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/* SSA operands management for trees.

   Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010

   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 "flags.h"

#include "function.h"

#include "diagnostic.h"

#include "tree-flow.h"

#include "tree-inline.h"

#include "tree-pass.h"

#include "ggc.h"

#include "timevar.h"

#include "toplev.h"

#include "langhooks.h"

#include "ipa-reference.h"

/* This file contains the code required to manage the operands cache of the

   SSA optimizer.  For every stmt, we maintain an operand cache in the stmt

   annotation.  This cache contains operands that will be of interest to

   optimizers and other passes wishing to manipulate the IL.

   The operand type are broken up into REAL and VIRTUAL operands.  The real

   operands are represented as pointers into the stmt's operand tree.  Thus

   any manipulation of the real operands will be reflected in the actual tree.

   Virtual operands are represented solely in the cache, although the base

   variable for the SSA_NAME may, or may not occur in the stmt's tree.

   Manipulation of the virtual operands will not be reflected in the stmt tree.

   The routines in this file are concerned with creating this operand cache

   from a stmt tree.

   The operand tree is the parsed by the various get_* routines which look

   through the stmt tree for the occurrence of operands which may be of

   interest, and calls are made to the append_* routines whenever one is

   found.  There are 4 of these routines, each representing one of the

   4 types of operands. Defs, Uses, Virtual Uses, and Virtual May Defs.

   The append_* routines check for duplication, and simply keep a list of

   unique objects for each operand type in the build_* extendable vectors.

   Once the stmt tree is completely parsed, the finalize_ssa_operands()

   routine is called, which proceeds to perform the finalization routine

   on each of the 4 operand vectors which have been built up.

   If the stmt had a previous operand cache, the finalization routines

   attempt to match up the new operands with the old ones.  If it's a perfect

   match, the old vector is simply reused.  If it isn't a perfect match, then

   a new vector is created and the new operands are placed there.  For

   virtual operands, if the previous cache had SSA_NAME version of a

   variable, and that same variable occurs in the same operands cache, then

   the new cache vector will also get the same SSA_NAME.

   i.e., if a stmt had a VUSE of 'a_5', and 'a' occurs in the new

   operand vector for VUSE, then the new vector will also be modified

   such that it contains 'a_5' rather than 'a'.  */

/* Structure storing statistics on how many call clobbers we have, and

   how many where avoided.  */

static struct

{

  /* Number of call-clobbered ops we attempt to add to calls in

     add_call_clobbered_mem_symbols.  */

  unsigned int clobbered_vars;

  /* Number of write-clobbers (VDEFs) avoided by using

     not_written information.  */

  unsigned int static_write_clobbers_avoided;

  /* Number of reads (VUSEs) avoided by using not_read information.  */

  unsigned int static_read_clobbers_avoided;

  /* Number of write-clobbers avoided because the variable can't escape to

     this call.  */

  unsigned int unescapable_clobbers_avoided;

  /* Number of read-only uses we attempt to add to calls in

     add_call_read_mem_symbols.  */

  unsigned int readonly_clobbers;

  /* Number of read-only uses we avoid using not_read information.  */

  unsigned int static_readonly_clobbers_avoided;

} clobber_stats;

/* Flags to describe operand properties in helpers.  */

/* By default, operands are loaded.  */

#define opf_use         0

/* Operand is the target of an assignment expression or a

   call-clobbered variable.  */

#define opf_def         (1 << 0)

/* No virtual operands should be created in the expression.  This is used

   when traversing ADDR_EXPR nodes which have different semantics than

   other expressions.  Inside an ADDR_EXPR node, the only operands that we

   need to consider are indices into arrays.  For instance, &a.b[i] should

   generate a USE of 'i' but it should not generate a VUSE for 'a' nor a

   VUSE for 'b'.  */

#define opf_no_vops     (1 << 1)

