pet_expr_filter: avoid introduction of constraints in index expression

[pet.git] / context.c

/*
 * Copyright 2011      Leiden University. All rights reserved.
 * Copyright 2014      Ecole Normale Superieure. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *    1. Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY LEIDEN UNIVERSITY ''AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL LEIDEN UNIVERSITY OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * The views and conclusions contained in the software and documentation
 * are those of the authors and should not be interpreted as
 * representing official policies, either expressed or implied, of
 * Leiden University.
 */

#include <isl/aff.h>

#include "context.h"
#include "expr.h"
#include "nest.h"

/* A pet_context represents the context in which a pet_expr
 * in converted to an affine expression.
 *
 * "domain" prescribes the domain of the affine expressions.
 *
 * "assignments" maps variable names to their currently known values.
 * The domains of the values are equal to the space of "domain".
 * If a variable has been assigned an unknown value (possibly because
 * it may be assigned a different expression in each iteration) or a value
 * that is not an affine expression, then the corresponding isl_pw_aff
 * is set to NaN.
 *
 * If "allow_nested" is set, then the affine expression created
 * in this context may involve new parameters that encode a pet_expr.
 */
struct pet_context {
        int ref;

        isl_set *domain;
        isl_id_to_pw_aff *assignments;
        int allow_nested;
};

/* Create a pet_context with the given domain, assignments,
 * and value for allow_nested.
 */
static __isl_give pet_context *context_alloc(__isl_take isl_set *domain,
        __isl_take isl_id_to_pw_aff *assignments, int allow_nested)
{
        pet_context *pc;

        if (!domain || !assignments)
                goto error;

        pc = isl_calloc_type(isl_set_get_ctx(domain), struct pet_context);
        if (!pc)
                goto error;

        pc->ref = 1;
        pc->domain = domain;
        pc->assignments = assignments;
        pc->allow_nested = allow_nested;

        return pc;
error:
        isl_set_free(domain);
        isl_id_to_pw_aff_free(assignments);
        return NULL;
}

/* Create a pet_context with the given domain.
 *
 * Initially, there are no assigned values and parameters that
 * encode a pet_expr are not allowed.
 */
__isl_give pet_context *pet_context_alloc(__isl_take isl_set *domain)
{
        isl_id_to_pw_aff *assignments;

        if (!domain)
                return NULL;

        assignments = isl_id_to_pw_aff_alloc(isl_set_get_ctx(domain), 0);;
        return context_alloc(domain, assignments, 0);
}

/* Return an independent duplicate of "pc".
 */
static __isl_give pet_context *pet_context_dup(__isl_keep pet_context *pc)
{
        pet_context *dup;

        if (!pc)
                return NULL;

        dup = context_alloc(isl_set_copy(pc->domain),
                            isl_id_to_pw_aff_copy(pc->assignments),
                            pc->allow_nested);

        return dup;
}

/* Return a pet_context that is equal to "pc" and that has only one reference.
 */
static __isl_give pet_context *pet_context_cow(__isl_take pet_context *pc)
{
        if (!pc)
                return NULL;

        if (pc->ref == 1)
                return pc;
        pc->ref--;
        return pet_context_dup(pc);
}

/* Return an extra reference to "pc".
 */
__isl_give pet_context *pet_context_copy(__isl_keep pet_context *pc)
{
        if (!pc)
                return NULL;

        pc->ref++;
        return pc;
}

/* Free a reference to "pc" and return NULL.
 */
__isl_null pet_context *pet_context_free(__isl_take pet_context *pc)
{
        if (!pc)
                return NULL;
        if (--pc->ref > 0)
                return NULL;

        isl_set_free(pc->domain);
        isl_id_to_pw_aff_free(pc->assignments);
        free(pc);
        return NULL;
}

/* Return the isl_ctx in which "pc" was created.
 */
isl_ctx *pet_context_get_ctx(__isl_keep pet_context *pc)
{
        return pc ? isl_set_get_ctx(pc->domain) : NULL;
}

/* Return the domain of "pc".
 */
__isl_give isl_set *pet_context_get_domain(__isl_keep pet_context *pc)
{
        if (!pc)
                return NULL;
        return isl_set_copy(pc->domain);
}

