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28

Fortran DVM Compiler

Detailed design

Март 30, 1999

Keldysh Institute of Applied Mathematics

Russia Academy of Sciences

Contents

1 Introduction 3

2 The General Scheme of Compiler 4

2.1 Parsing 4

2.2 Transforming internal form 4

2.3 Generating source code 5

3 Basic Data Structures 5

3.1 Parse Tree 5

3.2 Symbol and Type Table 5

4 Detailed Description of Basic Modules 7

4.1 Distributed Array Creation and Remapping 12

4.2 Distributed array referencing 16

4.3 Parallel loop 18

4.4 Input/Output (io.cpp module) 21

4.5 Inserting new statements in parse tree (stmt.cpp module) 24

1 Introduction

This report presents the detailed description of the Fortran-DVM (FDVM) compiler implementation. The basic data structures, the control scheme, and the functions of compiler modules are considered.

Fortran-DVM is the Fortran 77 language which is extended by special annotations for specifying parallel execution of the program. These annotations are called DVM directives. The FDVM compiler translates the parallel FDVM code into Fortran 77 code including Lib-DVM library calls.

The following command line start the compiler up:

fdvm [ options ] source-file

Source FDVM program is placed into input file source-file.

On the command-line options are the compiler options.

Overall options.

Debugging options.

2 The General Scheme of Compiler

Sage ++ system is used as a tool for designing FDVM compiler.

Sage++ is an object oriented toolkit for building program transformation systems for Fortran 77, Fortran 90, C and C++ languages. It is designed as an open C++ class library that provides the user with a set of parsers, a structured parse tree, a symbol and type table. The heart of the system is a set of functions that allow to restructure the parse tree and a mechanism (called unparsing) for generating new source code from the restructured internal form.

The FDVM compiler consists of three components:

• Parsing

• Transforming internal form

• Generating source code

2.1 Parsing

The Fortran parser of Sage++ which is based on the GNU Bison version of YACC is extended to add language extensions (DVM directives) to Fortran system. It consists of the following modules:

The parser reads the source, checks the concrete syntax, constructs a parse tree, and writes its internal representation in a .dep file.

2.2 Transforming internal form

Second phase of compiling involves analyzing and restructuring internal representation of FDVM program. A DVM directive is substituted for a sequence of Lib-DVM function calls. Afterwards new source code is generated from restructured internal form.

Back-end of the compiler is written in C++ language using Sage++ class library.

The Sage++ library is organized as a class hierarchy that provides access to the parse tree, symbol table and type table for each file in an application project. There are five basic families of classes in the library: Project and Files, Statements, Expressions, Symbols, and Types.

Project and Files correspond to source files. Statements correspond to the basic source statements in Fortran 77 and DVM directives. Expressions are contained within statements. Symbols are the basic user defined identifiers. Types are associated with each identifier and expression.

In addition, the SgAttribute class allows the users to add their own information to Sage++ objects.

The file libSage++.h contains all the class definitions.

There are six modules in the translator:

2.3 Generating source code

Generating new source code from the restructured internal form is implemented by the File class member function (unparse( )) of Sage++ class library.

3 Basic Data Structures

The definitions of data structures of internal representation are contained in the files:

• bif.h (parse tree node for statement)

• ll.h (parse tree node for expression)

• symb.h (Symbol and Type Table elements)

3.1 Parse Tree

The structures of parse tree nodes for a statement and an expression are given in Fig. 3.1 and Fig.3.2 accordingly. The Fig. 3.4 illustrates the fragment of parse tree.

3.2 Symbol and Type Table

The Fig.3.3 presents the Symbol and Type Table entries.

variant tag

identification tag

index

global line number

local line number

declaration specifier

pointer to the label

pointer to the next statement node

pointer to the source filename

pointer to the control parent node

property list

list of nodes(list of procedures)

pointer to the comment

symbol table entry

L-value expr tree

R-value expr tree

spare expr tree

do-label (used by do)

null

null

null

null

Fig. 3.1. Parse tree node representing a statement (bif node).

variant tag

identification tag

pointer to the next node (by allocation order)

pointer to the Type table element

constant value

pointer to the Symbol table element

L-value expr tree

R-value expr tree

Fig. 3.2. Parse tree node representing an expression (low level node).

Parse Tree

Характеристики

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