source: src/GenPoly/Specialize.cc @ 64cb860

//
// 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.
//
// Specialize.cc --
//
// Author           : Richard C. Bilson
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Mon Mar  6 23:13:00 2017
// Update Count     : 30
//

#include <cassert>

#include "Specialize.h"
#include "GenPoly.h"
#include "PolyMutator.h"

#include "Parser/ParseNode.h"

#include "SynTree/Expression.h"
#include "SynTree/Statement.h"
#include "SynTree/Type.h"
#include "SynTree/Attribute.h"
#include "SynTree/TypeSubstitution.h"
#include "SynTree/Mutator.h"
#include "ResolvExpr/FindOpenVars.h"
#include "Common/UniqueName.h"
#include "Common/utility.h"
#include "InitTweak/InitTweak.h"
#include "Tuples/Tuples.h"

namespace GenPoly {
        class Specialize final : public PolyMutator {
          public:
                using PolyMutator::mutate;
                virtual Expression * mutate( ApplicationExpr *applicationExpr ) override;
                virtual Expression * mutate( AddressExpr *castExpr ) override;
                virtual Expression * mutate( CastExpr *castExpr ) override;
                // virtual Expression * mutate( LogicalExpr *logicalExpr );
                // virtual Expression * mutate( ConditionalExpr *conditionalExpr );
                // virtual Expression * mutate( CommaExpr *commaExpr );

                void handleExplicitParams( ApplicationExpr *appExpr );
                Expression * createThunkFunction( FunctionType *funType, Expression *actual, InferredParams *inferParams );
                Expression * doSpecialization( Type *formalType, Expression *actual, InferredParams *inferParams = nullptr );

                std::string paramPrefix = "_p";
        };

        /// Looks up open variables in actual type, returning true if any of them are bound in the environment or formal type.
        bool needsPolySpecialization( Type *formalType, Type *actualType, TypeSubstitution *env ) {
                if ( env ) {
                        using namespace ResolvExpr;
                        OpenVarSet openVars, closedVars;
                        AssertionSet need, have;
                        findOpenVars( formalType, openVars, closedVars, need, have, false );
                        findOpenVars( actualType, openVars, closedVars, need, have, true );
                        for ( OpenVarSet::const_iterator openVar = openVars.begin(); openVar != openVars.end(); ++openVar ) {
                                Type *boundType = env->lookup( openVar->first );
                                if ( ! boundType ) continue;
                                if ( TypeInstType *typeInst = dynamic_cast< TypeInstType* >( boundType ) ) {
                                        if ( closedVars.find( typeInst->get_name() ) == closedVars.end() ) {
                                                return true;
                                        } // if
                                } else {
                                        return true;
                                } // if
                        } // for
                        return false;
                } else {
                        return false;
                } // if
        }

        bool needsTupleSpecialization( Type *formalType, Type *actualType, TypeSubstitution *env ) {
                if ( FunctionType * ftype = getFunctionType( formalType ) ) {
                        return ftype->isTtype();
                }
                return false;
        }

        bool needsSpecialization( Type *formalType, Type *actualType, TypeSubstitution *env ) {
                return needsPolySpecialization( formalType, actualType, env ) || needsTupleSpecialization( formalType, actualType, env );
        }

        Expression * Specialize::doSpecialization( Type *formalType, Expression *actual, InferredParams *inferParams ) {
                assertf( actual->has_result(), "attempting to specialize an untyped expression" );
                if ( needsSpecialization( formalType, actual->get_result(), env ) ) {
                        if ( FunctionType *funType = getFunctionType( formalType ) ) {
                                ApplicationExpr *appExpr;
                                VariableExpr *varExpr;
                                if ( ( appExpr = dynamic_cast<ApplicationExpr*>( actual ) ) ) {
                                        return createThunkFunction( funType, appExpr->get_function(), inferParams );
                                } else if ( ( varExpr = dynamic_cast<VariableExpr*>( actual ) ) ) {
                                        return createThunkFunction( funType, varExpr, inferParams );
                                } else {
                                        // This likely won't work, as anything that could build an ApplicationExpr probably hit one of the previous two branches
                                        return createThunkFunction( funType, actual, inferParams );
                                }
                        } else {
                                return actual;
                        } // if
                } else {
                        return actual;
                } // if
        }

        /// restructures arg to match the structure of a single formal parameter. Assumes that atomic types are compatible (as the Resolver should have ensured this)
        template< typename OutIterator >
        void matchOneFormal( Expression * arg, unsigned & idx, Type * formal, OutIterator out ) {
                if ( TupleType * tupleType = dynamic_cast< TupleType * >( formal ) ) {
                        std::list< Expression * > exprs;
                        for ( Type * t : *tupleType ) {
                                matchOneFormal( arg, idx, t, back_inserter( exprs ) );
                        }
                        *out++ = new TupleExpr( exprs );
                } else {
                        *out++ = new TupleIndexExpr( arg->clone(), idx++ );
                }
        }

        /// restructures the ttype argument to match the structure of the formal parameters of the actual function.
        /// [begin, end) are the formal parameters.
        /// args is the list of arguments currently given to the actual function, the last of which needs to be restructured.
        template< typename Iterator, typename OutIterator >
        void fixLastArg( Expression * last, Iterator begin, Iterator end, OutIterator out ) {
                if ( Tuples::isTtype( last->get_result() ) ) {
                        *out++ = last;
                } else {
                        // safe_dynamic_cast for the assertion
                        safe_dynamic_cast< TupleType * >( last->get_result() );
                        unsigned idx = 0;
                        for ( ; begin != end; ++begin ) {
                                DeclarationWithType * formal = *begin;
                                Type * formalType = formal->get_type();
                                matchOneFormal( last, idx, formalType, out );
                        }
                        delete last;
                }
        }

        /// Generates a thunk that calls `actual` with type `funType` and returns its address
        Expression * Specialize::createThunkFunction( FunctionType *funType, Expression *actual, InferredParams *inferParams ) {
                static UniqueName thunkNamer( "_thunk" );

                FunctionType *newType = funType->clone();
                if ( env ) {
                        // it is important to replace only occurrences of type variables that occur free in the
                        // thunk's type
                        env->applyFree( newType );
                } // if
                // create new thunk with same signature as formal type (C linkage, empty body)
                FunctionDecl *thunkFunc = new FunctionDecl( thunkNamer.newName(), DeclarationNode::StorageClasses(), LinkageSpec::C, newType, new CompoundStmt( noLabels ) );
                thunkFunc->fixUniqueId();

                // thunks may be generated and not used - silence warning with attribute
                thunkFunc->get_attributes().push_back( new Attribute( "unused" ) );

                // thread thunk parameters into call to actual function, naming thunk parameters as we go
                UniqueName paramNamer( paramPrefix );
                ApplicationExpr *appExpr = new ApplicationExpr( actual );

                FunctionType * actualType = getFunctionType( actual->get_result() )->clone();
                if ( env ) {
                        // need to apply the environment to the actual function's type, since it may itself be polymorphic
                        env->apply( actualType );
                }
                std::unique_ptr< FunctionType > actualTypeManager( actualType ); // for RAII
                std::list< DeclarationWithType * >::iterator actualBegin = actualType->get_parameters().begin();
                std::list< DeclarationWithType * >::iterator actualEnd = actualType->get_parameters().end();
                std::list< DeclarationWithType * >::iterator formalBegin = funType->get_parameters().begin();
                std::list< DeclarationWithType * >::iterator formalEnd = funType->get_parameters().end();

                for ( DeclarationWithType* param : thunkFunc->get_functionType()->get_parameters() ) {
                        // walk the parameters to the actual function alongside the parameters to the thunk to find the location where the ttype parameter begins to satisfy parameters in the actual function.
                        param->set_name( paramNamer.newName() );
                        assertf( formalBegin != formalEnd, "Reached end of formal parameters before finding ttype parameter" );
                        if ( Tuples::isTtype((*formalBegin)->get_type()) ) {
                                fixLastArg( new VariableExpr( param ), actualBegin, actualEnd, back_inserter( appExpr->get_args() ) );
                                break;
                        }
                        assertf( actualBegin != actualEnd, "reached end of actual function's arguments before finding ttype parameter" );
                        ++actualBegin;
                        ++formalBegin;

                        appExpr->get_args().push_back( new VariableExpr( param ) );
                } // for
                appExpr->set_env( maybeClone( env ) );
                if ( inferParams ) {
                        appExpr->get_inferParams() = *inferParams;
                } // if