/* Operand is an implicit reference.  This is used to distinguish

   explicit assignments in the form of MODIFY_EXPR from

   clobbering sites like function calls or ASM_EXPRs.  */

#define opf_implicit    (1 << 2)

/* Array for building all the def operands.  */

static VEC(tree,heap) *build_defs;

/* Array for building all the use operands.  */

static VEC(tree,heap) *build_uses;

/* The built VDEF operand.  */

static tree build_vdef;

/* The built VUSE operand.  */

static tree build_vuse;

/* Bitmap obstack for our datastructures that needs to survive across

   compilations of multiple functions.  */

static bitmap_obstack operands_bitmap_obstack;

static void get_expr_operands (gimple, tree *, int);

/* Number of functions with initialized ssa_operands.  */

static int n_initialized = 0;

/* Return the DECL_UID of the base variable of T.  */

static inline unsigned

get_name_decl (const_tree t)

{

  if (TREE_CODE (t) != SSA_NAME)

    return DECL_UID (t);

  else

    return DECL_UID (SSA_NAME_VAR (t));

}

/*  Return true if the SSA operands cache is active.  */

bool

ssa_operands_active (void)

{

  /* This function may be invoked from contexts where CFUN is NULL

     (IPA passes), return false for now.  FIXME: operands may be

     active in each individual function, maybe this function should

     take CFUN as a parameter.  */

  if (cfun == NULL)

    return false;

  return cfun->gimple_df && gimple_ssa_operands (cfun)->ops_active;

}

/* Create the VOP variable, an artificial global variable to act as a

   representative of all of the virtual operands FUD chain.  */

static void

create_vop_var (void)

{

  tree global_var;

  gcc_assert (cfun->gimple_df->vop == NULL_TREE);

  global_var = build_decl (BUILTINS_LOCATION, VAR_DECL,

                           get_identifier (".MEM"),

                           void_type_node);

  DECL_ARTIFICIAL (global_var) = 1;

  TREE_READONLY (global_var) = 0;

  DECL_EXTERNAL (global_var) = 1;

  TREE_STATIC (global_var) = 1;

  TREE_USED (global_var) = 1;

  DECL_CONTEXT (global_var) = NULL_TREE;

  TREE_THIS_VOLATILE (global_var) = 0;

  TREE_ADDRESSABLE (global_var) = 0;

  create_var_ann (global_var);

  add_referenced_var (global_var);

  cfun->gimple_df->vop = global_var;

}

/* These are the sizes of the operand memory buffer in bytes which gets

   allocated each time more operands space is required.  The final value is

   the amount that is allocated every time after that.

   In 1k we can fit 25 use operands (or 63 def operands) on a host with

   8 byte pointers, that would be 10 statements each with 1 def and 2

   uses.  */

#define OP_SIZE_INIT    0

#define OP_SIZE_1       (1024 - sizeof (void *))

#define OP_SIZE_2       (1024 * 4 - sizeof (void *))

#define OP_SIZE_3       (1024 * 16 - sizeof (void *))

/* Initialize the operand cache routines.  */

void

init_ssa_operands (void)

{

  if (!n_initialized++)

    {

      build_defs = VEC_alloc (tree, heap, 5);

      build_uses = VEC_alloc (tree, heap, 10);

      build_vuse = NULL_TREE;

      build_vdef = NULL_TREE;

      bitmap_obstack_initialize (&operands_bitmap_obstack);

    }

  gcc_assert (gimple_ssa_operands (cfun)->operand_memory == NULL);

  gimple_ssa_operands (cfun)->operand_memory_index

     = gimple_ssa_operands (cfun)->ssa_operand_mem_size;

  gimple_ssa_operands (cfun)->ops_active = true;

  memset (&clobber_stats, 0, sizeof (clobber_stats));

  gimple_ssa_operands (cfun)->ssa_operand_mem_size = OP_SIZE_INIT;

  create_vop_var ();

}

/* Dispose of anything required by the operand routines.  */

void

fini_ssa_operands (void)

{

  struct ssa_operand_memory_d *ptr;

  if (!--n_initialized)

    {

      VEC_free (tree, heap, build_defs);

      VEC_free (tree, heap, build_uses);

      build_vdef = NULL_TREE;

      build_vuse = NULL_TREE;

    }

  gimple_ssa_operands (cfun)->free_defs = NULL;

  gimple_ssa_operands (cfun)->free_uses = NULL;

  while ((ptr = gimple_ssa_operands (cfun)->operand_memory) != NULL)

    {

      gimple_ssa_operands (cfun)->operand_memory

        = gimple_ssa_operands (cfun)->operand_memory->next;

      ggc_free (ptr);

    }

  gimple_ssa_operands (cfun)->ops_active = false;

  if (!n_initialized)

    bitmap_obstack_release (&operands_bitmap_obstack);

  cfun->gimple_df->vop = NULL_TREE;

  if (dump_file && (dump_flags & TDF_STATS))

    {

      fprintf (dump_file, "Original clobbered vars:           %d\n",

               clobber_stats.clobbered_vars);

      fprintf (dump_file, "Static write clobbers avoided:     %d\n",

               clobber_stats.static_write_clobbers_avoided);

      fprintf (dump_file, "Static read clobbers avoided:      %d\n",

               clobber_stats.static_read_clobbers_avoided);

      fprintf (dump_file, "Unescapable clobbers avoided:      %d\n",

               clobber_stats.unescapable_clobbers_avoided);

      fprintf (dump_file, "Original read-only clobbers:       %d\n",

               clobber_stats.readonly_clobbers);

      fprintf (dump_file, "Static read-only clobbers avoided: %d\n",

               clobber_stats.static_readonly_clobbers_avoided);

    }

}

/* Return memory for an operand of size SIZE.  */

static inline void *

ssa_operand_alloc (unsigned size)

{

  char *ptr;

  gcc_assert (size == sizeof (struct use_optype_d)

              || size == sizeof (struct def_optype_d));

  if (gimple_ssa_operands (cfun)->operand_memory_index + size

      >= gimple_ssa_operands (cfun)->ssa_operand_mem_size)

    {

      struct ssa_operand_memory_d *ptr;

      switch (gimple_ssa_operands (cfun)->ssa_operand_mem_size)

        {

        case OP_SIZE_INIT:

          gimple_ssa_operands (cfun)->ssa_operand_mem_size = OP_SIZE_1;

          break;

        case OP_SIZE_1:

          gimple_ssa_operands (cfun)->ssa_operand_mem_size = OP_SIZE_2;

          break;

        case OP_SIZE_2:

        case OP_SIZE_3:

          gimple_ssa_operands (cfun)->ssa_operand_mem_size = OP_SIZE_3;

          break;

        default:

          gcc_unreachable ();

        }

      ptr = (struct ssa_operand_memory_d *)

              ggc_alloc (sizeof (void *)

                         + gimple_ssa_operands (cfun)->ssa_operand_mem_size);

      ptr->next = gimple_ssa_operands (cfun)->operand_memory;

      gimple_ssa_operands (cfun)->operand_memory = ptr;

      gimple_ssa_operands (cfun)->operand_memory_index = 0;

    }

  ptr = &(gimple_ssa_operands (cfun)->operand_memory

          ->mem[gimple_ssa_operands (cfun)->operand_memory_index]);

  gimple_ssa_operands (cfun)->operand_memory_index += size;

  return ptr;

}

/* Allocate a DEF operand.  */

static inline struct def_optype_d *

alloc_def (void)

{

  struct def_optype_d *ret;

  if (gimple_ssa_operands (cfun)->free_defs)

    {

      ret = gimple_ssa_operands (cfun)->free_defs;

      gimple_ssa_operands (cfun)->free_defs

        = gimple_ssa_operands (cfun)->free_defs->next;

    }

  else

    ret = (struct def_optype_d *)

          ssa_operand_alloc (sizeof (struct def_optype_d));

  return ret;

}

/* Allocate a USE operand.  */

static inline struct use_optype_d *

alloc_use (void)

{

  struct use_optype_d *ret;

  if (gimple_ssa_operands (cfun)->free_uses)

    {

      ret = gimple_ssa_operands (cfun)->free_uses;

      gimple_ssa_operands (cfun)->free_uses

        = gimple_ssa_operands (cfun)->free_uses->next;

    }

  else

    ret = (struct use_optype_d *)

          ssa_operand_alloc (sizeof (struct use_optype_d));

  return ret;

}

/* Adds OP to the list of defs after LAST.  */

static inline def_optype_p

add_def_op (tree *op, def_optype_p last)

{

  def_optype_p new_def;

  new_def = alloc_def ();

  DEF_OP_PTR (new_def) = op;

  last->next = new_def;

  new_def->next = NULL;

  return new_def;

}

/* Adds OP to the list of uses of statement STMT after LAST.  */

static inline use_optype_p

add_use_op (gimple stmt, tree *op, use_optype_p last)

{

  use_optype_p new_use;

  new_use = alloc_use ();

  USE_OP_PTR (new_use)->use = op;

  link_imm_use_stmt (USE_OP_PTR (new_use), *op, stmt);

  last->next = new_use;

  new_use->next = NULL;

  return new_use;

}

/* Takes elements from build_defs and turns them into def operands of STMT.

   TODO -- Make build_defs VEC of tree *.  */

static inline void

finalize_ssa_defs (gimple stmt)

{

  unsigned new_i;

  struct def_optype_d new_list;

  def_optype_p old_ops, last;

  unsigned int num = VEC_length (tree, build_defs);

  /* There should only be a single real definition per assignment.  */

  gcc_assert ((stmt && gimple_code (stmt) != GIMPLE_ASSIGN) || num <= 1);

  /* Pre-pend the vdef we may have built.  */

  if (build_vdef != NULL_TREE)

    {

      tree oldvdef = gimple_vdef (stmt);

      if (oldvdef

          && TREE_CODE (oldvdef) == SSA_NAME)

        oldvdef = SSA_NAME_VAR (oldvdef);

      if (oldvdef != build_vdef)

        gimple_set_vdef (stmt, build_vdef);

      VEC_safe_insert (tree, heap, build_defs, 0, (tree)gimple_vdef_ptr (stmt));

      ++num;

    }

  new_list.next = NULL;

  last = &new_list;

  old_ops = gimple_def_ops (stmt);

  new_i = 0;

  /* Clear and unlink a no longer necessary VDEF.  */

  if (build_vdef == NULL_TREE

      && gimple_vdef (stmt) != NULL_TREE)

    {

      if (TREE_CODE (gimple_vdef (stmt)) == SSA_NAME)

        {

          unlink_stmt_vdef (stmt);

          release_ssa_name (gimple_vdef (stmt));

        }

      gimple_set_vdef (stmt, NULL_TREE);

    }

  /* If we have a non-SSA_NAME VDEF, mark it for renaming.  */

  if (gimple_vdef (stmt)

      && TREE_CODE (gimple_vdef (stmt)) != SSA_NAME)

    mark_sym_for_renaming (gimple_vdef (stmt));

  /* Check for the common case of 1 def that hasn't changed.  */

  if (old_ops && old_ops->next == NULL && num == 1

      && (tree *) VEC_index (tree, build_defs, 0) == DEF_OP_PTR (old_ops))

    return;

  /* If there is anything in the old list, free it.  */

  if (old_ops)

    {

      old_ops->next = gimple_ssa_operands (cfun)->free_defs;

      gimple_ssa_operands (cfun)->free_defs = old_ops;

    }

  /* If there is anything remaining in the build_defs list, simply emit it.  */

  for ( ; new_i < num; new_i++)

    last = add_def_op ((tree *) VEC_index (tree, build_defs, new_i), last);

  /* Now set the stmt's operands.  */

  gimple_set_def_ops (stmt, new_list.next);

}

/* Takes elements from build_uses and turns them into use operands of STMT.

