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, 344 insertions, 0 deletions

diff --git a/third_party/llvm-project/DWARFExpression.cpp b/third_party/llvm-project/DWARFExpression.cpp
new file mode 100644
index 000000000..5009b1b7b
--- /dev/null
+++ b/third_party/llvm-project/DWARFExpression.cpp
@@ -0,0 +1,344 @@
+//===-- DWARFExpression.cpp -----------------------------------------------===//
+//
+// 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/DebugInfo/DWARF/DWARFExpression.h"
+#include "llvm/DebugInfo/DWARF/DWARFUnit.h"
+#include "llvm/BinaryFormat/Dwarf.h"
+#include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/Support/Format.h"
+#include <cassert>
+#include <cstdint>
+#include <vector>
+
+using namespace llvm;
+using namespace dwarf;
+
+namespace llvm {
+
+typedef std::vector<DWARFExpression::Operation::Description> DescVector;
+
+static DescVector getDescriptions() {
+  DescVector Descriptions;
+  typedef DWARFExpression::Operation Op;
+  typedef Op::Description Desc;
+
+  Descriptions.resize(0xff);
+  Descriptions[DW_OP_addr] = Desc(Op::Dwarf2, Op::SizeAddr);
+  Descriptions[DW_OP_deref] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_const1u] = Desc(Op::Dwarf2, Op::Size1);
+  Descriptions[DW_OP_const1s] = Desc(Op::Dwarf2, Op::SignedSize1);
+  Descriptions[DW_OP_const2u] = Desc(Op::Dwarf2, Op::Size2);
+  Descriptions[DW_OP_const2s] = Desc(Op::Dwarf2, Op::SignedSize2);
+  Descriptions[DW_OP_const4u] = Desc(Op::Dwarf2, Op::Size4);
+  Descriptions[DW_OP_const4s] = Desc(Op::Dwarf2, Op::SignedSize4);
+  Descriptions[DW_OP_const8u] = Desc(Op::Dwarf2, Op::Size8);
+  Descriptions[DW_OP_const8s] = Desc(Op::Dwarf2, Op::SignedSize8);
+  Descriptions[DW_OP_constu] = Desc(Op::Dwarf2, Op::SizeLEB);
+  Descriptions[DW_OP_consts] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
+  Descriptions[DW_OP_dup] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_drop] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_over] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_pick] = Desc(Op::Dwarf2, Op::Size1);
+  Descriptions[DW_OP_swap] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_rot] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_xderef] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_abs] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_and] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_div] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_minus] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_mod] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_mul] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_neg] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_not] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_or] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_plus] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_plus_uconst] = Desc(Op::Dwarf2, Op::SizeLEB);
+  Descriptions[DW_OP_shl] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_shr] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_shra] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_xor] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_skip] = Desc(Op::Dwarf2, Op::SignedSize2);
+  Descriptions[DW_OP_bra] = Desc(Op::Dwarf2, Op::SignedSize2);
+  Descriptions[DW_OP_eq] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_ge] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_gt] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_le] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_lt] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_ne] = Desc(Op::Dwarf2);
+  for (uint16_t LA = DW_OP_lit0; LA <= DW_OP_lit31; ++LA)
+    Descriptions[LA] = Desc(Op::Dwarf2);
+  for (uint16_t LA = DW_OP_reg0; LA <= DW_OP_reg31; ++LA)
+    Descriptions[LA] = Desc(Op::Dwarf2);
+  for (uint16_t LA = DW_OP_breg0; LA <= DW_OP_breg31; ++LA)
+    Descriptions[LA] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
+  Descriptions[DW_OP_regx] = Desc(Op::Dwarf2, Op::SizeLEB);
+  Descriptions[DW_OP_fbreg] = Desc(Op::Dwarf2, Op::SignedSizeLEB);
+  Descriptions[DW_OP_bregx] = Desc(Op::Dwarf2, Op::SizeLEB, Op::SignedSizeLEB);
+  Descriptions[DW_OP_piece] = Desc(Op::Dwarf2, Op::SizeLEB);
+  Descriptions[DW_OP_deref_size] = Desc(Op::Dwarf2, Op::Size1);
+  Descriptions[DW_OP_xderef_size] = Desc(Op::Dwarf2, Op::Size1);
+  Descriptions[DW_OP_nop] = Desc(Op::Dwarf2);
+  Descriptions[DW_OP_push_object_address] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_call2] = Desc(Op::Dwarf3, Op::Size2);
+  Descriptions[DW_OP_call4] = Desc(Op::Dwarf3, Op::Size4);
+  Descriptions[DW_OP_call_ref] = Desc(Op::Dwarf3, Op::SizeRefAddr);
+  Descriptions[DW_OP_form_tls_address] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_call_frame_cfa] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_bit_piece] = Desc(Op::Dwarf3, Op::SizeLEB, Op::SizeLEB);
+  Descriptions[DW_OP_implicit_value] =
+      Desc(Op::Dwarf3, Op::SizeLEB, Op::SizeBlock);
+  Descriptions[DW_OP_stack_value] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_GNU_push_tls_address] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_addrx] = Desc(Op::Dwarf4, Op::SizeLEB);
+  Descriptions[DW_OP_GNU_addr_index] = Desc(Op::Dwarf4, Op::SizeLEB);
+  Descriptions[DW_OP_GNU_const_index] = Desc(Op::Dwarf4, Op::SizeLEB);
+  Descriptions[DW_OP_GNU_entry_value] = Desc(Op::Dwarf4, Op::SizeLEB);
+
+  Descriptions[DW_OP_convert] = Desc(Op::Dwarf5, Op::BaseTypeRef);
+  Descriptions[DW_OP_entry_value] = Desc(Op::Dwarf5, Op::SizeLEB);
+
+  return Descriptions;
+}
+
+static DWARFExpression::Operation::Description getOpDesc(unsigned OpCode) {
+  // FIXME: Make this constexpr once all compilers are smart enough to do it.
