Notes on GIMPLE representation and code generation

GIMPLE is the machine-independent intermediate representation used in modern GCC releases (post version 4.0). While the GIMPLE API for code generation and manipulation has matured over time, the corresponding textual representation is yet to be in a stable form. This issue hampers many serious efforts for code generation from and to GIMPLE. Good candidates for the textual representation seem to have been in play for some time. The wiki site http://gcc.gnu.org/wiki/GIMPLE sketches the textual IR that is expected to be implemented by the GIMPLE frontend and backend (both under development). Another case of a textual GIMPLE are the formats generated as a GIMPLE dumps. We distignuish here two formats: the format in *.t004.gimple files (tagged GIMPLE) and the one e.g. in *.t140.optimized files (GIMPLE-C ). Both formats express the low-level GIMPLE representation, which is closer to classic three-address code than high-level GIMPLE; the latter is closer to the GENERIC AST representation. An extended form of GIMPLE dumps are expected to be established as the GIMPLE language semantics. For reference tagged GIMPLE is generated by the command-line option: