Commit Graph

70 Commits

Author SHA1 Message Date
Zachary Turner 946204c83e [PDB] Merge Global and Publics Builders.
The publics stream and globals stream are very similar. They both
contain a list of hash buckets that refer into a single shared stream,
the symbol record stream. Because of the need for each builder to manage
both an independent hash stream as well as a single shared record
stream, making the two builders be independent entities is not the right
design. This patch merges them into a single class, of which only a
single instance is needed to create all 3 streams.  PublicsStreamBuilder
and GlobalsStreamBuilder are now merged into the single GSIStreamBuilder
class, which writes all 3 streams at once.

Note that this patch does not contain any functionality change. So we're
still not yet writing any records to the globals stream. All we're doing
is making it so that when we do start writing records to the globals,
this refactor won't have to be part of that patch.

Differential Revision: https://reviews.llvm.org/D36489

llvm-svn: 310438
2017-08-09 04:23:25 +00:00
Adrian McCarthy b41f03e768 Enable llvm-pdbutil to list enumerations using native PDB reader
This extends the native reader to enable llvm-pdbutil to list the enums in a
PDB and it includes a simple test. It does not yet list the values in the
enumerations, which requires an actual implementation of
NativeEnumSymbol::FindChildren.

To exercise this code, use a command like:

    llvm-pdbutil pretty -native -enums foo.pdb

Differential Revision: https://reviews.llvm.org/D35738

llvm-svn: 310144
2017-08-04 22:37:58 +00:00
Zachary Turner 8d927b6bf9 [lld/pdb] Add an empty globals stream.
We don't write any actual symbols to this stream yet, but for
now we just create the stream and hook it up to the appropriate
places and give it a valid header.

Differential Revision: https://reviews.llvm.org/D35290

llvm-svn: 309608
2017-07-31 19:36:08 +00:00
Reid Kleckner 14d90fd05c [PDB] Improve GSI hash table dumping for publics and globals
The PDB "symbol stream" actually contains symbol records for the publics
and the globals stream. The globals and publics streams are essentially
hash tables that point into a single stream of records. In order to
match cvdump's behavior, we need to only dump symbol records referenced
from the hash table. This patch implements that, and then implements
global stream dumping, since it's just a subset of public stream
dumping.

Now we shouldn't see S_PROCREF or S_GDATA32 records when dumping
publics, and instead we should see those record in the globals stream.

llvm-svn: 309066
2017-07-26 00:40:36 +00:00
Reid Kleckner a842cd75e2 [codeview] Remove TypeServerHandler and PDBTypeServerHandler
Summary:
Instead of wiring these through the CVTypeVisitor interface, clients
should inspect the CVTypeArray before visiting it and potentially load
up the type server's TPI stream if they need it.

No tests relied on this functionality because LLD was the only client.

Reviewers: ruiu

Subscribers: mgorny, hiraditya, zturner, llvm-commits

Differential Revision: https://reviews.llvm.org/D35394

llvm-svn: 308212
2017-07-17 20:28:06 +00:00
Adrian McCarthy 8d090fc531 [PDB] Enable NativeSession to create symbols for built-in types on demand
Summary:
There is a reserved range of type indexes for built-in types (like integers).
This will create a symbol for a built-in type if the caller askes for one by
type index.  This is also plumbing for being able to recall symbols by type
index in general, but user-defined types will come in subsequent patches.

Reviewers: rnk, zturner

Subscribers: mgorny, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D35163

llvm-svn: 307834
2017-07-12 19:38:11 +00:00
Zachary Turner 7eaf1d96ad [lld/pdb] Create an empty public symbol record stream.
This is part of the continuing effort to increase parity between
LLD and MSVC PDBs.  link still doesn't like our PDBs, so the most
obvious thing to check was whether adding an empty publics stream
would get it to do something else.  It still fails in the same way
but at least this removes one more variable from the equation.
The next logical step would be to try creating an empty globals
stream.

