gcc/gcc/tree-data-ref.h

/* Data references and dependences detectors. 
   Copyright (C) 2003, 2004, 2005, 2006 Free Software Foundation, Inc.
   Contributed by Sebastian Pop <pop@cri.ensmp.fr>

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.  */

#ifndef GCC_TREE_DATA_REF_H
#define GCC_TREE_DATA_REF_H

#include "lambda.h"

/*
  The first location accessed by data-ref in the loop is the address of data-ref's 
  base (BASE_ADDRESS) plus the initial offset from the base. We divide the initial offset 
  into two parts: loop invariant offset (OFFSET) and constant offset (INIT). 
  STEP is the stride of data-ref in the loop in bytes.

                       Example 1                      Example 2
      data-ref         a[j].b[i][j]                   a + x + 16B (a is int*)
      
  First location info:
      base_address     &a                             a
      offset           j_0*D_j + i_0*D_i              x
      init             C_b + C_a                      16
      step             D_j                            4
      access_fn        NULL                           {16, +, 1}

  Base object info:
      base_object      a                              NULL
      access_fn        <access_fns of indexes of b>   NULL

  */
struct first_location_in_loop
{
  tree base_address;
  tree offset;
  tree init;
  tree step;
  /* Access function related to first location in the loop.  */
  VEC(tree,heap) *access_fns;
};

struct base_object_info
{
  /* The object.  */
  tree base_object;
  
  /* A list of chrecs.  Access functions related to BASE_OBJECT.  */
  VEC(tree,heap) *access_fns;
};

enum data_ref_type {
  ARRAY_REF_TYPE,
  POINTER_REF_TYPE
};

struct data_reference
{
  /* A pointer to the statement that contains this DR.  */
  tree stmt;
  
  /* A pointer to the ARRAY_REF node.  */
  tree ref;

  /* Auxiliary info specific to a pass.  */
  int aux;

  /* True when the data reference is in RHS of a stmt.  */
  bool is_read;

  /* First location accessed by the data-ref in the loop.  */
  struct first_location_in_loop first_location;

  /* Base object related info.  */
  struct base_object_info object_info;

  /* Aliasing information.  This field represents the symbol that
     should be aliased by a pointer holding the address of this data
     reference.  If the original data reference was a pointer
     dereference, then this field contains the memory tag that should
     be used by the new vector-pointer.  */
  tree memtag;
  struct ptr_info_def *ptr_info;
  subvar_t subvars;

  /* Alignment information.  
     MISALIGNMENT is the offset of the data-reference from its base in bytes.
     ALIGNED_TO is the maximum data-ref's alignment.  

     Example 1, 
       for i
          for (j = 3; j < N; j++)
            a[j].b[i][j] = 0;
	 
     For a[j].b[i][j], the offset from base (calculated in get_inner_reference() 
     will be 'i * C_i + j * C_j + C'. 
     We try to substitute the variables of the offset expression
     with initial_condition of the corresponding access_fn in the loop.
     'i' cannot be substituted, since its access_fn in the inner loop is i. 'j' 
     will be substituted with 3. 

     Example 2
        for (j = 3; j < N; j++)
          a[j].b[5][j] = 0; 

     Here the offset expression (j * C_j + C) will not contain variables after
     substitution of j=3 (3*C_j + C).

     Misalignment can be calculated only if all the variables can be 
     substituted with constants, otherwise, we record maximum possible alignment
     in ALIGNED_TO. In Example 1, since 'i' cannot be substituted, 
     MISALIGNMENT will be NULL_TREE, and the biggest divider of C_i (a power of 
     2) will be recorded in ALIGNED_TO.

     In Example 2, MISALIGNMENT will be the value of 3*C_j + C in bytes, and 
     ALIGNED_TO will be NULL_TREE.
  */
  tree misalignment;
  tree aligned_to;

  /* The type of the data-ref.  */
  enum data_ref_type type;
};

typedef struct data_reference *data_reference_p;
DEF_VEC_P(data_reference_p);
DEF_VEC_ALLOC_P (data_reference_p, heap);

#define DR_STMT(DR)                (DR)->stmt
#define DR_REF(DR)                 (DR)->ref
#define DR_BASE_OBJECT(DR)         (DR)->object_info.base_object
#define DR_TYPE(DR)                (DR)->type
#define DR_ACCESS_FNS(DR)\
  (DR_TYPE(DR) == ARRAY_REF_TYPE ?  \
   (DR)->object_info.access_fns : (DR)->first_location.access_fns)
#define DR_ACCESS_FN(DR, I)        VEC_index (tree, DR_ACCESS_FNS (DR), I)
#define DR_NUM_DIMENSIONS(DR)      VEC_length (tree, DR_ACCESS_FNS (DR))  
#define DR_IS_READ(DR)             (DR)->is_read
#define DR_BASE_ADDRESS(DR)        (DR)->first_location.base_address
#define DR_OFFSET(DR)              (DR)->first_location.offset
#define DR_INIT(DR)                (DR)->first_location.init
#define DR_STEP(DR)                (DR)->first_location.step
#define DR_MEMTAG(DR)              (DR)->memtag
#define DR_ALIGNED_TO(DR)          (DR)->aligned_to
#define DR_OFFSET_MISALIGNMENT(DR) (DR)->misalignment
#define DR_PTR_INFO(DR)            (DR)->ptr_info
#define DR_SUBVARS(DR)             (DR)->subvars

