properly handle generic conditions in for loops

[pet.git] / scan.cc

#include <set>
#include <map>
#include <iostream>
#include <clang/AST/ASTDiagnostic.h>
#include <clang/AST/Expr.h>
#include <clang/AST/RecursiveASTVisitor.h>

#include <isl/id.h>
#include <isl/dim.h>
#include <isl/aff.h>
#include <isl/set.h>

#include "scan.h"
#include "scop.h"
#include "scop_plus.h"

#include "config.h"

using namespace std;
using namespace clang;

/* Look for any assignments to variables in part of the parse
 * tree and set assigned_value to NULL for each of them.
 *
 * This ensures that we won't use any previously stored value
 * in the current subtree and its parents.
 */
struct clear_assignments : RecursiveASTVisitor<clear_assignments> {
        map<ValueDecl *, Expr *> &assigned_value;

        clear_assignments(map<ValueDecl *, Expr *> &assigned_value) :
                assigned_value(assigned_value) {}

        bool VisitBinaryOperator(BinaryOperator *expr) {
                Expr *lhs;
                DeclRefExpr *ref;
                ValueDecl *decl;

                if (!expr->isAssignmentOp())
                        return true;
                lhs = expr->getLHS();
                if (lhs->getStmtClass() != Stmt::DeclRefExprClass)
                        return true;
                ref = cast<DeclRefExpr>(lhs);
                decl = ref->getDecl();
                assigned_value[decl] = NULL;
                return true;
        }
};

/* Keep a copy of the currently assigned values.
 *
 * Any variable that is assigned a value inside the current scope
 * is removed again when we leave the scope (either because it wasn't
 * stored in the cache or because it has a different value in the cache).
 */
struct assigned_value_cache {
        map<ValueDecl *, Expr *> &assigned_value;
        map<ValueDecl *, Expr *> cache;

        assigned_value_cache(map<ValueDecl *, Expr *> &assigned_value) :
                assigned_value(assigned_value), cache(assigned_value) {}
        ~assigned_value_cache() {
                map<ValueDecl *, Expr *>::iterator it = cache.begin();
                for (it = assigned_value.begin(); it != assigned_value.end();
                     ++it) {
                        if (!it->second ||
                            (cache.find(it->first) != cache.end() &&
                             cache[it->first] != it->second))
                                cache[it->first] = NULL;
                }
                assigned_value = cache;
        }
};

/* Called if we found something we (currently) cannot handle.
 * We'll provide more informative warnings later.
 *
 * We only actually complain if autodetect is false.
 */
void PetScan::unsupported(Stmt *stmt)
{
        if (autodetect)
                return;

        SourceLocation loc = stmt->getLocStart();
        Diagnostic &diag = PP.getDiagnostics();
        unsigned id = diag.getCustomDiagID(Diagnostic::Warning, "unsupported");
        DiagnosticBuilder B = diag.Report(loc, id) << stmt->getSourceRange();
}

/* Extract an integer from "expr" and store it in "v".
 */
int PetScan::extract_int(IntegerLiteral *expr, isl_int *v)
{
        const Type *type = expr->getType().getTypePtr();
        int is_signed = type->hasSignedIntegerRepresentation();

        if (is_signed) {
                int64_t i = expr->getValue().getSExtValue();
                isl_int_set_si(*v, i);
        } else {
                uint64_t i = expr->getValue().getZExtValue();
                isl_int_set_ui(*v, i);
        }

        return 0;
}

/* Extract an affine expression from the IntegerLiteral "expr".
 */
__isl_give isl_pw_aff *PetScan::extract_affine(IntegerLiteral *expr)
{
        isl_dim *dim = isl_dim_set_alloc(ctx, 0, 0);
        isl_local_space *ls = isl_local_space_from_dim(isl_dim_copy(dim));
        isl_aff *aff = isl_aff_zero(ls);
        isl_set *dom = isl_set_universe(dim);
        isl_int v;

        isl_int_init(v);
        extract_int(expr, &v);
        aff = isl_aff_add_constant(aff, v);
        isl_int_clear(v);

        return isl_pw_aff_alloc(dom, aff);
}

/* Extract an affine expression from the APInt "val".
 */
__isl_give isl_pw_aff *PetScan::extract_affine(const llvm::APInt &val)
{
        isl_dim *dim = isl_dim_set_alloc(ctx, 0, 0);
        isl_local_space *ls = isl_local_space_from_dim(isl_dim_copy(dim));
        isl_aff *aff = isl_aff_zero(ls);
        isl_set *dom = isl_set_universe(dim);
        isl_int v;

        isl_int_init(v);
        isl_int_set_ui(v, val.getZExtValue());
        aff = isl_aff_add_constant(aff, v);
        isl_int_clear(v);

        return isl_pw_aff_alloc(dom, aff);
}

__isl_give isl_pw_aff *PetScan::extract_affine(ImplicitCastExpr *expr)
{
        return extract_affine(expr->getSubExpr());
}

/* Extract an affine expression from the DeclRefExpr "expr".
 *
 * If we have recorded an expression that was assigned to the variable
 * before, then we convert this expressoin to an isl_pw_aff if it is
 * affine and to an extra parameter otherwise (provided nesting_enabled is set).
 *
 * Otherwise, we simply return an expression that is equal
 * to a parameter corresponding to the referenced variable.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(DeclRefExpr *expr)
{
        ValueDecl *decl = expr->getDecl();
        const Type *type = decl->getType().getTypePtr();
        isl_id *id;
        isl_dim *dim;
        isl_aff *aff;
        isl_set *dom;

        if (!type->isIntegerType()) {
                unsupported(expr);
                return NULL;
        }

        if (assigned_value.find(decl) != assigned_value.end() &&
            assigned_value[decl] != NULL) {
                if (is_affine(assigned_value[decl]))
                        return extract_affine(assigned_value[decl]);
                else
                        return non_affine(expr);
        }

        id = isl_id_alloc(ctx, decl->getName().str().c_str(), decl);
        dim = isl_dim_set_alloc(ctx, 1, 0);

        dim = isl_dim_set_dim_id(dim, isl_dim_param, 0, id);

        dom = isl_set_universe(isl_dim_copy(dim));
        aff = isl_aff_zero(isl_local_space_from_dim(dim));
        aff = isl_aff_add_coefficient_si(aff, isl_dim_param, 0, 1);

        return isl_pw_aff_alloc(dom, aff);
}

/* Extract an affine expression from an integer division operation.
 * In particular, if "expr" is lhs/rhs, then return
 *
 *      lhs >= 0 ? floor(lhs/rhs) : ceil(lhs/rhs)
 *
 * The second argument (rhs) is required to be a (positive) integer constant.
 */
__isl_give isl_pw_aff *PetScan::extract_affine_div(BinaryOperator *expr)
{
        Expr *rhs_expr;
        isl_pw_aff *lhs, *lhs_f, *lhs_c;
        isl_pw_aff *res;
        isl_int v;
        isl_set *cond;

        rhs_expr = expr->getRHS();
        if (rhs_expr->getStmtClass() != Stmt::IntegerLiteralClass) {
                unsupported(expr);
                return NULL;
        }

        lhs = extract_affine(expr->getLHS());
        cond = isl_pw_aff_nonneg_set(isl_pw_aff_copy(lhs));

        isl_int_init(v);
        extract_int(cast<IntegerLiteral>(rhs_expr), &v);
        lhs = isl_pw_aff_scale_down(lhs, v);
        isl_int_clear(v);

        lhs_f = isl_pw_aff_floor(isl_pw_aff_copy(lhs));
        lhs_c = isl_pw_aff_ceil(lhs);
        res = isl_pw_aff_cond(cond, lhs_f, lhs_c);

        return res;
}

/* Extract an affine expression from a modulo operation.
 * In particular, if "expr" is lhs/rhs, then return
 *
 *      lhs - rhs * (lhs >= 0 ? floor(lhs/rhs) : ceil(lhs/rhs))
 *
 * The second argument (rhs) is required to be a (positive) integer constant.
 */
__isl_give isl_pw_aff *PetScan::extract_affine_mod(BinaryOperator *expr)
{
        Expr *rhs_expr;
        isl_pw_aff *lhs, *lhs_f, *lhs_c;
        isl_pw_aff *res;
        isl_int v;
        isl_set *cond;