Differential Revision: https://reviews.llvm.org/D35224

llvm-svn: 307598
2017-07-10 22:40:20 +00:00
Zachary Turner 1eb9a0297c [PDB] Don't build the entire source file list up front.
I tried to run llvm-pdbdump on a very large (~1.5GB) PDB to
try and identify show-stopping performance problems.  This
patch addresses the first such problem.

When loading the DBI stream, before anyone has even tried to
access a single record, we build an in memory map of every
source file for every module.  In the particular PDB I was
using, this was over 85 million files.  Specifically, the
complexity is O(m*n) where m is the number of modules and
n is the average number of source files (including headers)
per module.

The whole reason for doing this was so that we could have
constant time access to any module and any of its source
file lists.  However, we can still get O(1) access to the
source file list for a given module with a simple O(m)
precomputation, and access to the list of modules is
already O(1) anyway.

So this patches reduces the O(m*n) up-front precomputation
to an O(m) one, where n is ~6,500 and n*m is about 85 million
in my pathological test case.

Differential Revision: https://reviews.llvm.org/D32870

llvm-svn: 302205
2017-05-04 23:53:29 +00:00
Zachary Turner e204a6c9a3 Rename pdb::StringTable -> pdb::PDBStringTable.
With the forthcoming codeview::StringTable which a pdb::StringTable
would hold an instance of as one member, this ambiguity becomes
confusing.  Rename to PDBStringTable to avoid this.

llvm-svn: 301948
2017-05-02 18:00:13 +00:00
Zachary Turner 67c5601404 Rename some PDB classes.
We have a lot of very similarly named classes related to
dealing with module debug info.  This patch has NFC, it just
renames some classes to be more descriptive (albeit slightly
more to type).  The mapping from old to new class names is as
follows:

   Old          |        New
ModInfo         | DbiModuleDescriptor
ModuleSubstream | ModuleDebugFragment
ModStream       | ModuleDebugStream

With the corresponding Builder classes renamed accordingly.

Differential Revision: https://reviews.llvm.org/D32506

llvm-svn: 301555
2017-04-27 16:11:19 +00:00
Zachary Turner c883a8c6dc [llvm-pdbdump] More advanced class definition dumping.
Previously the dumping of class definitions was very primitive,
and it made it hard to do more than the most trivial of output
formats when dumping.  As such, we would only dump one line for
each field, and then dump non-layout items like nested types
and enums.

With this patch, we do a complete analysis of the object
hierarchy including aggregate types, bases, virtual bases,
vftable analysis, etc.  The only immediately visible effects
of this are that a) we can now dump a line for the vfptr where
before we would treat that as padding, and b) we now don't
treat virtual bases that come at the end of a class as padding
since we have a more detailed analysis of the class's storage
usage.

In subsequent patches, we should be able to use this analysis
to display a complete graphical view of a class's layout including
recursing arbitrarily deep into an object's base class / aggregate
member hierarchy.

llvm-svn: 300133
2017-04-12 23:18:21 +00:00
Adrian McCarthy 4d93d66ddd Re-land: "Make NativeExeSymbol a concrete subclass of NativeRawSymbol [PDB]"
This should work on all platforms now that r299006 has landed.  Tested locally
on Windows and Linux.

This moves exe symbol-specific method implementations out of NativeRawSymbol
into a concrete subclass. Also adds implementations for hasCTypes and
hasPrivateSymbols and a simple test to ensure the native reader can access the
summary information for the executable from the PDB.

Original Differential Revision: https://reviews.llvm.org/D31059

llvm-svn: 299019
2017-03-29 19:27:08 +00:00
Adrian McCarthy 3c0328e011 Somehow this still breaks because of ANSI color codes in test output on Linux.
Reverting until I can figure out the root cause.

Revert "Re-land:  Make NativeExeSymbol a concrete subclass of NativeRawSymbol [PDB]"

This reverts commit f461a70cc376f0f91c8b4917be79479cc86330a5.

llvm-svn: 298626
2017-03-23 17:18:50 +00:00
Adrian McCarthy 997a15c3c3 Re-land: Make NativeExeSymbol a concrete subclass of NativeRawSymbol [PDB]
The new test should pass on all platforms now that llvm-pdbdump has the
`-color-output` option.

