GCC

Configure terms

build: The machine GCC is built on.

host: The machine that GCC will be run on

target: The machine that the built GCC (on the host) will produce executables for.

native: build == host == target

cross: build == host, host != target

canadian: build != host, host != target, target != build

host-x-host / crossed native / cross-built native: host == target, build != target

The configure option --target=abc-def creates executables whose names are prependes with abc-def.

Directories

GCC treats /usr/local/include and /usr/local/lib specially: they're searched before the system directories.

Preprocessor

gcc allows to create a preprocessed file with the -E option:

gcc -E foo.c > foo.i

TODO

Link Time Optimazation (LTO)

lto-dump is a tool for dumping LTO object files.

Intermediate languages

While GCC compiles a program, it represents the program with trhee interemediate languages: GENERIC, GIMPLE and RTL.

GENERIC

GENERIC provides way of representing entire function in trees. This representation is possible for all languages supported by GCC.

GIMPLE

GIMPLE is for optimization which (as GENERIC) is independent from the language being compiled.

GIMPLE is a three-address representation derived from GENERIC by breaking down GENERIC expressions into tuples of no more than 3 operands (with some exceptions like function calls).

GIMPLE has no control flow structures.

Expressions with side effects are only allowed on the right hand side of assignments.

The gimplifier converts GENERIC into GIMPLE.

A C-like representation of the GIMPLE form can be dumped with -fdump-tree-gimple.

RTL (Register Transfer Language)

RTL is inspired by Lisp lists.

Plugins

A plugin extends the functionality of GCC.

GCC