source: src/Common/Eval.cc @ 4269d1b

//
// 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.
//
// Eval.cc -- Evaluate parts of the ast at compile time.
//
// Author           : Richard C. Bilson
// Created On       : Mon May 18 07:44:20 2015
// Last Modified By : Peter A. Buhr
// Last Modified On : Sat Aug  6 12:11:59 2022
// Update Count     : 119
//

#include "Eval.h"

#include <utility> // for pair

#include "AST/Inspect.hpp"
#include "Common/PassVisitor.h"
#include "CodeGen/OperatorTable.h"                                              // access: OperatorInfo
#include "AST/Pass.hpp"
#include "InitTweak/InitTweak.h"
#include "SynTree/Expression.h"

//-------------------------------------------------------------
// Old AST
struct EvalOld : public WithShortCircuiting {
        long long int value = 0;                                                        // compose the result of the constant expression
        bool valid = true;                                                                      // true => constant expression and value is the result
                                                                                                                // false => not constant expression, e.g., ++i
        bool cfavalid = true;                                                           // true => constant expression and value computable
                                                                                                                // false => constant expression but value not computable, e.g., sizeof(int)

        void previsit( const BaseSyntaxNode * ) { visit_children = false; }
        void postvisit( const BaseSyntaxNode * ) { valid = false; }

        void postvisit( const SizeofExpr * ) {
        }

        void postvisit( const ConstantExpr * expr ) {
                value = expr->intValue();
        }

        void postvisit( const CastExpr * expr ) {
                auto arg = eval(expr->arg);
                valid = arg.second;
                value = arg.first;
                // TODO: perform type conversion on value if valid
        }

        void postvisit( const VariableExpr * const expr ) {
                if ( EnumInstType * inst = dynamic_cast<EnumInstType *>(expr->result) ) {
                        if ( EnumDecl * decl = inst->baseEnum ) {
                                if ( decl->valueOf( expr->var, value ) ) { // value filled by valueOf
                                        return;
                                }
                        }
                }
                valid = false;
        }

        void postvisit( const ApplicationExpr * expr ) {
                DeclarationWithType * function = InitTweak::getFunction(const_cast<ApplicationExpr *>(expr));
                if ( ! function || function->linkage != LinkageSpec::Intrinsic ) { valid = false; return; }
                const std::string & fname = function->name;
                assertf( expr->args.size() == 1 || expr->args.size() == 2, "Intrinsic function with %zd arguments: %s", expr->args.size(), fname.c_str() );
                std::pair<long long int, bool> arg1, arg2;
                arg1 = eval(expr->args.front());
                valid = valid && arg1.second;
                if ( ! valid ) return;
                if ( expr->args.size() == 2 ) {
                        arg2 = eval(expr->args.back());
                        valid = valid && arg2.second;
                        if ( ! valid ) return;
                }
                if (fname == "?+?") {
                        value = arg1.first + arg2.first;
                } else if (fname == "?-?") {
                        value = arg1.first - arg2.first;
                } else if (fname == "?*?") {
                        value = arg1.first * arg2.first;
                } else if (fname == "?/?") {
                        value = arg1.first / arg2.first;
                } else if (fname == "?%?") {
                        value = arg1.first % arg2.first;
                } else {
                        valid = false;
                }
                // TODO: implement other intrinsic functions
        }
};

//-------------------------------------------------------------
// New AST
struct EvalNew : public ast::WithShortCircuiting {
        Evaluation result = { 0, true, true };

        void previsit( const ast::Node * ) { visit_children = false; }
        void postvisit( const ast::Node * ) { result.isEvaluableInGCC = result.hasKnownValue = false; }

        void postvisit( const ast::UntypedExpr * ) {
                assertf( false, "UntypedExpr in constant expression evaluation" ); // FIX ME, resolve variable
        }

        void postvisit( const ast::ConstantExpr * expr ) {      // only handle int constants
                result.knownValue = expr->intValue();
                result.hasKnownValue = true;
                result.isEvaluableInGCC = true;
        }

        void postvisit( const ast::SizeofExpr * ) {
                result.hasKnownValue = false;
                result.isEvaluableInGCC = true;
        }

        void postvisit( const ast::AlignofExpr * ) {
                result.hasKnownValue = false;
                result.isEvaluableInGCC = true;
        }

        void postvisit( const ast::OffsetofExpr * ) {
                result.hasKnownValue = false;
                result.isEvaluableInGCC = true;
        }

        void postvisit( const ast::LogicalExpr * expr ) {
                Evaluation arg1, arg2;
                arg1 = eval( expr->arg1 );
                result.isEvaluableInGCC &= arg1.isEvaluableInGCC;
                if ( ! result.isEvaluableInGCC ) return;
                arg2 = eval( expr->arg2 );
                result.isEvaluableInGCC &= arg2.isEvaluableInGCC;
                if ( ! result.isEvaluableInGCC ) return;

                result.hasKnownValue &= arg1.hasKnownValue;
                result.hasKnownValue &= arg2.hasKnownValue;
                if ( ! result.hasKnownValue ) return;

                if ( expr->isAnd ) {
                        result.knownValue = arg1.knownValue && arg2.knownValue;
                } else {
                        result.knownValue = arg1.knownValue || arg2.knownValue;
                } // if
        }

        void postvisit( const ast::ConditionalExpr * expr ) {
                Evaluation arg1, arg2, arg3;
                arg1 = eval( expr->arg1 );
                result.isEvaluableInGCC &= arg1.isEvaluableInGCC;
                if ( ! result.isEvaluableInGCC ) return;
                arg2 = eval( expr->arg2 );
                result.isEvaluableInGCC &= arg2.isEvaluableInGCC;
                if ( ! result.isEvaluableInGCC ) return;
                arg3 = eval( expr->arg3 );
                result.isEvaluableInGCC &= arg3.isEvaluableInGCC;
                if ( ! result.isEvaluableInGCC ) return;

                result.hasKnownValue &= arg1.hasKnownValue;
                result.hasKnownValue &= arg2.hasKnownValue;
                result.hasKnownValue &= arg3.hasKnownValue;
                if ( ! result.hasKnownValue ) return;

                result.knownValue = arg1.knownValue ? arg2.knownValue : arg3.knownValue;
        }

        void postvisit( const ast::CastExpr * expr ) {          
                // cfa-cc generates a cast before every constant and many other places, e.g., (int)3, 
                // so we must use the value from the cast argument, even though we lack any basis for evaluating wraparound effects, etc
                result = eval(expr->arg);
        }

        void postvisit( const ast::VariableExpr * expr ) {
                result.hasKnownValue = false;
                result.isEvaluableInGCC = false;
                if ( const ast::EnumInstType * inst = dynamic_cast<const ast::EnumInstType *>(expr->result.get()) ) {
                        if ( const ast::EnumDecl * decl = inst->base ) {
                                result.isEvaluableInGCC = true;
                                result.hasKnownValue = decl->valueOf( expr->var, result.knownValue ); // result.knownValue filled by valueOf
                        }
                }
        }

        void postvisit( const ast::ApplicationExpr * expr ) {
                const ast::DeclWithType * function = ast::getFunction(expr);
                if ( ! function || function->linkage != ast::Linkage::Intrinsic ) { 
                        result.isEvaluableInGCC = false;
                        result.hasKnownValue = false;
                        return;
                }
                const std::string & fname = function->name;
                assertf( expr->args.size() == 1 || expr->args.size() == 2, "Intrinsic function with %zd arguments: %s", expr->args.size(), fname.c_str() );

                if ( expr->args.size() == 1 ) {
                        // pre/postfix operators ++ and -- => assignment, which is not constant
                        Evaluation arg1;
                        arg1 = eval(expr->args.front());
                        result.isEvaluableInGCC &= arg1.isEvaluableInGCC;
                        if ( ! result.isEvaluableInGCC ) return;

