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, 540 insertions, 0 deletions

diff --git a/third_party/llvm-project/include/llvm/ADT/ArrayRef.h b/third_party/llvm-project/include/llvm/ADT/ArrayRef.h
new file mode 100644
index 000000000..f6455d3fa
--- /dev/null
+++ b/third_party/llvm-project/include/llvm/ADT/ArrayRef.h
@@ -0,0 +1,540 @@
+//===- ArrayRef.h - Array Reference Wrapper ---------------------*- 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_ADT_ARRAYREF_H
+#define LLVM_ADT_ARRAYREF_H
+
+#include "llvm/ADT/Hashing.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/Compiler.h"
+#include <algorithm>
+#include <array>
+#include <cassert>
+#include <cstddef>
+#include <initializer_list>
+#include <iterator>
+#include <memory>
+#include <type_traits>
+#include <vector>
+
+namespace llvm {
+
+  /// ArrayRef - Represent a constant reference to an array (0 or more elements
+  /// consecutively in memory), i.e. a start pointer and a length.  It allows
+  /// various APIs to take consecutive elements easily and conveniently.
+  ///
+  /// This class does not own the underlying data, it is expected to be used in
+  /// situations where the data resides in some other buffer, whose lifetime
+  /// extends past that of the ArrayRef. For this reason, it is not in general
+  /// safe to store an ArrayRef.
+  ///
+  /// This is intended to be trivially copyable, so it should be passed by
+  /// value.
+  template<typename T>
+  class LLVM_NODISCARD ArrayRef {
+  public:
+    using iterator = const T *;
+    using const_iterator = const T *;
+    using size_type = size_t;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+
+  private:
+    /// The start of the array, in an external buffer.
+    const T *Data = nullptr;
+
+    /// The number of elements.
+    size_type Length = 0;
+
+  public:
+    /// @name Constructors
+    /// @{
+
+    /// Construct an empty ArrayRef.
+    /*implicit*/ ArrayRef() = default;
+
+    /// Construct an empty ArrayRef from None.
+    /*implicit*/ ArrayRef(NoneType) {}
+
+    /// Construct an ArrayRef from a single element.
+    /*implicit*/ ArrayRef(const T &OneElt)
+      : Data(&OneElt), Length(1) {}
+
+    /// Construct an ArrayRef from a pointer and length.
+    /*implicit*/ ArrayRef(const T *data, size_t length)
+      : Data(data), Length(length) {}
+
+    /// Construct an ArrayRef from a range.
+    ArrayRef(const T *begin, const T *end)
+      : Data(begin), Length(end - begin) {}
+
+    /// Construct an ArrayRef from a SmallVector. This is templated in order to
+    /// avoid instantiating SmallVectorTemplateCommon<T> whenever we
+    /// copy-construct an ArrayRef.
+    template<typename U>
+    /*implicit*/ ArrayRef(const SmallVectorTemplateCommon<T, U> &Vec)
+      : Data(Vec.data()), Length(Vec.size()) {
+    }
+
+    /// Construct an ArrayRef from a std::vector.
+    template<typename A>
+    /*implicit*/ ArrayRef(const std::vector<T, A> &Vec)
+      : Data(Vec.data()), Length(Vec.size()) {}
+
+    /// Construct an ArrayRef from a std::array
+    template <size_t N>
+    /*implicit*/ constexpr ArrayRef(const std::array<T, N> &Arr)
+        : Data(Arr.data()), Length(N) {}
+
+    /// Construct an ArrayRef from a C array.
+    template <size_t N>
+    /*implicit*/ constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
+
+    /// Construct an ArrayRef from a std::initializer_list.
+    /*implicit*/ ArrayRef(const std::initializer_list<T> &Vec)
+    : Data(Vec.begin() == Vec.end() ? (T*)nullptr : Vec.begin()),
+      Length(Vec.size()) {}
+
+    /// Construct an ArrayRef<const T*> from ArrayRef<T*>. This uses SFINAE to
+    /// ensure that only ArrayRefs of pointers can be converted.
