pet_check_code.c: use pet_expr_extract_affine

[pet.git] / scan.cc

/*
 * Copyright 2011      Leiden University. All rights reserved.
 * Copyright 2012-2014 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 <string.h>
#include <set>
#include <map>
#include <iostream>
#include <llvm/Support/raw_ostream.h>
#include <clang/AST/ASTContext.h>
#include <clang/AST/ASTDiagnostic.h>
#include <clang/AST/Expr.h>
#include <clang/AST/RecursiveASTVisitor.h>

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

#include "aff.h"
#include "array.h"
#include "clang.h"
#include "context.h"
#include "expr.h"
#include "nest.h"
#include "options.h"
#include "scan.h"
#include "scop.h"
#include "scop_plus.h"
#include "tree.h"
#include "tree2scop.h"

#include "config.h"

using namespace std;
using namespace clang;

static enum pet_op_type UnaryOperatorKind2pet_op_type(UnaryOperatorKind kind)
{
        switch (kind) {
        case UO_Minus:
                return pet_op_minus;
        case UO_Not:
                return pet_op_not;
        case UO_LNot:
                return pet_op_lnot;
        case UO_PostInc:
                return pet_op_post_inc;
        case UO_PostDec:
                return pet_op_post_dec;
        case UO_PreInc:
                return pet_op_pre_inc;
        case UO_PreDec:
                return pet_op_pre_dec;
        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_Rem:
                return pet_op_mod;
        case BO_Shl:
                return pet_op_shl;
        case BO_Shr:
                return pet_op_shr;
        case BO_EQ:
                return pet_op_eq;
        case BO_NE:
                return pet_op_ne;
        case BO_LE:
                return pet_op_le;
        case BO_GE:
                return pet_op_ge;
        case BO_LT:
                return pet_op_lt;
        case BO_GT:
                return pet_op_gt;
        case BO_And:
                return pet_op_and;
        case BO_Xor:
                return pet_op_xor;
        case BO_Or:
                return pet_op_or;
        case BO_LAnd:
                return pet_op_land;
        case BO_LOr:
                return pet_op_lor;
        default:
                return pet_op_last;
        }
}

#if defined(DECLREFEXPR_CREATE_REQUIRES_BOOL)
static DeclRefExpr *create_DeclRefExpr(VarDecl *var)
{
        return DeclRefExpr::Create(var->getASTContext(), var->getQualifierLoc(),
                SourceLocation(), var, false, var->getInnerLocStart(),
                var->getType(), VK_LValue);
}
#elif defined(DECLREFEXPR_CREATE_REQUIRES_SOURCELOCATION)
static DeclRefExpr *create_DeclRefExpr(VarDecl *var)
{
        return DeclRefExpr::Create(var->getASTContext(), var->getQualifierLoc(),
                SourceLocation(), var, var->getInnerLocStart(), var->getType(),
                VK_LValue);
}
#else
static DeclRefExpr *create_DeclRefExpr(VarDecl *var)
{
        return DeclRefExpr::Create(var->getASTContext(), var->getQualifierLoc(),
                var, var->getInnerLocStart(), var->getType(), VK_LValue);
}
#endif

/* 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();
}

/* Create an isl_id that refers to the named declarator "decl".
 */
static __isl_give isl_id *create_decl_id(isl_ctx *ctx, NamedDecl *decl)
{
        return isl_id_alloc(ctx, decl->getName().str().c_str(), decl);
}

PetScan::~PetScan()
{
        std::map<const Type *, pet_expr *>::iterator it;

        for (it = type_size.begin(); it != type_size.end(); ++it)
                pet_expr_free(it->second);

        isl_union_map_free(value_bounds);
}

/* Report a diagnostic, unless autodetect is set.
 */
void PetScan::report(Stmt *stmt, unsigned id)
{
        if (options->autodetect)
                return;

        SourceLocation loc = stmt->getLocStart();
        DiagnosticsEngine &diag = PP.getDiagnostics();
        DiagnosticBuilder B = diag.Report(loc, id) << stmt->getSourceRange();
}

/* 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)
{
        DiagnosticsEngine &diag = PP.getDiagnostics();
        unsigned id = diag.getCustomDiagID(DiagnosticsEngine::Warning,
                                           "unsupported");
        report(stmt, id);
}

/* Report a missing prototype, unless autodetect is set.
 */
void PetScan::report_prototype_required(Stmt *stmt)
{
        DiagnosticsEngine &diag = PP.getDiagnostics();
        unsigned id = diag.getCustomDiagID(DiagnosticsEngine::Warning,
                                           "prototype required");
        report(stmt, id);
}

/* Report a missing increment, unless autodetect is set.
 */
void PetScan::report_missing_increment(Stmt *stmt)
{
        DiagnosticsEngine &diag = PP.getDiagnostics();
        unsigned id = diag.getCustomDiagID(DiagnosticsEngine::Warning,
                                           "missing increment");
        report(stmt, id);
}

/* Extract an integer from "expr".
 */
__isl_give isl_val *PetScan::extract_int(isl_ctx *ctx, IntegerLiteral *expr)
{
        const Type *type = expr->getType().getTypePtr();
        int is_signed = type->hasSignedIntegerRepresentation();
        llvm::APInt val = expr->getValue();
        int is_negative = is_signed && val.isNegative();
        isl_val *v;

        if (is_negative)
                val = -val;

        v = extract_unsigned(ctx, val);

        if (is_negative)
                v = isl_val_neg(v);
        return v;
}

/* Extract an integer from "val", which is assumed to be non-negative.
 */
__isl_give isl_val *PetScan::extract_unsigned(isl_ctx *ctx,
        const llvm::APInt &val)
{
        unsigned n;
        const uint64_t *data;

        data = val.getRawData();
        n = val.getNumWords();
        return isl_val_int_from_chunks(ctx, n, sizeof(uint64_t), data);
}

/* Extract an integer from "expr".
 * Return NULL if "expr" does not (obviously) represent an integer.
 */
__isl_give isl_val *PetScan::extract_int(clang::ParenExpr *expr)
{
        return extract_int(expr->getSubExpr());
}

/* Extract an integer from "expr".
 * Return NULL if "expr" does not (obviously) represent an integer.
 */
__isl_give isl_val *PetScan::extract_int(clang::Expr *expr)
{
        if (expr->getStmtClass() == Stmt::IntegerLiteralClass)
                return extract_int(ctx, cast<IntegerLiteral>(expr));
        if (expr->getStmtClass() == Stmt::ParenExprClass)
                return extract_int(cast<ParenExpr>(expr));

        unsupported(expr);
        return NULL;
}

/* Extract a pet_expr from the APInt "val", which is assumed
 * to be non-negative.
 */
__isl_give pet_expr *PetScan::extract_expr(const llvm::APInt &val)
{
        return pet_expr_new_int(extract_unsigned(ctx, val));
}