This moves exe symbol-specific method implementations out of NativeRawSymbol
into a concrete subclass. Also adds implementations for hasCTypes and
hasPrivateSymbols and a simple test to ensure the native reader can access
the summary information for the executable from the PDB.

Original Differential Revision: https://reviews.llvm.org/D31059

llvm-svn: 298623
2017-03-23 16:45:20 +00:00
Zachary Turner 2d9c082033 Revert "Make NativeExeSymbol a concrete subclass of NativeRawSymbol [PDB]"
For some reason this is causing ANSI color codes to be printed
even when run through FileCheck.

llvm-svn: 298026
2017-03-17 00:46:42 +00:00
Adrian McCarthy 21b54cf632 Make NativeExeSymbol a concrete subclass of NativeRawSymbol [PDB]
This moves exe symbol-specific method implementations out of NativeRawSymbol
into a concrete subclass. Also adds implementations for hasCTypes and
hasPrivateSymbols and a simple test to ensure the native reader can access
the summary information for the executable from the PDB.

Differential Revision: https://reviews.llvm.org/D31059

llvm-svn: 298005
2017-03-16 22:28:39 +00:00
Zachary Turner ea4e60754e [pdb] Write the module info and symbol record streams.
Previously we did not have support for writing detailed
module information for each module, as well as the symbol
records.  This patch adds support for this, and in doing
so enables the ability to construct minimal PDBs from
just a few lines of YAML.  A test is added to illustrate
this functionality.

llvm-svn: 297900
2017-03-15 22:18:53 +00:00
Adrian McCarthy 65d2688842 Introduce NativeEnumModules and NativeCompilandSymbol
Together, these allow lldb-pdbdump to list all the modules from a PDB using a
native reader (rather than DIA).

Note that I'll probably be specializing NativeRawSymbol in a subsequent patch.

Differential Revision: https://reviews.llvm.org/D30956

llvm-svn: 297883
2017-03-15 20:17:58 +00:00
Zachary Turner 7b327d051b [pdb] Add the ability to resolve TypeServer PDBs.
Some PDBs or object files can contain references to other PDBs
where the real type information lives.  When this happens,
all type indices in the original PDB are meaningless because
their records are not there.

With this patch we add the ability to pull type info from those
secondary PDBs.

Differential Revision: https://reviews.llvm.org/D29973

llvm-svn: 295382
2017-02-16 23:35:45 +00:00
Adrian McCarthy 0beb3323c5 Introduce NativeRawSymbol for PDB reading.
This is a stub for a new concrete implementation of IPDBRawSymbol.
Nothing uses this uses this implementation yet.  My plan is to
locally switch lldb-pdbdump from the DIA reader to the Native one
and flesh out the implementations of these method stubs in the order
they're needed.

llvm-svn: 294633
2017-02-09 21:51:19 +00:00
Adrian McCarthy 6b6b8c4fb9 NFC: Rename (PDB) RawSession to NativeSession
This eliminates one overload on the term Raw.

Differential Revision: https://reviews.llvm.org/D29098

llvm-svn: 293104
2017-01-25 22:38:55 +00:00
Zachary Turner 60667ca0b2 [pdb] Merge NamedStreamMapBuilder and NamedStreamMap.
While the builder pattern has proven useful for certain other
larger types, in this case it was hampering the ability to use
the data structure, as for runtime access we need a map that
we can efficiently read from and write to.  So the two are merged
into a single data structure that can efficiently be read to,
written from, deserialized from bytes, and serialized to bytes.

llvm-svn: 292664
2017-01-20 22:41:40 +00:00
Zachary Turner f04d6e8d52 [PDB] Rename some files to be more intuitive.
llvm-svn: 292663
2017-01-20 22:41:15 +00:00
Zachary Turner 11036a909f [pdb] Add HashTable data structure.
This was being parsed / serialized ad-hoc inside the code
for a specific PDB stream.  But this data structure is used
in multiple ways / places within the PDB format.  To be able
to re-use it we need to raise this code out and make it more
generic.  In doing so, a number of bugs are fixed in the
original implementation, and support is added for growing
the hash table and deleting items from the hash table,
which had either been omitted or incorrect implemented in
the initial version.