+  static DescVector Descriptions = getDescriptions();
+  // Handle possible corrupted or unsupported operation.
+  if (OpCode >= Descriptions.size())
+    return {};
+  return Descriptions[OpCode];
+}
+
+static uint8_t getRefAddrSize(uint8_t AddrSize, uint16_t Version) {
+  return (Version == 2) ? AddrSize : 4;
+}
+
+bool DWARFExpression::Operation::extract(DataExtractor Data, uint16_t Version,
+                                         uint8_t AddressSize, uint64_t Offset) {
+  Opcode = Data.getU8(&Offset);
+
+  Desc = getOpDesc(Opcode);
+  if (Desc.Version == Operation::DwarfNA) {
+    EndOffset = Offset;
+    return false;
+  }
+
+  for (unsigned Operand = 0; Operand < 2; ++Operand) {
+    unsigned Size = Desc.Op[Operand];
+    unsigned Signed = Size & Operation::SignBit;
+
+    if (Size == Operation::SizeNA)
+      break;
+
+    switch (Size & ~Operation::SignBit) {
+    case Operation::Size1:
+      Operands[Operand] = Data.getU8(&Offset);
+      if (Signed)
+        Operands[Operand] = (int8_t)Operands[Operand];
+      break;
+    case Operation::Size2:
+      Operands[Operand] = Data.getU16(&Offset);
+      if (Signed)
+        Operands[Operand] = (int16_t)Operands[Operand];
+      break;
+    case Operation::Size4:
+      Operands[Operand] = Data.getU32(&Offset);
+      if (Signed)
+        Operands[Operand] = (int32_t)Operands[Operand];
+      break;
+    case Operation::Size8:
+      Operands[Operand] = Data.getU64(&Offset);
+      break;
+    case Operation::SizeAddr:
+      if (AddressSize == 8) {
+        Operands[Operand] = Data.getU64(&Offset);
+      } else if (AddressSize == 4) {
+        Operands[Operand] = Data.getU32(&Offset);
+      } else {
+        assert(AddressSize == 2);
+        Operands[Operand] = Data.getU16(&Offset);
+      }
+      break;
+    case Operation::SizeRefAddr:
+      if (getRefAddrSize(AddressSize, Version) == 8) {
+        Operands[Operand] = Data.getU64(&Offset);
+      } else if (getRefAddrSize(AddressSize, Version) == 4) {
+        Operands[Operand] = Data.getU32(&Offset);
+      } else {
+        assert(getRefAddrSize(AddressSize, Version) == 2);
+        Operands[Operand] = Data.getU16(&Offset);
+      }
+      break;
+    case Operation::SizeLEB:
+      if (Signed)
+        Operands[Operand] = Data.getSLEB128(&Offset);
+      else
+        Operands[Operand] = Data.getULEB128(&Offset);
+      break;
+    case Operation::BaseTypeRef:
+      Operands[Operand] = Data.getULEB128(&Offset);
+      break;
+    case Operation::SizeBlock:
+      // We need a size, so this cannot be the first operand
+      if (Operand == 0)
+        return false;
+      // Store the offset of the block as the value.