+    template <typename U>
+    ArrayRef(
+        const ArrayRef<U *> &A,
+        typename std::enable_if<
+           std::is_convertible<U *const *, T const *>::value>::type * = nullptr)
+      : Data(A.data()), Length(A.size()) {}
+
+    /// Construct an ArrayRef<const T*> from a SmallVector<T*>. This is
+    /// templated in order to avoid instantiating SmallVectorTemplateCommon<T>
+    /// whenever we copy-construct an ArrayRef.
+    template<typename U, typename DummyT>
+    /*implicit*/ ArrayRef(
+      const SmallVectorTemplateCommon<U *, DummyT> &Vec,
+      typename std::enable_if<
+          std::is_convertible<U *const *, T const *>::value>::type * = nullptr)
+      : Data(Vec.data()), Length(Vec.size()) {
+    }
+
+    /// Construct an ArrayRef<const T*> from std::vector<T*>. This uses SFINAE
+    /// to ensure that only vectors of pointers can be converted.
+    template<typename U, typename A>
+    ArrayRef(const std::vector<U *, A> &Vec,
+             typename std::enable_if<
+                 std::is_convertible<U *const *, T const *>::value>::type* = 0)
+      : Data(Vec.data()), Length(Vec.size()) {}
+
+    /// @}
+    /// @name Simple Operations
+    /// @{
+
+    iterator begin() const { return Data; }
+    iterator end() const { return Data + Length; }
+
+    reverse_iterator rbegin() const { return reverse_iterator(end()); }
+    reverse_iterator rend() const { return reverse_iterator(begin()); }
+
+    /// empty - Check if the array is empty.
+    bool empty() const { return Length == 0; }
+
+    const T *data() const { return Data; }
+
+    /// size - Get the array size.
+    size_t size() const { return Length; }
+
+    /// front - Get the first element.
+    const T &front() const {
+      assert(!empty());
+      return Data[0];
+    }
+
+    /// back - Get the last element.
+    const T &back() const {
+      assert(!empty());
+      return Data[Length-1];
+    }
+
+    // copy - Allocate copy in Allocator and return ArrayRef<T> to it.
+    template <typename Allocator> ArrayRef<T> copy(Allocator &A) {
+      T *Buff = A.template Allocate<T>(Length);
+      std::uninitialized_copy(begin(), end(), Buff);
+      return ArrayRef<T>(Buff, Length);
+    }
+
+    /// equals - Check for element-wise equality.
+    bool equals(ArrayRef RHS) const {
+      if (Length != RHS.Length)
+        return false;
+      return std::equal(begin(), end(), RHS.begin());
+    }
+
+    /// slice(n, m) - Chop off the first N elements of the array, and keep M
+    /// elements in the array.
+    ArrayRef<T> slice(size_t N, size_t M) const {
+      assert(N+M <= size() && "Invalid specifier");
+      return ArrayRef<T>(data()+N, M);
+    }
+
+    /// slice(n) - Chop off the first N elements of the array.
+    ArrayRef<T> slice(size_t N) const { return slice(N, size() - N); }
+
+    /// Drop the first \p N elements of the array.
+    ArrayRef<T> drop_front(size_t N = 1) const {
+      assert(size() >= N && "Dropping more elements than exist");
+      return slice(N, size() - N);
+    }
+
+    /// Drop the last \p N elements of the array.
+    ArrayRef<T> drop_back(size_t N = 1) const {
+      assert(size() >= N && "Dropping more elements than exist");
+      return slice(0, size() - N);
+    }
+
+    /// Return a copy of *this with the first N elements satisfying the
+    /// given predicate removed.
+    template <class PredicateT> ArrayRef<T> drop_while(PredicateT Pred) const {
+      return ArrayRef<T>(find_if_not(*this, Pred), end());
+    }
+
+    /// Return a copy of *this with the first N elements not satisfying
+    /// the given predicate removed.
+    template <class PredicateT> ArrayRef<T> drop_until(PredicateT Pred) const {
+      return ArrayRef<T>(find_if(*this, Pred), end());
+    }
+
+    /// Return a copy of *this with only the first \p N elements.