/* Return the domain space of "pc".
 *
 * The domain of "pc" may have constraints involving parameters
 * that encode a pet_expr.  These parameters are not relevant
 * outside this domain.  Furthermore, they need to be resolved
 * from the final result, so we do not want to propagate them needlessly.
 */
__isl_give isl_space *pet_context_get_space(__isl_keep pet_context *pc)
{
        isl_space *space;

        if (!pc)
                return NULL;

        space = isl_set_get_space(pc->domain);
        space = pet_nested_remove_from_space(space);
        return space;
}

/* Return the dimension of the domain space of "pc".
 */
unsigned pet_context_dim(__isl_keep pet_context *pc)
{
        if (!pc)
                return 0;
        return isl_set_dim(pc->domain, isl_dim_set);
}

/* Return the assignments of "pc".
 */
__isl_give isl_id_to_pw_aff *pet_context_get_assignments(
        __isl_keep pet_context *pc)
{
        if (!pc)
                return NULL;
        return isl_id_to_pw_aff_copy(pc->assignments);
}

/* Is "id" assigned any value in "pc"?
 */
int pet_context_is_assigned(__isl_keep pet_context *pc, __isl_keep isl_id *id)
{
        if (!pc || !id)
                return -1;
        return isl_id_to_pw_aff_has(pc->assignments, id);
}

/* Return the value assigned to "id" in "pc".
 */
__isl_give isl_pw_aff *pet_context_get_value(__isl_keep pet_context *pc,
        __isl_take isl_id *id)
{
        if (!pc || !id)
                goto error;

        return isl_id_to_pw_aff_get(pc->assignments, id);
error:
        isl_id_free(id);
        return NULL;
}

/* Assign the value "value" to "id" in "pc", replacing the previously
 * assigned value, if any.
 */
__isl_give pet_context *pet_context_set_value(__isl_take pet_context *pc,
        __isl_take isl_id *id, isl_pw_aff *value)
{
        pc = pet_context_cow(pc);
        if (!pc)
                goto error;
        pc->assignments = isl_id_to_pw_aff_set(pc->assignments, id, value);
        if (!pc->assignments)
                return pet_context_free(pc);
        return pc;
error:
        isl_id_free(id);
        isl_pw_aff_free(value);
        return NULL;
}

/* Remove any assignment to "id" in "pc".
 */
__isl_give pet_context *pet_context_clear_value(__isl_keep pet_context *pc,
        __isl_take isl_id *id)
{
        pc = pet_context_cow(pc);
        if (!pc)
                goto error;
        pc->assignments = isl_id_to_pw_aff_drop(pc->assignments, id);
        if (!pc->assignments)
                return pet_context_free(pc);
        return pc;
error:
        isl_id_free(id);
        return NULL;
}

/* Return a piecewise affine expression defined on the specified domain
 * that represents NaN.
 */
static __isl_give isl_pw_aff *nan_on_domain(__isl_take isl_space *space)
{
        return isl_pw_aff_nan_on_domain(isl_local_space_from_space(space));
}

/* Assign the value NaN to "id" in "pc", marked it as having an unknown
 * value.
 */
__isl_give pet_context *pet_context_mark_unknown(__isl_take pet_context *pc,
        __isl_take isl_id *id)
{
        isl_pw_aff *pa;

        pa = nan_on_domain(pet_context_get_space(pc));
        pc = pet_context_set_value(pc, id, pa);

        return pc;
}

/* Internal data structure used inside clear_assigned_parameter.
 *
 * "pc" is the context that is updated by clear_assigned_parameter.
 * "id" is the identifier that was assigned an unknown value.
 */
struct pet_context_mark_assigned_parameter_data {
        pet_context *pc;
        isl_id *id;
};