#define DR_ACCESS_FNS_ADDR(DR)       \
  (DR_TYPE(DR) == ARRAY_REF_TYPE ?   \
   &((DR)->object_info.access_fns) : &((DR)->first_location.access_fns))
#define DR_SET_ACCESS_FNS(DR, ACC_FNS)         \
{                                              \
  if (DR_TYPE(DR) == ARRAY_REF_TYPE)           \
    (DR)->object_info.access_fns = ACC_FNS;    \
  else                                         \
    (DR)->first_location.access_fns = ACC_FNS; \
}
#define DR_FREE_ACCESS_FNS(DR)                              \
{                                                           \
  if (DR_TYPE(DR) == ARRAY_REF_TYPE)                        \
    VEC_free (tree, heap, (DR)->object_info.access_fns);    \
  else                                                      \
    VEC_free (tree, heap, (DR)->first_location.access_fns); \
}

enum data_dependence_direction {
  dir_positive, 
  dir_negative, 
  dir_equal, 
  dir_positive_or_negative,
  dir_positive_or_equal,
  dir_negative_or_equal,
  dir_star,
  dir_independent
};

/* The description of the grid of iterations that overlap.  At most
   two loops are considered at the same time just now, hence at most
   two functions are needed.  For each of the functions, we store
   the vector of coefficients, f[0] + x * f[1] + y * f[2] + ...,
   where x, y, ... are variables.  */

#define MAX_DIM 2

/* Special values of N.  */
#define NO_DEPENDENCE 0
#define NOT_KNOWN (MAX_DIM + 1)
#define CF_NONTRIVIAL_P(CF) ((CF)->n != NO_DEPENDENCE && (CF)->n != NOT_KNOWN)
#define CF_NOT_KNOWN_P(CF) ((CF)->n == NOT_KNOWN)
#define CF_NO_DEPENDENCE_P(CF) ((CF)->n == NO_DEPENDENCE)

typedef VEC (tree, heap) *affine_fn;

typedef struct
{
  unsigned n;
  affine_fn fns[MAX_DIM];
} conflict_function;

/* What is a subscript?  Given two array accesses a subscript is the
   tuple composed of the access functions for a given dimension.
   Example: Given A[f1][f2][f3] and B[g1][g2][g3], there are three
   subscripts: (f1, g1), (f2, g2), (f3, g3).  These three subscripts
   are stored in the data_dependence_relation structure under the form
   of an array of subscripts.  */

struct subscript
{
  /* A description of the iterations for which the elements are
     accessed twice.  */
  conflict_function *conflicting_iterations_in_a;
  conflict_function *conflicting_iterations_in_b;
  
  /* This field stores the information about the iteration domain
     validity of the dependence relation.  */
  tree last_conflict;
  
  /* Distance from the iteration that access a conflicting element in
     A to the iteration that access this same conflicting element in
     B.  The distance is a tree scalar expression, i.e. a constant or a
     symbolic expression, but certainly not a chrec function.  */
  tree distance;
};

typedef struct subscript *subscript_p;
DEF_VEC_P(subscript_p);
DEF_VEC_ALLOC_P (subscript_p, heap);

#define SUB_CONFLICTS_IN_A(SUB) SUB->conflicting_iterations_in_a
#define SUB_CONFLICTS_IN_B(SUB) SUB->conflicting_iterations_in_b
#define SUB_LAST_CONFLICT(SUB) SUB->last_conflict
#define SUB_DISTANCE(SUB) SUB->distance

/* A data_dependence_relation represents a relation between two
   data_references A and B.  */

struct data_dependence_relation
{
  
  struct data_reference *a;
  struct data_reference *b;

  /* When the dependence relation is affine, it can be represented by
     a distance vector.  */
  bool affine_p;

  /* A "yes/no/maybe" field for the dependence relation:
     
     - when "ARE_DEPENDENT == NULL_TREE", there exist a dependence
       relation between A and B, and the description of this relation
       is given in the SUBSCRIPTS array,
     
     - when "ARE_DEPENDENT == chrec_known", there is no dependence and
       SUBSCRIPTS is empty,
     
     - when "ARE_DEPENDENT == chrec_dont_know", there may be a dependence,
       but the analyzer cannot be more specific.  */
  tree are_dependent;
  