+    ArrayRef<T> take_front(size_t N = 1) const {
+      if (N >= size())
+        return *this;
+      return drop_back(size() - N);
+    }
+
+    /// Return a copy of *this with only the last \p N elements.
+    ArrayRef<T> take_back(size_t N = 1) const {
+      if (N >= size())
+        return *this;
+      return drop_front(size() - N);
+    }
+
+    /// Return the first N elements of this Array that satisfy the given
+    /// predicate.
+    template <class PredicateT> ArrayRef<T> take_while(PredicateT Pred) const {
+      return ArrayRef<T>(begin(), find_if_not(*this, Pred));
+    }
+
+    /// Return the first N elements of this Array that don't satisfy the
+    /// given predicate.
+    template <class PredicateT> ArrayRef<T> take_until(PredicateT Pred) const {
+      return ArrayRef<T>(begin(), find_if(*this, Pred));
+    }
+
+    /// @}
+    /// @name Operator Overloads
+    /// @{
+    const T &operator[](size_t Index) const {
+      assert(Index < Length && "Invalid index!");
+      return Data[Index];
+    }
+
+    /// Disallow accidental assignment from a temporary.
+    ///
+    /// The declaration here is extra complicated so that "arrayRef = {}"
+    /// continues to select the move assignment operator.
+    template <typename U>
+    typename std::enable_if<std::is_same<U, T>::value, ArrayRef<T>>::type &
+    operator=(U &&Temporary) = delete;
+
+    /// Disallow accidental assignment from a temporary.
+    ///
+    /// The declaration here is extra complicated so that "arrayRef = {}"
+    /// continues to select the move assignment operator.
+    template <typename U>
+    typename std::enable_if<std::is_same<U, T>::value, ArrayRef<T>>::type &
+    operator=(std::initializer_list<U>) = delete;
+
+    /// @}
+    /// @name Expensive Operations
+    /// @{
+    std::vector<T> vec() const {
+      return std::vector<T>(Data, Data+Length);
+    }
+
+    /// @}
+    /// @name Conversion operators
+    /// @{
+    operator std::vector<T>() const {
+      return std::vector<T>(Data, Data+Length);
+    }
+
+    /// @}
+  };
+
+  /// MutableArrayRef - Represent a mutable reference to an array (0 or more
+  /// elements consecutively in memory), i.e. a start pointer and a length.  It
+  /// allows various APIs to take and modify consecutive elements easily and
+  /// conveniently.
+  ///
+  /// This class does not own the underlying data, it is expected to be used in
+  /// situations where the data resides in some other buffer, whose lifetime
+  /// extends past that of the MutableArrayRef. For this reason, it is not in
+  /// general safe to store a MutableArrayRef.
+  ///
+  /// This is intended to be trivially copyable, so it should be passed by
+  /// value.
+  template<typename T>
+  class LLVM_NODISCARD MutableArrayRef : public ArrayRef<T> {
+  public:
+    using iterator = T *;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+
+    /// Construct an empty MutableArrayRef.
+    /*implicit*/ MutableArrayRef() = default;
+
+    /// Construct an empty MutableArrayRef from None.
+    /*implicit*/ MutableArrayRef(NoneType) : ArrayRef<T>() {}
+
+    /// Construct an MutableArrayRef from a single element.
+    /*implicit*/ MutableArrayRef(T &OneElt) : ArrayRef<T>(OneElt) {}
+
+    /// Construct an MutableArrayRef from a pointer and length.
+    /*implicit*/ MutableArrayRef(T *data, size_t length)
+      : ArrayRef<T>(data, length) {}
+
+    /// Construct an MutableArrayRef from a range.
+    MutableArrayRef(T *begin, T *end) : ArrayRef<T>(begin, end) {}
+
+    /// Construct an MutableArrayRef from a SmallVector.
+    /*implicit*/ MutableArrayRef(SmallVectorImpl<T> &Vec)
+    : ArrayRef<T>(Vec) {}
+
+    /// Construct a MutableArrayRef from a std::vector.
