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Diffstat (limited to 'gcc/tree-parloops.c')
| -rw-r--r-- | gcc/tree-parloops.c | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/gcc/tree-parloops.c b/gcc/tree-parloops.c index 96759cb..9a11f80 100644 --- a/gcc/tree-parloops.c +++ b/gcc/tree-parloops.c @@ -240,6 +240,125 @@ name_to_copy_elt_hash (const void *aa) return (hashval_t) a->version; } +/* A transformation matrix, which is a self-contained ROWSIZE x COLSIZE + matrix. Rather than use floats, we simply keep a single DENOMINATOR that + represents the denominator for every element in the matrix. */ +typedef struct lambda_trans_matrix_s +{ + lambda_matrix matrix; + int rowsize; + int colsize; + int denominator; +} *lambda_trans_matrix; +#define LTM_MATRIX(T) ((T)->matrix) +#define LTM_ROWSIZE(T) ((T)->rowsize) +#define LTM_COLSIZE(T) ((T)->colsize) +#define LTM_DENOMINATOR(T) ((T)->denominator) + +/* Allocate a new transformation matrix. */ + +static lambda_trans_matrix +lambda_trans_matrix_new (int colsize, int rowsize, + struct obstack * lambda_obstack) +{ + lambda_trans_matrix ret; + + ret = (lambda_trans_matrix) + obstack_alloc (lambda_obstack, sizeof (struct lambda_trans_matrix_s)); + LTM_MATRIX (ret) = lambda_matrix_new (rowsize, colsize, lambda_obstack); + LTM_ROWSIZE (ret) = rowsize; + LTM_COLSIZE (ret) = colsize; + LTM_DENOMINATOR (ret) = 1; + return ret; +} + +/* Multiply a vector VEC by a matrix MAT. + MAT is an M*N matrix, and VEC is a vector with length N. The result + is stored in DEST which must be a vector of length M. */ + +static void +lambda_matrix_vector_mult (lambda_matrix matrix, int m, int n, + lambda_vector vec, lambda_vector dest) +{ + int i, j; + + lambda_vector_clear (dest, m); + for (i = 0; i < m; i++) + for (j = 0; j < n; j++) + dest[i] += matrix[i][j] * vec[j]; +} + +/* Return true if TRANS is a legal transformation matrix that respects + the dependence vectors in DISTS and DIRS. The conservative answer + is false. + + "Wolfe proves that a unimodular transformation represented by the + matrix T is legal when applied to a loop nest with a set of + lexicographically non-negative distance vectors RDG if and only if + for each vector d in RDG, (T.d >= 0) is lexicographically positive. + i.e.: if and only if it transforms the lexicographically positive + distance vectors to lexicographically positive vectors. Note that + a unimodular matrix must transform the zero vector (and only it) to + the zero vector." S.Muchnick. */ + +static bool +lambda_transform_legal_p (lambda_trans_matrix trans, + int nb_loops, + VEC (ddr_p, heap) *dependence_relations) +{ + unsigned int i, j; + lambda_vector distres; + struct data_dependence_relation *ddr; + + gcc_assert (LTM_COLSIZE (trans) == nb_loops + && LTM_ROWSIZE (trans) == nb_loops); + + /* When there are no dependences, the transformation is correct. */ + if (VEC_length (ddr_p, dependence_relations) == 0) + return true; + + ddr = VEC_index (ddr_p, dependence_relations, 0); + if (ddr == NULL) + return true; + + /* When there is an unknown relation in the dependence_relations, we + know that it is no worth looking at this loop nest: give up. */ + if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know) + return false; + + distres = lambda_vector_new (nb_loops); + + /* For each distance vector in the dependence graph. */ + FOR_EACH_VEC_ELT (ddr_p, dependence_relations, i, ddr) + { + /* Don't care about relations for which we know that there is no + dependence, nor about read-read (aka. output-dependences): + these data accesses can happen in any order. */ + if (DDR_ARE_DEPENDENT (ddr) == chrec_known + || (DR_IS_READ (DDR_A (ddr)) && DR_IS_READ (DDR_B (ddr)))) + continue; + + /* Conservatively answer: "this transformation is not valid". */ + if (DDR_ARE_DEPENDENT (ddr) == chrec_dont_know) + return false; + + /* If the dependence could not be captured by a distance vector, + conservatively answer that the transform is not valid. */ + if (DDR_NUM_DIST_VECTS (ddr) == 0) + return false; + + /* Compute trans.dist_vect */ + for (j = 0; j < DDR_NUM_DIST_VECTS (ddr); j++) + { + lambda_matrix_vector_mult (LTM_MATRIX (trans), nb_loops, nb_loops, + DDR_DIST_VECT (ddr, j), distres); + + if (!lambda_vector_lexico_pos (distres, nb_loops)) + return false; + } + } + return true; +} /* Data dependency analysis. Returns true if the iterations of LOOP are independent on each other (that is, if we can execute them |