AST reader.
The global module index tracks all of the identifiers known to a set
of module files. Lookup of those identifiers looks first in the global
module index, which returns the set of module files in which that
identifier can be found. The AST reader only needs to look into those
module files and any module files not known to the global index (e.g.,
because they were (re)built after the global index), reducing the
number of on-disk hash tables to visit. For an example source I'm
looking at, we go from 237844 total identifier lookups into on-disk
hash tables down to 126817.
Unfortunately, this does not translate into a performance advantage.
At best, it's a wash once the global module index has been built, but
that's ignore the cost of building the global module index (which
is itself fairly large). Profiles show that the global module index
code is far less efficient than it should be; optimizing it might give
enough of an advantage to justify its continued inclusion.
llvm-svn: 173405
generational scheme for identifiers that avoids searching the hash
tables of a given module more than once for a given
identifier. Previously, loading any new module invalidated all of the
previous lookup results for all identifiers, causing us to perform the
lookups repeatedly.
llvm-svn: 148412
library, since modules cut across all of the libraries. Rename
serialization::Module to serialization::ModuleFile to side-step the
annoying naming conflict. Prune a bunch of ModuleMap.h includes that
are no longer needed (most files only needed the Module type).
llvm-svn: 145538
