source: src/InitTweak/FixGlobalInit.cc@ b3f9684c

//
// 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.
//
// FixGlobalInit.cc --
//
// Author           : Rob Schluntz
// Created On       : Mon May 04 15:14:56 2016
// Last Modified By : Peter A. Buhr
// Last Modified On : Fri Dec 13 23:41:10 2019
// Update Count     : 19
//

#include "FixGlobalInit.h"

#include <cassert>                 // for assert
#include <stddef.h>                // for NULL
#include <algorithm>               // for replace_if

#include "Common/PassVisitor.h"
#include "Common/UniqueName.h"     // for UniqueName
#include "InitTweak.h"             // for isIntrinsicSingleArgCallStmt
#include "SynTree/LinkageSpec.h"   // for C
#include "SynTree/Attribute.h"     // for Attribute
#include "SynTree/Constant.h"      // for Constant
#include "SynTree/Declaration.h"   // for FunctionDecl, ObjectDecl, Declaration
#include "SynTree/Expression.h"    // for ConstantExpr, Expression (ptr only)
#include "SynTree/Initializer.h"   // for ConstructorInit, Initializer
#include "SynTree/Label.h"         // for Label
#include "SynTree/Statement.h"     // for CompoundStmt, Statement (ptr only)
#include "SynTree/Type.h"          // for Type, Type::StorageClasses, Functi...
#include "SynTree/Visitor.h"       // for acceptAll, Visitor

namespace InitTweak {
        class GlobalFixer : public WithShortCircuiting {
          public:
                GlobalFixer( bool inLibrary );

                void previsit( ObjectDecl *objDecl );
                void previsit( FunctionDecl *functionDecl );
                void previsit( StructDecl *aggregateDecl );
                void previsit( UnionDecl *aggregateDecl );
                void previsit( EnumDecl *aggregateDecl );
                void previsit( TraitDecl *aggregateDecl );
                void previsit( TypeDecl *typeDecl );

                UniqueName tempNamer;
                FunctionDecl * initFunction;
                FunctionDecl * destroyFunction;
        };

        void fixGlobalInit( std::list< Declaration * > & translationUnit, bool inLibrary ) {
                PassVisitor<GlobalFixer> visitor( inLibrary );
                acceptAll( translationUnit, visitor );
                GlobalFixer & fixer = visitor.pass;
                // don't need to include function if it's empty
                if ( fixer.initFunction->get_statements()->get_kids().empty() ) {
                        delete fixer.initFunction;
                } else {
                        translationUnit.push_back( fixer.initFunction );
                } // if

                if ( fixer.destroyFunction->get_statements()->get_kids().empty() ) {
                        delete fixer.destroyFunction;
                } else {
                        translationUnit.push_back( fixer.destroyFunction );
                } // if
        }

        GlobalFixer::GlobalFixer( bool inLibrary ) : tempNamer( "_global_init" ) {
                std::list< Expression * > ctorParameters;
                std::list< Expression * > dtorParameters;
                if ( inLibrary ) {
                        // Constructor/destructor attributes take a single parameter which
                        // is the priority, with lower numbers meaning higher priority.
                        // Functions specified with priority are guaranteed to run before
                        // functions without a priority. To ensure that constructors and destructors
                        // for library code are run before constructors and destructors for user code,
                        // specify a priority when building the library. Priorities 0-100 are reserved by gcc.
                        // Priorities 101-200 are reserved by cfa, so use priority 200 for CFA library globals,
                        // allowing room for overriding with a higher priority.
                        ctorParameters.push_back( new ConstantExpr( Constant::from_int( 200 ) ) );
                        dtorParameters.push_back( new ConstantExpr( Constant::from_int( 200 ) ) );
                }
                initFunction = new FunctionDecl( "__global_init__", Type::StorageClasses( Type::Static ), LinkageSpec::C, new FunctionType( Type::Qualifiers(), false ), new CompoundStmt() );
                initFunction->get_attributes().push_back( new Attribute( "constructor", ctorParameters ) );
                destroyFunction = new FunctionDecl( "__global_destroy__", Type::StorageClasses( Type::Static ), LinkageSpec::C, new FunctionType( Type::Qualifiers(), false ), new CompoundStmt() );
                destroyFunction->get_attributes().push_back( new Attribute( "destructor", dtorParameters ) );
        }

        void GlobalFixer::previsit( ObjectDecl *objDecl ) {
                std::list< Statement * > & initStatements = initFunction->get_statements()->get_kids();
                std::list< Statement * > & destroyStatements = destroyFunction->get_statements()->get_kids();

                // C allows you to initialize objects with constant expressions
                // xxx - this is an optimization. Need to first resolve constructors before we decide
                // to keep C-style initializer.
                // if ( isConstExpr( objDecl->get_init() ) ) return;

                if ( ConstructorInit * ctorInit = dynamic_cast< ConstructorInit * >( objDecl->get_init() ) ) {
                        // a decision should have been made by the resolver, so ctor and init are not both non-NULL
                        assert( ! ctorInit->ctor || ! ctorInit->init );

                        Statement * dtor = ctorInit->dtor;
                        if ( dtor && ! isIntrinsicSingleArgCallStmt( dtor ) ) {
                                // don't need to call intrinsic dtor, because it does nothing, but
                                // non-intrinsic dtors must be called
                                destroyStatements.push_front( dtor );
                                ctorInit->dtor = nullptr;
                        } // if
                        if ( Statement * ctor = ctorInit->ctor ) {
                                // Translation 1: Add this attribute on the global declaration:
                                //    __attribute__((section (".data#")))
                                // which makes gcc put the global in the data section,
                                // so that the global is writeable (via a const cast) in the init function.
                                // The trailing # is an injected assembly comment, to suppress the "a" in
                                //    .section .data,"a"
                                //    .section .data#,"a"
                                // to avoid assembler warning "ignoring changed section attributes for .data"
                                Type *strLitT = new PointerType( Type::Qualifiers( ),
                                        new BasicType( Type::Qualifiers( ), BasicType::Char ) );
                                std::list< Expression * > attr_params;
                                attr_params.push_back( 
                                        new ConstantExpr( Constant( strLitT, "\".data#\"", std::nullopt ) ) );
                                objDecl->attributes.push_back(new Attribute("section", attr_params));
                                // Translation 2: Move the initizliation off the global declaration,
                                // into the startup function.
                                initStatements.push_back( ctor );
                                objDecl->init = nullptr;
                                ctorInit->ctor = nullptr;
                        } else if ( Initializer * init = ctorInit->init ) {
                                objDecl->init = init;
                                ctorInit->init = nullptr;
                        } else {
                                // no constructor and no initializer, which is okay
                                objDecl->init = nullptr;
                        } // if
                        delete ctorInit;
                } // if
        }

        // only modify global variables
        void GlobalFixer::previsit( FunctionDecl * ) { visit_children = false; }
        void GlobalFixer::previsit( StructDecl * ) { visit_children = false; }
        void GlobalFixer::previsit( UnionDecl * ) { visit_children = false; }
        void GlobalFixer::previsit( EnumDecl * ) { visit_children = false; }
        void GlobalFixer::previsit( TraitDecl * ) { visit_children = false; }
        void GlobalFixer::previsit( TypeDecl * ) { visit_children = false; }

} // namespace InitTweak

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