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, 263 insertions, 0 deletions

diff --git a/third_party/llvm-project/NativeFormatting.cpp b/third_party/llvm-project/NativeFormatting.cpp
new file mode 100644
index 000000000..3731e0c56
--- /dev/null
+++ b/third_party/llvm-project/NativeFormatting.cpp
@@ -0,0 +1,263 @@
+//===- NativeFormatting.cpp - Low level formatting helpers -------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Support/NativeFormatting.h"
+
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/Support/Format.h"
+
+#include <float.h>
+
+using namespace llvm;
+
+template<typename T, std::size_t N>
+static int format_to_buffer(T Value, char (&Buffer)[N]) {
+  char *EndPtr = std::end(Buffer);
+  char *CurPtr = EndPtr;
+
+  do {
+    *--CurPtr = '0' + char(Value % 10);
+    Value /= 10;
+  } while (Value);
+  return EndPtr - CurPtr;
+}
+
+static void writeWithCommas(raw_ostream &S, ArrayRef<char> Buffer) {
+  assert(!Buffer.empty());
+
+  ArrayRef<char> ThisGroup;
+  int InitialDigits = ((Buffer.size() - 1) % 3) + 1;
+  ThisGroup = Buffer.take_front(InitialDigits);
+  S.write(ThisGroup.data(), ThisGroup.size());
+
+  Buffer = Buffer.drop_front(InitialDigits);
+  assert(Buffer.size() % 3 == 0);
+  while (!Buffer.empty()) {
+    S << ',';
+    ThisGroup = Buffer.take_front(3);
+    S.write(ThisGroup.data(), 3);
+    Buffer = Buffer.drop_front(3);
+  }
+}
+
+template <typename T>
+static void write_unsigned_impl(raw_ostream &S, T N, size_t MinDigits,
+                                IntegerStyle Style, bool IsNegative) {
+  static_assert(std::is_unsigned<T>::value, "Value is not unsigned!");
+
+  char NumberBuffer[128];
+  std::memset(NumberBuffer, '0', sizeof(NumberBuffer));
+
+  size_t Len = 0;
+  Len = format_to_buffer(N, NumberBuffer);
+
+  if (IsNegative)
+    S << '-';
+
+  if (Len < MinDigits && Style != IntegerStyle::Number) {
+    for (size_t I = Len; I < MinDigits; ++I)
+      S << '0';
+  }
+
+  if (Style == IntegerStyle::Number) {
+    writeWithCommas(S, ArrayRef<char>(std::end(NumberBuffer) - Len, Len));
+  } else {
+    S.write(std::end(NumberBuffer) - Len, Len);
+  }
+}
+
+template <typename T>
+static void write_unsigned(raw_ostream &S, T N, size_t MinDigits,
+                           IntegerStyle Style, bool IsNegative = false) {
+  // Output using 32-bit div/mod if possible.
+  if (N == static_cast<uint32_t>(N))
+    write_unsigned_impl(S, static_cast<uint32_t>(N), MinDigits, Style,
+                        IsNegative);
+  else
+    write_unsigned_impl(S, N, MinDigits, Style, IsNegative);
+}
+
+template <typename T>
+static void write_signed(raw_ostream &S, T N, size_t MinDigits,
+                         IntegerStyle Style) {
+  static_assert(std::is_signed<T>::value, "Value is not signed!");
+
+  using UnsignedT = typename std::make_unsigned<T>::type;
+
+  if (N >= 0) {
+    write_unsigned(S, static_cast<UnsignedT>(N), MinDigits, Style);
+    return;
+  }
+
+  UnsignedT UN = -(UnsignedT)N;
+  write_unsigned(S, UN, MinDigits, Style, true);
+}
+
+void llvm::write_integer(raw_ostream &S, unsigned int N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_unsigned(S, N, MinDigits, Style);
+}
+
+void llvm::write_integer(raw_ostream &S, int N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_signed(S, N, MinDigits, Style);
+}
+
+void llvm::write_integer(raw_ostream &S, unsigned long N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_unsigned(S, N, MinDigits, Style);
+}
+
+void llvm::write_integer(raw_ostream &S, long N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_signed(S, N, MinDigits, Style);
+}
+
+void llvm::write_integer(raw_ostream &S, unsigned long long N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_unsigned(S, N, MinDigits, Style);
+}
+
+void llvm::write_integer(raw_ostream &S, long long N, size_t MinDigits,
+                         IntegerStyle Style) {
+  write_signed(S, N, MinDigits, Style);