        rhs_expr = expr->getRHS();
        if (rhs_expr->getStmtClass() != Stmt::IntegerLiteralClass) {
                unsupported(expr);
                return NULL;
        }

        lhs = extract_affine(expr->getLHS());
        cond = isl_pw_aff_nonneg_set(isl_pw_aff_copy(lhs));

        isl_int_init(v);
        extract_int(cast<IntegerLiteral>(rhs_expr), &v);
        res = isl_pw_aff_scale_down(isl_pw_aff_copy(lhs), v);

        lhs_f = isl_pw_aff_floor(isl_pw_aff_copy(res));
        lhs_c = isl_pw_aff_ceil(res);
        res = isl_pw_aff_cond(cond, lhs_f, lhs_c);

        res = isl_pw_aff_scale(res, v);
        isl_int_clear(v);

        res = isl_pw_aff_sub(lhs, res);

        return res;
}

/* Extract an affine expression from a multiplication operation.
 * This is only allowed if at least one of the two arguments
 * is a (piecewise) constant.
 */
__isl_give isl_pw_aff *PetScan::extract_affine_mul(BinaryOperator *expr)
{
        isl_pw_aff *lhs;
        isl_pw_aff *rhs;

        lhs = extract_affine(expr->getLHS());
        rhs = extract_affine(expr->getRHS());

        if (!isl_pw_aff_is_cst(lhs) && !isl_pw_aff_is_cst(rhs)) {
                isl_pw_aff_free(lhs);
                isl_pw_aff_free(rhs);
                unsupported(expr);
                return NULL;
        }

        return isl_pw_aff_mul(lhs, rhs);
}

/* Extract an affine expression from some binary operations.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(BinaryOperator *expr)
{
        isl_pw_aff *lhs;
        isl_pw_aff *rhs;
        isl_pw_aff *res;

        switch (expr->getOpcode()) {
        case BO_Add:
        case BO_Sub:
                break;
        case BO_Div:
                return extract_affine_div(expr);
        case BO_Rem:
                return extract_affine_mod(expr);
        case BO_Mul:
                return extract_affine_mul(expr);
        default:
                unsupported(expr);
                return NULL;
        }

        lhs = extract_affine(expr->getLHS());
        rhs = extract_affine(expr->getRHS());

        switch (expr->getOpcode()) {
        case BO_Add:
                res = isl_pw_aff_add(lhs, rhs);
                break;
        case BO_Sub:
                res = isl_pw_aff_sub(lhs, rhs);
                break;
        default:
                ;
        }

        return res;
}

/* Extract an affine expression from a negation operation.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(UnaryOperator *expr)
{
        if (expr->getOpcode() == UO_Minus)
                return isl_pw_aff_neg(extract_affine(expr->getSubExpr()));

        unsupported(expr);
        return NULL;
}

__isl_give isl_pw_aff *PetScan::extract_affine(ParenExpr *expr)
{
        return extract_affine(expr->getSubExpr());
}

/* Extract an affine expression from some special function calls.
 * In particular, we handle "min", "max", "ceild" and "floord".
 * In case of the latter two, the second argument needs to be
 * a (positive) integer constant.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(CallExpr *expr)
{
        FunctionDecl *fd;
        string name;
        isl_pw_aff *aff1, *aff2;

        fd = expr->getDirectCallee();
        if (!fd) {
                unsupported(expr);
                return NULL;
        }

        name = fd->getDeclName().getAsString();
        if (!(expr->getNumArgs() == 2 && name == "min") &&
            !(expr->getNumArgs() == 2 && name == "max") &&
            !(expr->getNumArgs() == 2 && name == "floord") &&
            !(expr->getNumArgs() == 2 && name == "ceild")) {
                unsupported(expr);
                return NULL;
        }

        if (name == "min" || name == "max") {
                aff1 = extract_affine(expr->getArg(0));
                aff2 = extract_affine(expr->getArg(1));

                if (name == "min")
                        aff1 = isl_pw_aff_min(aff1, aff2);
                else
                        aff1 = isl_pw_aff_max(aff1, aff2);
        } else if (name == "floord" || name == "ceild") {
                isl_int v;
                Expr *arg2 = expr->getArg(1);

                if (arg2->getStmtClass() != Stmt::IntegerLiteralClass) {
                        unsupported(expr);
                        return NULL;
                }
                aff1 = extract_affine(expr->getArg(0));
                isl_int_init(v);
                extract_int(cast<IntegerLiteral>(arg2), &v);
                aff1 = isl_pw_aff_scale_down(aff1, v);
                isl_int_clear(v);
                if (name == "floord")
                        aff1 = isl_pw_aff_floor(aff1);
                else
                        aff1 = isl_pw_aff_ceil(aff1);
        } else {
                unsupported(expr);
                return NULL;
        }

        return aff1;

}

/* This method is called when we come across a non-affine expression.
 * If nesting is allowed, we return a new parameter that corresponds
 * to the non-affine expression.  Otherwise, we simply complain.
 *
 * The new parameter is resolved in resolve_nested.
 */
isl_pw_aff *PetScan::non_affine(Expr *expr)
{
        isl_id *id;
        isl_dim *dim;
        isl_aff *aff;
        isl_set *dom;

        if (!nesting_enabled) {
                unsupported(expr);
                return NULL;
        }

        id = isl_id_alloc(ctx, NULL, expr);
        dim = isl_dim_set_alloc(ctx, 1, 0);

        dim = isl_dim_set_dim_id(dim, isl_dim_param, 0, id);

        dom = isl_set_universe(isl_dim_copy(dim));
        aff = isl_aff_zero(isl_local_space_from_dim(dim));
        aff = isl_aff_add_coefficient_si(aff, isl_dim_param, 0, 1);

        return isl_pw_aff_alloc(dom, aff);
}

/* Affine expressions are not supposed to contain array accesses,
 * but if nesting is allowed, we return a parameter corresponding
 * to the array access.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(ArraySubscriptExpr *expr)
{
        return non_affine(expr);
}

/* Extract an affine expression from a conditional operation.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(ConditionalOperator *expr)
{
        isl_set *cond;
        isl_pw_aff *lhs, *rhs;

        cond = extract_condition(expr->getCond());
        lhs = extract_affine(expr->getTrueExpr());
        rhs = extract_affine(expr->getFalseExpr());

        return isl_pw_aff_cond(cond, lhs, rhs);
}

/* Extract an affine expression, if possible, from "expr".
 * Otherwise return NULL.
 */
__isl_give isl_pw_aff *PetScan::extract_affine(Expr *expr)
{
        switch (expr->getStmtClass()) {
        case Stmt::ImplicitCastExprClass:
                return extract_affine(cast<ImplicitCastExpr>(expr));
        case Stmt::IntegerLiteralClass:
                return extract_affine(cast<IntegerLiteral>(expr));
        case Stmt::DeclRefExprClass:
                return extract_affine(cast<DeclRefExpr>(expr));
        case Stmt::BinaryOperatorClass:
                return extract_affine(cast<BinaryOperator>(expr));
        case Stmt::UnaryOperatorClass:
                return extract_affine(cast<UnaryOperator>(expr));
        case Stmt::ParenExprClass:
                return extract_affine(cast<ParenExpr>(expr));
        case Stmt::CallExprClass:
                return extract_affine(cast<CallExpr>(expr));
        case Stmt::ArraySubscriptExprClass:
                return extract_affine(cast<ArraySubscriptExpr>(expr));
        case Stmt::ConditionalOperatorClass:
                return extract_affine(cast<ConditionalOperator>(expr));
        default:
                unsupported(expr);
        }
        return NULL;
}

__isl_give isl_map *PetScan::extract_access(ImplicitCastExpr *expr)
{
        return extract_access(expr->getSubExpr());
}

