Hi, all. Currently GCC allows dynamic plugins to register custom attributes and pragmas. I would like to propose to add API for registering custom built-in functions.
AFAIK, current plugin API can be used to emulate this feature, for example by creating a function declaration in PLUGIN_START_UNIT and then replacing calls to such function in a custom lowering pass. But this solution seems inelegant: it would be better, if user-defined built-in functions could use the same "machinery" as normal ones, i.e. use common classification and flags (RTL-level vs GIMPLE-level; external library equivalents vs compiler-generated entities), and have unified API for creating declarations, GIMPLE (or even RTL) expansion, inlining (callback for is_inexpensive_builtin), etc. Possible applications of this plugin API include: * Generating optimized pattern matching functions (e.g. precomputing tables for Boyer-Moore matcher). * Generating functions for parsing (compile-time regular expressions). * Marshalling functions with compile-time type checking (something like binary printf/scanf with custom format specifiers). * String formatting and conversion. By the way, there is a guy, who has written a perl wrapper for GCC, which preprocesses calls to snprintf to make it work faster: https://github.com/h2o/qrintf... though it's probably worth enhancing snprintf in GCC, rather than reimplementing it in plugin - but that's a different story. * (to some extent): lazy evaluation. * Custom instrumentation of source code (user or framework-specific fortification or performance profiling). Any thoughts on this? Is such API useful for GCC? -- Regards, Mikhail Maltsev
