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When code generation occurs at runtime, as in just-in-time compilation (JIT), it is important that the entire process be efficient with respect to space and time. For example, when regular expressions are interpreted and used to generate code at runtime, a non-deterministic finite-state machine is often generated instead of a deterministic one, because usually the former can be created more ...
This phase typically builds a parse tree, which replaces the linear sequence of tokens with a tree structure built according to the rules of a formal grammar which define the language's syntax. The parse tree is often analyzed, augmented, and transformed by later phases in the compiler. [55]
Most compilers are organized into three stages: a front end, an optimizer, and a back end. The front end is responsible for understanding the program. It makes sure a program is valid and transforms it into an intermediate representation, a data structure used by the compiler to represent
Most compilers have at least the following compiler phases (which therefore occur at compile-time): syntax analysis, semantic analysis, and code generation.During optimization phases, constant expressions in the source code can also be evaluated at compile-time using compile-time execution, which reduces the constant expressions to a single value.
The JIT compiler reads the bytecodes in many sections (or in full, rarely) and compiles them dynamically into machine code so the program can run faster. This can be done per-file, per-function or even on any arbitrary code fragment; the code can be compiled when it is about to be executed (hence the name "just-in-time"), and then cached and ...
Program lifecycle phases are the stages a computer program undergoes, from initial creation to deployment and execution. The phases are edit time, compile time, link time, distribution time, installation time, load time, and run time. Lifecycle phases do not necessarily happen in a linear order, and they can be intertwined in various ways.
A tracing JIT compiler goes through various phases at runtime. First, profiling information for loops is collected. After a hot loop has been identified, a special tracing phase is entered, which records all executed operations of that loop. This sequence of operations is called a trace.
Refinements also vary in their specification of what happens after the transition phase. In the rational unified process the transition phase is typically followed by a new inception phase. In the enterprise unified process the transition phase is followed by a production phase. The number of unified process refinements and variations are ...