+      Operands[Operand] = Offset;
+      Offset += Operands[Operand - 1];
+      break;
+    default:
+      llvm_unreachable("Unknown DWARFExpression Op size");
+    }
+
+    OperandEndOffsets[Operand] = Offset;
+  }
+
+  EndOffset = Offset;
+  return true;
+}
+
+static bool prettyPrintRegisterOp(raw_ostream &OS, uint8_t Opcode,
+                                  uint64_t Operands[2],
+                                  const MCRegisterInfo *MRI, bool isEH) {
+  if (!MRI)
+    return false;
+
+  uint64_t DwarfRegNum;
+  unsigned OpNum = 0;
+
+  if (Opcode == DW_OP_bregx || Opcode == DW_OP_regx)
+    DwarfRegNum = Operands[OpNum++];
+  else if (Opcode >= DW_OP_breg0 && Opcode < DW_OP_bregx)
+    DwarfRegNum = Opcode - DW_OP_breg0;
+  else
+    DwarfRegNum = Opcode - DW_OP_reg0;
+
+  if (Optional<unsigned> LLVMRegNum = MRI->getLLVMRegNum(DwarfRegNum, isEH)) {
+    if (const char *RegName = MRI->getName(*LLVMRegNum)) {
+      if ((Opcode >= DW_OP_breg0 && Opcode <= DW_OP_breg31) ||
+          Opcode == DW_OP_bregx)
+        OS << format(" %s%+" PRId64, RegName, Operands[OpNum]);
+      else
+        OS << ' ' << RegName;
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool DWARFExpression::Operation::print(raw_ostream &OS,
+                                       const DWARFExpression *Expr,
+                                       const MCRegisterInfo *RegInfo,
+                                       DWARFUnit *U,
+                                       bool isEH) {
+  if (Error) {
+    OS << "<decoding error>";
+    return false;
+  }
+
+  StringRef Name = OperationEncodingString(Opcode);
+  assert(!Name.empty() && "DW_OP has no name!");
+  OS << Name;
+
+  if ((Opcode >= DW_OP_breg0 && Opcode <= DW_OP_breg31) ||
+      (Opcode >= DW_OP_reg0 && Opcode <= DW_OP_reg31) ||
+      Opcode == DW_OP_bregx || Opcode == DW_OP_regx)
+    if (prettyPrintRegisterOp(OS, Opcode, Operands, RegInfo, isEH))
+      return true;
+
+  for (unsigned Operand = 0; Operand < 2; ++Operand) {
+    unsigned Size = Desc.Op[Operand];
+    unsigned Signed = Size & Operation::SignBit;
+
+    if (Size == Operation::SizeNA)
+      break;
+
+    if (Size == Operation::BaseTypeRef && U) {
+      auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
+      if (Die && Die.getTag() == dwarf::DW_TAG_base_type) {
+        OS << format(" (0x%08" PRIx64 ")", U->getOffset() + Operands[Operand]);
+        if (auto Name = Die.find(dwarf::DW_AT_name))
+          OS << " \"" << Name->getAsCString() << "\"";
+      } else {
+        OS << format(" <invalid base_type ref: 0x%" PRIx64 ">",
+                     Operands[Operand]);
+      }
+    } else if (Size == Operation::SizeBlock) {
+      uint64_t Offset = Operands[Operand];
+      for (unsigned i = 0; i < Operands[Operand - 1]; ++i)
+        OS << format(" 0x%02x", Expr->Data.getU8(&Offset));
+    } else {
+      if (Signed)
+        OS << format(" %+" PRId64, (int64_t)Operands[Operand]);
+      else if (Opcode != DW_OP_entry_value &&
+               Opcode != DW_OP_GNU_entry_value)
+        OS << format(" 0x%" PRIx64, Operands[Operand]);
+    }
+  }
+  return true;
+}
+
+void DWARFExpression::print(raw_ostream &OS, const MCRegisterInfo *RegInfo,
+                            DWARFUnit *U, bool IsEH) const {
+  uint32_t EntryValExprSize = 0;
+  for (auto &Op : *this) {
+    if (!Op.print(OS, this, RegInfo, U, IsEH)) {
+      uint64_t FailOffset = Op.getEndOffset();
+      while (FailOffset < Data.getData().size())
+        OS << format(" %02x", Data.getU8(&FailOffset));
+      return;
+    }
+
+    if (Op.getCode() == DW_OP_entry_value ||
+        Op.getCode() == DW_OP_GNU_entry_value) {
+      OS << "(";
+      EntryValExprSize = Op.getRawOperand(0);
+      continue;
+    }
+
+    if (EntryValExprSize) {
+      EntryValExprSize--;
+      if (EntryValExprSize == 0)
+        OS << ")";
+    }
+
+    if (Op.getEndOffset() < Data.getData().size())
+      OS << ", ";
+  }
+}
+
+bool DWARFExpression::Operation::verify(DWARFUnit *U) {
+
+  for (unsigned Operand = 0; Operand < 2; ++Operand) {
+    unsigned Size = Desc.Op[Operand];
+
+    if (Size == Operation::SizeNA)
+      break;
+
+    if (Size == Operation::BaseTypeRef) {
+      auto Die = U->getDIEForOffset(U->getOffset() + Operands[Operand]);
+      if (!Die || Die.getTag() != dwarf::DW_TAG_base_type) {
+        Error = true;
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+bool DWARFExpression::verify(DWARFUnit *U) {
+  for (auto &Op : *this)
+    if (!Op.verify(U))
+      return false;
+
+  return true;
+}
+
+} // namespace llvm