/* Return the depth of an array of the given type.
 */
static int array_depth(const Type *type)
{
        if (type->isPointerType())
                return 1 + array_depth(type->getPointeeType().getTypePtr());
        if (type->isArrayType()) {
                const ArrayType *atype;
                type = type->getCanonicalTypeInternal().getTypePtr();
                atype = cast<ArrayType>(type);
                return 1 + array_depth(atype->getElementType().getTypePtr());
        }
        return 0;
}

/* Return the element type of the given array type.
 */
static QualType base_type(QualType qt)
{
        const Type *type = qt.getTypePtr();

        if (type->isPointerType())
                return base_type(type->getPointeeType());
        if (type->isArrayType()) {
                const ArrayType *atype;
                type = type->getCanonicalTypeInternal().getTypePtr();
                atype = cast<ArrayType>(type);
                return base_type(atype->getElementType());
        }
        return qt;
}

/* Check if the element type corresponding to the given array type
 * has a const qualifier.
 */
static bool const_base(QualType qt)
{
        const Type *type = qt.getTypePtr();

        if (type->isPointerType())
                return const_base(type->getPointeeType());
        if (type->isArrayType()) {
                const ArrayType *atype;
                type = type->getCanonicalTypeInternal().getTypePtr();
                atype = cast<ArrayType>(type);
                return const_base(atype->getElementType());
        }

        return qt.isConstQualified();
}

/* Extract an access relation from a reference to a variable.
 * If the variable has name "A" and its type corresponds to an
 * array of depth d, then the returned access relation is of the
 * form
 *
 *      { [] -> A[i_1,...,i_d] }
 */
__isl_give isl_map *PetScan::extract_access(DeclRefExpr *expr)
{
        ValueDecl *decl = expr->getDecl();
        int depth = array_depth(decl->getType().getTypePtr());
        isl_id *id = isl_id_alloc(ctx, decl->getName().str().c_str(), decl);
        isl_dim *dim = isl_dim_alloc(ctx, 0, 0, depth);
        isl_map *access_rel;

        dim = isl_dim_set_tuple_id(dim, isl_dim_out, id);

        access_rel = isl_map_universe(dim);

        return access_rel;
}

/* Extract an access relation from an integer contant.
 * If the value of the constant is "v", then the returned access relation
 * is
 *
 *      { [] -> [v] }
 */
__isl_give isl_map *PetScan::extract_access(IntegerLiteral *expr)
{
        return isl_map_from_pw_aff(extract_affine(expr));
}

/* Try and extract an access relation from the given Expr.
 * Return NULL if it doesn't work out.
 */
__isl_give isl_map *PetScan::extract_access(Expr *expr)
{
        switch (expr->getStmtClass()) {
        case Stmt::ImplicitCastExprClass:
                return extract_access(cast<ImplicitCastExpr>(expr));
        case Stmt::DeclRefExprClass:
                return extract_access(cast<DeclRefExpr>(expr));
        case Stmt::ArraySubscriptExprClass:
                return extract_access(cast<ArraySubscriptExpr>(expr));
        default:
                unsupported(expr);
        }
        return NULL;
}

/* Assign the affine expression "index" to the output dimension "pos" of "map"
 * and return the result.
 */
__isl_give isl_map *set_index(__isl_take isl_map *map, int pos,
        __isl_take isl_pw_aff *index)
{
        isl_map *index_map;
        int len = isl_map_dim(map, isl_dim_out);
        isl_id *id;

        index_map = isl_map_from_pw_aff(index);
        index_map = isl_map_insert(index_map, isl_dim_out, 0, pos);
        index_map = isl_map_add_dims(index_map, isl_dim_out, len - pos - 1);
        id = isl_map_get_tuple_id(map, isl_dim_out);
        index_map = isl_map_set_tuple_id(index_map, isl_dim_out, id);

        map = isl_map_intersect(map, index_map);

        return map;
}

/* Extract an access relation from the given array subscript expression.
 * If nesting is allowed in general, then we turn it on while
 * examining the index expression.
 *
 * We first extract an access relation from the base.
 * This will result in an access relation with a range that corresponds
 * to the array being accessed and with earlier indices filled in already.
 * We then extract the current index and fill that in as well.
 * The position of the current index is based on the type of base.
 * If base is the actual array variable, then the depth of this type
 * will be the same as the depth of the array and we will fill in
 * the first array index.
 * Otherwise, the depth of the base type will be smaller and we will fill
 * in a later index.
 */
__isl_give isl_map *PetScan::extract_access(ArraySubscriptExpr *expr)
{
        Expr *base = expr->getBase();
        Expr *idx = expr->getIdx();
        isl_pw_aff *index;
        isl_map *base_access;
        isl_map *access;
        int depth = array_depth(base->getType().getTypePtr());
        int pos;
        bool save_nesting = nesting_enabled;

        nesting_enabled = allow_nested;

        base_access = extract_access(base);
        index = extract_affine(idx);

        nesting_enabled = save_nesting;

        pos = isl_map_dim(base_access, isl_dim_out) - depth;
        access = set_index(base_access, pos, index);

        return access;
}

/* Check if "expr" calls function "minmax" with two arguments and if so
 * make lhs and rhs refer to these two arguments.
 */
static bool is_minmax(Expr *expr, const char *minmax, Expr *&lhs, Expr *&rhs)
{
        CallExpr *call;
        FunctionDecl *fd;
        string name;

        if (expr->getStmtClass() != Stmt::CallExprClass)
                return false;

        call = cast<CallExpr>(expr);
        fd = call->getDirectCallee();
        if (!fd)
                return false;

        if (call->getNumArgs() != 2)
                return false;

        name = fd->getDeclName().getAsString();
        if (name != minmax)
                return false;

        lhs = call->getArg(0);
        rhs = call->getArg(1);

        return true;
}

/* Check if "expr" is of the form min(lhs, rhs) and if so make
 * lhs and rhs refer to the two arguments.
 */
static bool is_min(Expr *expr, Expr *&lhs, Expr *&rhs)
{
        return is_minmax(expr, "min", lhs, rhs);
}

/* Check if "expr" is of the form max(lhs, rhs) and if so make
 * lhs and rhs refer to the two arguments.
 */
static bool is_max(Expr *expr, Expr *&lhs, Expr *&rhs)
{
        return is_minmax(expr, "max", lhs, rhs);
}

/* Extract a set of values satisfying the comparison "LHS op RHS"
 * "comp" is the original expression that "LHS op RHS" is derived from
 * and is used for diagnostics.
 *
 * If the comparison is of the form
 *
 *      a <= min(b,c)
 *
 * then the set is constructed as the intersection of the set corresponding
 * to the comparisons
 *
 *      a <= b          and             a <= c
 *
 * A similar optimization is performed for max(a,b) <= c.
 * We do this because that will lead to simpler representations of the set.
 * If isl is ever enhanced to explicitly deal with min and max expressions,
 * this optimization can be removed.
 */
__isl_give isl_set *PetScan::extract_comparison(BinaryOperatorKind op,
        Expr *LHS, Expr *RHS, Expr *comp)
{
        isl_pw_aff *lhs;
        isl_pw_aff *rhs;
        isl_set *cond;

        if (op == BO_GT)
                return extract_comparison(BO_LT, RHS, LHS, comp);
        if (op == BO_GE)
                return extract_comparison(BO_LE, RHS, LHS, comp);

        if (op == BO_LT || op == BO_LE) {
                Expr *expr1, *expr2;
                isl_set *set1, *set2;
                if (is_min(RHS, expr1, expr2)) {
                        set1 = extract_comparison(op, LHS, expr1, comp);
                        set2 = extract_comparison(op, LHS, expr2, comp);
                        return isl_set_intersect(set1, set2);
                }
                if (is_max(LHS, expr1, expr2)) {
                        set1 = extract_comparison(op, expr1, RHS, comp);
                        set2 = extract_comparison(op, expr2, RHS, comp);
                        return isl_set_intersect(set1, set2);
                }
        }

        lhs = extract_affine(LHS);
        rhs = extract_affine(RHS);

        switch (op) {
        case BO_LT:
                cond = isl_pw_aff_lt_set(lhs, rhs);
                break;
        case BO_LE:
                cond = isl_pw_aff_le_set(lhs, rhs);
                break;
        case BO_EQ:
                cond = isl_pw_aff_eq_set(lhs, rhs);
                break;
        case BO_NE:
                cond = isl_pw_aff_ne_set(lhs, rhs);
                break;
        default:
                isl_pw_aff_free(lhs);
                isl_pw_aff_free(rhs);
                unsupported(comp);
                return NULL;
        }

        cond = isl_set_coalesce(cond);

        return cond;
}

__isl_give isl_set *PetScan::extract_comparison(BinaryOperator *comp)
{
        return extract_comparison(comp->getOpcode(), comp->getLHS(),
                                comp->getRHS(), comp);
}