                // handle any specializations that may still be present
                std::string oldParamPrefix = paramPrefix;
                paramPrefix += "p";
                // save stmtsToAdd in oldStmts
                std::list< Statement* > oldStmts;
                oldStmts.splice( oldStmts.end(), stmtsToAdd );
                mutate( appExpr );
                paramPrefix = oldParamPrefix;
                // write any statements added for recursive specializations into the thunk body
                thunkFunc->get_statements()->get_kids().splice( thunkFunc->get_statements()->get_kids().end(), stmtsToAdd );
                // restore oldStmts into stmtsToAdd
                stmtsToAdd.splice( stmtsToAdd.end(), oldStmts );

                // add return (or valueless expression) to the thunk
                Statement *appStmt;
                if ( funType->get_returnVals().empty() ) {
                        appStmt = new ExprStmt( noLabels, appExpr );
                } else {
                        appStmt = new ReturnStmt( noLabels, appExpr );
                } // if
                thunkFunc->get_statements()->get_kids().push_back( appStmt );

                // add thunk definition to queue of statements to add
                stmtsToAdd.push_back( new DeclStmt( noLabels, thunkFunc ) );
                // return address of thunk function as replacement expression
                return new AddressExpr( new VariableExpr( thunkFunc ) );
        }

        void Specialize::handleExplicitParams( ApplicationExpr *appExpr ) {
                // create thunks for the explicit parameters
                assert( appExpr->get_function()->has_result() );
                FunctionType *function = getFunctionType( appExpr->get_function()->get_result() );
                assert( function );
                std::list< DeclarationWithType* >::iterator formal;
                std::list< Expression* >::iterator actual;
                for ( formal = function->get_parameters().begin(), actual = appExpr->get_args().begin(); formal != function->get_parameters().end() && actual != appExpr->get_args().end(); ++formal, ++actual ) {
                        *actual = doSpecialization( (*formal )->get_type(), *actual, &appExpr->get_inferParams() );
                }
        }

        Expression * Specialize::mutate( ApplicationExpr *appExpr ) {
                appExpr->get_function()->acceptMutator( *this );
                mutateAll( appExpr->get_args(), *this );

                if ( ! InitTweak::isIntrinsicCallExpr( appExpr ) ) {
                        // create thunks for the inferred parameters
                        // don't need to do this for intrinsic calls, because they aren't actually passed
                        // need to handle explicit params before inferred params so that explicit params do not recieve a changed set of inferParams (and change them again)
                        // alternatively, if order starts to matter then copy appExpr's inferParams and pass them to handleExplicitParams.
                        handleExplicitParams( appExpr );
                        for ( InferredParams::iterator inferParam = appExpr->get_inferParams().begin(); inferParam != appExpr->get_inferParams().end(); ++inferParam ) {
                                inferParam->second.expr = doSpecialization( inferParam->second.formalType, inferParam->second.expr, inferParam->second.inferParams.get() );
                        }
                }
                return appExpr;
        }

        Expression * Specialize::mutate( AddressExpr *addrExpr ) {
                addrExpr->get_arg()->acceptMutator( *this );
                assert( addrExpr->has_result() );
                addrExpr->set_arg( doSpecialization( addrExpr->get_result(), addrExpr->get_arg() ) );
                return addrExpr;
        }

        Expression * Specialize::mutate( CastExpr *castExpr ) {
                castExpr->get_arg()->acceptMutator( *this );
                if ( castExpr->get_result()->isVoid() ) {
                        // can't specialize if we don't have a return value
                        return castExpr;
                }
                Expression *specialized = doSpecialization( castExpr->get_result(), castExpr->get_arg() );
                if ( specialized != castExpr->get_arg() ) {
                        // assume here that the specialization incorporates the cast
                        return specialized;
                } else {
                        return castExpr;
                }
        }

        // Removing these for now. Richard put these in for some reason, but it's not clear why.
        // In particular, copy constructors produce a comma expression, and with this code the parts
        // of that comma expression are not specialized, which causes problems.

        // Expression * Specialize::mutate( LogicalExpr *logicalExpr ) {
        //      return logicalExpr;
        // }

        // Expression * Specialize::mutate( ConditionalExpr *condExpr ) {
        //      return condExpr;
        // }

        // Expression * Specialize::mutate( CommaExpr *commaExpr ) {
        //      return commaExpr;
        // }

        void convertSpecializations( std::list< Declaration* >& translationUnit ) {
                Specialize spec;
                mutateAll( translationUnit, spec );
        }
} // namespace GenPoly

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