Differential Revision: https://reviews.llvm.org/D28715

llvm-svn: 292535
2017-01-19 23:31:24 +00:00
Rui Ueyama dcd32937dc PDB: Add a class to create the /names stream contents.
This patch adds a new class NameHashTableBuilder which creates /names streams.
This patch contains a test to confirm that a stream created by
NameHashTableBuilder can be read by NameHashTable reader class.

Differential Revision: https://reviews.llvm.org/D28707

llvm-svn: 292040
2017-01-15 00:36:02 +00:00
Michal Gorny 89b6f16b3e [cmake] Add LLVM_ENABLE_DIA_SDK option, and expose it in LLVMConfig
Add an explicit LLVM_ENABLE_DIA_SDK option to control building support
for DIA SDK-based debugging. Control its value to match whether DIA SDK
support was found and expose it in LLVMConfig (alike LLVM_ENABLE_ZLIB).

Its value is needed for LLDB to determine whether to run tests requiring
DIA support. Currently it is obtained from llvm/Config/config.h;
however, this file is not available for standalone builds. Following
this change, LLDB will be modified to use the value from LLVMConfig.

Differential Revision: https://reviews.llvm.org/D26255

llvm-svn: 290818
2017-01-02 18:19:35 +00:00
Bob Haarman 653baa2aaa [pdb] added support for dumping globals stream
Summary: This adds support for dumping the globals stream from PDB files using llvm-pdbdump, similar to the support we have for the publics stream.

Reviewers: ruiu, zturner

Subscribers: beanz, mgorny, modocache

Differential Revision: https://reviews.llvm.org/D25801

llvm-svn: 284861
2016-10-21 19:43:19 +00:00
Zachary Turner 620961deb9 [pdb] Write TPI hash values to the TPI stream.
This completes being able to write all the interesting
values of a PDB TPI stream.

Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D24370

llvm-svn: 281555
2016-09-14 23:00:02 +00:00
Zachary Turner c6d54da891 [pdb] Write PDB TPI Stream from Yaml.
This writes the full sequence of type records described in
Yaml to the TPI stream of the PDB file.

Reviewed By: rnk
Differential Revision: https://reviews.llvm.org/D24316

llvm-svn: 281063
2016-09-09 17:46:17 +00:00
Zachary Turner bac69d33d0 [msf] Create LLVMDebugInfoMsf
This provides a better layering of responsibilities among different
aspects of PDB writing code.  Some of the MSF related code was
contained in CodeView, and some was in PDB prior to this.  Further,
we were often saying PDB when we meant MSF, and the two are
actually independent of each other since in theory you can have
other types of data besides PDB data in an MSF.  So, this patch
separates the MSF specific code into its own library, with no
dependencies on anything else, and DebugInfoCodeView and
DebugInfoPDB take dependencies on DebugInfoMsf.

llvm-svn: 276458
2016-07-22 19:56:05 +00:00
Zachary Turner faa554b2fd [pdb] Use MsfBuilder to handle the writing PDBs.
Previously we would read a PDB, then write some of it back out,
but write the directory, super block, and other pertinent metadata
back out unchanged.  This generates incorrect PDBs since the amount
of data written was not always the same as the amount of data read.

This patch changes things to use the newly introduced `MsfBuilder`
class to write out a correct and accurate set of Msf metadata for
the data *actually* written, which opens up the door for adding and
removing type records, symbol records, and other types of data to
an existing PDB.

llvm-svn: 275627
2016-07-15 22:16:56 +00:00
Zachary Turner f52a899f4a [pdb] Introduce MsfBuilder for laying out PDB files.
Reviewed by: ruiu
Differential Revision: https://reviews.llvm.org/D22308

llvm-svn: 275611
2016-07-15 20:43:38 +00:00
Zachary Turner dbeaea7b35 Refactor the PDB writing to use a builder approach
llvm-svn: 275110
2016-07-11 21:45:26 +00:00
Rui Ueyama 170988f21f [PDB] Move PDB functions to a separate file.
We are going to use the hash functions from TPI streams.

