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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 ...
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.
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. [3]
One example for such a place are if statements. The guard is a quick check to determine whether the original condition is still true. If a guard fails, the execution of the trace is aborted. Since tracing is done during execution, the trace can be made to contain runtime information (e.g. type information). This information can later be used in ...
A multi-pass compiler is a type of compiler that processes the source code or abstract syntax tree of a program several times. This is in contrast to a one-pass compiler, which traverses the program only once. Each pass takes the result of the previous pass as the input, and creates an intermediate output.
The most common example of this is the C preprocessor, which takes lines beginning with '#' as directives. The C preprocessor does not expect its input to use the syntax of the C language. Some languages take a different approach and use built-in language features to achieve similar things. For example:
Building a self-hosting compiler is a bootstrapping problem, i.e. the first such compiler for a language must be either hand written machine code, compiled by a compiler written in another language, or compiled by running the compiler's source on itself in an interpreter.
Tombstone diagram representing an Ada compiler written in C that produces machine code. Representation of the process of bootstrapping a C compiler written in C, by compiling it using another compiler written in machine code. To explain, the lefthand T is a C compiler written in C that produces machine code.