This PR updates the OffloadBinary format from version 1 to version 2,
enabling support for multiple offloading entries in a single binary.
This allows combining multiple device images into a single binary with
common global metadata while maintaining backwards compatibility with
version 1 binaries.
# Key Changes
## Binary Format Enhancements
**Version 2 Format Changes:**
- Changed from single-entry to multi-entry design
- Updated `Header` structure:
- Renamed `EntryOffset` → `EntriesOffset` (offset to entries array)
- Renamed `EntrySize` → `EntriesCount` (number of entries)
- Added `StringEntry::ValueSize` field to support explicit string value
sizes (enables non-null-terminated strings)
- Introduced `OffloadEntryFlags` enum with `OIF_Metadata` flag for
metadata-only entries (entries without binary images)
**API Changes:**
- `OffloadBinary::create()` now returns
`Expected<SmallVector<std::unique_ptr<OffloadBinary>>>` instead of
single binary
- Added optional `Index` parameter to extract specific entry:
`create(Buffer, std::optional<uint64_t> Index)`
- `OffloadBinary::write()` now accepts `ArrayRef<OffloadingImage>`
instead of single image
- Added `OffloadBinary::extractHeader()` for header extraction
**Memory Management:**
- Implemented `SharedMemoryBuffer` class to enable memory sharing across
multiple `OffloadBinary` instances from the same file
- Multiple entries from a single serialized binary share the underlying
buffer
## Testing
**Unit Tests (`unittests/Object/OffloadingTest.cpp`):**
- `checkMultiEntryBinaryExtraction`: Tests extracting all entries from a
multi-entry binary
- `checkIndexBasedExtraction`: Tests extracting specific entries by
index, including out-of-bounds validation
- `checkEdgeCases`: Tests edge cases including:
- Empty string metadata
- Empty image data
- Large string values (4KB)
**Other Tests:**
- Updated `test/ObjectYAML/Offload/multiple_members.yaml` to include
metadata-only entry
---------
Co-authored-by: Joseph Huber <huberjn@outlook.com>
SmallString<0> is more flexible and avoids an unneeded copy in
ObjectYAML/OffloadEmitter.cpp.
Reviewed By: jhuber6
Differential Revision: https://reviews.llvm.org/D159335
This patchs adds the necessary code for inspecting or creating offloading
binaries using the standing `obj2yaml` and `yaml2obj` features in LLVM.
Depends on D127774
Reviewed By: jhenderson
Differential Revision: https://reviews.llvm.org/D127776