/* Extract a set of values satisfying the negation (logical not)
 * of a subexpression.
 */
__isl_give isl_set *PetScan::extract_boolean(UnaryOperator *op)
{
        isl_set *cond;

        cond = extract_condition(op->getSubExpr());

        return isl_set_complement(cond);
}

/* Extract a set of values satisfying the union (logical or)
 * or intersection (logical and) of two subexpressions.
 */
__isl_give isl_set *PetScan::extract_boolean(BinaryOperator *comp)
{
        isl_set *lhs;
        isl_set *rhs;
        isl_set *cond;

        lhs = extract_condition(comp->getLHS());
        rhs = extract_condition(comp->getRHS());

        switch (comp->getOpcode()) {
        case BO_LAnd:
                cond = isl_set_intersect(lhs, rhs);
                break;
        case BO_LOr:
                cond = isl_set_union(lhs, rhs);
                break;
        default:
                isl_set_free(lhs);
                isl_set_free(rhs);
                unsupported(comp);
                return NULL;
        }

        return cond;
}

__isl_give isl_set *PetScan::extract_condition(UnaryOperator *expr)
{
        switch (expr->getOpcode()) {
        case UO_LNot:
                return extract_boolean(expr);
        default:
                unsupported(expr);
                return NULL;
        }
}

/* Extract a set of values satisfying the condition "expr != 0".
 */
__isl_give isl_set *PetScan::extract_implicit_condition(Expr *expr)
{
        return isl_pw_aff_non_zero_set(extract_affine(expr));
}

/* Extract a set of values satisfying the condition expressed by "expr".
 *
 * If the expression doesn't look like a condition, we assume it
 * is an affine expression and return the condition "expr != 0".
 */
__isl_give isl_set *PetScan::extract_condition(Expr *expr)
{
        BinaryOperator *comp;

        if (!expr)
                return isl_set_universe(isl_dim_set_alloc(ctx, 0, 0));

        if (expr->getStmtClass() == Stmt::ParenExprClass)
                return extract_condition(cast<ParenExpr>(expr)->getSubExpr());

        if (expr->getStmtClass() == Stmt::UnaryOperatorClass)
                return extract_condition(cast<UnaryOperator>(expr));

        if (expr->getStmtClass() != Stmt::BinaryOperatorClass)
                return extract_implicit_condition(expr);

        comp = cast<BinaryOperator>(expr);
        switch (comp->getOpcode()) {
        case BO_LT:
        case BO_LE:
        case BO_GT:
        case BO_GE:
        case BO_EQ:
        case BO_NE:
                return extract_comparison(comp);
        case BO_LAnd:
        case BO_LOr:
                return extract_boolean(comp);
        default:
                return extract_implicit_condition(expr);
        }
}

static enum pet_op_type UnaryOperatorKind2pet_op_type(UnaryOperatorKind kind)
{
        switch (kind) {
        case UO_Minus:
                return pet_op_minus;
        default:
                return pet_op_last;
        }
}

static enum pet_op_type BinaryOperatorKind2pet_op_type(BinaryOperatorKind kind)
{
        switch (kind) {
        case BO_AddAssign:
                return pet_op_add_assign;
        case BO_SubAssign:
                return pet_op_sub_assign;
        case BO_MulAssign:
                return pet_op_mul_assign;
        case BO_DivAssign:
                return pet_op_div_assign;
        case BO_Assign:
                return pet_op_assign;
        case BO_Add:
                return pet_op_add;
        case BO_Sub:
                return pet_op_sub;
        case BO_Mul:
                return pet_op_mul;
        case BO_Div:
                return pet_op_div;
        case BO_LE:
                return pet_op_le;
        case BO_LT:
                return pet_op_lt;
        case BO_GT:
                return pet_op_gt;
        default:
                return pet_op_last;
        }
}

/* Construct a pet_expr representing a unary operator expression.
 */
struct pet_expr *PetScan::extract_expr(UnaryOperator *expr)
{
        struct pet_expr *arg;
        enum pet_op_type op;

        op = UnaryOperatorKind2pet_op_type(expr->getOpcode());
        if (op == pet_op_last) {
                unsupported(expr);
                return NULL;
        }

        arg = extract_expr(expr->getSubExpr());

        return pet_expr_new_unary(ctx, op, arg);
}

/* Construct a pet_expr representing a binary operator expression.
 *
 * If the top level operator is an assignment and the LHS is an access,
 * then we mark that access as a write.  If the operator is a compound
 * assignment, the access is marked as both a read and a write.
 *
 * If "expr" assigns something to a scalar variable, then we keep track
 * of the assigned expression in assigned_value so that we can plug
 * it in when we later come across the same variable.
 */
struct pet_expr *PetScan::extract_expr(BinaryOperator *expr)
{
        struct pet_expr *lhs, *rhs;
        enum pet_op_type op;

        op = BinaryOperatorKind2pet_op_type(expr->getOpcode());
        if (op == pet_op_last) {
                unsupported(expr);
                return NULL;
        }

        lhs = extract_expr(expr->getLHS());
        rhs = extract_expr(expr->getRHS());

        if (expr->isAssignmentOp() && lhs && lhs->type == pet_expr_access) {
                lhs->acc.write = 1;
                if (!expr->isCompoundAssignmentOp())
                        lhs->acc.read = 0;
        }

        if (expr->getOpcode() == BO_Assign &&
            lhs && lhs->type == pet_expr_access &&
            isl_map_dim(lhs->acc.access, isl_dim_out) == 0) {
                isl_id *id = isl_map_get_tuple_id(lhs->acc.access, isl_dim_out);
                ValueDecl *decl = (ValueDecl *) isl_id_get_user(id);
                assigned_value[decl] = expr->getRHS();
                isl_id_free(id);
        }

        return pet_expr_new_binary(ctx, op, lhs, rhs);
}

/* Construct a pet_expr representing a conditional operation.
 */
struct pet_expr *PetScan::extract_expr(ConditionalOperator *expr)
{
        struct pet_expr *cond, *lhs, *rhs;

        cond = extract_expr(expr->getCond());
        lhs = extract_expr(expr->getTrueExpr());
        rhs = extract_expr(expr->getFalseExpr());

        return pet_expr_new_ternary(ctx, cond, lhs, rhs);
}

struct pet_expr *PetScan::extract_expr(ImplicitCastExpr *expr)
{
        return extract_expr(expr->getSubExpr());
}

/* Construct a pet_expr representing a floating point value.
 */
struct pet_expr *PetScan::extract_expr(FloatingLiteral *expr)
{
        return pet_expr_new_double(ctx, expr->getValueAsApproximateDouble());
}

/* Extract an access relation from "expr" and then convert it into
 * a pet_expr.
 */
struct pet_expr *PetScan::extract_access_expr(Expr *expr)
{
        isl_map *access;
        struct pet_expr *pe;

        switch (expr->getStmtClass()) {
        case Stmt::ArraySubscriptExprClass:
                access = extract_access(cast<ArraySubscriptExpr>(expr));
                break;
        case Stmt::DeclRefExprClass:
                access = extract_access(cast<DeclRefExpr>(expr));
                break;
        case Stmt::IntegerLiteralClass:
                access = extract_access(cast<IntegerLiteral>(expr));
                break;
        default:
                unsupported(expr);
                return NULL;
        }

        pe = pet_expr_from_access(access);

        return pe;
}

struct pet_expr *PetScan::extract_expr(ParenExpr *expr)
{
        return extract_expr(expr->getSubExpr());
}