+}
+
+void llvm::write_hex(raw_ostream &S, uint64_t N, HexPrintStyle Style,
+                     Optional<size_t> Width) {
+  const size_t kMaxWidth = 128u;
+
+  size_t W = std::min(kMaxWidth, Width.getValueOr(0u));
+
+  unsigned Nibbles = (64 - countLeadingZeros(N) + 3) / 4;
+  bool Prefix = (Style == HexPrintStyle::PrefixLower ||
+                 Style == HexPrintStyle::PrefixUpper);
+  bool Upper =
+      (Style == HexPrintStyle::Upper || Style == HexPrintStyle::PrefixUpper);
+  unsigned PrefixChars = Prefix ? 2 : 0;
+  unsigned NumChars =
+      std::max(static_cast<unsigned>(W), std::max(1u, Nibbles) + PrefixChars);
+
+  char NumberBuffer[kMaxWidth];
+  ::memset(NumberBuffer, '0', llvm::array_lengthof(NumberBuffer));
+  if (Prefix)
+    NumberBuffer[1] = 'x';
+  char *EndPtr = NumberBuffer + NumChars;
+  char *CurPtr = EndPtr;
+  while (N) {
+    unsigned char x = static_cast<unsigned char>(N) % 16;
+    *--CurPtr = hexdigit(x, !Upper);
+    N /= 16;
+  }
+
+  S.write(NumberBuffer, NumChars);
+}
+
+void llvm::write_double(raw_ostream &S, double N, FloatStyle Style,
+                        Optional<size_t> Precision) {
+  size_t Prec = Precision.getValueOr(getDefaultPrecision(Style));
+
+  if (std::isnan(N)) {
+    S << "nan";
+    return;
+  } else if (std::isinf(N)) {
+    S << "INF";
+    return;
+  }
+
+  char Letter;
+  if (Style == FloatStyle::Exponent)
+    Letter = 'e';
+  else if (Style == FloatStyle::ExponentUpper)
+    Letter = 'E';
+  else
+    Letter = 'f';
+
+  SmallString<8> Spec;
+  llvm::raw_svector_ostream Out(Spec);
+  Out << "%." << Prec << Letter;
+
+  if (Style == FloatStyle::Exponent || Style == FloatStyle::ExponentUpper) {
+#ifdef _WIN32
+// On MSVCRT and compatible, output of %e is incompatible to Posix
+// by default. Number of exponent digits should be at least 2. "%+03d"
+// FIXME: Implement our formatter to here or Support/Format.h!
+#if defined(__MINGW32__)
+    // FIXME: It should be generic to C++11.
+    if (N == 0.0 && std::signbit(N)) {
+      char NegativeZero[] = "-0.000000e+00";
+      if (Style == FloatStyle::ExponentUpper)
+        NegativeZero[strlen(NegativeZero) - 4] = 'E';
+      S << NegativeZero;
+      return;
+    }
+#else
+    int fpcl = _fpclass(N);
+
+    // negative zero
+    if (fpcl == _FPCLASS_NZ) {
+      char NegativeZero[] = "-0.000000e+00";
+      if (Style == FloatStyle::ExponentUpper)
+        NegativeZero[strlen(NegativeZero) - 4] = 'E';
+      S << NegativeZero;
+      return;
+    }
+#endif
+
+    char buf[32];
+    unsigned len;
+    len = format(Spec.c_str(), N).snprint(buf, sizeof(buf));
+    if (len <= sizeof(buf) - 2) {
+      if (len >= 5 && (buf[len - 5] == 'e' || buf[len - 5] == 'E') &&
+          buf[len - 3] == '0') {
+        int cs = buf[len - 4];
+        if (cs == '+' || cs == '-') {
+          int c1 = buf[len - 2];
+          int c0 = buf[len - 1];
+          if (isdigit(static_cast<unsigned char>(c1)) &&
+              isdigit(static_cast<unsigned char>(c0))) {
+            // Trim leading '0': "...e+012" -> "...e+12\0"
+            buf[len - 3] = c1;
+            buf[len - 2] = c0;
+            buf[--len] = 0;
+          }
+        }
+      }
+      S << buf;
+      return;
+    }
+#endif
+  }
+
+  if (Style == FloatStyle::Percent)
+    N *= 100.0;
+
+  char Buf[32];
+  format(Spec.c_str(), N).snprint(Buf, sizeof(Buf));
+  S << Buf;
+  if (Style == FloatStyle::Percent)
+    S << '%';
+}
+
+bool llvm::isPrefixedHexStyle(HexPrintStyle S) {
+  return (S == HexPrintStyle::PrefixLower || S == HexPrintStyle::PrefixUpper);
+}
+
+size_t llvm::getDefaultPrecision(FloatStyle Style) {
+  switch (Style) {
+  case FloatStyle::Exponent:
+  case FloatStyle::ExponentUpper:
+    return 6; // Number of decimal places.
+  case FloatStyle::Fixed:
+  case FloatStyle::Percent:
+    return 2; // Number of decimal places.
+  }
+  LLVM_BUILTIN_UNREACHABLE;
+}