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/* Data references and dependences detectors.
Copyright (C) 2003-2015 Free Software Foundation, Inc.
Contributed by Sebastian Pop <>
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
GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
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
<>. */
#include "graphds.h"
#include "omega.h"
#include "tree-chrec.h"
innermost_loop_behavior describes the evolution of the address of the memory
reference in the innermost enclosing loop. The address is expressed as
BASE + STEP * # of iteration, and base is further decomposed as the base
pointer (BASE_ADDRESS), loop invariant offset (OFFSET) and
constant offset (INIT). Examples, in loop nest
for (i = 0; i < 100; i++)
for (j = 3; j < 100; j++)
Example 1 Example 2
data-ref a[j].b[i][j] *(p + x + 16B + 4B * j)
base_address &a p
offset i * D_i x
init 3 * D_j + offsetof (b) 28
step D_j 4
struct innermost_loop_behavior
tree base_address;
tree offset;
tree init;
tree step;
/* Alignment information. ALIGNED_TO is set to the largest power of two
that divides OFFSET. */
tree aligned_to;
/* Describes the evolutions of indices of the memory reference. The indices
are indices of the ARRAY_REFs, indexes in artificial dimensions
added for member selection of records and the operands of MEM_REFs.
BASE_OBJECT is the part of the reference that is loop-invariant
(note that this reference does not have to cover the whole object
being accessed, in which case UNCONSTRAINED_BASE is set; hence it is
not recommended to use BASE_OBJECT in any code generation).
For the examples above,
base_object: a *(p + x + 4B * j_0)
indices: {j_0, +, 1}_2 {16, +, 4}_2
{i_0, +, 1}_1
{j_0, +, 1}_2
struct indices
/* The object. */
tree base_object;
/* A list of chrecs. Access functions of the indices. */
vec<tree> access_fns;
/* Whether BASE_OBJECT is an access representing the whole object
or whether the access could not be constrained. */
bool unconstrained_base;
struct dr_alias
/* The alias information that should be used for new pointers to this
location. */
struct ptr_info_def *ptr_info;
/* An integer vector. A vector formally consists of an element of a vector
space. A vector space is a set that is closed under vector addition
and scalar multiplication. In this vector space, an element is a list of
integers. */
typedef int *lambda_vector;
/* An integer matrix. A matrix consists of m vectors of length n (IE
all vectors are the same length). */
typedef lambda_vector *lambda_matrix;
struct data_reference
/* A pointer to the statement that contains this DR. */
gimple stmt;
/* A pointer to the memory reference. */
tree ref;
/* Auxiliary info specific to a pass. */
void *aux;
/* True when the data reference is in RHS of a stmt. */
bool is_read;
/* Behavior of the memory reference in the innermost loop. */
struct innermost_loop_behavior innermost;
/* Subscripts of this data reference. */
struct indices indices;
/* Alias information for the data reference. */
struct dr_alias alias;
#define DR_STMT(DR) (DR)->stmt
#define DR_REF(DR) (DR)->ref
#define DR_BASE_OBJECT(DR) (DR)->indices.base_object
#define DR_UNCONSTRAINED_BASE(DR) (DR)->indices.unconstrained_base
#define DR_ACCESS_FNS(DR) (DR)->indices.access_fns
#define DR_IS_READ(DR) (DR)->is_read
#define DR_IS_WRITE(DR) (!DR_IS_READ (DR))
#define DR_BASE_ADDRESS(DR) (DR)->innermost.base_address
#define DR_OFFSET(DR) (DR)->innermost.offset
#define DR_INIT(DR) (DR)->innermost.init
#define DR_STEP(DR) (DR)->innermost.step
#define DR_PTR_INFO(DR) (DR)->alias.ptr_info
#define DR_ALIGNED_TO(DR) (DR)->innermost.aligned_to
typedef struct data_reference *data_reference_p;
enum data_dependence_direction {
/* 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 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)
typedef vec<tree> affine_fn;
struct conflict_function
unsigned n;
affine_fn fns[MAX_DIM];
/* 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;
#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;
/* 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> subscripts;
/* The analyzed loop nest. */
vec<loop_p> loop_nest;
/* The classic direction vector. */
vec<lambda_vector> dir_vects;
/* The classic distance vector. */
vec<lambda_vector> dist_vects;
/* An index in loop_nest for the innermost loop that varies for
this data dependence relation. */
unsigned inner_loop;
/* Is the dependence reversed with respect to the lexicographic order? */
bool reversed_p;
