Daniel Berlin wrote:
I am working on interprocedural data flow analysis(IPDFA) and need some feedback on scalability issues in IPDFA. Firstly since one file is compiled at a time, we can do IPDFA only within a file.
For starters, we're working on this.
(I was curious, so I searched a bit. It looks like gcc-4.0 supports building parts of itself in this mode? Though only C and Java stuff right now, not C++. Related keywords are --enable-intermodule (see the thread http://gcc.gnu.org/ml/gcc-patches/2003-07/msg01146.html) --enable-libgcj-multifile (see http://gcc.gnu.org/ml/java-patches/2003-q3/msg00658.html) and IMI. It seems that just listing multiple source files on the commandline is enough to get it to happen?)
But that would prevent us from doing analysis for funcitons which are called in file A, but are defined in some other file B.
You just have to make conservative assumptions, of course.
You almost *never* have the whole program at once, except in benchmarks :)
True, but hey, if you really need that one server to run fast, you might actually feed the whole program to the compiler at once. Or at least a big part of it.
Morever even if we are able to store information of large number of functions, it would cost heavily in memory, and threfore non scalable.
Uh, not necessarily.
Speaking as a user, it's ok if whole-program optimization takes more memory than normal compilation. (Though you may end up needing a 64 bit processor to use it on anything really big.) - Dan
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