   TODO -- Make build_uses VEC of tree *.  */

static inline void

finalize_ssa_uses (gimple stmt)

{

  unsigned new_i;

  struct use_optype_d new_list;

  use_optype_p old_ops, ptr, last;

  /* Pre-pend the VUSE we may have built.  */

  if (build_vuse != NULL_TREE)

    {

      tree oldvuse = gimple_vuse (stmt);

      if (oldvuse

          && TREE_CODE (oldvuse) == SSA_NAME)

        oldvuse = SSA_NAME_VAR (oldvuse);

      if (oldvuse != (build_vuse != NULL_TREE

                      ? build_vuse : build_vdef))

        gimple_set_vuse (stmt, NULL_TREE);

      VEC_safe_insert (tree, heap, build_uses, 0, (tree)gimple_vuse_ptr (stmt));

    }

  new_list.next = NULL;

  last = &new_list;

  old_ops = gimple_use_ops (stmt);

  /* Clear a no longer necessary VUSE.  */

  if (build_vuse == NULL_TREE

      && gimple_vuse (stmt) != NULL_TREE)

    gimple_set_vuse (stmt, NULL_TREE);

  /* If there is anything in the old list, free it.  */

  if (old_ops)

    {

      for (ptr = old_ops; ptr; ptr = ptr->next)

        delink_imm_use (USE_OP_PTR (ptr));

      old_ops->next = gimple_ssa_operands (cfun)->free_uses;

      gimple_ssa_operands (cfun)->free_uses = old_ops;

    }

  /* If we added a VUSE, make sure to set the operand if it is not already

     present and mark it for renaming.  */

  if (build_vuse != NULL_TREE

      && gimple_vuse (stmt) == NULL_TREE)

    {

      gimple_set_vuse (stmt, gimple_vop (cfun));

      mark_sym_for_renaming (gimple_vop (cfun));

    }

  /* Now create nodes for all the new nodes.  */

  for (new_i = 0; new_i < VEC_length (tree, build_uses); new_i++)

    last = add_use_op (stmt,

                       (tree *) VEC_index (tree, build_uses, new_i),

                       last);

  /* Now set the stmt's operands.  */

  gimple_set_use_ops (stmt, new_list.next);

}

/* Clear the in_list bits and empty the build array for VDEFs and

   VUSEs.  */

static inline void

cleanup_build_arrays (void)

{

  build_vdef = NULL_TREE;

  build_vuse = NULL_TREE;

  VEC_truncate (tree, build_defs, 0);

  VEC_truncate (tree, build_uses, 0);

}

/* Finalize all the build vectors, fill the new ones into INFO.  */

static inline void

finalize_ssa_stmt_operands (gimple stmt)

{

  finalize_ssa_defs (stmt);

  finalize_ssa_uses (stmt);

  cleanup_build_arrays ();

}

/* Start the process of building up operands vectors in INFO.  */

static inline void

start_ssa_stmt_operands (void)

{

  gcc_assert (VEC_length (tree, build_defs) == 0);

  gcc_assert (VEC_length (tree, build_uses) == 0);

  gcc_assert (build_vuse == NULL_TREE);

  gcc_assert (build_vdef == NULL_TREE);

}

/* Add DEF_P to the list of pointers to operands.  */

static inline void

append_def (tree *def_p)

{

  VEC_safe_push (tree, heap, build_defs, (tree) def_p);

}

/* Add USE_P to the list of pointers to operands.  */

static inline void

append_use (tree *use_p)

{

  VEC_safe_push (tree, heap, build_uses, (tree) use_p);