/* Return the number of bits needed to represent the type "qt",
 * if it is an integer type.  Otherwise return 0.
 * If qt is signed then return the opposite of the number of bits.
 */
static int get_type_size(QualType qt, ASTContext &ast_context)
{
        int size;

        if (!qt->isIntegerType())
                return 0;

        size = ast_context.getIntWidth(qt);
        if (!qt->isUnsignedIntegerType())
                size = -size;

        return size;
}

/* Return the number of bits needed to represent the type of "decl",
 * if it is an integer type.  Otherwise return 0.
 * If qt is signed then return the opposite of the number of bits.
 */
static int get_type_size(ValueDecl *decl)
{
        return get_type_size(decl->getType(), decl->getASTContext());
}

/* Bound parameter "pos" of "set" to the possible values of "decl".
 */
static __isl_give isl_set *set_parameter_bounds(__isl_take isl_set *set,
        unsigned pos, ValueDecl *decl)
{
        int type_size;
        isl_ctx *ctx;
        isl_val *bound;

        ctx = isl_set_get_ctx(set);
        type_size = get_type_size(decl);
        if (type_size == 0)
                isl_die(ctx, isl_error_invalid, "not an integer type",
                        return isl_set_free(set));
        if (type_size > 0) {
                set = isl_set_lower_bound_si(set, isl_dim_param, pos, 0);
                bound = isl_val_int_from_ui(ctx, type_size);
                bound = isl_val_2exp(bound);
                bound = isl_val_sub_ui(bound, 1);
                set = isl_set_upper_bound_val(set, isl_dim_param, pos, bound);
        } else {
                bound = isl_val_int_from_ui(ctx, -type_size - 1);
                bound = isl_val_2exp(bound);
                bound = isl_val_sub_ui(bound, 1);
                set = isl_set_upper_bound_val(set, isl_dim_param, pos,
                                                isl_val_copy(bound));
                bound = isl_val_neg(bound);
                bound = isl_val_sub_ui(bound, 1);
                set = isl_set_lower_bound_val(set, isl_dim_param, pos, bound);
        }

        return set;
}

__isl_give pet_expr *PetScan::extract_index_expr(ImplicitCastExpr *expr)
{
        return extract_index_expr(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 depth of the array accessed by the index expression "index".
 * If "index" is an affine expression, i.e., if it does not access
 * any array, then return 1.
 * If "index" represent a member access, i.e., if its range is a wrapped
 * relation, then return the sum of the depth of the array of structures
 * and that of the member inside the structure.
 */
static int extract_depth(__isl_keep isl_multi_pw_aff *index)
{
        isl_id *id;
        ValueDecl *decl;

        if (!index)
                return -1;

        if (isl_multi_pw_aff_range_is_wrapping(index)) {
                int domain_depth, range_depth;
                isl_multi_pw_aff *domain, *range;

                domain = isl_multi_pw_aff_copy(index);
                domain = isl_multi_pw_aff_range_factor_domain(domain);
                domain_depth = extract_depth(domain);
                isl_multi_pw_aff_free(domain);
                range = isl_multi_pw_aff_copy(index);
                range = isl_multi_pw_aff_range_factor_range(range);
                range_depth = extract_depth(range);
                isl_multi_pw_aff_free(range);

                return domain_depth + range_depth;
        }

        if (!isl_multi_pw_aff_has_tuple_id(index, isl_dim_out))
                return 1;

        id = isl_multi_pw_aff_get_tuple_id(index, isl_dim_out);
        if (!id)
                return -1;
        decl = (ValueDecl *) isl_id_get_user(id);
        isl_id_free(id);

        return array_depth(decl->getType().getTypePtr());
}

/* Return the depth of the array accessed by the access expression "expr".
 */
static int extract_depth(__isl_keep pet_expr *expr)
{
        isl_multi_pw_aff *index;
        int depth;

        index = pet_expr_access_get_index(expr);
        depth = extract_depth(index);
        isl_multi_pw_aff_free(index);

        return depth;
}

/* Construct a pet_expr representing an index expression for an access
 * to the variable referenced by "expr".
 */
__isl_give pet_expr *PetScan::extract_index_expr(DeclRefExpr *expr)
{
        return extract_index_expr(expr->getDecl());
}

/* Construct a pet_expr representing an index expression for an access
 * to the variable "decl".
 */
__isl_give pet_expr *PetScan::extract_index_expr(ValueDecl *decl)
{
        isl_id *id = create_decl_id(ctx, decl);
        isl_space *space = isl_space_alloc(ctx, 0, 0, 0);

        space = isl_space_set_tuple_id(space, isl_dim_out, id);

        return pet_expr_from_index(isl_multi_pw_aff_zero(space));
}

/* Construct a pet_expr representing the index expression "expr"
 * Return NULL on error.
 */
__isl_give pet_expr *PetScan::extract_index_expr(Expr *expr)
{
        switch (expr->getStmtClass()) {
        case Stmt::ImplicitCastExprClass:
                return extract_index_expr(cast<ImplicitCastExpr>(expr));
        case Stmt::DeclRefExprClass:
                return extract_index_expr(cast<DeclRefExpr>(expr));
        case Stmt::ArraySubscriptExprClass:
                return extract_index_expr(cast<ArraySubscriptExpr>(expr));
        case Stmt::IntegerLiteralClass:
                return extract_expr(cast<IntegerLiteral>(expr));
        case Stmt::MemberExprClass:
                return extract_index_expr(cast<MemberExpr>(expr));
        default:
                unsupported(expr);
        }
        return NULL;
}

/* Extract an index expression from the given array subscript expression.
 *
 * We first extract an index expression from the base.
 * This will result in an index expression with a range that corresponds
 * to the earlier indices.
 * We then extract the current index and let
 * pet_expr_access_subscript combine the two.
 */
__isl_give pet_expr *PetScan::extract_index_expr(ArraySubscriptExpr *expr)
{
        Expr *base = expr->getBase();
        Expr *idx = expr->getIdx();
        pet_expr *index;
        pet_expr *base_expr;

        base_expr = extract_index_expr(base);
        index = extract_expr(idx);

        base_expr = pet_expr_access_subscript(base_expr, index);

        return base_expr;
}

/* Extract an index expression from a member expression.
 *
 * If the base access (to the structure containing the member)
 * is of the form
 *
 *      A[..]
 *
 * and the member is called "f", then the member access is of
 * the form
 *
 *      A_f[A[..] -> f[]]
 *
 * If the member access is to an anonymous struct, then simply return
 *
 *      A[..]
 *
 * If the member access in the source code is of the form
 *
 *      A->f
 *
 * then it is treated as
 *
 *      A[0].f
 */
__isl_give pet_expr *PetScan::extract_index_expr(MemberExpr *expr)
{
        Expr *base = expr->getBase();
        FieldDecl *field = cast<FieldDecl>(expr->getMemberDecl());
        pet_expr *base_index;
        isl_id *id;

        base_index = extract_index_expr(base);

        if (expr->isArrow()) {
                pet_expr *index = pet_expr_new_int(isl_val_zero(ctx));
                base_index = pet_expr_access_subscript(base_index, index);
        }

        if (field->isAnonymousStructOrUnion())
                return base_index;