/* When the dependence relation is affine, it can be represented by
a distance vector. */
bool affine_p;
/* Set to true when the dependence relation is on the same data
access. */
bool self_reference_p;
typedef struct data_dependence_relation *ddr_p;
#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_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) (DDR_LOOP_NEST (DDR).length ())
#define DDR_INNER_LOOP(DDR) DDR->inner_loop
#define DDR_SELF_REFERENCE(DDR) DDR->self_reference_p
#define DDR_DIST_VECTS(DDR) ((DDR)->dist_vects)
#define DDR_DIR_VECTS(DDR) ((DDR)->dir_vects)
(DDR_DIST_VECTS (DDR).length ())
(DDR_DIR_VECTS (DDR).length ())
#define DDR_DIR_VECT(DDR, I) \
#define DDR_DIST_VECT(DDR, I) \
#define DDR_REVERSED_P(DDR) DDR->reversed_p
bool dr_analyze_innermost (struct data_reference *, struct loop *);
extern bool compute_data_dependences_for_loop (struct loop *, bool,
vec<loop_p> *,
vec<data_reference_p> *,
vec<ddr_p> *);
extern bool compute_data_dependences_for_bb (basic_block, bool,
vec<data_reference_p> *,
vec<ddr_p> *);
extern void debug_ddrs (vec<ddr_p> );
extern void dump_data_reference (FILE *, struct data_reference *);
extern void debug (data_reference &ref);
extern void debug (data_reference *ptr);
extern void debug_data_reference (struct data_reference *);
extern void debug_data_references (vec<data_reference_p> );
extern void debug (vec<data_reference_p> &ref);
extern void debug (vec<data_reference_p> *ptr);
extern void debug_data_dependence_relation (struct data_dependence_relation *);
extern void dump_data_dependence_relations (FILE *, vec<ddr_p> );
extern void debug (vec<ddr_p> &ref);
extern void debug (vec<ddr_p> *ptr);
extern void debug_data_dependence_relations (vec<ddr_p> );
extern void free_dependence_relation (struct data_dependence_relation *);
extern void free_dependence_relations (vec<ddr_p> );
extern void free_data_ref (data_reference_p);
extern void free_data_refs (vec<data_reference_p> );
extern bool find_data_references_in_stmt (struct loop *, gimple,
vec<data_reference_p> *);
extern bool graphite_find_data_references_in_stmt (loop_p, loop_p, gimple,
vec<data_reference_p> *);
tree find_data_references_in_loop (struct loop *, vec<data_reference_p> *);
struct data_reference *create_data_ref (loop_p, loop_p, tree, gimple, bool);
extern bool find_loop_nest (struct loop *, vec<loop_p> *);
extern struct data_dependence_relation *initialize_data_dependence_relation
(struct data_reference *, struct data_reference *, vec<loop_p>);
extern void compute_affine_dependence (struct data_dependence_relation *,
extern void compute_self_dependence (struct data_dependence_relation *);
extern bool compute_all_dependences (vec<data_reference_p> ,
vec<ddr_p> *,
vec<loop_p>, bool);
extern tree find_data_references_in_bb (struct loop *, basic_block,
vec<data_reference_p> *);
extern bool dr_may_alias_p (const struct data_reference *,
const struct data_reference *, bool);
extern bool dr_equal_offsets_p (struct data_reference *,
struct data_reference *);
extern void tree_check_data_deps (void);
/* Return true when the base objects of data references A and B are
the same memory object. */
static inline bool
same_data_refs_base_objects (data_reference_p a, data_reference_p b)
&& operand_equal_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b), 0);
/* Return true when the data references A and B are accessing the same
memory object with the same access functions. */
static inline bool
same_data_refs (data_reference_p a, data_reference_p b)
unsigned int i;
/* The references are exactly the same. */
if (operand_equal_p (DR_REF (a), DR_REF (b), 0))
return true;
if (!same_data_refs_base_objects (a, b))
return false;
for (i = 0; i < DR_NUM_DIMENSIONS (a); i++)
if (!eq_evolutions_p (DR_ACCESS_FN (a, i), DR_ACCESS_FN (b, i)))
return false;
return true;
/* Return true when the DDR contains two data references that have the
same access functions. */
static inline bool
same_access_functions (const struct data_dependence_relation *ddr)
unsigned i;
for (i = 0; i < DDR_NUM_SUBSCRIPTS (ddr); i++)
if (!eq_evolutions_p (DR_ACCESS_FN (DDR_A (ddr), i),
DR_ACCESS_FN (DDR_B (ddr), i)))
return false;
return true;
/* Returns true when all the dependences are computable. */
inline bool
known_dependences_p (vec<ddr_p> dependence_relations)
ddr_p ddr;
unsigned int i;
FOR_EACH_VEC_ELT (dependence_relations, i, ddr)
if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know)
return false;
return true;
/* Returns the dependence level for a vector DIST of size LENGTH.
