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

1 files changed, 168 insertions, 0 deletions

diff --git a/third_party/llvm-project/Error.cpp b/third_party/llvm-project/Error.cpp
new file mode 100644
index 000000000..bb13c836d
--- /dev/null
+++ b/third_party/llvm-project/Error.cpp
@@ -0,0 +1,168 @@
+//===----- lib/Support/Error.cpp - Error and associated utilities ---------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/Error.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/ManagedStatic.h"
+#include <system_error>
+
+using namespace llvm;
+
+namespace {
+
+  enum class ErrorErrorCode : int {
+    MultipleErrors = 1,
+    FileError,
+    InconvertibleError
+  };
+
+  // FIXME: This class is only here to support the transition to llvm::Error. It
+  // will be removed once this transition is complete. Clients should prefer to
+  // deal with the Error value directly, rather than converting to error_code.
+  class ErrorErrorCategory : public std::error_category {
+  public:
+    const char *name() const noexcept override { return "Error"; }
+
+    std::string message(int condition) const override {
+      switch (static_cast<ErrorErrorCode>(condition)) {
+      case ErrorErrorCode::MultipleErrors:
+        return "Multiple errors";
+      case ErrorErrorCode::InconvertibleError:
+        return "Inconvertible error value. An error has occurred that could "
+               "not be converted to a known std::error_code. Please file a "
+               "bug.";
+      case ErrorErrorCode::FileError:
+          return "A file error occurred.";
+      }
+      llvm_unreachable("Unhandled error code");
+    }
+  };
+
+}
+
+#if 0 // XXX BINARYEN
+static ManagedStatic<ErrorErrorCategory> ErrorErrorCat;
+#endif
+
+namespace llvm {
+
+void ErrorInfoBase::anchor() {}
+char ErrorInfoBase::ID = 0;
+char ErrorList::ID = 0;
+void ECError::anchor() {}
+char ECError::ID = 0;
+char StringError::ID = 0;
+char FileError::ID = 0;
+
+void logAllUnhandledErrors(Error E, raw_ostream &OS, Twine ErrorBanner) {
+  if (!E)
+    return;
+  OS << ErrorBanner;
+  handleAllErrors(std::move(E), [&](const ErrorInfoBase &EI) {
+    EI.log(OS);
+    OS << "\n";
+  });
+}
+
+
+std::error_code ErrorList::convertToErrorCode() const {
+  llvm_unreachable("convert error code");
+}
+
+std::error_code inconvertibleErrorCode() {
+  llvm_unreachable("inconvertible error code");
+}
+
+std::error_code FileError::convertToErrorCode() const {
+  llvm_unreachable("(file) convert error code");
+}
+
+Error errorCodeToError(std::error_code EC) {
+  if (!EC)
+    return Error::success();
+  return Error(std::make_unique<ECError>(ECError(EC)));
+}
+
+std::error_code errorToErrorCode(Error Err) {
+  std::error_code EC;
+  handleAllErrors(std::move(Err), [&](const ErrorInfoBase &EI) {
+    EC = EI.convertToErrorCode();
+  });
+  if (EC == inconvertibleErrorCode())
+    report_fatal_error(EC.message());
+  return EC;
+}
+
+#if LLVM_ENABLE_ABI_BREAKING_CHECKS
+void Error::fatalUncheckedError() const {
+  dbgs() << "Program aborted due to an unhandled Error:\n";
+  if (getPtr())
+    getPtr()->log(dbgs());
+  else
+    dbgs() << "Error value was Success. (Note: Success values must still be "
+              "checked prior to being destroyed).\n";
+  abort();
+}
+#endif
+
+StringError::StringError(std::error_code EC, const Twine &S)
+    : Msg(S.str()), EC(EC) {}
+
+StringError::StringError(const Twine &S, std::error_code EC)
+    : Msg(S.str()), EC(EC), PrintMsgOnly(true) {}
+
+void StringError::log(raw_ostream &OS) const {
+  if (PrintMsgOnly) {
+    OS << Msg;
+  } else {
+    OS << EC.message();
+    if (!Msg.empty())
+      OS << (" " + Msg);
+  }
+}
+
+std::error_code StringError::convertToErrorCode() const {
+  return EC;
+}
+
+Error createStringError(std::error_code EC, char const *Msg) {
+  return make_error<StringError>(Msg, EC);
+}
+
+void report_fatal_error(Error Err, bool GenCrashDiag) {
+  assert(Err && "report_fatal_error called with success value");
+  std::string ErrMsg;
+  {
+    raw_string_ostream ErrStream(ErrMsg);
+    logAllUnhandledErrors(std::move(Err), ErrStream);
+  }
+  report_fatal_error(ErrMsg);
+}
+
+} // end namespace llvm
+
+LLVMErrorTypeId LLVMGetErrorTypeId(LLVMErrorRef Err) {
+  return reinterpret_cast<ErrorInfoBase *>(Err)->dynamicClassID();
+}
+
+void LLVMConsumeError(LLVMErrorRef Err) { consumeError(unwrap(Err)); }
+
+char *LLVMGetErrorMessage(LLVMErrorRef Err) {
+  std::string Tmp = toString(unwrap(Err));
+  char *ErrMsg = new char[Tmp.size() + 1];
+  memcpy(ErrMsg, Tmp.data(), Tmp.size());
+  ErrMsg[Tmp.size()] = '\0';
+  return ErrMsg;
+}
+
+void LLVMDisposeErrorMessage(char *ErrMsg) { delete[] ErrMsg; }
+
+LLVMErrorTypeId LLVMGetStringErrorTypeId() {
+  return reinterpret_cast<void *>(&StringError::ID);
+}