/* Construct a pet_expr representing a function call.
 *
 * If we are passing along a pointer to an array element
 * or an entire row or even higher dimensional slice of an array,
 * then the function being called may write into the array.
 *
 * We assume here that if the function is declared to take a pointer
 * to a const type, then the function will perform a read
 * and that otherwise, it will perform a write.
 */
struct pet_expr *PetScan::extract_expr(CallExpr *expr)
{
        struct pet_expr *res = NULL;
        FunctionDecl *fd;
        string name;

        fd = expr->getDirectCallee();
        if (!fd) {
                unsupported(expr);
                return NULL;
        }

        name = fd->getDeclName().getAsString();
        res = pet_expr_new_call(ctx, name.c_str(), expr->getNumArgs());
        if (!res)
                return NULL;

        for (int i = 0; i < expr->getNumArgs(); ++i) {
                Expr *arg = expr->getArg(i);
                int is_addr = 0;

                if (arg->getStmtClass() == Stmt::ImplicitCastExprClass) {
                        ImplicitCastExpr *ice = cast<ImplicitCastExpr>(arg);
                        arg = ice->getSubExpr();
                }
                if (arg->getStmtClass() == Stmt::UnaryOperatorClass) {
                        UnaryOperator *op = cast<UnaryOperator>(arg);
                        if (op->getOpcode() == UO_AddrOf) {
                                is_addr = 1;
                                arg = op->getSubExpr();
                        }
                }
                res->args[i] = PetScan::extract_expr(arg);
                if (!res->args[i])
                        goto error;
                if (arg->getStmtClass() == Stmt::ArraySubscriptExprClass &&
                    array_depth(arg->getType().getTypePtr()) > 0)
                        is_addr = 1;
                if (is_addr && res->args[i]->type == pet_expr_access) {
                        ParmVarDecl *parm = fd->getParamDecl(i);
                        if (!const_base(parm->getType())) {
                                res->args[i]->acc.write = 1;
                                res->args[i]->acc.read = 0;
                        }
                }
        }

        return res;
error:
        pet_expr_free(res);
        return NULL;
}

/* Try and onstruct a pet_expr representing "expr".
 */
struct pet_expr *PetScan::extract_expr(Expr *expr)
{
        switch (expr->getStmtClass()) {
        case Stmt::UnaryOperatorClass:
                return extract_expr(cast<UnaryOperator>(expr));
        case Stmt::CompoundAssignOperatorClass:
        case Stmt::BinaryOperatorClass:
                return extract_expr(cast<BinaryOperator>(expr));
        case Stmt::ImplicitCastExprClass:
                return extract_expr(cast<ImplicitCastExpr>(expr));
        case Stmt::ArraySubscriptExprClass:
        case Stmt::DeclRefExprClass:
        case Stmt::IntegerLiteralClass:
                return extract_access_expr(expr);
        case Stmt::FloatingLiteralClass:
                return extract_expr(cast<FloatingLiteral>(expr));
        case Stmt::ParenExprClass:
                return extract_expr(cast<ParenExpr>(expr));
        case Stmt::ConditionalOperatorClass:
                return extract_expr(cast<ConditionalOperator>(expr));
        case Stmt::CallExprClass:
                return extract_expr(cast<CallExpr>(expr));
        default:
                unsupported(expr);
        }
        return NULL;
}

/* Extract the initialization part of a for loop.
 * The initialization is required to be an assignment.
 * Return this assignment operator.
 */
BinaryOperator *PetScan::extract_initialization(ForStmt *stmt)
{
        Stmt *init = stmt->getInit();
        BinaryOperator *ass;

        if (!init) {
                unsupported(stmt);
                return NULL;
        }

        if (init->getStmtClass() != Stmt::BinaryOperatorClass) {
                unsupported(init);
                return NULL;
        }

        ass = cast<BinaryOperator>(init);
        if (ass->getOpcode() != BO_Assign) {
                unsupported(init);
                return NULL;
        }

        return ass;
}

/* Given the assignment operator in the initialization of a for loop,
 * extract the induction variable, i.e., the (integer)variable being
 * assigned.
 */
ValueDecl *PetScan::extract_induction_variable(BinaryOperator *init)
{
        Expr *lhs;
        DeclRefExpr *ref;
        ValueDecl *decl;
        const Type *type;

        lhs = init->getLHS();
        if (lhs->getStmtClass() != Stmt::DeclRefExprClass) {
                unsupported(init);
                return NULL;
        }

        ref = cast<DeclRefExpr>(lhs);
        decl = ref->getDecl();
        type = decl->getType().getTypePtr();

        if (!type->isIntegerType()) {
                unsupported(lhs);
                return NULL;
        }

        return decl;
}

/* Check that the increment of the given for loop increments
 * (or decrements) the induction variable "iv".
 * "up" is set to true if the induction variable is incremented.
 */
bool PetScan::check_increment(ForStmt *stmt, ValueDecl *iv, bool &up)
{
        Stmt *inc = stmt->getInc();
        UnaryOperator *op;
        Expr *sub;
        DeclRefExpr *ref;

        if (!inc) {
                unsupported(stmt);
                return false;
        }

        if (inc->getStmtClass() != Stmt::UnaryOperatorClass) {
                unsupported(inc);
                return false;
        }

        op = cast<UnaryOperator>(inc);
        if (!op->isIncrementDecrementOp()) {
                unsupported(inc);
                return false;
        }

        up = op->isIncrementOp();

        sub = op->getSubExpr();
        if (sub->getStmtClass() != Stmt::DeclRefExprClass) {
                unsupported(inc);
                return false;
        }

        ref = cast<DeclRefExpr>(sub);
        if (ref->getDecl() != iv) {
                unsupported(inc);
                return false;
        }

        return true;
}

/* Embed the given iteration domain in an extra outer loop
 * with induction variable "var".
 * If this variable appeared as a parameter in the constraints,
 * it is replaced by the new outermost dimension.
 */
static __isl_give isl_set *embed(__isl_take isl_set *set,
        __isl_take isl_id *var)
{
        int pos;

        set = isl_set_insert(set, isl_dim_set, 0, 1);
        pos = isl_set_find_dim_by_id(set, isl_dim_param, var);
        if (pos >= 0) {
                set = isl_set_equate(set, isl_dim_param, pos, isl_dim_set, 0);
                set = isl_set_project_out(set, isl_dim_param, pos, 1);
        }

        isl_id_free(var);
        return set;
}

/* Construct a pet_scop for an infinite loop, i.e., a loop of the form
 *
 *      for (;;)
 *              body
 *
 * We extract a pet_scop for the body and then embed it in a loop with
 * iteration domain
 *
 *      { [t] : t >= 0 }
 *
 * and schedule
 *
 *      { [t] -> [t] }
 */
struct pet_scop *PetScan::extract_infinite_for(ForStmt *stmt)
{
        isl_id *id;
        isl_dim *dim;
        isl_set *domain;
        isl_map *sched;
        struct pet_scop *scop;

        scop = extract(stmt->getBody());
        if (!scop)
                return NULL;

        id = isl_id_alloc(ctx, "t", NULL);
        domain = isl_set_nat_universe(isl_dim_set_alloc(ctx, 0, 1));
        domain = isl_set_set_dim_id(domain, isl_dim_set, 0, isl_id_copy(id));
        dim = isl_dim_from_domain(isl_set_get_dim(domain));
        dim = isl_dim_add(dim, isl_dim_out, 1);
        sched = isl_map_universe(dim);
        sched = isl_map_equate(sched, isl_dim_in, 0, isl_dim_out, 0);
        scop = pet_scop_embed(scop, domain, sched, id);

