Commit Graph

4 Commits

Author SHA1 Message Date
Eric Christopher
2dd5e1e64d Move the hash function to using and taking a StringRef.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144024 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-07 21:49:35 +00:00
Eric Christopher
e77546c3c3 Simple destructor to delete the hash data we created earlier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@144023 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-07 21:49:28 +00:00
Eric Christopher
09ac3d8413 Add the support code to enable the dwarf accelerator tables. Upcoming patches
to fix the types section (all types, not just global types), and testcases.

The code to do the final emission is disabled by default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143923 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-07 09:24:32 +00:00
Eric Christopher
bcbd3a4637 Add a new dwarf accelerator table prototype with the goal of replacing
the pubnames and pubtypes tables. LLDB can currently use this format
and a full spec is forthcoming and submission for standardization is planned.

A basic summary:

The dwarf accelerator tables are an indirect hash table optimized
for null lookup rather than access to known data. They are output into
an on-disk format that looks like this:

.-------------.
|  HEADER     |
|-------------|
|  BUCKETS    |
|-------------|
|  HASHES     |
|-------------|
|  OFFSETS    |
|-------------|
|  DATA       |
`-------------'

where the header contains a magic number, version, type of hash function,
the number of buckets, total number of hashes, and room for a special
struct of data and the length of that struct.

The buckets contain an index (e.g. 6) into the hashes array. The hashes
section contains all of the 32-bit hash values in contiguous memory, and
the offsets contain the offset into the data area for the particular
hash.

For a lookup example, we could hash a function name and take it modulo the
number of buckets giving us our bucket. From there we take the bucket value
as an index into the hashes table and look at each successive hash as long
as the hash value is still the same modulo result (bucket value) as earlier.
If we have a match we look at that same entry in the offsets table and
grab the offset in the data for our final match.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143921 91177308-0d34-0410-b5e6-96231b3b80d8
2011-11-07 09:18:42 +00:00