source: src/AST/Expr.cpp@ 81da70a5

//
// Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo
//
// The contents of this file are covered under the licence agreement in the
// file "LICENCE" distributed with Cforall.
//
// Expr.cpp --
//
// Author           : Aaron B. Moss
// Created On       : Wed May 15 17:00:00 2019
// Last Modified By : Peter A. Buhr
// Created On       : Thr Jun 13 13:38:00 2019
// Update Count     : 6
//

#include "Expr.hpp"

#include <cassert>                 // for strict_dynamic_cast
#include <string>                  // for to_string
#include <vector>

#include "Copy.hpp"                // for shallowCopy
#include "Eval.hpp"                // for call
#include "GenericSubstitution.hpp"
#include "LinkageSpec.hpp"
#include "Stmt.hpp"
#include "Type.hpp"
#include "TypeSubstitution.hpp"
#include "Common/utility.h"
#include "Common/SemanticError.h"
#include "GenPoly/Lvalue.h"        // for referencesPermissable
#include "InitTweak/InitTweak.h"   // for getFunction, getPointerBase
#include "ResolvExpr/typeops.h"    // for extractResultType
#include "Tuples/Tuples.h"         // for makeTupleType

namespace ast {

namespace {
        std::set<std::string> const lvalueFunctionNames = {"*?", "?[?]"};
}

// --- Expr
bool Expr::get_lvalue() const {
        return false;
}

// --- ApplicationExpr

ApplicationExpr::ApplicationExpr( const CodeLocation & loc, const Expr * f,
        std::vector<ptr<Expr>> && as )
: Expr( loc ), func( f ), args( std::move(as) ) {
        // ensure that `ApplicationExpr` result type is `FuncExpr`
        const PointerType * pt = strict_dynamic_cast< const PointerType * >( f->result.get() );
        const FunctionType * fn = strict_dynamic_cast< const FunctionType * >( pt->base.get() );

        result = ResolvExpr::extractResultType( fn );
        assert( result );
}

bool ApplicationExpr::get_lvalue() const {
        if ( const DeclWithType * func = InitTweak::getFunction( this ) ) {
                return func->linkage == Linkage::Intrinsic && lvalueFunctionNames.count( func->name );
        }
        return false;
}

// --- UntypedExpr

UntypedExpr * UntypedExpr::createDeref( const CodeLocation & loc, Expr * arg ) {
        assert( arg );

        UntypedExpr * ret = call( loc, "*?", arg );
        if ( const Type * ty = arg->result ) {
                const Type * base = InitTweak::getPointerBase( ty );
                assertf( base, "expected pointer type in dereference (type was %s)", toString( ty ).c_str() );

                if ( GenPoly::referencesPermissable() ) {
                        // if references are still allowed in the AST, dereference returns a reference
                        ret->result = new ReferenceType{ base };
                } else {
                        // references have been removed, in which case dereference returns an lvalue of the
                        // base type
                        ret->result = base;
                }
        }
        return ret;
}

bool UntypedExpr::get_lvalue() const {
        std::string fname = InitTweak::getFunctionName( this );
        return lvalueFunctionNames.count( fname );
}

UntypedExpr * UntypedExpr::createAssign( const CodeLocation & loc, Expr * lhs, Expr * rhs ) {
        assert( lhs && rhs );

        UntypedExpr * ret = call( loc, "?=?", lhs, rhs );
        if ( lhs->result && rhs->result ) {
                // if both expressions are typed, assumes that this assignment is a C bitwise assignment,
                // so the result is the type of the RHS
                ret->result = rhs->result;
        }
        return ret;
}

// --- AddressExpr

// Address expressions are typed based on the following inference rules:
//    E : lvalue T  &..& (n references)
//   &E :        T *&..& (n references)
//
//    E : T  &..&        (m references)
//   &E : T *&..&        (m-1 references)

namespace {
        /// The type of the address of a type.
        /// Caller is responsible for managing returned memory
        Type * addrType( const Type * type ) {
                if ( const ReferenceType * refType = dynamic_cast< const ReferenceType * >( type ) ) {
                        return new ReferenceType{ addrType( refType->base ), refType->qualifiers };
                } else {
                        return new PointerType{ type };
                }
        }
}