        id = create_decl_id(ctx, field);

        return pet_expr_access_member(base_index, id);
}

/* Mark the given access pet_expr as a write.
 */
static __isl_give pet_expr *mark_write(__isl_take pet_expr *access)
{
        access = pet_expr_access_set_write(access, 1);
        access = pet_expr_access_set_read(access, 0);

        return access;
}

/* Construct a pet_expr representing a unary operator expression.
 */
__isl_give pet_expr *PetScan::extract_expr(UnaryOperator *expr)
{
        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());

        if (expr->isIncrementDecrementOp() &&
            pet_expr_get_type(arg) == pet_expr_access) {
                arg = mark_write(arg);
                arg = pet_expr_access_set_read(arg, 1);
        }

        return pet_expr_new_unary(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.
 */
__isl_give pet_expr *PetScan::extract_expr(BinaryOperator *expr)
{
        int type_size;
        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() &&
            pet_expr_get_type(lhs) == pet_expr_access) {
                lhs = mark_write(lhs);
                if (expr->isCompoundAssignmentOp())
                        lhs = pet_expr_access_set_read(lhs, 1);
        }

        type_size = get_type_size(expr->getType(), ast_context);
        return pet_expr_new_binary(type_size, op, lhs, rhs);
}

/* Construct a pet_tree for a (single) variable declaration.
 */
__isl_give pet_tree *PetScan::extract(DeclStmt *stmt)
{
        Decl *decl;
        VarDecl *vd;
        pet_expr *lhs, *rhs;
        pet_tree *tree;

        if (!stmt->isSingleDecl()) {
                unsupported(stmt);
                return NULL;
        }

        decl = stmt->getSingleDecl();
        vd = cast<VarDecl>(decl);

        lhs = extract_access_expr(vd);
        lhs = mark_write(lhs);
        if (!vd->getInit())
                tree = pet_tree_new_decl(lhs);
        else {
                rhs = extract_expr(vd->getInit());
                tree = pet_tree_new_decl_init(lhs, rhs);
        }

        return tree;
}

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

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

        return pet_expr_new_ternary(cond, lhs, rhs);
}

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

/* Construct a pet_expr representing a floating point value.
 *
 * If the floating point literal does not appear in a macro,
 * then we use the original representation in the source code
 * as the string representation.  Otherwise, we use the pretty
 * printer to produce a string representation.
 */
__isl_give pet_expr *PetScan::extract_expr(FloatingLiteral *expr)
{
        double d;
        string s;
        const LangOptions &LO = PP.getLangOpts();
        SourceLocation loc = expr->getLocation();

        if (!loc.isMacroID()) {
                SourceManager &SM = PP.getSourceManager();
                unsigned len = Lexer::MeasureTokenLength(loc, SM, LO);
                s = string(SM.getCharacterData(loc), len);
        } else {
                llvm::raw_string_ostream S(s);
                expr->printPretty(S, 0, PrintingPolicy(LO));
                S.str();
        }
        d = expr->getValueAsApproximateDouble();
        return pet_expr_new_double(ctx, d, s.c_str());
}

/* Convert the index expression "index" into an access pet_expr of type "qt".
 */
__isl_give pet_expr *PetScan::extract_access_expr(QualType qt,
        __isl_take pet_expr *index)
{
        int depth;
        int type_size;

        depth = extract_depth(index);
        type_size = get_type_size(qt, ast_context);

        index = pet_expr_set_type_size(index, type_size);
        index = pet_expr_access_set_depth(index, depth);

        return index;
}

/* Extract an index expression from "expr" and then convert it into
 * an access pet_expr.
 */
__isl_give pet_expr *PetScan::extract_access_expr(Expr *expr)
{
        return extract_access_expr(expr->getType(), extract_index_expr(expr));
}

/* Extract an index expression from "decl" and then convert it into
 * an access pet_expr.
 */
__isl_give pet_expr *PetScan::extract_access_expr(ValueDecl *decl)
{
        return extract_access_expr(decl->getType(), extract_index_expr(decl));
}

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

/* Extract an assume statement from the argument "expr"
 * of a __pencil_assume statement.
 */
__isl_give pet_expr *PetScan::extract_assume(Expr *expr)
{
        return pet_expr_new_unary(pet_op_assume, extract_expr(expr));
}

/* Construct a pet_expr corresponding to the function call argument "expr".
 * The argument appears in position "pos" of a call to function "fd".
 *
 * 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.
 */
__isl_give pet_expr *PetScan::extract_argument(FunctionDecl *fd, int pos,
        Expr *expr)
{
        pet_expr *res;
        int is_addr = 0, is_partial = 0;
        Stmt::StmtClass sc;

        if (expr->getStmtClass() == Stmt::ImplicitCastExprClass) {
                ImplicitCastExpr *ice = cast<ImplicitCastExpr>(expr);
                expr = ice->getSubExpr();
        }
        if (expr->getStmtClass() == Stmt::UnaryOperatorClass) {
                UnaryOperator *op = cast<UnaryOperator>(expr);
                if (op->getOpcode() == UO_AddrOf) {
                        is_addr = 1;
                        expr = op->getSubExpr();
                }
        }
        res = extract_expr(expr);
        if (!res)
                return NULL;
        sc = expr->getStmtClass();
        if ((sc == Stmt::ArraySubscriptExprClass ||
             sc == Stmt::MemberExprClass) &&
            array_depth(expr->getType().getTypePtr()) > 0)
                is_partial = 1;
        if ((is_addr || is_partial) &&
            pet_expr_get_type(res) == pet_expr_access) {
                ParmVarDecl *parm;
                if (!fd->hasPrototype()) {
                        report_prototype_required(expr);
                        return pet_expr_free(res);
                }
                parm = fd->getParamDecl(pos);
                if (!const_base(parm->getType()))
                        res = mark_write(res);
        }

        if (is_addr)
                res = pet_expr_new_unary(pet_op_address_of, res);
        return res;
}

/* Construct a pet_expr representing a function call.
 *
 * In the special case of a "call" to __pencil_assume,
 * construct an assume expression instead.
 */
__isl_give pet_expr *PetScan::extract_expr(CallExpr *expr)
{
        pet_expr *res = NULL;
        FunctionDecl *fd;
        string name;
        unsigned n_arg;

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

        name = fd->getDeclName().getAsString();
        n_arg = expr->getNumArgs();

        if (n_arg == 1 && name == "__pencil_assume")
                return extract_assume(expr->getArg(0));

        res = pet_expr_new_call(ctx, name.c_str(), n_arg);
        if (!res)
                return NULL;

        for (int i = 0; i < n_arg; ++i) {
                Expr *arg = expr->getArg(i);
                res = pet_expr_set_arg(res, i,
                                        PetScan::extract_argument(fd, i, arg));
        }

        return res;
}

/* Construct a pet_expr representing a (C style) cast.
 */
__isl_give pet_expr *PetScan::extract_expr(CStyleCastExpr *expr)
{
        pet_expr *arg;
        QualType type;

        arg = extract_expr(expr->getSubExpr());
        if (!arg)
                return NULL;

        type = expr->getTypeAsWritten();
        return pet_expr_new_cast(type.getAsString().c_str(), arg);
}