LEVEL = 0 means a lexicographic dependence, i.e. a dependence due
to the sequence of statements, not carried by any loop. */
static inline unsigned
dependence_level (lambda_vector dist_vect, int length)
int i;
for (i = 0; i < length; i++)
if (dist_vect[i] != 0)
return i + 1;
return 0;
/* Return the dependence level for the DDR relation. */
static inline unsigned
ddr_dependence_level (ddr_p ddr)
unsigned vector;
unsigned level = 0;
if (DDR_DIST_VECTS (ddr).exists ())
level = dependence_level (DDR_DIST_VECT (ddr, 0), DDR_NB_LOOPS (ddr));
for (vector = 1; vector < DDR_NUM_DIST_VECTS (ddr); vector++)
level = MIN (level, dependence_level (DDR_DIST_VECT (ddr, vector),
DDR_NB_LOOPS (ddr)));
return level;
/* Return the index of the variable VAR in the LOOP_NEST array. */
static inline int
index_in_loop_nest (int var, vec<loop_p> loop_nest)
struct loop *loopi;
int var_index;
for (var_index = 0; loop_nest.iterate (var_index, &loopi);
if (loopi->num == var)
return var_index;
/* Returns true when the data reference DR the form "A[i] = ..."
with a stride equal to its unit type size. */
static inline bool
adjacent_dr_p (struct data_reference *dr)
/* If this is a bitfield store bail out. */
return false;
if (!DR_STEP (dr)
return false;
return tree_int_cst_equal (fold_unary (ABS_EXPR, TREE_TYPE (DR_STEP (dr)),
DR_STEP (dr)),
void split_constant_offset (tree , tree *, tree *);
/* Compute the greatest common divisor of a VECTOR of SIZE numbers. */
static inline int
lambda_vector_gcd (lambda_vector vector, int size)
int i;
int gcd1 = 0;
if (size > 0)
gcd1 = vector[0];
for (i = 1; i < size; i++)
gcd1 = gcd (gcd1, vector[i]);
return gcd1;
/* Allocate a new vector of given SIZE. */
static inline lambda_vector
lambda_vector_new (int size)
/* ??? We shouldn't abuse the GC allocator here. */
return ggc_cleared_vec_alloc<int> (size);
/* Clear out vector VEC1 of length SIZE. */
static inline void
lambda_vector_clear (lambda_vector vec1, int size)
memset (vec1, 0, size * sizeof (*vec1));
/* Returns true when the vector V is lexicographically positive, in
other words, when the first nonzero element is positive. */
static inline bool
lambda_vector_lexico_pos (lambda_vector v,
unsigned n)
unsigned i;
for (i = 0; i < n; i++)
if (v[i] == 0)
if (v[i] < 0)
return false;
if (v[i] > 0)
return true;
return true;
/* Return true if vector VEC1 of length SIZE is the zero vector. */
static inline bool
lambda_vector_zerop (lambda_vector vec1, int size)
int i;
for (i = 0; i < size; i++)
if (vec1[i] != 0)
return false;
return true;
/* Allocate a matrix of M rows x N cols. */
static inline lambda_matrix
lambda_matrix_new (int m, int n, struct obstack *lambda_obstack)
lambda_matrix mat;
int i;
mat = XOBNEWVEC (lambda_obstack, lambda_vector, m);
for (i = 0; i < m; i++)
mat[i] = XOBNEWVEC (lambda_obstack, int, n);
return mat;
#endif /* GCC_TREE_DATA_REF_H */