AddressExpr::AddressExpr( const CodeLocation & loc, const Expr * a ) : Expr( loc ), arg( a ) {
        if ( arg->result ) {
                if ( arg->get_lvalue() ) {
                        // lvalue, retains all levels of reference, and gains a pointer inside the references
                        Type * res = addrType( arg->result );
                        result = res;
                } else {
                        // taking address of non-lvalue, must be a reference, loses one layer of reference
                        if ( const ReferenceType * refType =
                                        dynamic_cast< const ReferenceType * >( arg->result.get() ) ) {
                                Type * res = addrType( refType->base );
                                result = res;
                        } else {
                                SemanticError( loc, arg->result.get(),
                                        "Attempt to take address of non-lvalue expression: " );
                        }
                }
        }
}

// --- LabelAddressExpr

// label address always has type `void*`
LabelAddressExpr::LabelAddressExpr( const CodeLocation & loc, Label && a )
: Expr( loc, new PointerType{ new VoidType{} } ), arg( a ) {}

// --- CastExpr

CastExpr::CastExpr( const CodeLocation & loc, const Expr * a, GeneratedFlag g )
: Expr( loc, new VoidType{} ), arg( a ), isGenerated( g ) {}

bool CastExpr::get_lvalue() const {
        // This is actually wrong by C, but it works with our current set-up.
        return arg->get_lvalue();
}

// --- KeywordCastExpr

const char * KeywordCastExpr::targetString() const {
        return AggregateDecl::aggrString( target );
}

// --- UntypedMemberExpr

bool UntypedMemberExpr::get_lvalue() const {
        return aggregate->get_lvalue();
}

// --- MemberExpr

MemberExpr::MemberExpr( const CodeLocation & loc, const DeclWithType * mem, const Expr * agg )
: Expr( loc ), member( mem ), aggregate( agg ) {
        assert( member );
        assert( aggregate );
        assert( aggregate->result );

        // Deep copy on result type avoids mutation on transitively multiply referenced object.
        //
        // Example, adapted from parts of builtins and bootloader:
        //
        // forall(dtype T)
        // struct __Destructor {
        //   T * object;
        //   void (*dtor)(T *);
        // };
        //
        // forall(dtype S)
        // void foo(__Destructor(S) &d) {
        //   if (d.dtor) {  // here
        //   }
        // }
        //
        // Let e be the "d.dtor" guard espression, which is MemberExpr after resolve.  Let d be the
        // declaration of member __Destructor.dtor (an ObjectDecl), as accessed via the top-level
        // declaration of __Destructor.  Consider the types e.result and d.type.  In the old AST, one
        // is a clone of the other.  Ordinary new-AST use would set them up as a multiply-referenced
        // object.
        //
        // e.result: PointerType
        // .base: FunctionType
        // .params.front(): ObjectDecl, the anonymous parameter of type T*
        // .type: PointerType
        // .base: TypeInstType
        // let x = that
        // let y = similar, except start from d.type
        //
        // Consider two code lines down, genericSubstitution(...).apply(result).
        //
        // Applying this chosen-candidate's type substitution means modifying x, substituting
        // S for T.  This mutation should affect x and not y.

        result = deepCopy(mem->get_type());

        // substitute aggregate generic parameters into member type
        genericSubstitution( aggregate->result ).apply( result );
        // ensure appropriate restrictions from aggregate type
        add_qualifiers( result, aggregate->result->qualifiers );
}

MemberExpr::MemberExpr( const CodeLocation & loc, const DeclWithType * mem, const Expr * agg,
    MemberExpr::NoOpConstruction overloadSelector )
: Expr( loc ), member( mem ), aggregate( agg ) {
        assert( member );
        assert( aggregate );
        assert( aggregate->result );
        (void) overloadSelector;
}

bool MemberExpr::get_lvalue() const {
        // This is actually wrong by C, but it works with our current set-up.
        return true;
}

// --- VariableExpr

VariableExpr::VariableExpr( const CodeLocation & loc )
: Expr( loc ), var( nullptr ) {}

