Until now, our use case for the visitor has been to take a stream of bytes
representing a type stream, deserialize the records in sequence, and do
something with them, where "something" is determined by how the user
implements a particular set of callbacks on an abstract class.
For actually writing PDBs, however, we want to do the reverse. We have
some kind of description of the list of records in their in-memory format,
and we want to process each one. Perhaps by serializing them to a byte
stream, or perhaps by converting them from one description format (Yaml)
to another (in-memory representation).
This was difficult in the current model because deserialization and
invoking the callbacks were tightly coupled.
With this patch we change this so that TypeDeserializer is itself an
implementation of the particular set of callbacks. This decouples
deserialization from the iteration over a list of records and invocation
of the callbacks. TypeDeserializer is initialized with another
implementation of the callback interface, so that upon deserialization it
can pass the deserialized record through to the next set of callbacks. In
a sense this is like an implementation of the Decorator design pattern,
where the Deserializer is a decorator.
This will be useful for writing Pdbs from yaml, where we have a
description of the type records in Yaml format. In this case, the visitor
implementation would have each visitation callback method implemented in
such a way as to extract the proper set of fields from the Yaml, and it
could maintain state that builds up a list of these records. Finally at
the end we can pass this information through to another set of callbacks
which serializes them into a byte stream.
Reviewed By: majnemer, ruiu, rnk
Differential Revision: https://reviews.llvm.org/D23177
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277871 91177308-0d34-0410-b5e6-96231b3b80d8
Summary:
This code is intended to be used as part of LLD's PDB writing. Until
that exists, this is exposed via llvm-readobj for testing purposes.
Type stream merging uses the following algorithm:
- Begin with a new empty stream, and a new empty hash table that maps
from type record contents to new type index.
- For each new type stream, maintain a map from source type index to
destination type index.
- For each record, copy it and rewrite its type indices to be valid in
the destination type stream.
- If the new type record is not already present in the destination
stream hash table, append it to the destination type stream, assign it
the next type index, and update the two hash tables.
- If the type record already exists in the destination stream, discard
it and update the type index map to forward the source type index to
the existing destination type index.
Reviewers: zturner, ruiu
Subscribers: llvm-commits
Differential Revision: http://reviews.llvm.org/D20122
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@269521 91177308-0d34-0410-b5e6-96231b3b80d8
Summary: This diff is the initial implementation of the LLVM CodeView library. There is much more work to be done, namely a CodeView dumper and tests. This patch should help others make progress on the LLVM->CodeView debug info emission while I continue with the implementation of the dumper and tests.
This library implements support for emitting debug info in the CodeView format. This phase of the implementation only includes support for CodeView type records. Clients that need to emit type records will use a class derived from TypeTableBuilder. TypeTableBuilder provides member functions for writing each kind of type record; each of these functions eventually calls the writeRecord virtual function to emit the actual bits of the record. Derived classes override writeRecord to implement the folding of duplicate records and the actual emission to the appropriate destination. LLVMCodeView provides MemoryTypeTableBuilder, which creates the table in memory. In the future, other classes derived from TypeTableBuilder will write to other destinations, such as the type stream in a PDB.
The rest of the types in LLVMCodeView define the actual CodeView type records and all of the supporting enums and other types used in the type records. The TypeIndex class is of particular interest, because it is used by clients as a handle to a type in the type table.
The library provides a relatively low-level interface based on the actual on-disk format of CodeView. For example, type records refer to other type records by TypeIndex, rather than by an actual pointer to the referent record. This allows clients to emit type records one at a time, rather than having to keep the entire transitive closure of type records in memory until everything has been emitted. At some point, having a higher-level interface layered on top of this one may be useful for debuggers and other tools that want a more holistic view of the debug info. The lower-level interface should be sufficient for compilers and linkers to do the debug info manipulation that they need to do efficiently.
Reviewers: rnk, majnemer
Subscribers: silvas, rnk, jevinskie, llvm-commits
Differential Revision: http://reviews.llvm.org/D14961
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@256385 91177308-0d34-0410-b5e6-96231b3b80d8