/* Construct a pet_expr representing an integer.
 */
__isl_give pet_expr *PetScan::extract_expr(IntegerLiteral *expr)
{
        return pet_expr_new_int(extract_int(expr));
}

/* Try and construct a pet_expr representing "expr".
 */
__isl_give 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::MemberExprClass:
                return extract_access_expr(expr);
        case Stmt::IntegerLiteralClass:
                return extract_expr(cast<IntegerLiteral>(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));
        case Stmt::CStyleCastExprClass:
                return extract_expr(cast<CStyleCastExpr>(expr));
        default:
                unsupported(expr);
        }
        return NULL;
}

/* Check if the given initialization statement is an assignment.
 * If so, return that assignment.  Otherwise return NULL.
 */
BinaryOperator *PetScan::initialization_assignment(Stmt *init)
{
        BinaryOperator *ass;

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

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

        return ass;
}

/* Check if the given initialization statement is a declaration
 * of a single variable.
 * If so, return that declaration.  Otherwise return NULL.
 */
Decl *PetScan::initialization_declaration(Stmt *init)
{
        DeclStmt *decl;

        if (init->getStmtClass() != Stmt::DeclStmtClass)
                return NULL;

        decl = cast<DeclStmt>(init);

        if (!decl->isSingleDecl())
                return NULL;

        return decl->getSingleDecl();
}

/* 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;
}

/* Given the initialization statement of a for loop and the single
 * declaration in this initialization statement,
 * extract the induction variable, i.e., the (integer) variable being
 * declared.
 */
VarDecl *PetScan::extract_induction_variable(Stmt *init, Decl *decl)
{
        VarDecl *vd;

        vd = cast<VarDecl>(decl);

        const QualType type = vd->getType();
        if (!type->isIntegerType()) {
                unsupported(init);
                return NULL;
        }

        if (!vd->getInit()) {
                unsupported(init);
                return NULL;
        }

        return vd;
}

/* Check that op is of the form iv++ or iv--.
 * Return a pet_expr representing "1" or "-1" accordingly.
 */
__isl_give pet_expr *PetScan::extract_unary_increment(
        clang::UnaryOperator *op, clang::ValueDecl *iv)
{
        Expr *sub;
        DeclRefExpr *ref;
        isl_val *v;

        if (!op->isIncrementDecrementOp()) {
                unsupported(op);
                return NULL;
        }

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

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

        if (op->isIncrementOp())
                v = isl_val_one(ctx);
        else
                v = isl_val_negone(ctx);

        return pet_expr_new_int(v);
}

/* Check if op is of the form
 *
 *      iv = expr
 *
 * and return the increment "expr - iv" as a pet_expr.
 */
__isl_give pet_expr *PetScan::extract_binary_increment(BinaryOperator *op,
        clang::ValueDecl *iv)
{
        int type_size;
        Expr *lhs;
        DeclRefExpr *ref;
        pet_expr *expr, *expr_iv;

        if (op->getOpcode() != BO_Assign) {
                unsupported(op);
                return NULL;
        }

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

        ref = cast<DeclRefExpr>(lhs);
        if (ref->getDecl() != iv) {
                unsupported(op);
                return NULL;
        }

        expr = extract_expr(op->getRHS());
        expr_iv = extract_expr(lhs);

        type_size = get_type_size(iv->getType(), ast_context);
        return pet_expr_new_binary(type_size, pet_op_sub, expr, expr_iv);
}

/* Check that op is of the form iv += cst or iv -= cst
 * and return a pet_expr corresponding to cst or -cst accordingly.
 */
__isl_give pet_expr *PetScan::extract_compound_increment(
        CompoundAssignOperator *op, clang::ValueDecl *iv)
{
        Expr *lhs;
        DeclRefExpr *ref;
        bool neg = false;
        pet_expr *expr;
        BinaryOperatorKind opcode;

        opcode = op->getOpcode();
        if (opcode != BO_AddAssign && opcode != BO_SubAssign) {
                unsupported(op);
                return NULL;
        }
        if (opcode == BO_SubAssign)
                neg = true;

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

        ref = cast<DeclRefExpr>(lhs);
        if (ref->getDecl() != iv) {
                unsupported(op);
                return NULL;
        }

        expr = extract_expr(op->getRHS());
        if (neg)
                expr = pet_expr_new_unary(pet_op_minus, expr);

        return expr;
}

/* Check that the increment of the given for loop increments
 * (or decrements) the induction variable "iv" and return
 * the increment as a pet_expr if successful.
 */
__isl_give pet_expr *PetScan::extract_increment(clang::ForStmt *stmt,
        ValueDecl *iv)
{
        Stmt *inc = stmt->getInc();

        if (!inc) {
                report_missing_increment(stmt);
                return NULL;
        }

        if (inc->getStmtClass() == Stmt::UnaryOperatorClass)
                return extract_unary_increment(cast<UnaryOperator>(inc), iv);
        if (inc->getStmtClass() == Stmt::CompoundAssignOperatorClass)
                return extract_compound_increment(
                                cast<CompoundAssignOperator>(inc), iv);
        if (inc->getStmtClass() == Stmt::BinaryOperatorClass)
                return extract_binary_increment(cast<BinaryOperator>(inc), iv);

        unsupported(inc);
        return NULL;
}

/* Construct a pet_tree for a while loop.
 *
 * If we were only able to extract part of the body, then simply
 * return that part.
 */
__isl_give pet_tree *PetScan::extract(WhileStmt *stmt)
{
        pet_expr *pe_cond;
        pet_tree *tree;

        tree = extract(stmt->getBody());
        if (partial)
                return tree;
        pe_cond = extract_expr(stmt->getCond());
        tree = pet_tree_new_while(pe_cond, tree);

        return tree;
}

/* Construct a pet_tree for a for statement.
 * The for loop is required to be of one of the following forms
 *
 *      for (i = init; condition; ++i)
 *      for (i = init; condition; --i)
 *      for (i = init; condition; i += constant)
 *      for (i = init; condition; i -= constant)
 *
 * We extract a pet_tree for the body and then include it in a pet_tree
 * of type pet_tree_for.
 *
 * As a special case, we also allow a for loop of the form
 *
 *      for (;;)
 *
 * in which case we return a pet_tree of type pet_tree_infinite_loop.
 *
 * If we were only able to extract part of the body, then simply
 * return that part.
 */
__isl_give pet_tree *PetScan::extract_for(ForStmt *stmt)
{
        BinaryOperator *ass;
        Decl *decl;
        Stmt *init;
        Expr *lhs, *rhs;
        ValueDecl *iv;
        pet_tree *tree;
        struct pet_scop *scop;
        int declared;
        pet_expr *pe_init, *pe_inc, *pe_iv, *pe_cond;

        if (!stmt->getInit() && !stmt->getCond() && !stmt->getInc()) {
                tree = extract(stmt->getBody());
                if (partial)
                        return tree;
                tree = pet_tree_new_infinite_loop(tree);
                return tree;
        }

