ad	324	continue;
a2fd87ad	325
d977f485	326	/* Check if we can move the loads. The def stmt of the virtual use
	327	needs to be in a different basic block dominating bb. */
	328	vuse = gimple_vuse (use_stmt);
	329	def_stmt = SSA_NAME_DEF_STMT (vuse);
	330	if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
	331	&& (gimple_bb (def_stmt) == bb
	332	\|\| !dominated_by_p (CDI_DOMINATORS,
	333	bb, gimple_bb (def_stmt))))
	334	goto next;
a2fd87ad	335
	336	/* Found a proper dereference. Insert a phi node if this
	337	is the first load transformation. */
	338	if (!phi_inserted)
	339	{
	340	res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
16952c2c	341	type = TREE_TYPE (res);
a2fd87ad	342
	343	/* Remember the value we created for ptr. /
	344	phivn[SSA_NAME_VERSION (ptr)].value = res;
d977f485	345	phivn[SSA_NAME_VERSION (ptr)].vuse = vuse;
a2fd87ad	346
	347	/* Remove old stmt. The phi is taken care of by DCE, if we
	348	want to delete it here we also have to delete all intermediate
	349	copies. */
75a70cf9	350	gsi = gsi_for_stmt (use_stmt);
a5dcf840	351	gsi_remove (&gsi, true);
a2fd87ad	352
	353	phi_inserted = true;
	354	}
	355	else
	356	{
	357	/* Further replacements are easy, just make a copy out of the
	358	load. */
75a70cf9	359	gimple_assign_set_rhs1 (use_stmt, res);
a2fd87ad	360	update_stmt (use_stmt);
	361	}
	362
	363	next:;
	364	/* Continue searching for a proper dereference. */
	365	}
	366
	367	return phi_inserted;
	368	}
	369
a2fd87ad	370	/* Main entry for phiprop pass. */
a2fd87ad	371
65b0537f	372	namespace {
	373
	374	const pass_data pass_data_phiprop =
	375	{
	376	GIMPLE_PASS, /* type */
	377	"phiprop", /* name */
	378	OPTGROUP_NONE, /* optinfo_flags */
65b0537f	379	TV_TREE_PHIPROP, /* tv_id */
	380	( PROP_cfg \| PROP_ssa ), /* properties_required */
	381	0, /* properties_provided */
	382	0, /* properties_destroyed */
	383	0, /* todo_flags_start */
8b88439e	384	TODO_update_ssa, /* todo_flags_finish */
65b0537f	385	};
	386
	387	class pass_phiprop : public gimple_opt_pass
	388	{
	389	public:
	390	pass_phiprop (gcc::context *ctxt)
	391	: gimple_opt_pass (pass_data_phiprop, ctxt)
	392	{}
	393
	394	/* opt_pass methods: */
	395	virtual bool gate (function *) { return flag_tree_phiprop; }
	396	virtual unsigned int execute (function *);
	397
	398	}; // class pass_phiprop
	399
	400	unsigned int
	401	pass_phiprop::execute (function *fun)
a2fd87ad	402	{
f1f41a6c	403	vec<basic_block> bbs;
a2fd87ad	404	struct phiprop_d *phivn;
48e1416a	405	bool did_something = false;
59f3ea59	406	basic_block bb;
1a91d914	407	gphi_iterator gsi;
59f3ea59	408	unsigned i;
80a26b8b	409	size_t n;
a2fd87ad	410
a2fd87ad	411	calculate_dominance_info (CDI_DOMINATORS);
335252cb	412	calculate_dominance_info (CDI_POST_DOMINATORS);
a2fd87ad	413
80a26b8b	414	n = num_ssa_names;
80a26b8b	415	phivn = XCNEWVEC (struct phiprop_d, n);
a2fd87ad	416
59f3ea59	417	/* Walk the dominator tree in preorder. */
59f3ea59	418	bbs = get_all_dominated_blocks (CDI_DOMINATORS,
65b0537f	419	single_succ (ENTRY_BLOCK_PTR_FOR_FN (fun)));
f1f41a6c	420	FOR_EACH_VEC_ELT (bbs, i, bb)
59f3ea59	421	for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1a91d914	422	did_something \|= propagate_with_phi (bb, gsi.phi (), phivn, n);
59f3ea59	423
59f3ea59	424	if (did_something)
75a70cf9	425	gsi_commit_edge_inserts ();
a2fd87ad	426
f1f41a6c	427	bbs.release ();
a2fd87ad	428	free (phivn);
a2fd87ad	429
335252cb	430	free_dominance_info (CDI_POST_DOMINATORS);
335252cb	431
a2fd87ad	432	return 0;
	433	}
	434
cbe8bda8	435	} // anon namespace
	436
	437	gimple_opt_pass *
	438	make_pass_phiprop (gcc::context *ctxt)
	439	{
	440	return new pass_phiprop (ctxt);
	441	}