Differential Revision: http://reviews.llvm.org/D21142

llvm-svn: 272223
2016-06-08 23:11:14 +00:00
Zachary Turner d8447990b0 [pdb] Use MappedBlockStream to parse the PDB directory.
In order to efficiently write PDBs, we need to be able to make a
StreamWriter class similar to a StreamReader, which can transparently deal
with writing to discontiguous streams, and we need to use this for all
writing, similar to how we use StreamReader for all reading.

Most discontiguous streams are the typical numbered streams that appear in
a PDB file and are described by the directory, but the exception to this,
that until now has been parsed by hand, is the directory itself.
MappedBlockStream works by querying the directory to find out which blocks
a stream occupies and various other things, so naturally the same logic
could not possibly work to describe the blocks that the directory itself
resided on.

To solve this, I've introduced an abstraction IPDBStreamData, which allows
the client to query for the list of blocks occupied by the stream, as well
as the stream length. I provide two implementations of this: one which
queries the directory (for indexed streams), and one which queries the
super block (for the directory stream).

This has the side benefit of vastly simplifying the code to parse the
directory. Whereas before a mini state machine was rolled by hand, now we
simply use FixedStreamArray to read out the stream sizes, then build a
vector of FixedStreamArrays for the stream map, all in just a few lines of
code.

Reviewed By: ruiu
Differential Revision: http://reviews.llvm.org/D21046

llvm-svn: 271982
2016-06-07 05:28:55 +00:00
Zachary Turner a96cce64a5 [codeview] Dump line number and column information.
To facilitate this, a couple of changes had to be made:

1. `ModuleSubstream` got moved from `DebugInfo/PDB` to
`DebugInfo/CodeView`, and various codeview related types are defined
there.  It turns out `DebugInfo/CodeView/Line.h` already defines many of
these structures, but this is really old code that is not endian aware,
doesn't interact well with `StreamInterface` and not very helpful for
getting stuff out of a PDB.  Eventually we should migrate the old readobj
`COFFDumper` code to these new structures, or at least merge their
functionality somehow.

2. A `ModuleSubstream` visitor is introduced.  Depending on where your
module substream array comes from, different subsets of record types can
be expected.  We are already hand parsing these substream arrays in many
places especially in `COFFDumper.cpp`.  In the future we can migrate these
paths to the visitor as well, which should reduce a lot of code in
`COFFDumper.cpp`.

Differential Revision: http://reviews.llvm.org/D20936
Reviewed By: ruiu, majnemer

llvm-svn: 271621
2016-06-03 03:25:59 +00:00
Zachary Turner 7eb6d358af [llvm-pdbdump] Dump CodeView line information.
This first pass only splits apart the records and dumps the line
info kinds and binary data.  Subsequent patches will parse out
the binary data into more useful information and dump it in
detail.

llvm-svn: 271576
2016-06-02 20:11:22 +00:00
Zachary Turner 93839cb4ac [pdb] Parse and dump section map and section contribs
Differential Revision: http://reviews.llvm.org/D20876
Reviewed By: rnk, ruiu

llvm-svn: 271488
2016-06-02 05:07:49 +00:00
Zachary Turner 8dbe3629a0 [codeview,pdb] Try really hard to conserve memory when reading.
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
2016-05-27 01:54:44 +00:00
Zachary Turner d5d37dcf83 [codeview] Move StreamInterface and StreamReader to libcodeview.
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
2016-05-25 20:37:03 +00:00
Rui Ueyama 0fcd82605e pdbdump: print out symbol names referred by publics stream.
DBI stream contains a stream number of the symbol record stream.
Symbol record streams is an array of length-type-value members.
Each member represents one symbol.

Publics stream contains offsets to the symbol record stream.
This patch is to print out all symbols that are referenced by
the publics stream.

Note that even with this patch, llvm-pdbdump cannot dump all the
information in a publics stream since it contains more information
than symbol names. I'll improve it in followup patches.