        init = stmt->getInit();
        if (!init) {
                unsupported(stmt);
                return NULL;
        }
        if ((ass = initialization_assignment(init)) != NULL) {
                iv = extract_induction_variable(ass);
                if (!iv)
                        return NULL;
                lhs = ass->getLHS();
                rhs = ass->getRHS();
        } else if ((decl = initialization_declaration(init)) != NULL) {
                VarDecl *var = extract_induction_variable(init, decl);
                if (!var)
                        return NULL;
                iv = var;
                rhs = var->getInit();
                lhs = create_DeclRefExpr(var);
        } else {
                unsupported(stmt->getInit());
                return NULL;
        }

        declared = !initialization_assignment(stmt->getInit());
        tree = extract(stmt->getBody());
        if (partial)
                return tree;
        pe_iv = extract_access_expr(iv);
        pe_iv = mark_write(pe_iv);
        pe_init = extract_expr(rhs);
        if (!stmt->getCond())
                pe_cond = pet_expr_new_int(isl_val_one(ctx));
        else
                pe_cond = extract_expr(stmt->getCond());
        pe_inc = extract_increment(stmt, iv);
        tree = pet_tree_new_for(declared, pe_iv, pe_init, pe_cond,
                                pe_inc, tree);
        return tree;
}

/* Try and construct a pet_tree corresponding to a compound statement.
 *
 * "skip_declarations" is set if we should skip initial declarations
 * in the children of the compound statements.  This then implies
 * that this sequence of children should not be treated as a block
 * since the initial statements may be skipped.
 */
__isl_give pet_tree *PetScan::extract(CompoundStmt *stmt,
        bool skip_declarations)
{
        return extract(stmt->children(), !skip_declarations, skip_declarations);
}

/* Return the file offset of the expansion location of "Loc".
 */
static unsigned getExpansionOffset(SourceManager &SM, SourceLocation Loc)
{
        return SM.getFileOffset(SM.getExpansionLoc(Loc));
}

#ifdef HAVE_FINDLOCATIONAFTERTOKEN

/* Return a SourceLocation for the location after the first semicolon
 * after "loc".  If Lexer::findLocationAfterToken is available, we simply
 * call it and also skip trailing spaces and newline.
 */
static SourceLocation location_after_semi(SourceLocation loc, SourceManager &SM,
        const LangOptions &LO)
{
        return Lexer::findLocationAfterToken(loc, tok::semi, SM, LO, true);
}

#else

/* Return a SourceLocation for the location after the first semicolon
 * after "loc".  If Lexer::findLocationAfterToken is not available,
 * we look in the underlying character data for the first semicolon.
 */
static SourceLocation location_after_semi(SourceLocation loc, SourceManager &SM,
        const LangOptions &LO)
{
        const char *semi;
        const char *s = SM.getCharacterData(loc);

        semi = strchr(s, ';');
        if (!semi)
                return SourceLocation();
        return loc.getFileLocWithOffset(semi + 1 - s);
}

#endif

/* If the token at "loc" is the first token on the line, then return
 * a location referring to the start of the line.
 * Otherwise, return "loc".
 *
 * This function is used to extend a scop to the start of the line
 * if the first token of the scop is also the first token on the line.
 *
 * We look for the first token on the line.  If its location is equal to "loc",
 * then the latter is the location of the first token on the line.
 */
static SourceLocation move_to_start_of_line_if_first_token(SourceLocation loc,
        SourceManager &SM, const LangOptions &LO)
{
        std::pair<FileID, unsigned> file_offset_pair;
        llvm::StringRef file;
        const char *pos;
        Token tok;
        SourceLocation token_loc, line_loc;
        int col;

        loc = SM.getExpansionLoc(loc);
        col = SM.getExpansionColumnNumber(loc);
        line_loc = loc.getLocWithOffset(1 - col);
        file_offset_pair = SM.getDecomposedLoc(line_loc);
        file = SM.getBufferData(file_offset_pair.first, NULL);
        pos = file.data() + file_offset_pair.second;

        Lexer lexer(SM.getLocForStartOfFile(file_offset_pair.first), LO,
                                        file.begin(), pos, file.end());
        lexer.LexFromRawLexer(tok);
        token_loc = tok.getLocation();

        if (token_loc == loc)
                return line_loc;
        else
                return loc;
}

/* Construct a pet_loc corresponding to the region covered by "range".
 * If "skip_semi" is set, then we assume "range" is followed by
 * a semicolon and also include this semicolon.
 */
__isl_give pet_loc *PetScan::construct_pet_loc(SourceRange range,
        bool skip_semi)
{
        SourceLocation loc = range.getBegin();
        SourceManager &SM = PP.getSourceManager();
        const LangOptions &LO = PP.getLangOpts();
        int line = PP.getSourceManager().getExpansionLineNumber(loc);
        unsigned start, end;

        loc = move_to_start_of_line_if_first_token(loc, SM, LO);
        start = getExpansionOffset(SM, loc);
        loc = range.getEnd();
        if (skip_semi)
                loc = location_after_semi(loc, SM, LO);
        else
                loc = PP.getLocForEndOfToken(loc);
        end = getExpansionOffset(SM, loc);

        return pet_loc_alloc(ctx, start, end, line);
}

/* Convert a top-level pet_expr to an expression pet_tree.
 */
__isl_give pet_tree *PetScan::extract(__isl_take pet_expr *expr,
        SourceRange range, bool skip_semi)
{
        pet_loc *loc;
        pet_tree *tree;

        tree = pet_tree_new_expr(expr);
        loc = construct_pet_loc(range, skip_semi);
        tree = pet_tree_set_loc(tree, loc);

        return tree;
}

/* Construct a pet_tree for an if statement.
 */
__isl_give pet_tree *PetScan::extract(IfStmt *stmt)
{
        pet_expr *pe_cond;
        pet_tree *tree, *tree_else;
        struct pet_scop *scop;
        int int_size;

        pe_cond = extract_expr(stmt->getCond());
        tree = extract(stmt->getThen());
        if (stmt->getElse()) {
                tree_else = extract(stmt->getElse());
                if (options->autodetect) {
                        if (tree && !tree_else) {
                                partial = true;
                                pet_expr_free(pe_cond);
                                return tree;
                        }
                        if (!tree && tree_else) {
                                partial = true;
                                pet_expr_free(pe_cond);
                                return tree_else;
                        }
                }
                tree = pet_tree_new_if_else(pe_cond, tree, tree_else);
        } else
                tree = pet_tree_new_if(pe_cond, tree);
        return tree;
}

/* Try and construct a pet_tree for a label statement.
 * We currently only allow labels on expression statements.
 */
__isl_give pet_tree *PetScan::extract(LabelStmt *stmt)
{
        isl_id *label;
        pet_tree *tree;
        Stmt *sub;

        sub = stmt->getSubStmt();
        if (!isa<Expr>(sub)) {
                unsupported(stmt);
                return NULL;
        }

        label = isl_id_alloc(ctx, stmt->getName(), NULL);

        tree = extract(extract_expr(cast<Expr>(sub)), stmt->getSourceRange(),
                        true);
        tree = pet_tree_set_label(tree, label);
        return tree;
}