/* This function is called for each assignment in a pet_context
 * when data->id is assigned an unknown value where it was not
 * assigned any value before.
 * Since it was not assigned any value before, it may have been
 * treated as a parameter.
 *
 * If the value "value" does indeed refer to data->id as a parameter,
 * then it is marked as unknown in data->pc since data->id can no
 * longer be treated as a parameter and the current value has
 * therefore been invalidated.
 */
static int mark_assigned_parameter(__isl_take isl_id *id,
        __isl_take isl_pw_aff *value, void *user)
{
        struct pet_context_mark_assigned_parameter_data *data;
        isl_space *space;

        data = (struct pet_context_mark_assigned_parameter_data *) user;

        space = isl_pw_aff_get_space(value);
        if (isl_space_find_dim_by_id(space, isl_dim_param, data->id) >= 0)
                data->pc = pet_context_mark_unknown(data->pc, id);
        else
                isl_id_free(id);

        isl_space_free(space);
        isl_pw_aff_free(value);

        return 0;
}

/* This function is called when "id" may have been assigned some value.
 *
 * Mark "id" as having an unknown value in "pc".
 *
 * Furthermore, if no (known or unknown) value was assigned to "id" before,
 * then it may have been treated as a parameter before and may
 * therefore appear in a value assigned to another variable.
 * If so, this assignment needs to be turned into an unknown value too.
 */
__isl_give pet_context *pet_context_mark_assigned(__isl_take pet_context *pc,
        __isl_take isl_id *id)
{
        int was_assigned;
        isl_id_to_pw_aff *assignments;
        struct pet_context_mark_assigned_parameter_data data;

        was_assigned = pet_context_is_assigned(pc, id);

        pc = pet_context_mark_unknown(pc, isl_id_copy(id));

        if (was_assigned) {
                isl_id_free(id);
                return pc;
        }

        assignments = pet_context_get_assignments(pc);
        data.pc = pc;
        data.id = id;
        if (isl_id_to_pw_aff_foreach(assignments,
                                    &mark_assigned_parameter, &data) < 0)
                data.pc = pet_context_free(data.pc);
        isl_id_to_pw_aff_free(assignments);

        isl_id_free(id);
        return data.pc;
}

/* Are affine expressions created in this context allowed to involve
 * parameters that encode a pet_expr?
 */
int pet_context_allow_nesting(__isl_keep pet_context *pc)
{
        if (!pc)
                return -1;
        return pc->allow_nested;
}

/* Allow affine expressions created in this context to involve
 * parameters that encode a pet_expr based on the value of "allow_nested".
 */
__isl_give pet_context *pet_context_set_allow_nested(__isl_take pet_context *pc,
        int allow_nested)
{
        if (!pc)
                return NULL;
        if (pc->allow_nested == allow_nested)
                return pc;
        pc = pet_context_cow(pc);
        if (!pc)
                return NULL;
        pc->allow_nested = allow_nested;
        return pc;
}

/* If the access expression "expr" writes to a (non-virtual) scalar,
 * then mark the scalar as having an unknown value in "pc".
 */
static int clear_write(__isl_keep pet_expr *expr, void *user)
{
        isl_id *id;
        pet_context **pc = (pet_context **) user;

        if (!pet_expr_access_is_write(expr))
                return 0;
        if (!pet_expr_is_scalar_access(expr))
                return 0;

        id = pet_expr_access_get_id(expr);
        if (isl_id_get_user(id))
                *pc = pet_context_mark_assigned(*pc, id);
        else
                isl_id_free(id);

        return 0;
}

/* Look for any writes to scalar variables in "expr" and
 * mark them as having an unknown value in "pc".
 */
__isl_give pet_context *pet_context_clear_writes_in_expr(
        __isl_take pet_context *pc, __isl_keep pet_expr *expr)
{
        if (pet_expr_foreach_access_expr(expr, &clear_write, &pc) < 0)
                pc = pet_context_free(pc);

        return pc;
}

/* Look for any writes to scalar variables in "tree" and
 * mark them as having an unknown value in "pc".
 */
__isl_give pet_context *pet_context_clear_writes_in_tree(
        __isl_take pet_context *pc, __isl_keep pet_tree *tree)
{
        if (pet_tree_foreach_access_expr(tree, &clear_write, &pc) < 0)
                pc = pet_context_free(pc);

        return pc;
}

void pet_context_dump(__isl_keep pet_context *pc)
{
        if (!pc)
                return;
        fprintf(stderr, "domain: ");
        isl_set_dump(pc->domain);
        fprintf(stderr, "assignments: ");
        isl_id_to_pw_aff_dump(pc->assignments);
        fprintf(stderr, "nesting allowed: %d\n", pc->allow_nested);
}