C and tcc

Abstract

Dynamic code generation allows programmers to use run-time information in order to achieve performance and expressiveness superior to those of static code. The 'C( Tick C ) language is a superset of ANSI C that supports efficient and high-level use of dynamic code generation. 'C provides dynamic code generation at the level of C expressions and statements and supports the composition of dynamic code at run time. These features enable programmers to add dynamic code generation to existing C code incrementally and to write important applications (such as “just-in-time” compilers) easily. The article presents many examples of how 'C can be used to solve practical problems. The tcc compiler is an efficient, portable, and freely available implementation of 'C. tcc allows programmers to trade dynamic compilation speed for dynamic code quality: in some aplications, it is most important to generate code quickly, while in others code quality matters more than compilation speed. The overhead of dynamic compilation is on the order of 100 to 600 cycles per generated instruction, depending on the level of dynamic optimizaton. Measurements show that the use of dynamic code generation can improve performance by almost an order of magnitude; two- to four-fold speedups are common. In most cases, the overhead of dynamic compilation is recovered in under 100 uses of the dynamic code; sometimes it can be recovered within one use.