/* Update the location of "tree" to include the source range of "stmt".
 *
 * Actually, we create a new location based on the source range of "stmt" and
 * then extend this new location to include the region of the original location.
 * This ensures that the line number of the final location refers to "stmt".
 */
__isl_give pet_tree *PetScan::update_loc(__isl_take pet_tree *tree, Stmt *stmt)
{
        pet_loc *loc, *tree_loc;

        tree_loc = pet_tree_get_loc(tree);
        loc = construct_pet_loc(stmt->getSourceRange(), false);
        loc = pet_loc_update_start_end_from_loc(loc, tree_loc);
        pet_loc_free(tree_loc);

        tree = pet_tree_set_loc(tree, loc);
        return tree;
}

/* Try and construct a pet_tree corresponding to "stmt".
 *
 * If "stmt" is a compound statement, then "skip_declarations"
 * indicates whether we should skip initial declarations in the
 * compound statement.
 *
 * If the constructed pet_tree is not a (possibly) partial representation
 * of "stmt", we update start and end of the pet_scop to those of "stmt".
 * In particular, if skip_declarations is set, then we may have skipped
 * declarations inside "stmt" and so the pet_scop may not represent
 * the entire "stmt".
 * Note that this function may be called with "stmt" referring to the entire
 * body of the function, including the outer braces.  In such cases,
 * skip_declarations will be set and the braces will not be taken into
 * account in tree->loc.
 */
__isl_give pet_tree *PetScan::extract(Stmt *stmt, bool skip_declarations)
{
        pet_tree *tree;

        if (isa<Expr>(stmt))
                return extract(extract_expr(cast<Expr>(stmt)),
                                stmt->getSourceRange(), true);

        switch (stmt->getStmtClass()) {
        case Stmt::WhileStmtClass:
                tree = extract(cast<WhileStmt>(stmt));
                break;
        case Stmt::ForStmtClass:
                tree = extract_for(cast<ForStmt>(stmt));
                break;
        case Stmt::IfStmtClass:
                tree = extract(cast<IfStmt>(stmt));
                break;
        case Stmt::CompoundStmtClass:
                tree = extract(cast<CompoundStmt>(stmt), skip_declarations);
                break;
        case Stmt::LabelStmtClass:
                tree = extract(cast<LabelStmt>(stmt));
                break;
        case Stmt::ContinueStmtClass:
                tree = pet_tree_new_continue(ctx);
                break;
        case Stmt::BreakStmtClass:
                tree = pet_tree_new_break(ctx);
                break;
        case Stmt::DeclStmtClass:
                tree = extract(cast<DeclStmt>(stmt));
                break;
        default:
                unsupported(stmt);
                return NULL;
        }

        if (partial || skip_declarations)
                return tree;

        return update_loc(tree, stmt);
}

/* Try and construct a pet_tree corresponding to (part of)
 * a sequence of statements.
 *
 * "block" is set if the sequence respresents the children of
 * a compound statement.
 * "skip_declarations" is set if we should skip initial declarations
 * in the sequence of statements.
 *
 * If autodetect is set, then we allow the extraction of only a subrange
 * of the sequence of statements.  However, if there is at least one statement
 * for which we could not construct a scop and the final range contains
 * either no statements or at least one kill, then we discard the entire
 * range.
 */
__isl_give pet_tree *PetScan::extract(StmtRange stmt_range, bool block,
        bool skip_declarations)
{
        StmtIterator i;
        int j;
        bool has_kills = false;
        bool partial_range = false;
        pet_tree *tree;
        set<struct pet_stmt *> kills;
        set<struct pet_stmt *>::iterator it;

        for (i = stmt_range.first, j = 0; i != stmt_range.second; ++i, ++j)
                ;

        tree = pet_tree_new_block(ctx, block, j);

        for (i = stmt_range.first; i != stmt_range.second; ++i) {
                Stmt *child = *i;
                pet_tree *tree_i;

                if (pet_tree_block_n_child(tree) == 0 && skip_declarations &&
                    child->getStmtClass() == Stmt::DeclStmtClass)
                        continue;

                tree_i = extract(child);
                if (pet_tree_block_n_child(tree) != 0 && partial) {
                        pet_tree_free(tree_i);
                        break;
                }
                if (tree_i && child->getStmtClass() == Stmt::DeclStmtClass &&
                    block)
                        has_kills = true;
                if (options->autodetect) {
                        if (tree_i)
                                tree = pet_tree_block_add_child(tree, tree_i);
                        else
                                partial_range = true;
                        if (pet_tree_block_n_child(tree) != 0 && !tree_i)
                                partial = true;
                } else {
                        tree = pet_tree_block_add_child(tree, tree_i);
                }

                if (partial || !tree)
                        break;
        }

        if (tree && partial_range) {
                if (pet_tree_block_n_child(tree) == 0 || has_kills) {
                        pet_tree_free(tree);
                        return NULL;
                }
                partial = true;
        }

        return tree;
}

/* Is "T" the type of a variable length array with static size?
 */
static bool is_vla_with_static_size(QualType T)
{
        const VariableArrayType *vlatype;

        if (!T->isVariableArrayType())
                return false;
        vlatype = cast<VariableArrayType>(T);
        return vlatype->getSizeModifier() == VariableArrayType::Static;
}

/* Return the type of "decl" as an array.
 *
 * In particular, if "decl" is a parameter declaration that
 * is a variable length array with a static size, then
 * return the original type (i.e., the variable length array).
 * Otherwise, return the type of decl.
 */
static QualType get_array_type(ValueDecl *decl)
{
        ParmVarDecl *parm;
        QualType T;

        parm = dyn_cast<ParmVarDecl>(decl);
        if (!parm)
                return decl->getType();

        T = parm->getOriginalType();
        if (!is_vla_with_static_size(T))
                return decl->getType();
        return T;
}

extern "C" {
        static __isl_give pet_expr *get_array_size(__isl_keep pet_expr *access,
                void *user);
        static struct pet_array *extract_array(__isl_keep pet_expr *access,
                __isl_keep pet_context *pc, void *user);
}

/* Construct a pet_expr that holds the sizes of the array accessed
 * by "access".
 * This function is used as a callback to pet_context_add_parameters,
 * which is also passed a pointer to the PetScan object.
 */
static __isl_give pet_expr *get_array_size(__isl_keep pet_expr *access,
        void *user)
{
        PetScan *ps = (PetScan *) user;
        isl_id *id;
        ValueDecl *decl;
        const Type *type;

        id = pet_expr_access_get_id(access);
        decl = (ValueDecl *) isl_id_get_user(id);
        isl_id_free(id);
        type = get_array_type(decl).getTypePtr();
        return ps->get_array_size(type);
}