  /* For each subscript in the dependence test, there is an element in
     this array.  This is the attribute that labels the edge A->B of
     the data_dependence_relation.  */
  VEC (subscript_p, heap) *subscripts;

  /* The analyzed loop nest.  */
  VEC (loop_p, heap) *loop_nest;

  /* The classic direction vector.  */
  VEC (lambda_vector, heap) *dir_vects;

  /* The classic distance vector.  */
  VEC (lambda_vector, heap) *dist_vects;
};

typedef struct data_dependence_relation *ddr_p;
DEF_VEC_P(ddr_p);
DEF_VEC_ALLOC_P(ddr_p,heap);

#define DDR_A(DDR) DDR->a
#define DDR_B(DDR) DDR->b
#define DDR_AFFINE_P(DDR) DDR->affine_p
#define DDR_ARE_DEPENDENT(DDR) DDR->are_dependent
#define DDR_SUBSCRIPTS(DDR) DDR->subscripts
#define DDR_SUBSCRIPT(DDR, I) VEC_index (subscript_p, DDR_SUBSCRIPTS (DDR), I)
#define DDR_NUM_SUBSCRIPTS(DDR) VEC_length (subscript_p, DDR_SUBSCRIPTS (DDR))

#define DDR_LOOP_NEST(DDR) DDR->loop_nest
/* The size of the direction/distance vectors: the number of loops in
   the loop nest.  */
#define DDR_NB_LOOPS(DDR) (VEC_length (loop_p, DDR_LOOP_NEST (DDR)))

#define DDR_DIST_VECTS(DDR) ((DDR)->dist_vects)
#define DDR_DIR_VECTS(DDR) ((DDR)->dir_vects)
#define DDR_NUM_DIST_VECTS(DDR) \
  (VEC_length (lambda_vector, DDR_DIST_VECTS (DDR)))
#define DDR_NUM_DIR_VECTS(DDR) \
  (VEC_length (lambda_vector, DDR_DIR_VECTS (DDR)))
#define DDR_DIR_VECT(DDR, I) \
  VEC_index (lambda_vector, DDR_DIR_VECTS (DDR), I)
#define DDR_DIST_VECT(DDR, I) \
  VEC_index (lambda_vector, DDR_DIST_VECTS (DDR), I)



/* Describes a location of a memory reference.  */

typedef struct data_ref_loc_d
{
  /* Position of the memory reference.  */
  tree *pos;

  /* True if the memory reference is read.  */
  bool is_read;
} data_ref_loc;

DEF_VEC_O (data_ref_loc);
DEF_VEC_ALLOC_O (data_ref_loc, heap);

bool get_references_in_stmt (tree, VEC (data_ref_loc, heap) **);
extern tree find_data_references_in_loop (struct loop *,
					  VEC (data_reference_p, heap) **);
extern void compute_data_dependences_for_loop (struct loop *, bool,
					       VEC (data_reference_p, heap) **,
					       VEC (ddr_p, heap) **);
extern void print_direction_vector (FILE *, lambda_vector, int);
extern void print_dir_vectors (FILE *, VEC (lambda_vector, heap) *, int);
extern void print_dist_vectors (FILE *, VEC (lambda_vector, heap) *, int);
extern void dump_subscript (FILE *, struct subscript *);
extern void dump_ddrs (FILE *, VEC (ddr_p, heap) *);
extern void dump_dist_dir_vectors (FILE *, VEC (ddr_p, heap) *);
extern void dump_data_reference (FILE *, struct data_reference *);
extern void dump_data_references (FILE *, VEC (data_reference_p, heap) *);
extern void debug_data_dependence_relation (struct data_dependence_relation *);
extern void dump_data_dependence_relation (FILE *, 
					   struct data_dependence_relation *);
extern void dump_data_dependence_relations (FILE *, VEC (ddr_p, heap) *);
extern void dump_data_dependence_direction (FILE *, 
					    enum data_dependence_direction);
extern void free_dependence_relation (struct data_dependence_relation *);
extern void free_dependence_relations (VEC (ddr_p, heap) *);
extern void free_data_refs (VEC (data_reference_p, heap) *);
extern struct data_reference *analyze_array (tree, tree, bool);


/* Return the index of the variable VAR in the LOOP_NEST array.  */

static inline int
index_in_loop_nest (int var, VEC (loop_p, heap) *loop_nest)
{
  struct loop *loopi;
  int var_index;

  for (var_index = 0; VEC_iterate (loop_p, loop_nest, var_index, loopi);
       var_index++)
    if (loopi->num == var)
      break;

  return var_index;
}

/* In lambda-code.c  */
bool lambda_transform_legal_p (lambda_trans_matrix, int, VEC (ddr_p, heap) *);

#endif  /* GCC_TREE_DATA_REF_H  */