pardo@cs.washington.edu (David Keppel) (09/12/89)
>>>[Ongoing discussion of multi-target gcc] >>[Make it load arch info dynamically] eho@clarity.Princeton.EDU (Eric Ho) writes: >[No flag, same as before. Flag, read in arch info] As it stands, gcc has lots of macros describing the target machine(s). Those macros are expanded when the compiler is built. The code that gets produced is very dependent on the arch. info. The choices seem to be: * Replace the macros with lookups in to runtime data structures. * Compile separate machine-dependent parts for each target. * Compile for the default target and for a generic target. Replacing the macros with dynamic lookups will make a slow compiler. Compiling for each target will produce a fast compiler. It doesn't let you `fiddle' with the target unless you rebuild the compiler. In the case of `gcc', the machine description lives a lot of places in the compiler. This makes a faster compiler, but would make each machine-dependent part large. Compiling for a `hard' target and for a generic target would generally make a maintainence problem. You would be maintaining two versions of lots of peices of code; one for the version that gets compioled to a single target, and one for the version that looks up in the data structures. You could write a machine description for a `generic target'. That target has macros that do lookups in to a data structure rather than compiling to hard constants. Then build two versions of `gcc', one for the hard target and one for runtime binding of the md. Folloups to comp.lang.misc ;-D on ( Retargetable postings ) Pardo -- pardo@cs.washington.edu {rutgers,cornell,ucsd,ubc-cs,tektronix}!uw-beaver!june!pardo