                        result.hasKnownValue &= arg1.hasKnownValue;
                        if ( ! result.hasKnownValue ) return;

                        if (fname == "+?") {
                                result.knownValue = arg1.knownValue;
                        } else if (fname == "-?") {
                                result.knownValue = -arg1.knownValue;
                        } else if (fname == "~?") {
                                result.knownValue = ~arg1.knownValue;
                        } else if (fname == "!?") {
                                result.knownValue = ! arg1.knownValue;
                        } else {
                                result.isEvaluableInGCC = false;
                                result.hasKnownValue = false;
                        } // if
                } else { // => expr->args.size() == 2
                        // infix assignment operators => assignment, which is not constant
                        Evaluation arg1, arg2;
                        arg1 = eval(expr->args.front());
                        result.isEvaluableInGCC &= arg1.isEvaluableInGCC;
                        if ( ! result.isEvaluableInGCC ) return;
                        arg2 = eval(expr->args.back());
                        result.isEvaluableInGCC &= arg2.isEvaluableInGCC;
                        if ( ! result.isEvaluableInGCC ) return;

                        result.hasKnownValue &= arg1.hasKnownValue;
                        result.hasKnownValue &= arg2.hasKnownValue;
                        if ( ! result.hasKnownValue ) return;

                        if (fname == "?+?") {
                                result.knownValue = arg1.knownValue + arg2.knownValue;
                        } else if (fname == "?-?") {
                                result.knownValue = arg1.knownValue - arg2.knownValue;
                        } else if (fname == "?*?") {
                                result.knownValue = arg1.knownValue * arg2.knownValue;
                        } else if (fname == "?/?") {
                                if ( arg2.knownValue ) result.knownValue = arg1.knownValue / arg2.knownValue;
                        } else if (fname == "?%?") {
                                if ( arg2.knownValue ) result.knownValue = arg1.knownValue % arg2.knownValue;
                        } else if (fname == "?<<?") {
                                result.knownValue = arg1.knownValue << arg2.knownValue;
                        } else if (fname == "?>>?") {
                                result.knownValue = arg1.knownValue >> arg2.knownValue;
                        } else if (fname == "?<?") {
                                result.knownValue = arg1.knownValue < arg2.knownValue;
                        } else if (fname == "?>?") {
                                result.knownValue = arg1.knownValue > arg2.knownValue;
                        } else if (fname == "?<=?") {
                                result.knownValue = arg1.knownValue <= arg2.knownValue;
                        } else if (fname == "?>=?") {
                                result.knownValue = arg1.knownValue >= arg2.knownValue;
                        } else if (fname == "?==?") {
                                result.knownValue = arg1.knownValue == arg2.knownValue;
                        } else if (fname == "?!=?") {
                                result.knownValue = arg1.knownValue != arg2.knownValue;
                        } else if (fname == "?&?") {
                                result.knownValue = arg1.knownValue & arg2.knownValue;
                        } else if (fname == "?^?") {
                                result.knownValue = arg1.knownValue ^ arg2.knownValue;
                        } else if (fname == "?|?") {
                                result.knownValue = arg1.knownValue | arg2.knownValue;
                        } else {
                                result.isEvaluableInGCC = false;
                                result.hasKnownValue = false;
                        }
                } // if
                // TODO: implement other intrinsic functions
        }
};

std::pair<long long int, bool> eval( const Expression * expr ) {
        PassVisitor<EvalOld> ev;
        if ( expr ) {
                expr->accept( ev );
                return std::make_pair( ev.pass.value, ev.pass.valid );
        } else {
                return std::make_pair( 0, false );
        }
}

Evaluation eval( const ast::Expr * expr ) {
        if ( expr ) {

                return ast::Pass<EvalNew>::read(expr);
                // Evaluation ret = ast::Pass<EvalNew>::read(expr);
                // ret.knownValue = 777;
                // return ret;

        } else {
                return { 0, false, false };
        }
}

// Local Variables: //
// tab-width: 4 //
// mode: c++ //
// compile-command: "make install" //
// End: //