+    /*implicit*/ MutableArrayRef(std::vector<T> &Vec)
+    : ArrayRef<T>(Vec) {}
+
+    /// Construct an ArrayRef from a std::array
+    template <size_t N>
+    /*implicit*/ constexpr MutableArrayRef(std::array<T, N> &Arr)
+        : ArrayRef<T>(Arr) {}
+
+    /// Construct an MutableArrayRef from a C array.
+    template <size_t N>
+    /*implicit*/ constexpr MutableArrayRef(T (&Arr)[N]) : ArrayRef<T>(Arr) {}
+
+    T *data() const { return const_cast<T*>(ArrayRef<T>::data()); }
+
+    iterator begin() const { return data(); }
+    iterator end() const { return data() + this->size(); }
+
+    reverse_iterator rbegin() const { return reverse_iterator(end()); }
+    reverse_iterator rend() const { return reverse_iterator(begin()); }
+
+    /// front - Get the first element.
+    T &front() const {
+      assert(!this->empty());
+      return data()[0];
+    }
+
+    /// back - Get the last element.
+    T &back() const {
+      assert(!this->empty());
+      return data()[this->size()-1];
+    }
+
+    /// slice(n, m) - Chop off the first N elements of the array, and keep M
+    /// elements in the array.
+    MutableArrayRef<T> slice(size_t N, size_t M) const {
+      assert(N + M <= this->size() && "Invalid specifier");
+      return MutableArrayRef<T>(this->data() + N, M);
+    }
+
+    /// slice(n) - Chop off the first N elements of the array.
+    MutableArrayRef<T> slice(size_t N) const {
+      return slice(N, this->size() - N);
+    }
+
+    /// Drop the first \p N elements of the array.
+    MutableArrayRef<T> drop_front(size_t N = 1) const {
+      assert(this->size() >= N && "Dropping more elements than exist");
+      return slice(N, this->size() - N);
+    }
+
+    MutableArrayRef<T> drop_back(size_t N = 1) const {
+      assert(this->size() >= N && "Dropping more elements than exist");
+      return slice(0, this->size() - N);
+    }
+
+    /// Return a copy of *this with the first N elements satisfying the
+    /// given predicate removed.
+    template <class PredicateT>
+    MutableArrayRef<T> drop_while(PredicateT Pred) const {
+      return MutableArrayRef<T>(find_if_not(*this, Pred), end());
+    }
+
+    /// Return a copy of *this with the first N elements not satisfying
+    /// the given predicate removed.
+    template <class PredicateT>
+    MutableArrayRef<T> drop_until(PredicateT Pred) const {
+      return MutableArrayRef<T>(find_if(*this, Pred), end());
+    }
+
+    /// Return a copy of *this with only the first \p N elements.
+    MutableArrayRef<T> take_front(size_t N = 1) const {
+      if (N >= this->size())
+        return *this;
+      return drop_back(this->size() - N);
+    }
+
+    /// Return a copy of *this with only the last \p N elements.
+    MutableArrayRef<T> take_back(size_t N = 1) const {
+      if (N >= this->size())
+        return *this;
+      return drop_front(this->size() - N);
+    }
+
+    /// Return the first N elements of this Array that satisfy the given
+    /// predicate.
+    template <class PredicateT>
+    MutableArrayRef<T> take_while(PredicateT Pred) const {
+      return MutableArrayRef<T>(begin(), find_if_not(*this, Pred));
+    }
+
+    /// Return the first N elements of this Array that don't satisfy the
+    /// given predicate.
+    template <class PredicateT>
+    MutableArrayRef<T> take_until(PredicateT Pred) const {
+      return MutableArrayRef<T>(begin(), find_if(*this, Pred));
+    }
+
+    /// @}
+    /// @name Operator Overloads
+    /// @{
+    T &operator[](size_t Index) const {
+      assert(Index < this->size() && "Invalid index!");
+      return data()[Index];
+    }
+  };
+
+  /// This is a MutableArrayRef that owns its array.