        return scop;
}

/* Check whether "expr" expresses a simple loop bound on "iv".
 * In particular, if "up" is set then "expr" should be of the form
 *
 *      iv < ...        or      iv <= ...
 *
 * otherwise, it should be of the form
 *
 *      iv > ...        or      iv >= ...
 */
static bool is_simple_bound(Expr *expr, ValueDecl *iv, bool up)
{
        BinaryOperator *op;
        BinaryOperatorKind opcode;
        Expr *lhs;

        if (!expr)
                return false;

        if (expr->getStmtClass() != Stmt::BinaryOperatorClass)
                return false;

        op = cast<BinaryOperator>(expr);
        opcode = op->getOpcode();

        if (up) {
                if (opcode != BO_LT && opcode != BO_LE)
                        return false;
        } else {
                if (opcode != BO_GT && opcode != BO_GE)
                        return false;
        }

        lhs = op->getLHS();
        if (lhs->getStmtClass() == Stmt::ImplicitCastExprClass)
                lhs = cast<ImplicitCastExpr>(lhs)->getSubExpr();
        if (lhs->getStmtClass() != Stmt::DeclRefExprClass)
                return false;

        if (cast<DeclRefExpr>(lhs)->getDecl() != iv)
                return false;

        return true;
}

/* Extend a condition on a given iteration of a loop to one that
 * imposes the same condition on all previous iterations.
 * "domain" expresses the lower [upper] bound on the iterations
 * when up is set [not set].
 *
 * In particular, we construct the condition (when up is set)
 *
 *      forall i' : (domain(i') and i' <= i) => cond(i')
 *
 * which is equivalent to
 *
 *      not exists i' : domain(i') and i' <= i and not cond(i')
 *
 * We construct this set by negating cond, applying a map
 *
 *      { [i'] -> [i] : domain(i') and i' <= i }
 *
 * and then negating the result again.
 */
static __isl_give isl_set *valid_for_each_iteration(__isl_take isl_set *cond,
        __isl_take isl_set *domain, bool up)
{
        isl_map *previous_to_this;

        if (up)
                previous_to_this = isl_map_lex_le(isl_set_get_dim(domain));
        else
                previous_to_this = isl_map_lex_ge(isl_set_get_dim(domain));

        previous_to_this = isl_map_intersect_domain(previous_to_this, domain);

        cond = isl_set_complement(cond);
        cond = isl_set_apply(cond, previous_to_this);
        cond = isl_set_complement(cond);

        return cond;
}

/* Construct a pet_scop for a for statement.
 * The for loop is required to be of the form
 *
 *      for (i = init; condition; ++i)
 *
 * or
 *
 *      for (i = init; condition; --i)
 *
 * We extract a pet_scop for the body and then embed it in a loop with
 * iteration domain and schedule
 *
 *      { [i] : i >= init and condition' }
 *      { [i] -> [i] }
 *
 * or
 *
 *      { [i] : i <= init and condition' }
 *      { [i] -> [-i] }
 *
 * Where condition' is equal to condition if the latter is
 * a simple upper [lower] bound and a condition that is extended
 * to apply to all previous iterations otherwise.
 *
 * Before extracting a pet_scop from the body we remove all
 * assignments in assigned_value to variables that are assigned
 * somewhere in the body of the loop.
 */
struct pet_scop *PetScan::extract_for(ForStmt *stmt)
{
        BinaryOperator *init;
        ValueDecl *iv;
        isl_dim *dim;
        isl_set *domain;
        isl_map *sched;
        isl_set *cond;
        isl_id *id;
        struct pet_scop *scop;
        bool up = true;
        assigned_value_cache cache(assigned_value);

        if (!stmt->getInit() && !stmt->getCond() && !stmt->getInc())
                return extract_infinite_for(stmt);

        init = PetScan::extract_initialization(stmt);
        if (!init)
                return NULL;
        iv = extract_induction_variable(init);
        if (!iv)
                return NULL;

        if (!check_increment(stmt, iv, up))
                return NULL;

        assigned_value[iv] = NULL;
        clear_assignments clear(assigned_value);
        clear.TraverseStmt(stmt->getBody());

        domain = extract_comparison(up ? BO_GE : BO_LE,
                        init->getLHS(), init->getRHS(), init);

        id = isl_id_alloc(ctx, iv->getName().str().c_str(), iv);

        cond = extract_condition(stmt->getCond());
        cond = embed(cond, isl_id_copy(id));
        domain = embed(domain, isl_id_copy(id));
        if (!is_simple_bound(stmt->getCond(), iv, up))
                cond = valid_for_each_iteration(cond, isl_set_copy(domain), up);
        domain = isl_set_intersect(domain, cond);
        domain = isl_set_set_dim_id(domain, isl_dim_set, 0, isl_id_copy(id));
        dim = isl_dim_from_domain(isl_set_get_dim(domain));
        dim = isl_dim_add(dim, isl_dim_out, 1);
        sched = isl_map_universe(dim);
        if (up)
                sched = isl_map_equate(sched, isl_dim_in, 0, isl_dim_out, 0);
        else
                sched = isl_map_oppose(sched, isl_dim_in, 0, isl_dim_out, 0);

        scop = extract(stmt->getBody());
        scop = pet_scop_embed(scop, domain, sched, id);

        return scop;
}

struct pet_scop *PetScan::extract(CompoundStmt *stmt)
{
        return extract(stmt->children());
}

/* Look for parameters in any access relation in "expr" that
 * refer to non-affine constructs.  In particular, these are
 * parameters with no name.
 *
 * If there are any such parameters, then the domain of the access
 * relation, which is still [] at this point, is replaced by
 * [[] -> [t_1,...,t_n]], with n the number of these parameters
 * (after identifying identical non-affine constructs).
 * The parameters are then equated to the corresponding t dimensions
 * and subsequently projected out.
 * param2pos maps the position of the parameter to the position
 * of the corresponding t dimension.
 */
struct pet_expr *PetScan::resolve_nested(struct pet_expr *expr)
{
        int n;
        int nparam;
        int n_in;
        isl_dim *dim;
        isl_map *map;
        std::map<int,int> param2pos;

        if (!expr)
                return expr;

        for (int i = 0; i < expr->n_arg; ++i) {
                expr->args[i] = resolve_nested(expr->args[i]);
                if (!expr->args[i]) {
                        pet_expr_free(expr);
                        return NULL;
                }
        }

        if (expr->type != pet_expr_access)
                return expr;

        nparam = isl_map_dim(expr->acc.access, isl_dim_param);
        n = 0;
        for (int i = 0; i < nparam; ++i) {
                isl_id *id = isl_map_get_dim_id(expr->acc.access,
                                                isl_dim_param, i);
                if (id && isl_id_get_user(id) && !isl_id_get_name(id))
                        n++;
                isl_id_free(id);
        }

        if (n == 0)
                return expr;

        expr->n_arg = n;
        expr->args = isl_calloc_array(ctx, struct pet_expr *, n);
        if (!expr->args)
                goto error;

        n_in = isl_map_dim(expr->acc.access, isl_dim_in);
        for (int i = 0, pos = 0; i < nparam; ++i) {
                int j;
                isl_id *id = isl_map_get_dim_id(expr->acc.access,
                                                isl_dim_param, i);
                Expr *nested;

                if (!(id && isl_id_get_user(id) && !isl_id_get_name(id))) {
                        isl_id_free(id);
                        continue;
                }

                nested = (Expr *) isl_id_get_user(id);
                expr->args[pos] = extract_expr(nested);

                for (j = 0; j < pos; ++j)
                        if (pet_expr_is_equal(expr->args[j], expr->args[pos]))
                                break;

                if (j < pos) {
                        pet_expr_free(expr->args[pos]);
                        param2pos[i] = n_in + j;
                        n--;
                } else
                        param2pos[i] = n_in + pos++;

                isl_id_free(id);
        }
        expr->n_arg = n;

