vendor/lld/lld-trunk-r338150

1 files changed, 295 insertions, 0 deletions

diff --git a/wasm/InputChunks.cpp b/wasm/InputChunks.cpp
new file mode 100644
index 000000000000..fcefac7d99b8
--- /dev/null
+++ b/wasm/InputChunks.cpp
@@ -0,0 +1,295 @@
+//===- InputChunks.cpp ----------------------------------------------------===//
+//
+//                             The LLVM Linker
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "InputChunks.h"
+#include "Config.h"
+#include "OutputSegment.h"
+#include "WriterUtils.h"
+#include "lld/Common/ErrorHandler.h"
+#include "lld/Common/LLVM.h"
+#include "llvm/Support/LEB128.h"
+
+#define DEBUG_TYPE "lld"
+
+using namespace llvm;
+using namespace llvm::wasm;
+using namespace llvm::support::endian;
+using namespace lld;
+using namespace lld::wasm;
+
+static StringRef ReloctTypeToString(uint8_t RelocType) {
+  switch (RelocType) {
+#define WASM_RELOC(NAME, REL) case REL: return #NAME;
+#include "llvm/BinaryFormat/WasmRelocs.def"
+#undef WASM_RELOC
+  }
+  llvm_unreachable("unknown reloc type");
+}
+
+std::string lld::toString(const InputChunk *C) {
+  return (toString(C->File) + ":(" + C->getName() + ")").str();
+}
+
+StringRef InputChunk::getComdatName() const {
+  uint32_t Index = getComdat();
+  if (Index == UINT32_MAX)
+    return StringRef();
+  return File->getWasmObj()->linkingData().Comdats[Index];
+}
+
+void InputChunk::copyRelocations(const WasmSection &Section) {
+  if (Section.Relocations.empty())
+    return;
+  size_t Start = getInputSectionOffset();
+  size_t Size = getInputSize();
+  for (const WasmRelocation &R : Section.Relocations)
+    if (R.Offset >= Start && R.Offset < Start + Size)
+      Relocations.push_back(R);
+}
+
+void InputChunk::verifyRelocTargets() const {
+  for (const WasmRelocation &Rel : Relocations) {
+    uint32_t ExistingValue;
+    unsigned BytesRead = 0;
+    uint32_t Offset = Rel.Offset - getInputSectionOffset();
+    const uint8_t *Loc = data().data() + Offset;
+    switch (Rel.Type) {
+    case R_WEBASSEMBLY_TYPE_INDEX_LEB:
+    case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+    case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
+      ExistingValue = decodeULEB128(Loc, &BytesRead);
+      break;
+    case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
+      ExistingValue = static_cast<uint32_t>(decodeSLEB128(Loc, &BytesRead));
+      break;
+    case R_WEBASSEMBLY_TABLE_INDEX_I32:
+    case R_WEBASSEMBLY_MEMORY_ADDR_I32:
+    case R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
+    case R_WEBASSEMBLY_SECTION_OFFSET_I32:
+      ExistingValue = static_cast<uint32_t>(read32le(Loc));
+      break;
+    default:
+      llvm_unreachable("unknown relocation type");
+    }
+
+    if (BytesRead && BytesRead != 5)
+      warn("expected LEB at relocation site be 5-byte padded");
+    uint32_t ExpectedValue = File->calcExpectedValue(Rel);
+    if (ExpectedValue != ExistingValue)
+      warn("unexpected existing value for " + ReloctTypeToString(Rel.Type) +
+           ": existing=" + Twine(ExistingValue) +
+           " expected=" + Twine(ExpectedValue));
+  }
+}
+
+// Copy this input chunk to an mmap'ed output file and apply relocations.