Differential Revision: http://reviews.llvm.org/D20480

llvm-svn: 270262
2016-05-20 19:55:17 +00:00
Rui Ueyama 1f6b6e2c53 pdbdump: Print "Publics" stream.
Publics stream seems to contain information as to public symbols.
It actually contains a serialized hash table along with fixed-sized
headers. This patch is not complete. It scans only till the end of
the stream and dump the header information. I'll write code to
de-serialize the hash table later.

Reviewers: zturner

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D20256

llvm-svn: 269484
2016-05-13 21:21:53 +00:00
Zachary Turner 06c2b4be25 [pdb] Parse the module info stream for each module.
Differential Revision: http://reviews.llvm.org/D20026
Reviewed By: rnk

llvm-svn: 268942
2016-05-09 17:45:21 +00:00
Zachary Turner 819e77d196 Port DebugInfoPDB over to using llvm::Error.
Differential Revision: http://reviews.llvm.org/D19940
Reviewed By: rnk

llvm-svn: 268791
2016-05-06 20:51:57 +00:00
Zachary Turner f5c59654f7 Parse the TPI (type information) stream of PDB files.
This parses the TPI stream (stream 2) from the PDB file. This stream
contains some header information followed by a series of codeview records.
There is some additional complexity here in that alongside this stream of
codeview records is a serialized hash table in order to efficiently query
the types. We parse the necessary bookkeeping information to allow us to
reconstruct the hash table, but we do not actually construct it yet as
there are still a few things that need to be understood first.

Differential Revision: http://reviews.llvm.org/D19840
Reviewed By: ruiu, rnk

llvm-svn: 268343
2016-05-03 00:28:21 +00:00
Zachary Turner 0eace0bae5 Parse PDB Name Hash Table
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
2016-05-02 18:09:14 +00:00
Zachary Turner 2f09b5091c Put PDB parsing code into a pdb namespace.
llvm-svn: 268072
2016-04-29 17:28:47 +00:00
Zachary Turner 6ba65deeb9 Refactor the PDB Stream reading interface.
The motivation for this change is that PDB has the notion of
streams and substreams.  Substreams often consist of variable
length structures that are convenient to be able to treat as
guaranteed, contiguous byte arrays, whereas the streams they
are contained in are not necessarily so, as a single stream
could be spread across many discontiguous blocks.

So, when processing data from a substream, we want to be able
to assume that we have a contiguous byte array so that we can
cast pointers to variable length arrays and such.

This leads to the question of how to be able to read the same
data structure from either a stream or a substream using the
same interface, which is where this patch comes in.

We separate out the stream's read state from the underlying
representation, and introduce a `StreamReader` class.  Then
we change the name of `PDBStream` to `MappedBlockStream`, and
introduce a second kind of stream called a `ByteStream` which is
simply a sequence of contiguous bytes.  Finally, we update all
of the std::vectors in `PDBDbiStream` to use `ByteStream` instead
as a proof of concept.

llvm-svn: 268071
2016-04-29 17:22:58 +00:00
Zachary Turner 1822af542f Parse module information from DBI stream.
This gets more data out of the DBI strema of the PDB.  In
particular it extracts the metadata for the list of modules
(compilands) that this PDB contains info about, and adds support
for dumping these fields to llvm-pdbdump.

Differential Revision: http://reviews.llvm.org/D19570
Reviewed By: ruiu

llvm-svn: 267818
2016-04-27 23:41:42 +00:00
Zachary Turner 53a65ba5c9 Parse and dump PDB DBI Stream Header Information
The DBI stream contains a lot of bookkeeping information for other
streams. In particular it contains information about section contributions
and linked modules. This patch is a first attempt at parsing some of the
information out of the DBI stream. It currently only parses and dumps the
headers of the DBI stream, so none of the module data or section
contribution data is pulled out.

This is just a proof of concept that we understand the basic properties of
the DBI stream's metadata, and followup patches will try to extract more
detailed information out.

Differential Revision: http://reviews.llvm.org/D19500
Reviewed By: majnemer, ruiu

llvm-svn: 267585
2016-04-26 18:42:34 +00:00