/* Construct and return a pet_array corresponding to the variable
 * accessed by "access".
 * This function is used as a callback to pet_scop_from_pet_tree,
 * which is also passed a pointer to the PetScan object.
 */
static struct pet_array *extract_array(__isl_keep pet_expr *access,
        __isl_keep pet_context *pc, void *user)
{
        PetScan *ps = (PetScan *) user;
        isl_ctx *ctx;
        isl_id *id;
        ValueDecl *iv;

        ctx = pet_expr_get_ctx(access);
        id = pet_expr_access_get_id(access);
        iv = (ValueDecl *) isl_id_get_user(id);
        isl_id_free(id);
        return ps->extract_array(ctx, iv, NULL, pc);
}

/* Extract a pet_scop from "tree".
 *
 * We simply call pet_scop_from_pet_tree with the appropriate arguments and
 * then add pet_arrays for all accessed arrays.
 * We populate the pet_context with assignments for all parameters used
 * inside "tree" or any of the size expressions for the arrays accessed
 * by "tree" so that they can be used in affine expressions.
 */
struct pet_scop *PetScan::extract_scop(__isl_take pet_tree *tree)
{
        int int_size;
        isl_set *domain;
        pet_context *pc;
        pet_scop *scop;

        int_size = ast_context.getTypeInfo(ast_context.IntTy).first / 8;

        domain = isl_set_universe(isl_space_set_alloc(ctx, 0, 0));
        pc = pet_context_alloc(domain);
        pc = pet_context_add_parameters(pc, tree, &::get_array_size, this);
        scop = pet_scop_from_pet_tree(tree, int_size,
                                        &::extract_array, this, pc);
        scop = scan_arrays(scop, pc);
        pet_context_free(pc);

        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 = getExpansionOffset(SM, stmt->getLocStart());
        end_off = getExpansionOffset(SM, 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_scop(extract(stmt));

        StmtIterator start;
        for (start = stmt->child_begin(); start != stmt->child_end(); ++start) {
                Stmt *child = *start;
                if (!child)
                        continue;
                start_off = getExpansionOffset(SM, child->getLocStart());
                end_off = getExpansionOffset(SM, 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_scop(extract(StmtRange(start, end), false, false));
}

/* 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_space *dim;
        isl_aff *aff;
        isl_pw_aff *index;
        isl_id *id;

        if (!array)
                goto error;

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

        dim = isl_set_get_space(array->extent);
        aff = isl_aff_zero_on_domain(isl_local_space_from_space(dim));
        aff = isl_aff_add_coefficient_si(aff, isl_dim_in, pos, 1);
        univ = isl_set_universe(isl_aff_get_domain_space(aff));
        index = isl_pw_aff_alloc(univ, aff);

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

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

        if (!array->context || !array->extent)
                return pet_array_free(array);

        return array;
error:
        isl_pw_aff_free(size);
        return NULL;
}

/* Figure out the size of the array at position "pos" and all
 * subsequent positions from "type" and update the corresponding
 * argument of "expr" accordingly.
 */
__isl_give pet_expr *PetScan::set_upper_bounds(__isl_take pet_expr *expr,
        const Type *type, int pos)
{
        const ArrayType *atype;
        pet_expr *size;

        if (!expr)
                return NULL;

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

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

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

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

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

/* Construct a pet_expr that holds the sizes of an array of the given type.
 * The returned expression is a call expression with as arguments
 * the sizes in each dimension.  If we are unable to derive the size
 * in a given dimension, then the corresponding argument is set to infinity.
 * In fact, we initialize all arguments to infinity and then update
 * them if we are able to figure out the size.
 *
 * The result is stored in the type_size cache so that we can reuse
 * it if this method gets called on the same type again later on.
 */
__isl_give pet_expr *PetScan::get_array_size(const Type *type)
{
        int depth;
        pet_expr *expr, *inf;

        if (type_size.find(type) != type_size.end())
                return pet_expr_copy(type_size[type]);

        depth = array_depth(type);
        inf = pet_expr_new_int(isl_val_infty(ctx));
        expr = pet_expr_new_call(ctx, "bounds", depth);
        for (int i = 0; i < depth; ++i)
                expr = pet_expr_set_arg(expr, i, pet_expr_copy(inf));
        pet_expr_free(inf);

        expr = set_upper_bounds(expr, type, 0);
        type_size[type] = pet_expr_copy(expr);

        return expr;
}

/* Does "expr" represent the "integer" infinity?
 */
static int is_infty(__isl_keep pet_expr *expr)
{
        isl_val *v;
        int res;

        if (pet_expr_get_type(expr) != pet_expr_int)
                return 0;
        v = pet_expr_int_get_val(expr);
        res = isl_val_is_infty(v);
        isl_val_free(v);

        return res;
}

/* Figure out the dimensions of an array "array" based on its type
 * "type" and update "array" accordingly.
 *
 * We first construct a pet_expr that holds the sizes of the array
 * in each dimension.  The resulting expression may containing
 * infinity values for dimension where we are unable to derive
 * a size expression.
 *
 * The arguments of the size expression that have a value different from
 * infinity are then converted to an affine expression
 * within the context "pc" and incorporated into the size of "array".
 * If we are unable to convert a size expression to an affine expression,
 * then we leave the corresponding size of "array" untouched.
 */
struct pet_array *PetScan::set_upper_bounds(struct pet_array *array,
        const Type *type, __isl_keep pet_context *pc)
{
        int n;
        pet_expr *expr;

        if (!array)
                return NULL;

        expr = get_array_size(type);

        n = pet_expr_get_n_arg(expr);
        for (int i = 0; i < n; ++i) {
                pet_expr *arg;
                isl_pw_aff *size;

                arg = pet_expr_get_arg(expr, i);
                if (!is_infty(arg)) {
                        size = pet_expr_extract_affine(arg, pc);
                        if (!size)
                                array = pet_array_free(array);
                        else if (isl_pw_aff_involves_nan(size))
                                isl_pw_aff_free(size);
                        else
                                array = update_size(array, i, size);
                }
                pet_expr_free(arg);
        }
        pet_expr_free(expr);

        return array;
}

/* Does "decl" have definition that we can keep track of in a pet_type?
 */
static bool has_printable_definition(RecordDecl *decl)
{
        if (!decl->getDeclName())
                return false;
        return decl->getLexicalDeclContext() == decl->getDeclContext();
}

/* 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.  The upper bounds are converted
 * to affine expressions within the context "pc".
 *
 * If the base type is that of a record with a top-level definition and
 * if "types" is not null, then the RecordDecl corresponding to the type
 * is added to "types".
 *
 * If the base type is that of a record with no top-level definition,
 * then we replace it by "<subfield>".
 */
struct pet_array *PetScan::extract_array(isl_ctx *ctx, ValueDecl *decl,
        lex_recorddecl_set *types, __isl_keep pet_context *pc)
{
        struct pet_array *array;
        QualType qt = get_array_type(decl);
        const Type *type = qt.getTypePtr();
        int depth = array_depth(type);
        QualType base = pet_clang_base_type(qt);
        string name;
        isl_id *id;
        isl_space *dim;

