Since we want to move toward zero-copy access to stream data, we
want to remove all instances of copying operations. So get rid
of some of those here.
Differential Revision: http://reviews.llvm.org/D20720
Reviewed By: ruiu
llvm-svn: 270960
PDBs can be extremely large. We're already mapping the entire
PDB into the process's address space, but to make matters worse
the blocks of the PDB are not arranged contiguously. So, when
we have something like an array or a string embedded into the
stream, we have to make a copy. Since it's convenient to use
traditional data structures to iterate and manipulate these
records, we need the memory to be contiguous.
As a result of this, we were using roughly twice as much memory
as the file size of the PDB, because every stream was copied
out and re-stitched together contiguously.
This patch addresses this by improving the MappedBlockStream
to allocate from a BumpPtrAllocator only when a read requires
a discontiguous read. Furthermore, it introduces some data
structures backed by a stream which can iterate over both
fixed and variable length records of a PDB. Since everything
is backed by a stream and not a buffer, we can read almost
everything from the PDB with zero copies.
Differential Revision: http://reviews.llvm.org/D20654
Reviewed By: ruiu
llvm-svn: 270951
We have need to reuse this functionality, including making
additional generic stream types that are smarter about how and
when they copy memory versus referencing the original memory.
So all of these structures belong in the common library
rather than being pdb specific.
llvm-svn: 270751
name_ids() did not return all IDs but only the first NameCount items.
The number of non-zero entries in IDs vector is NameCount, but it
does not mean that all non-zero entries are at the beginning of IDs
vector.
Differential Revision: http://reviews.llvm.org/D20611
llvm-svn: 270656
PDB has a lot of similar data structures. We already have code
for parsing a Name Map, but PDB seems to have a different but
very similar structure that is a hash table. This is the
beginning of code needed in order to parse the name hash table,
but it is not yet complete. It parses the basic metadata of
the hash table, the bucket array, and the names buffer, but
doesn't use any of these fields yet as the data structure
requires a non-trivial amount of work to understand.
llvm-svn: 268268
Rui Ueyama