Discuss the various applications of compiler technology

Ø High-level programming language defines a programming abstraction
Ø Low-level language have more control over computation and produce efficient code
Ø Hard to write, less portable, prone to errors and harder to maintain
Ø Example : register  keyword
Ø Common programming languages (C, Fortran, Cobol) support
Ø User-defined aggregate data types (arrays, structures, control flow )
Ø Data-flow optimizations
Ø Analyze flow of data through the program and remove redundancies
Ø Key ideas behind object oriented languages are Data Abstraction
      and Inheritance of properties
Ø Java has features that make programming easier
Ø Type-safe – an object cannot be used as an object of an unrelated type
Ø Array accesses are checked to ensure that they lie within the bounds
Ø Built in garbage-collection facility
Ø Optimizations developed to overcome the overhead by eliminating unnecessary range checks

Ø Parallelism
Ø Instruction level : multiple operations are executed simultaneously
Ø Processor level : different threads of the same application run on different processors
Ø Memory hierarchies
Ø Consists of several levels of storage with different speeds and sizes
Ø Average memory access time is reduces
Ø Using registers effectively is the most important problem in optimizing a program
Ø Caches and physical memories are managed by the hardware
Ø Improve effectiveness by changing the layout of data or order of instructions accessing the data

Ø RISC (Reduced Instruction-Set Computer)
Ø CISC (Complex Instruction-Set Computer) –
Ø Make assembly programming easier
Ø Include complex memory addressing modes
Ø Optimizations reduce these instructions to a small number of simpler operations
Ø PowerPC, SPARC, MIPS, Alpha and PA-RISC
Ø Specialized Architectures
Ø Data flow machines, vector machines, VLIW, SIMD, systolic arrays
Ø Made way into the designs of embedded machines
Ø Entire systems can fit on a single chip
Ø Compiler technology helps to evaluate architectural designs

4. Program Translations
Ø Binary Translation
Ø Translate binary code of one machine to that of another
Ø Allow machine to run programs compiled for another instruction set
Ø Used to increase the availability of software for their machines
Ø Can provide backward compatibility
Ø Hardware synthesis
Ø Hardware designs are described in high-level hardware description languages like Verilog and VHDL
Ø Described at register transfer level (RTL)
Ø Variables represent registers
Ø Expressions represent combinational logic
Ø Tools translate RTL descriptions into gates, which are then mapped to transistors and eventually to physical layout
Ø Database Query Interpreters
Ø Languages are useful in other applications
Ø Query languages like SQL are used to search databases
Ø Queries consist of predicates containing relational and boolean operators
Ø Can be interpreted or compiled into commands to search a database
Ø Compiled Simulation
Ø Simulation Technique used in scientific and engg disciplines,Understand a phenomenon or validate a design
Ø Inputs include description of the design and specific input parameters for that run

5. Software Productivity Tools
Ø Testing is a primary technique for locating errors in a program
Ø Use data flow analysis to locate errors statically
Ø Problem of finding all program errors is undecidable
Ø Ways in which program analysis has improved software productivity
Ø Type Checking
Ø Catch inconsistencies in the program
Ø Operation applied to wrong type of object
Ø Parameters to a procedure do not match the signature
Ø Go beyond finding type errors by analyzing flow of data
Ø If pointer is assigned null and then dereferenced, the program is clearly in error
Ø Bounds Checking
Ø Security breaches are caused by buffer overflows in programs written in C
Ø Data-flow analysis can be used to locate buffer overflows
Ø Failing to identify a buffer overflow may compromise the security of the system
Ø Memory-management tools
Ø Automatic memory management removes all memory-management errors like memory leaks
Tools developed to help programmers find memory management errors

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   Raj Kumar
Computer Science And Engineering