+void InputChunk::writeTo(uint8_t *Buf) const {
+  // Copy contents
+  memcpy(Buf + OutputOffset, data().data(), data().size());
+
+  // Apply relocations
+  if (Relocations.empty())
+    return;
+
+#ifndef NDEBUG
+  verifyRelocTargets();
+#endif
+
+  LLVM_DEBUG(dbgs() << "applying relocations: " << getName()
+                    << " count=" << Relocations.size() << "\n");
+  int32_t Off = OutputOffset - getInputSectionOffset();
+
+  for (const WasmRelocation &Rel : Relocations) {
+    uint8_t *Loc = Buf + Rel.Offset + Off;
+    uint32_t Value = File->calcNewValue(Rel);
+    LLVM_DEBUG(dbgs() << "apply reloc: type=" << ReloctTypeToString(Rel.Type)
+                      << " addend=" << Rel.Addend << " index=" << Rel.Index
+                      << " value=" << Value << " offset=" << Rel.Offset
+                      << "\n");
+
+    switch (Rel.Type) {
+    case R_WEBASSEMBLY_TYPE_INDEX_LEB:
+    case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+    case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
+      encodeULEB128(Value, Loc, 5);
+      break;
+    case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
+      encodeSLEB128(static_cast<int32_t>(Value), Loc, 5);
+      break;
+    case R_WEBASSEMBLY_TABLE_INDEX_I32:
+    case R_WEBASSEMBLY_MEMORY_ADDR_I32:
+    case R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
+    case R_WEBASSEMBLY_SECTION_OFFSET_I32:
+      write32le(Loc, Value);
+      break;
+    default:
+      llvm_unreachable("unknown relocation type");
+    }
+  }
+}
+
+// Copy relocation entries to a given output stream.
+// This function is used only when a user passes "-r". For a regular link,
+// we consume relocations instead of copying them to an output file.
+void InputChunk::writeRelocations(raw_ostream &OS) const {
+  if (Relocations.empty())
+    return;
+
+  int32_t Off = OutputOffset - getInputSectionOffset();
+  LLVM_DEBUG(dbgs() << "writeRelocations: " << File->getName()
+                    << " offset=" << Twine(Off) << "\n");
+
+  for (const WasmRelocation &Rel : Relocations) {
+    writeUleb128(OS, Rel.Type, "reloc type");
+    writeUleb128(OS, Rel.Offset + Off, "reloc offset");
+    writeUleb128(OS, File->calcNewIndex(Rel), "reloc index");
+
+    switch (Rel.Type) {
+    case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
+    case R_WEBASSEMBLY_MEMORY_ADDR_I32:
+    case R_WEBASSEMBLY_FUNCTION_OFFSET_I32:
+    case R_WEBASSEMBLY_SECTION_OFFSET_I32:
+      writeSleb128(OS, File->calcNewAddend(Rel), "reloc addend");
+      break;
+    }
+  }
+}
+
+void InputFunction::setFunctionIndex(uint32_t Index) {
+  LLVM_DEBUG(dbgs() << "InputFunction::setFunctionIndex: " << getName()
+                    << " -> " << Index << "\n");
+  assert(!hasFunctionIndex());
+  FunctionIndex = Index;
+}
+
+void InputFunction::setTableIndex(uint32_t Index) {
+  LLVM_DEBUG(dbgs() << "InputFunction::setTableIndex: " << getName() << " -> "
+                    << Index << "\n");
+  assert(!hasTableIndex());
+  TableIndex = Index;
+}
+
+// Write a relocation value without padding and return the number of bytes
+// witten.
+static unsigned writeCompressedReloc(uint8_t *Buf, const WasmRelocation &Rel,
+                                     uint32_t Value) {
+  switch (Rel.Type) {
+  case R_WEBASSEMBLY_TYPE_INDEX_LEB:
+  case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+  case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
+  case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
+    return encodeULEB128(Value, Buf);
+  case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+  case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
+    return encodeSLEB128(static_cast<int32_t>(Value), Buf);
+  default:
+    llvm_unreachable("unexpected relocation type");
+  }
+}
+
+static unsigned getRelocWidthPadded(const WasmRelocation &Rel) {
+  switch (Rel.Type) {
+  case R_WEBASSEMBLY_TYPE_INDEX_LEB:
+  case R_WEBASSEMBLY_FUNCTION_INDEX_LEB:
+  case R_WEBASSEMBLY_GLOBAL_INDEX_LEB:
+  case R_WEBASSEMBLY_MEMORY_ADDR_LEB:
+  case R_WEBASSEMBLY_TABLE_INDEX_SLEB:
+  case R_WEBASSEMBLY_MEMORY_ADDR_SLEB:
+    return 5;
+  default:
+    llvm_unreachable("unexpected relocation type");
+  }
+}
+
+static unsigned getRelocWidth(const WasmRelocation &Rel, uint32_t Value) {
+  uint8_t Buf[5];
+  return writeCompressedReloc(Buf, Rel, Value);
+}
+
+// Relocations of type LEB and SLEB in the code section are padded to 5 bytes
+// so that a fast linker can blindly overwrite them without needing to worry
+// about the number of bytes needed to encode the values.