}

/* Add VAR to the set of variables that require a VDEF operator.  */

static inline void

append_vdef (tree var)

{

  if (!optimize)

    return;

  gcc_assert ((build_vdef == NULL_TREE

               || build_vdef == var)

              && (build_vuse == NULL_TREE

                  || build_vuse == var));

  build_vdef = var;

  build_vuse = var;

}

/* Add VAR to the set of variables that require a VUSE operator.  */

static inline void

append_vuse (tree var)

{

  if (!optimize)

    return;

  gcc_assert (build_vuse == NULL_TREE

              || build_vuse == var);

  build_vuse = var;

}

/* Add virtual operands for STMT.  FLAGS is as in get_expr_operands.  */

static void

add_virtual_operand (gimple stmt ATTRIBUTE_UNUSED, int flags)

{

  /* Add virtual operands to the stmt, unless the caller has specifically

     requested not to do that (used when adding operands inside an

     ADDR_EXPR expression).  */

  if (flags & opf_no_vops)

    return;

  gcc_assert (!is_gimple_debug (stmt));

  if (flags & opf_def)

    append_vdef (gimple_vop (cfun));

  else

    append_vuse (gimple_vop (cfun));

}

/* Add *VAR_P to the appropriate operand array for statement STMT.

   FLAGS is as in get_expr_operands.  If *VAR_P is a GIMPLE register,

   it will be added to the statement's real operands, otherwise it is

   added to virtual operands.  */

static void

add_stmt_operand (tree *var_p, gimple stmt, int flags)

{

  tree var, sym;

  gcc_assert (SSA_VAR_P (*var_p));

  var = *var_p;

  sym = (TREE_CODE (var) == SSA_NAME ? SSA_NAME_VAR (var) : var);

  /* Mark statements with volatile operands.  */

  if (TREE_THIS_VOLATILE (sym))

    gimple_set_has_volatile_ops (stmt, true);

  if (is_gimple_reg (sym))

    {

      /* The variable is a GIMPLE register.  Add it to real operands.  */

      if (flags & opf_def)

        append_def (var_p);

      else

        append_use (var_p);

    }

  else

    add_virtual_operand (stmt, flags);

}

/* Mark the base address of REF as having its address taken.

   REF may be a single variable whose address has been taken or any

   other valid GIMPLE memory reference (structure reference, array,

   etc).  */

static void

mark_address_taken (tree ref)

{

  tree var;

  /* Note that it is *NOT OKAY* to use the target of a COMPONENT_REF

     as the only thing we take the address of.  If VAR is a structure,

     taking the address of a field means that the whole structure may

     be referenced using pointer arithmetic.  See PR 21407 and the

     ensuing mailing list discussion.  */

  var = get_base_address (ref);

  if (var && DECL_P (var))

    TREE_ADDRESSABLE (var) = 1;

}

/* A subroutine of get_expr_operands to handle INDIRECT_REF,

   ALIGN_INDIRECT_REF and MISALIGNED_INDIRECT_REF.

   STMT is the statement being processed, EXPR is the INDIRECT_REF

      that got us here.

   FLAGS is as in get_expr_operands.

   RECURSE_ON_BASE should be set to true if we want to continue

      calling get_expr_operands on the base pointer, and false if

      something else will do it for us.  */

static void

get_indirect_ref_operands (gimple stmt, tree expr, int flags,

                           bool recurse_on_base)

{

  tree *pptr = &TREE_OPERAND (expr, 0);

  if (TREE_THIS_VOLATILE (expr))

    gimple_set_has_volatile_ops (stmt, true);

  /* Add the VOP.  */

  add_virtual_operand (stmt, flags);

  /* If requested, add a USE operand for the base pointer.  */

  if (recurse_on_base)

    get_expr_operands (stmt, pptr,

                       opf_use | (flags & opf_no_vops));

}

/* A subroutine of get_expr_operands to handle TARGET_MEM_REF.  */