VariableExpr::VariableExpr( const CodeLocation & loc, const DeclWithType * v )
: Expr( loc ), var( v ) {
        assert( var );
        assert( var->get_type() );
        result = shallowCopy( var->get_type() );
}

bool VariableExpr::get_lvalue() const {
        // It isn't always an lvalue, but it is never an rvalue.
        return true;
}

VariableExpr * VariableExpr::functionPointer(
                const CodeLocation & loc, const FunctionDecl * decl ) {
        // wrap usually-determined result type in a pointer
        VariableExpr * funcExpr = new VariableExpr{ loc, decl };
        funcExpr->result = new PointerType{ funcExpr->result };
        return funcExpr;
}

// --- ConstantExpr

long long int ConstantExpr::intValue() const {
        if ( const BasicType * bty = result.as< BasicType >() ) {
                if ( bty->isInteger() ) {
                        assert(ival);
                        return ival.value();
                }
        } else if ( result.as< ZeroType >() ) {
                return 0;
        } else if ( result.as< OneType >() ) {
                return 1;
        }
        SemanticError( this, "Constant expression of non-integral type " );
}

ConstantExpr * ConstantExpr::from_bool( const CodeLocation & loc, bool b ) {
        return new ConstantExpr{
                loc, new BasicType{ BasicType::Bool }, b ? "1" : "0", (unsigned long long)b };
}

ConstantExpr * ConstantExpr::from_int( const CodeLocation & loc, int i ) {
        return new ConstantExpr{
                loc, new BasicType{ BasicType::SignedInt }, std::to_string( i ), (unsigned long long)i };
}

ConstantExpr * ConstantExpr::from_ulong( const CodeLocation & loc, unsigned long i ) {
        return new ConstantExpr{
                loc, new BasicType{ BasicType::LongUnsignedInt }, std::to_string( i ),
                (unsigned long long)i };
}

ConstantExpr * ConstantExpr::null( const CodeLocation & loc, const Type * ptrType ) {
        return new ConstantExpr{
                loc, ptrType ? ptrType : new PointerType{ new VoidType{} }, "0", (unsigned long long)0 };
}

// --- SizeofExpr

SizeofExpr::SizeofExpr( const CodeLocation & loc, const Expr * e )
: Expr( loc, new BasicType{ BasicType::LongUnsignedInt } ), expr( e ), type( nullptr ) {}

SizeofExpr::SizeofExpr( const CodeLocation & loc, const Type * t )
: Expr( loc, new BasicType{ BasicType::LongUnsignedInt } ), expr( nullptr ), type( t ) {}

// --- AlignofExpr

AlignofExpr::AlignofExpr( const CodeLocation & loc, const Expr * e )
: Expr( loc, new BasicType{ BasicType::LongUnsignedInt } ), expr( e ), type( nullptr ) {}

AlignofExpr::AlignofExpr( const CodeLocation & loc, const Type * t )
: Expr( loc, new BasicType{ BasicType::LongUnsignedInt } ), expr( nullptr ), type( t ) {}

// --- OffsetofExpr

OffsetofExpr::OffsetofExpr( const CodeLocation & loc, const Type * ty, const DeclWithType * mem )
: Expr( loc, new BasicType{ BasicType::LongUnsignedInt } ), type( ty ), member( mem ) {
        assert( type );
        assert( member );
}

// --- OffsetPackExpr

OffsetPackExpr::OffsetPackExpr( const CodeLocation & loc, const StructInstType * ty )
: Expr( loc, new ArrayType{
        new BasicType{ BasicType::LongUnsignedInt }, nullptr, FixedLen, DynamicDim }
), type( ty ) {
        assert( type );
}

// --- LogicalExpr

LogicalExpr::LogicalExpr(
        const CodeLocation & loc, const Expr * a1, const Expr * a2, LogicalFlag ia )
: Expr( loc, new BasicType{ BasicType::SignedInt } ), arg1( a1 ), arg2( a2 ), isAnd( ia ) {}

// --- CommaExpr
bool CommaExpr::get_lvalue() const {
        // This is wrong by C, but the current implementation uses it.
        // (ex: Specialize, Lvalue and Box)
        return arg2->get_lvalue();
}