+  template <typename T> class OwningArrayRef : public MutableArrayRef<T> {
+  public:
+    OwningArrayRef() = default;
+    OwningArrayRef(size_t Size) : MutableArrayRef<T>(new T[Size], Size) {}
+
+    OwningArrayRef(ArrayRef<T> Data)
+        : MutableArrayRef<T>(new T[Data.size()], Data.size()) {
+      std::copy(Data.begin(), Data.end(), this->begin());
+    }
+
+    OwningArrayRef(OwningArrayRef &&Other) { *this = std::move(Other); }
+
+    OwningArrayRef &operator=(OwningArrayRef &&Other) {
+      delete[] this->data();
+      this->MutableArrayRef<T>::operator=(Other);
+      Other.MutableArrayRef<T>::operator=(MutableArrayRef<T>());
+      return *this;
+    }
+
+    ~OwningArrayRef() { delete[] this->data(); }
+  };
+
+  /// @name ArrayRef Convenience constructors
+  /// @{
+
+  /// Construct an ArrayRef from a single element.
+  template<typename T>
+  ArrayRef<T> makeArrayRef(const T &OneElt) {
+    return OneElt;
+  }
+
+  /// Construct an ArrayRef from a pointer and length.
+  template<typename T>
+  ArrayRef<T> makeArrayRef(const T *data, size_t length) {
+    return ArrayRef<T>(data, length);
+  }
+
+  /// Construct an ArrayRef from a range.
+  template<typename T>
+  ArrayRef<T> makeArrayRef(const T *begin, const T *end) {
+    return ArrayRef<T>(begin, end);
+  }
+
+  /// Construct an ArrayRef from a SmallVector.
+  template <typename T>
+  ArrayRef<T> makeArrayRef(const SmallVectorImpl<T> &Vec) {
+    return Vec;
+  }
+
+  /// Construct an ArrayRef from a SmallVector.
+  template <typename T, unsigned N>
+  ArrayRef<T> makeArrayRef(const SmallVector<T, N> &Vec) {
+    return Vec;
+  }
+
+  /// Construct an ArrayRef from a std::vector.
+  template<typename T>
+  ArrayRef<T> makeArrayRef(const std::vector<T> &Vec) {
+    return Vec;
+  }
+
+  /// Construct an ArrayRef from a std::array.
+  template <typename T, std::size_t N>
+  ArrayRef<T> makeArrayRef(const std::array<T, N> &Arr) {
+    return Arr;
+  }
+
+  /// Construct an ArrayRef from an ArrayRef (no-op) (const)
+  template <typename T> ArrayRef<T> makeArrayRef(const ArrayRef<T> &Vec) {
+    return Vec;
+  }
+
+  /// Construct an ArrayRef from an ArrayRef (no-op)
+  template <typename T> ArrayRef<T> &makeArrayRef(ArrayRef<T> &Vec) {
+    return Vec;
+  }
+
+  /// Construct an ArrayRef from a C array.
+  template<typename T, size_t N>
+  ArrayRef<T> makeArrayRef(const T (&Arr)[N]) {
+    return ArrayRef<T>(Arr);
+  }
+
+  /// Construct a MutableArrayRef from a single element.
+  template<typename T>
+  MutableArrayRef<T> makeMutableArrayRef(T &OneElt) {
+    return OneElt;
+  }
+
+  /// Construct a MutableArrayRef from a pointer and length.
+  template<typename T>
+  MutableArrayRef<T> makeMutableArrayRef(T *data, size_t length) {
+    return MutableArrayRef<T>(data, length);
+  }
+
+  /// @}
+  /// @name ArrayRef Comparison Operators
+  /// @{
+
+  template<typename T>
+  inline bool operator==(ArrayRef<T> LHS, ArrayRef<T> RHS) {
+    return LHS.equals(RHS);
+  }
+
+  template<typename T>
+  inline bool operator!=(ArrayRef<T> LHS, ArrayRef<T> RHS) {
+    return !(LHS == RHS);
+  }
+
+  /// @}
+
+  template <typename T> hash_code hash_value(ArrayRef<T> S) {
+    return hash_combine_range(S.begin(), S.end());
+  }
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_ARRAYREF_H