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| author | Alon Zakai <azakai@google.com> | 2019-12-19 09:04:08 -0800 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2019-12-19 09:04:08 -0800 |
| commit | 4d28d3f32e7f213e300b24bc61c3f0ac9d6e1ab6 (patch) | |
| tree | 91bffc2d47b1fe4bba01e7ada77006ef340bd138 /third_party/llvm-project/include/llvm/Support/BinaryStream.h | |
| parent | 0048f5b004ddf50e750aa335d0be314a73852058 (diff) | |
| download | binaryen-4d28d3f32e7f213e300b24bc61c3f0ac9d6e1ab6.tar.gz binaryen-4d28d3f32e7f213e300b24bc61c3f0ac9d6e1ab6.tar.bz2 binaryen-4d28d3f32e7f213e300b24bc61c3f0ac9d6e1ab6.zip | |
DWARF parsing and writing support using LLVM (#2520)
This imports LLVM code for DWARF handling. That code has the
Apache 2 license like us. It's also the same code used to
emit DWARF in the common toolchain, so it seems like a safe choice.
This adds two passes: --dwarfdump which runs the same code LLVM
runs for llvm-dwarfdump. This shows we can parse it ok, and will
be useful for debugging. And --dwarfupdate writes out the DWARF
sections (unchanged from what we read, so it just roundtrips - for
updating we need #2515).
This puts LLVM in thirdparty which is added here.
All the LLVM code is behind USE_LLVM_DWARF, which is on
by default, but off in JS for now, as it increases code size by 20%.
This current approach imports the LLVM files directly. This is not
how they are intended to be used, so it required a bunch of
local changes - more than I expected actually, for the platform-specific
stuff. For now this seems to work, so it may be good enough, but
in the long term we may want to switch to linking against libllvm.
A downside to doing that is that binaryen users would need to
have an LLVM build, and even in the waterfall builds we'd have a
problem - while we ship LLVM there anyhow, we constantly update
it, which means that binaryen would need to be on latest llvm all
the time too (which otherwise, given DWARF is quite stable, we
might not need to constantly update).
An even larger issue is that as I did this work I learned about how
DWARF works in LLVM, and while the reading code is easy to
reuse, the writing code is trickier. The main code path is heavily
integrated with the MC layer, which we don't have - we might want
to create a "fake MC layer" for that, but it sounds hard. Instead,
there is the YAML path which is used mostly for testing, and which
can convert DWARF to and from YAML and from binary. Using
the non-YAML parts there, we can convert binary DWARF to
the YAML layer's nice Info data, then convert that to binary. This
works, however, this is not the path LLVM uses normally, and it
supports only some basic DWARF sections - I had to add ranges
support, in fact. So if we need more complex things, we may end
up needing to use the MC layer approach, or consider some other
DWARF library. However, hopefully that should not affect the core
binaryen code which just calls a library for DWARF stuff.
Helps #2400
Diffstat (limited to 'third_party/llvm-project/include/llvm/Support/BinaryStream.h')
| -rw-r--r-- | third_party/llvm-project/include/llvm/Support/BinaryStream.h | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/third_party/llvm-project/include/llvm/Support/BinaryStream.h b/third_party/llvm-project/include/llvm/Support/BinaryStream.h new file mode 100644 index 000000000..fcf439855 --- /dev/null +++ b/third_party/llvm-project/include/llvm/Support/BinaryStream.h @@ -0,0 +1,101 @@ +//===- BinaryStream.h - Base interface for a stream of data -----*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +#ifndef LLVM_SUPPORT_BINARYSTREAM_H +#define LLVM_SUPPORT_BINARYSTREAM_H + +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/BitmaskEnum.h" +#include "llvm/Support/BinaryStreamError.h" +#include "llvm/Support/Endian.h" +#include "llvm/Support/Error.h" +#include <cstdint> + +namespace llvm { + +enum BinaryStreamFlags { + BSF_None = 0, + BSF_Write = 1, // Stream supports writing. + BSF_Append = 2, // Writing can occur at offset == length. + LLVM_MARK_AS_BITMASK_ENUM(/* LargestValue = */ BSF_Append) +}; + +/// An interface for accessing data in a stream-like format, but which +/// discourages copying. Instead of specifying a buffer in which to copy +/// data on a read, the API returns an ArrayRef to data owned by the stream's +/// implementation. Since implementations may not necessarily store data in a +/// single contiguous buffer (or even in memory at all), in such cases a it may +/// be necessary for an implementation to cache such a buffer so that it can +/// return it. +class BinaryStream { +public: + virtual ~BinaryStream() = default; + + virtual llvm::support::endianness getEndian() const = 0; + + /// Given an offset into the stream and a number of bytes, attempt to + /// read the bytes and set the output ArrayRef to point to data owned by the + /// stream. + virtual Error readBytes(uint32_t Offset, uint32_t Size, + ArrayRef<uint8_t> &Buffer) = 0; + + /// Given an offset into the stream, read as much as possible without + /// copying any data. + virtual Error readLongestContiguousChunk(uint32_t Offset, + ArrayRef<uint8_t> &Buffer) = 0; + + /// Return the number of bytes of data in this stream. + virtual uint32_t getLength() = 0; + + /// Return the properties of this stream. + virtual BinaryStreamFlags getFlags() const { return BSF_None; } + +protected: + Error checkOffsetForRead(uint32_t Offset, uint32_t DataSize) { + if (Offset > getLength()) + return make_error<BinaryStreamError>(stream_error_code::invalid_offset); + if (getLength() < DataSize + Offset) + return make_error<BinaryStreamError>(stream_error_code::stream_too_short); + return Error::success(); + } +}; + +/// A BinaryStream which can be read from as well as written to. Note +/// that writing to a BinaryStream always necessitates copying from the input +/// buffer to the stream's backing store. Streams are assumed to be buffered +/// so that to be portable it is necessary to call commit() on the stream when +/// all data has been written. +class WritableBinaryStream : public BinaryStream { +public: + ~WritableBinaryStream() override = default; + + /// Attempt to write the given bytes into the stream at the desired + /// offset. This will always necessitate a copy. Cannot shrink or grow the + /// stream, only writes into existing allocated space. + virtual Error writeBytes(uint32_t Offset, ArrayRef<uint8_t> Data) = 0; + + /// For buffered streams, commits changes to the backing store. + virtual Error commit() = 0; + + /// Return the properties of this stream. + BinaryStreamFlags getFlags() const override { return BSF_Write; } + +protected: + Error checkOffsetForWrite(uint32_t Offset, uint32_t DataSize) { + if (!(getFlags() & BSF_Append)) + return checkOffsetForRead(Offset, DataSize); + + if (Offset > getLength()) + return make_error<BinaryStreamError>(stream_error_code::invalid_offset); + return Error::success(); + } +}; + +} // end namespace llvm + +#endif // LLVM_SUPPORT_BINARYSTREAM_H |