+// However, for optimal output the code section can be compressed to remove
+// the padding then outputting non-relocatable files.
+// In this case we need to perform a size calculation based on the value at each
+// relocation.  At best we end up saving 4 bytes for each relocation entry.
+//
+// This function only computes the final output size.  It must be called
+// before getSize() is used to calculate of layout of the code section.
+void InputFunction::calculateSize() {
+  if (!File || !Config->CompressRelocTargets)
+    return;
+
+  LLVM_DEBUG(dbgs() << "calculateSize: " << getName() << "\n");
+
+  const uint8_t *SecStart = File->CodeSection->Content.data();
+  const uint8_t *FuncStart = SecStart + getInputSectionOffset();
+  uint32_t FunctionSizeLength;
+  decodeULEB128(FuncStart, &FunctionSizeLength);
+
+  uint32_t Start = getInputSectionOffset();
+  uint32_t End = Start + Function->Size;
+
+  uint32_t LastRelocEnd = Start + FunctionSizeLength;
+  for (WasmRelocation &Rel : Relocations) {
+    LLVM_DEBUG(dbgs() << "  region: " << (Rel.Offset - LastRelocEnd) << "\n");
+    CompressedFuncSize += Rel.Offset - LastRelocEnd;
+    CompressedFuncSize += getRelocWidth(Rel, File->calcNewValue(Rel));
+    LastRelocEnd = Rel.Offset + getRelocWidthPadded(Rel);
+  }
+  LLVM_DEBUG(dbgs() << "  final region: " << (End - LastRelocEnd) << "\n");
+  CompressedFuncSize += End - LastRelocEnd;
+
+  // Now we know how long the resulting function is we can add the encoding
+  // of its length
+  uint8_t Buf[5];
+  CompressedSize = CompressedFuncSize + encodeULEB128(CompressedFuncSize, Buf);
+
+  LLVM_DEBUG(dbgs() << "  calculateSize orig: " << Function->Size << "\n");
+  LLVM_DEBUG(dbgs() << "  calculateSize  new: " << CompressedSize << "\n");
+}
+
+// Override the default writeTo method so that we can (optionally) write the
+// compressed version of the function.
+void InputFunction::writeTo(uint8_t *Buf) const {
+  if (!File || !Config->CompressRelocTargets)
+    return InputChunk::writeTo(Buf);
+
+  Buf += OutputOffset;
+  uint8_t *Orig = Buf; (void)Orig;
+
+  const uint8_t *SecStart = File->CodeSection->Content.data();
+  const uint8_t *FuncStart = SecStart + getInputSectionOffset();
+  const uint8_t *End = FuncStart + Function->Size;
+  uint32_t Count;
+  decodeULEB128(FuncStart, &Count);
+  FuncStart += Count;
+
+  LLVM_DEBUG(dbgs() << "write func: " << getName() << "\n");
+  Buf += encodeULEB128(CompressedFuncSize, Buf);
+  const uint8_t *LastRelocEnd = FuncStart;
+  for (const WasmRelocation &Rel : Relocations) {
+    unsigned ChunkSize = (SecStart + Rel.Offset) - LastRelocEnd;
+    LLVM_DEBUG(dbgs() << "  write chunk: " << ChunkSize << "\n");
+    memcpy(Buf, LastRelocEnd, ChunkSize);
+    Buf += ChunkSize;
+    Buf += writeCompressedReloc(Buf, Rel, File->calcNewValue(Rel));
+    LastRelocEnd = SecStart + Rel.Offset + getRelocWidthPadded(Rel);
+  }
+
+  unsigned ChunkSize = End - LastRelocEnd;
+  LLVM_DEBUG(dbgs() << "  write final chunk: " << ChunkSize << "\n");
+  memcpy(Buf, LastRelocEnd, ChunkSize);
+  LLVM_DEBUG(dbgs() << "  total: " << (Buf + ChunkSize - Orig) << "\n");
+}