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The GNU Compiler Collection is one compiler known to perform instruction scheduling, using the -march (both instruction set and scheduling) or -mtune (only scheduling) flags. It uses descriptions of instruction latencies and what instructions can be run in parallel (or equivalently, which "port" each use) for each microarchitecture to perform ...
For example, YACC (Yet Another Compiler-Compiler) takes input in Backus–Naur form and converts it to a parser in C. Though it was originally created for automatic generation of a parser for a compiler, yacc is also often used to automate writing code that needs to be modified each time specifications are changed.
A compiler is likely to perform some or all of the following operations, often called phases: preprocessing, lexical analysis, parsing, semantic analysis (syntax-directed translation), conversion of input programs to an intermediate representation, code optimization and machine specific code generation.
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 book may be called the "green dragon book" to distinguish it from its successor, Aho, Sethi & Ullman's Compilers: Principles, Techniques, and Tools, which is the "red dragon book". [1] The second edition of Compilers: Principles, Techniques, and Tools added a fourth author, Monica S. Lam, and the dragon became purple; hence becoming the ...
System cost or reliability may be more important than the code speed. For example, compilers for embedded software usually offer options that reduce code size at the expense of speed. The code's timing may need to be predictable, rather than as fast as possible, so code caching might be disabled, along with compiler optimizations that require it.
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.
For example, the trap instruction is one method of switching execution models. This difference is what distinguishes an API-invoked execution model, such as Pthreads, from a usual software library. Both Pthreads calls and software library calls are invoked via an API, but Pthreads behavior cannot be understood in terms of the language of the call.