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

        id = create_decl_id(ctx, decl);
        dim = isl_space_set_alloc(ctx, 0, depth);
        dim = isl_space_set_tuple_id(dim, isl_dim_set, id);

        array->extent = isl_set_nat_universe(dim);

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

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

        name = base.getAsString();

        if (types && base->isRecordType()) {
                RecordDecl *decl = pet_clang_record_decl(base);
                if (has_printable_definition(decl))
                        types->insert(decl);
                else
                        name = "<subfield>";
        }

        array->element_type = strdup(name.c_str());
        array->element_is_record = base->isRecordType();
        array->element_size = decl->getASTContext().getTypeInfo(base).first / 8;

        return array;
}

/* Construct and return a pet_array corresponding to the sequence
 * of declarations "decls".
 * The upper bounds of the array are converted to affine expressions
 * within the context "pc".
 * If the sequence contains a single declaration, then it corresponds
 * to a simple array access.  Otherwise, it corresponds to a member access,
 * with the declaration for the substructure following that of the containing
 * structure in the sequence of declarations.
 * We start with the outermost substructure and then combine it with
 * information from the inner structures.
 *
 * Additionally, keep track of all required types in "types".
 */
struct pet_array *PetScan::extract_array(isl_ctx *ctx,
        vector<ValueDecl *> decls, lex_recorddecl_set *types,
        __isl_keep pet_context *pc)
{
        struct pet_array *array;
        vector<ValueDecl *>::iterator it;

        it = decls.begin();

        array = extract_array(ctx, *it, types, pc);

        for (++it; it != decls.end(); ++it) {
                struct pet_array *parent;
                const char *base_name, *field_name;
                char *product_name;

                parent = array;
                array = extract_array(ctx, *it, types, pc);
                if (!array)
                        return pet_array_free(parent);

                base_name = isl_set_get_tuple_name(parent->extent);
                field_name = isl_set_get_tuple_name(array->extent);
                product_name = pet_array_member_access_name(ctx,
                                                        base_name, field_name);

                array->extent = isl_set_product(isl_set_copy(parent->extent),
                                                array->extent);
                if (product_name)
                        array->extent = isl_set_set_tuple_name(array->extent,
                                                                product_name);
                array->context = isl_set_intersect(array->context,
                                                isl_set_copy(parent->context));

                pet_array_free(parent);
                free(product_name);

                if (!array->extent || !array->context || !product_name)
                        return pet_array_free(array);
        }

        return array;
}

/* Add a pet_type corresponding to "decl" to "scop, provided
 * it is a member of "types" and it has not been added before
 * (i.e., it is not a member of "types_done".
 *
 * Since we want the user to be able to print the types
 * in the order in which they appear in the scop, we need to
 * make sure that types of fields in a structure appear before
 * that structure.  We therefore call ourselves recursively
 * on the types of all record subfields.
 */
static struct pet_scop *add_type(isl_ctx *ctx, struct pet_scop *scop,
        RecordDecl *decl, Preprocessor &PP, lex_recorddecl_set &types,
        lex_recorddecl_set &types_done)
{
        string s;
        llvm::raw_string_ostream S(s);
        RecordDecl::field_iterator it;

        if (types.find(decl) == types.end())
                return scop;
        if (types_done.find(decl) != types_done.end())
                return scop;

        for (it = decl->field_begin(); it != decl->field_end(); ++it) {
                RecordDecl *record;
                QualType type = it->getType();

                if (!type->isRecordType())
                        continue;
                record = pet_clang_record_decl(type);
                scop = add_type(ctx, scop, record, PP, types, types_done);
        }

        if (strlen(decl->getName().str().c_str()) == 0)
                return scop;

        decl->print(S, PrintingPolicy(PP.getLangOpts()));
        S.str();

        scop->types[scop->n_type] = pet_type_alloc(ctx,
                                    decl->getName().str().c_str(), s.c_str());
        if (!scop->types[scop->n_type])
                return pet_scop_free(scop);

        types_done.insert(decl);

        scop->n_type++;

        return scop;
}

/* 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 upper bounds of the arrays are converted to affine expressions
 * within the context "pc".
 *
 * The context of "scop" is updated with the intersection of
 * the contexts of all arrays, i.e., constraints on the parameters
 * that ensure that the arrays have a valid (non-negative) size.
 *
 * If the any of the extracted arrays refers to a member access,
 * then also add the required types to "scop".
 */
struct pet_scop *PetScan::scan_arrays(struct pet_scop *scop,
        __isl_keep pet_context *pc)
{
        int i;
        array_desc_set arrays;
        array_desc_set::iterator it;
        lex_recorddecl_set types;
        lex_recorddecl_set types_done;
        lex_recorddecl_set::iterator types_it;
        int n_array;
        struct pet_array **scop_arrays;

        if (!scop)
                return NULL;

        pet_scop_collect_arrays(scop, arrays);
        if (arrays.size() == 0)
                return scop;

        n_array = scop->n_array;

        scop_arrays = isl_realloc_array(ctx, scop->arrays, struct pet_array *,
                                        n_array + arrays.size());
        if (!scop_arrays)
                goto error;
        scop->arrays = scop_arrays;

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

        if (types.size() == 0)
                return scop;

        scop->types = isl_alloc_array(ctx, struct pet_type *, types.size());
        if (!scop->types)
                goto error;

        for (types_it = types.begin(); types_it != types.end(); ++types_it)
                scop = add_type(ctx, scop, *types_it, PP, types, types_done);

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

/* Bound all parameters in scop->context to the possible values
 * of the corresponding C variable.
 */
static struct pet_scop *add_parameter_bounds(struct pet_scop *scop)
{
        int n;

        if (!scop)
                return NULL;

        n = isl_set_dim(scop->context, isl_dim_param);
        for (int i = 0; i < n; ++i) {
                isl_id *id;
                ValueDecl *decl;

                id = isl_set_get_dim_id(scop->context, isl_dim_param, i);
                if (pet_nested_in_id(id)) {
                        isl_id_free(id);
                        isl_die(isl_set_get_ctx(scop->context),
                                isl_error_internal,
                                "unresolved nested parameter", goto error);
                }
                decl = (ValueDecl *) isl_id_get_user(id);
                isl_id_free(id);

                scop->context = set_parameter_bounds(scop->context, i, decl);

                if (!scop->context)
                        goto error;
        }

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

/* Construct a pet_scop from the given function.
 *
 * If the scop was delimited by scop and endscop pragmas, then we override
 * the file offsets by those derived from the pragmas.
 */
struct pet_scop *PetScan::scan(FunctionDecl *fd)
{
        pet_scop *scop;
        Stmt *stmt;

        stmt = fd->getBody();

        if (options->autodetect) {
                scop = extract_scop(extract(stmt, true));
        } else {
                scop = scan(stmt);
                scop = pet_scop_update_start_end(scop, loc.start, loc.end);
        }
        scop = add_parameter_bounds(scop);
        scop = pet_scop_gist(scop, value_bounds);

        return scop;
}