Applications of Compiler Technology

Implementation of High-Level Programming Languages

• Abstraction: All modern languages support abstraction. Data-flow analysis permits optimizations that significantly reduce the execution time cost of abstractions.
• Inheritance: The increasing use of smaller, but more numerous, methods has made interprocedural analysis important. Also optimizations have improved virtual method dispatch.
• Array bounds checking in Java and Ada: Optimizations have been produced that eliminate many checks.
• Garbage collection in Java: Improved algorithms.
• Dynamic compilation in Java: Optimizations to predict/determine parts of the program that will be heavily executed and thus should be the first/only parts dynamically compiled into native code.

Optimization for Computer Architectures

Parallelism

Major research efforts had lead to improvements in

• Automatic parallelization: Examine serial programs to determine and expose potential parallelism.
• Compilation of explicitly parallel languages.

Memory Hierarchies

All machines have a limited number of registers, which can be accessed much faster than central memory. All but the simplest compilers devote effort to using this scarce resource effectively. Modern processors have several levels of caches and advanced compilers produce code designed to utilize the caches well.

Design of New Computer Architectures

RISC (Reduced Instruction Set Computer)

RISC computers have comparatively simple instructions, complicated instructions require several RISC instructions. A CISC, Complex Instruction Set Computer, contains both complex and simple instructions. A sequence of CISC instructions would be a larger sequence of RISC instructions. Advanced optimizations are able to find commonality in this larger sequence and lower the total number of instructions. The CISC Intel x86 processor line 8086/80286/80386/... had a major change with the 686 (a.k.a. pentium pro). In this processor, the CISC instructions were decomposed into RISC instructions by the processor itself. Currently, code for x86 processors normally achieves highest performance when the (optimizing) compiler emits primarily simple instructions.

Specialized Architectures

A great variety has emerged. Compilers are produced before the processors are fabricated. Indeed, compilation plus simulated execution of the generated machine code is used to evaluate proposed designs.