        dim = isl_map_get_dim(expr->acc.access);
        dim = isl_dim_domain(dim);
        dim = isl_dim_from_domain(dim);
        dim = isl_dim_add(dim, isl_dim_out, n);
        map = isl_map_universe(dim);
        map = isl_map_domain_map(map);
        map = isl_map_reverse(map);
        expr->acc.access = isl_map_apply_domain(expr->acc.access, map);

        for (int i = nparam - 1; i >= 0; --i) {
                isl_id *id = isl_map_get_dim_id(expr->acc.access,
                                                isl_dim_param, i);
                if (!(id && isl_id_get_user(id) && !isl_id_get_name(id))) {
                        isl_id_free(id);
                        continue;
                }

                expr->acc.access = isl_map_equate(expr->acc.access,
                                        isl_dim_param, i, isl_dim_in,
                                        param2pos[i]);
                expr->acc.access = isl_map_project_out(expr->acc.access,
                                        isl_dim_param, i, 1);

                isl_id_free(id);
        }

        return expr;
error:
        pet_expr_free(expr);
        return NULL;
}

/* Convert a top-level pet_expr to a pet_scop with one statement.
 * This mainly involves resolving nested expression parameters
 * and setting the name of the iteration space.
 */
struct pet_scop *PetScan::extract(Stmt *stmt, struct pet_expr *expr)
{
        struct pet_stmt *ps;
        SourceLocation loc = stmt->getLocStart();
        int line = PP.getSourceManager().getExpansionLineNumber(loc);

        expr = resolve_nested(expr);
        ps = pet_stmt_from_pet_expr(ctx, line, n_stmt++, expr);
        return pet_scop_from_pet_stmt(ctx, ps);
}

/* Check whether "expr" is an affine expression.
 * We turn on autodetection so that we won't generate any warnings
 * and turn off nesting, so that we won't accept any non-affine constructs.
 */
bool PetScan::is_affine(Expr *expr)
{
        isl_pw_aff *pwaff;
        int save_autodetect = autodetect;
        bool save_nesting = nesting_enabled;

        autodetect = 1;
        nesting_enabled = false;

        pwaff = extract_affine(expr);
        isl_pw_aff_free(pwaff);

        autodetect = save_autodetect;
        nesting_enabled = save_nesting;

        return pwaff != NULL;
}

/* Check whether "expr" is an affine constraint.
 * We turn on autodetection so that we won't generate any warnings
 * and turn off nesting, so that we won't accept any non-affine constructs.
 */
bool PetScan::is_affine_condition(Expr *expr)
{
        isl_set *set;
        int save_autodetect = autodetect;
        bool save_nesting = nesting_enabled;

        autodetect = 1;
        nesting_enabled = false;

        set = extract_condition(expr);
        isl_set_free(set);

        autodetect = save_autodetect;
        nesting_enabled = save_nesting;

        return set != NULL;
}

/* If the top-level expression of "stmt" is an assignment, then
 * return that assignment as a BinaryOperator.
 * Otherwise return NULL.
 */
static BinaryOperator *top_assignment_or_null(Stmt *stmt)
{
        BinaryOperator *ass;

        if (!stmt)
                return NULL;
        if (stmt->getStmtClass() != Stmt::BinaryOperatorClass)
                return NULL;

        ass = cast<BinaryOperator>(stmt);
        if(ass->getOpcode() != BO_Assign)
                return NULL;

        return ass;
}

/* Check if the given if statement is a conditional assignement
 * with a non-affine condition.  If so, construct a pet_scop
 * corresponding to this conditional assignment.  Otherwise return NULL.
 *
 * In particular we check if "stmt" is of the form
 *
 *      if (condition)
 *              a = f(...);
 *      else
 *              a = g(...);
 *
 * where a is some array or scalar access.
 * The constructed pet_scop then corresponds to the expression
 *
 *      a = condition ? f(...) : g(...)
 *
 * All access relations in f(...) are intersected with condition
 * while all access relation in g(...) are intersected with the complement.
 */
struct pet_scop *PetScan::extract_conditional_assignment(IfStmt *stmt)
{
        BinaryOperator *ass_then, *ass_else;
        isl_map *write_then, *write_else;
        isl_set *cond, *comp;
        isl_map *map, *map_true, *map_false;
        int equal;
        struct pet_expr *pe_cond, *pe_then, *pe_else, *pe, *pe_write;
        bool save_nesting = nesting_enabled;

        ass_then = top_assignment_or_null(stmt->getThen());
        ass_else = top_assignment_or_null(stmt->getElse());

        if (!ass_then || !ass_else)
                return NULL;

        if (is_affine_condition(stmt->getCond()))
                return NULL;

        write_then = extract_access(ass_then->getLHS());
        write_else = extract_access(ass_else->getLHS());

        equal = isl_map_is_equal(write_then, write_else);
        isl_map_free(write_else);
        if (equal < 0 || !equal) {
                isl_map_free(write_then);
                return NULL;
        }

        nesting_enabled = allow_nested;
        cond = extract_condition(stmt->getCond());
        nesting_enabled = save_nesting;
        comp = isl_set_complement(isl_set_copy(cond));
        map_true = isl_map_from_domain(isl_set_copy(cond));
        map_true = isl_map_add_dims(map_true, isl_dim_out, 1);
        map_true = isl_map_fix_si(map_true, isl_dim_out, 0, 1);
        map_false = isl_map_from_domain(isl_set_copy(comp));
        map_false = isl_map_add_dims(map_false, isl_dim_out, 1);
        map_false = isl_map_fix_si(map_false, isl_dim_out, 0, 0);
        map = isl_map_union_disjoint(map_true, map_false);

        pe_cond = pet_expr_from_access(map);

        pe_then = extract_expr(ass_then->getRHS());
        pe_then = pet_expr_restrict(pe_then, cond);
        pe_else = extract_expr(ass_else->getRHS());
        pe_else = pet_expr_restrict(pe_else, comp);

        pe = pet_expr_new_ternary(ctx, pe_cond, pe_then, pe_else);
        pe_write = pet_expr_from_access(write_then);
        if (pe_write) {
                pe_write->acc.write = 1;
                pe_write->acc.read = 0;
        }
        pe = pet_expr_new_binary(ctx, pet_op_assign, pe_write, pe);
        return extract(stmt, pe);
}

/* Construct a pet_scop for an if statement.
 */
struct pet_scop *PetScan::extract(IfStmt *stmt)
{
        isl_set *cond;
        struct pet_scop *scop_then, *scop_else, *scop;
        assigned_value_cache cache(assigned_value);

        scop = extract_conditional_assignment(stmt);
        if (scop)
                return scop;

        scop_then = extract(stmt->getThen());

        if (stmt->getElse()) {
                scop_else = extract(stmt->getElse());
                if (autodetect) {
                        if (scop_then && !scop_else) {
                                partial = true;
                                return scop_then;
                        }
                        if (!scop_then && scop_else) {
                                partial = true;
                                return scop_else;
                        }
                }
        }

        cond = extract_condition(stmt->getCond());
        scop = pet_scop_restrict(scop_then, isl_set_copy(cond));

        if (stmt->getElse()) {
                cond = isl_set_complement(cond);
                scop_else = pet_scop_restrict(scop_else, cond);
                scop = pet_scop_add(ctx, scop, scop_else);
        } else
                isl_set_free(cond);

        return scop;
}

/* Try and construct a pet_scop corresponding to "stmt".
 */
struct pet_scop *PetScan::extract(Stmt *stmt)
{
        if (isa<Expr>(stmt))
                return extract(stmt, extract_expr(cast<Expr>(stmt)));

        switch (stmt->getStmtClass()) {
        case Stmt::ForStmtClass:
                return extract_for(cast<ForStmt>(stmt));
        case Stmt::IfStmtClass:
                return extract(cast<IfStmt>(stmt));
        case Stmt::CompoundStmtClass:
                return extract(cast<CompoundStmt>(stmt));
        default:
                unsupported(stmt);
        }