// --- ConstructorExpr

ConstructorExpr::ConstructorExpr( const CodeLocation & loc, const Expr * call )
: Expr( loc ), callExpr( call ) {
        // allow resolver to type a constructor used as an expression if it has the same type as its
        // first argument
        assert( callExpr );
        const Expr * arg = InitTweak::getCallArg( callExpr, 0 );
        assert( arg );
        result = arg->result;
}

// --- CompoundLiteralExpr

CompoundLiteralExpr::CompoundLiteralExpr( const CodeLocation & loc, const Type * t, const Init * i )
: Expr( loc ), init( i ) {
        assert( t && i );
        result = t;
}

bool CompoundLiteralExpr::get_lvalue() const {
        return true;
}

// --- TupleExpr

TupleExpr::TupleExpr( const CodeLocation & loc, std::vector<ptr<Expr>> && xs )
: Expr( loc, Tuples::makeTupleType( xs ) ), exprs( xs ) {}

// --- TupleIndexExpr

TupleIndexExpr::TupleIndexExpr( const CodeLocation & loc, const Expr * t, unsigned i )
: Expr( loc ), tuple( t ), index( i ) {
        const TupleType * type = strict_dynamic_cast< const TupleType * >( tuple->result.get() );
        assertf( type->size() > index, "TupleIndexExpr index out of bounds: tuple size %d, requested "
                "index %d in expr %s", type->size(), index, toString( tuple ).c_str() );
        // like MemberExpr, TupleIndexExpr is always an lvalue
        result = type->types[ index ];
}

bool TupleIndexExpr::get_lvalue() const {
        return tuple->get_lvalue();
}

// --- TupleAssignExpr

TupleAssignExpr::TupleAssignExpr(
        const CodeLocation & loc, std::vector<ptr<Expr>> && assigns,
        std::vector<ptr<ObjectDecl>> && tempDecls )
: Expr( loc, Tuples::makeTupleType( assigns ) ), stmtExpr() {
        // convert internally into a StmtExpr which contains the declarations and produces the tuple of
        // the assignments
        std::list<ptr<Stmt>> stmts;
        for ( const ObjectDecl * obj : tempDecls ) {
                stmts.emplace_back( new DeclStmt{ loc, obj } );
        }
        TupleExpr * tupleExpr = new TupleExpr{ loc, std::move(assigns) };
        assert( tupleExpr->result );
        stmts.emplace_back( new ExprStmt{ loc, tupleExpr } );
        stmtExpr = new StmtExpr{ loc, new CompoundStmt{ loc, std::move(stmts) } };
}

TupleAssignExpr::TupleAssignExpr(
        const CodeLocation & loc, const Type * result, const StmtExpr * s )
: Expr( loc, result ), stmtExpr() {
        stmtExpr = s;
}

// --- StmtExpr

StmtExpr::StmtExpr( const CodeLocation & loc, const CompoundStmt * ss )
: Expr( loc ), stmts( ss ), returnDecls(), dtors() { computeResult(); }

void StmtExpr::computeResult() {
        assert( stmts );
        const std::list<ptr<Stmt>> & body = stmts->kids;
        if ( ! returnDecls.empty() ) {
                // prioritize return decl for result type, since if a return decl exists, then the StmtExpr
                // is currently in an intermediate state where the body will always give a void result type
                result = returnDecls.front()->get_type();
        } else if ( ! body.empty() ) {
                if ( const ExprStmt * exprStmt = body.back().as< ExprStmt >() ) {
                        result = exprStmt->expr->result;
                }
        }
        // ensure a result type exists
        if ( ! result ) { result = new VoidType{}; }
}

// --- UniqueExpr

unsigned long long UniqueExpr::nextId = 0;

UniqueExpr::UniqueExpr( const CodeLocation & loc, const Expr * e, unsigned long long i )
: Expr( loc, e->result ), expr( e ), id( i ) {
        assert( expr );
        if ( id == -1ull ) {
                assert( nextId != -1ull );
                id = nextId++;
        }
}

}

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// mode: c++ //
// compile-command: "make install" //
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