        return NULL;
}

/* Try and construct a pet_scop corresponding to (part of)
 * a sequence of statements.
 */
struct pet_scop *PetScan::extract(StmtRange stmt_range)
{
        pet_scop *scop;
        StmtIterator i;
        int j;
        bool partial_range = false;

        if (autodetect)
                scop = NULL;
        else
                scop = pet_scop_empty(ctx);
        for (i = stmt_range.first, j = 0; i != stmt_range.second; ++i, ++j) {
                Stmt *child = *i;
                struct pet_scop *scop_i;
                scop_i = extract(child);
                if (scop && partial) {
                        pet_scop_free(scop_i);
                        break;
                }
                scop_i = pet_scop_prefix(scop_i, j);
                if (autodetect) {
                        if (!scop) {
                                if (j != 0)
                                        partial_range = true;
                                scop = scop_i;
                        } else if (scop_i)
                                scop = pet_scop_add(ctx, scop, scop_i);
                        else
                                partial = true;
                } else {
                        scop = pet_scop_add(ctx, scop, scop_i);
                }
                if (partial)
                        break;
        }

        if (scop && partial_range)
                partial = true;

        return scop;
}

/* Check if the scop marked by the user is exactly this Stmt
 * or part of this Stmt.
 * If so, return a pet_scop corresponding to the marked region.
 * Otherwise, return NULL.
 */
struct pet_scop *PetScan::scan(Stmt *stmt)
{
        SourceManager &SM = PP.getSourceManager();
        unsigned start_off, end_off;

        start_off = SM.getFileOffset(stmt->getLocStart());
        end_off = SM.getFileOffset(stmt->getLocEnd());

        if (start_off > loc.end)
                return NULL;
        if (end_off < loc.start)
                return NULL;
        if (start_off >= loc.start && end_off <= loc.end) {
                return extract(stmt);
        }

        StmtIterator start;
        for (start = stmt->child_begin(); start != stmt->child_end(); ++start) {
                Stmt *child = *start;
                start_off = SM.getFileOffset(child->getLocStart());
                end_off = SM.getFileOffset(child->getLocEnd());
                if (start_off < loc.start && end_off > loc.end)
                        return scan(child);
                if (start_off >= loc.start)
                        break;
        }

        StmtIterator end;
        for (end = start; end != stmt->child_end(); ++end) {
                Stmt *child = *end;
                start_off = SM.getFileOffset(child->getLocStart());
                if (start_off >= loc.end)
                        break;
        }

        return extract(StmtRange(start, end));
}

/* Set the size of index "pos" of "array" to "size".
 * In particular, add a constraint of the form
 *
 *      i_pos < size
 *
 * to array->extent and a constraint of the form
 *
 *      size >= 0
 *
 * to array->context.
 */
static struct pet_array *update_size(struct pet_array *array, int pos,
        __isl_take isl_pw_aff *size)
{
        isl_set *valid;
        isl_set *univ;
        isl_set *bound;
        isl_dim *dim;
        isl_aff *aff;
        isl_pw_aff *index;
        isl_id *id;

        valid = isl_pw_aff_nonneg_set(isl_pw_aff_copy(size));
        array->context = isl_set_intersect(array->context, valid);

        dim = isl_set_get_dim(array->extent);
        aff = isl_aff_zero(isl_local_space_from_dim(dim));
        aff = isl_aff_add_coefficient_si(aff, isl_dim_set, pos, 1);
        univ = isl_set_universe(isl_aff_get_dim(aff));
        index = isl_pw_aff_alloc(univ, aff);

        size = isl_pw_aff_add_dims(size, isl_dim_set,
                                isl_set_dim(array->extent, isl_dim_set));
        id = isl_set_get_tuple_id(array->extent);
        size = isl_pw_aff_set_tuple_id(size, id);
        bound = isl_pw_aff_lt_set(index, size);

        array->extent = isl_set_intersect(array->extent, bound);

        if (!array->context || !array->extent)
                goto error;

        return array;
error:
        pet_array_free(array);
        return NULL;
}

/* Figure out the size of the array at position "pos" and all
 * subsequent positions from "type" and update "array" accordingly.
 */
struct pet_array *PetScan::set_upper_bounds(struct pet_array *array,
        const Type *type, int pos)
{
        const ArrayType *atype;
        isl_pw_aff *size;

        if (type->isPointerType()) {
                type = type->getPointeeType().getTypePtr();
                return set_upper_bounds(array, type, pos + 1);
        }
        if (!type->isArrayType())
                return array;

        type = type->getCanonicalTypeInternal().getTypePtr();
        atype = cast<ArrayType>(type);

        if (type->isConstantArrayType()) {
                const ConstantArrayType *ca = cast<ConstantArrayType>(atype);
                size = extract_affine(ca->getSize());
                array = update_size(array, pos, size);
        } else if (type->isVariableArrayType()) {
                const VariableArrayType *vla = cast<VariableArrayType>(atype);
                size = extract_affine(vla->getSizeExpr());
                array = update_size(array, pos, size);
        }

        type = atype->getElementType().getTypePtr();

        return set_upper_bounds(array, type, pos + 1);
}

/* Construct and return a pet_array corresponding to the variable "decl".
 * In particular, initialize array->extent to
 *
 *      { name[i_1,...,i_d] : i_1,...,i_d >= 0 }
 *
 * and then call set_upper_bounds to set the upper bounds on the indices
 * based on the type of the variable.
 */
struct pet_array *PetScan::extract_array(isl_ctx *ctx, ValueDecl *decl)
{
        struct pet_array *array;
        QualType qt = decl->getType();
        const Type *type = qt.getTypePtr();
        int depth = array_depth(type);
        QualType base = base_type(qt);
        string name;
        isl_id *id;
        isl_dim *dim;

        array = isl_calloc_type(ctx, struct pet_array);
        if (!array)
                return NULL;

        id = isl_id_alloc(ctx, decl->getName().str().c_str(), decl);
        dim = isl_dim_set_alloc(ctx, 0, depth);
        dim = isl_dim_set_tuple_id(dim, isl_dim_set, id);

        array->extent = isl_set_nat_universe(dim);

        dim = isl_dim_set_alloc(ctx, 0, 0);
        array->context = isl_set_universe(dim);

        array = set_upper_bounds(array, type, 0);
        if (!array)
                return NULL;

        name = base.getAsString();
        array->element_type = strdup(name.c_str());

        return array;
}

/* Construct a list of pet_arrays, one for each array (or scalar)
 * accessed inside "scop" add this list to "scop" and return the result.
 *
 * The context of "scop" is updated with the intesection of
 * the contexts of all arrays, i.e., constraints on the parameters
 * that ensure that the arrays have a valid (non-negative) size.
 */
struct pet_scop *PetScan::scan_arrays(struct pet_scop *scop)
{
        int i;
        set<ValueDecl *> arrays;
        set<ValueDecl *>::iterator it;

        if (!scop)
                return NULL;

        pet_scop_collect_arrays(scop, arrays);

        scop->n_array = arrays.size();
        if (scop->n_array == 0)
                return scop;

        scop->arrays = isl_calloc_array(ctx, struct pet_array *, scop->n_array);
        if (!scop->arrays)
                goto error;

        for (it = arrays.begin(), i = 0; it != arrays.end(); ++it, ++i) {
                struct pet_array *array;
                scop->arrays[i] = array = extract_array(ctx, *it);
                if (!scop->arrays[i])
                        goto error;
                scop->context = isl_set_intersect(scop->context,
                                                isl_set_copy(array->context));
                if (!scop->context)
                        goto error;
        }

        return scop;
error:
        pet_scop_free(scop);
        return NULL;
}

/* Construct a pet_scop from the given function.
 */
struct pet_scop *PetScan::scan(FunctionDecl *fd)
{
        pet_scop *scop;
        Stmt *stmt;

        stmt = fd->getBody();

        if (autodetect)
                scop = extract(stmt);
        else
                scop = scan(stmt);
        scop = pet_scop_detect_parameter_accesses(scop);
        scop = scan_arrays(scop);

        return scop;
}