[wasm] Remove dead code from module decoder

The DecodeWasmFunctionOffsets method was used for debugging, but is not
needed any more. The FindSection function was only used in
DecodeWasmFunctionOffsets. This CL removes both.

R=ahaas@chromium.org

Change-Id: Id4aa05419298ff271766676ec8453134c6e98a69
Reviewed-on: https://chromium-review.googlesource.com/457316Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43932}

src/wasm/module-decoder.cc

@@ -1149,31 +1149,6 @@ class FunctionError : public FunctionResult {
   }
 };
 
-// Find section with given section code. Return Vector of the payload, or null
-// Vector if section is not found or module bytes are invalid.
-Vector<const byte> FindSection(const byte* module_start, const byte* module_end,
-                               WasmSectionCode code) {
-  Decoder decoder(module_start, module_end);
-
-  uint32_t magic_word = decoder.consume_u32("wasm magic");
-  if (magic_word != kWasmMagic) decoder.error("wrong magic word");
-
-  uint32_t magic_version = decoder.consume_u32("wasm version");
-  if (magic_version != kWasmVersion) decoder.error("wrong wasm version");
-
-  WasmSectionIterator section_iter(decoder);
-  while (section_iter.more()) {
-    if (section_iter.section_code() == code) {
-      return Vector<const uint8_t>(section_iter.payload_start(),
-                                   section_iter.payload_length());
-    }
-    decoder.consume_bytes(section_iter.payload_length(), "section payload");
-    section_iter.advance();
-  }
-
-  return Vector<const uint8_t>();
-}
-
 }  // namespace
 
 ModuleResult DecodeWasmModule(Isolate* isolate, const byte* module_start,
@@ -1232,38 +1207,6 @@ FunctionResult DecodeWasmFunction(Isolate* isolate, Zone* zone,
   return decoder.DecodeSingleFunction(module_env, function);
 }
 
-FunctionOffsetsResult DecodeWasmFunctionOffsets(const byte* module_start,
-                                                const byte* module_end) {
-  // Find and decode the code section.
-  Vector<const byte> code_section =
-      FindSection(module_start, module_end, kCodeSectionCode);
-  Decoder decoder(code_section.start(), code_section.end());
-  FunctionOffsets table;
-  if (!code_section.start()) {
-    decoder.error("no code section");
-    return decoder.toResult(std::move(table));
-  }
-
-  uint32_t functions_count = decoder.consume_u32v("functions count");
-  // Reserve space for the entries, taking care of invalid input.
-  if (functions_count < static_cast<unsigned>(code_section.length()) / 2) {
-    table.reserve(functions_count);
-  }
-
-  int section_offset = static_cast<int>(code_section.start() - module_start);
-  DCHECK_LE(0, section_offset);
-  for (uint32_t i = 0; i < functions_count && decoder.ok(); ++i) {
-    uint32_t size = decoder.consume_u32v("body size");
-    int offset = static_cast<int>(section_offset + decoder.pc_offset());
-    table.emplace_back(offset, static_cast<int>(size));
-    DCHECK(table.back().first >= 0 && table.back().second >= 0);
-    decoder.consume_bytes(size);
-  }
-  if (decoder.more()) decoder.error("unexpected additional bytes");
-
-  return decoder.toResult(std::move(table));
-}
-
 AsmJsOffsetsResult DecodeAsmJsOffsets(const byte* tables_start,
                                       const byte* tables_end) {
   AsmJsOffsets table;

src/wasm/module-decoder.h

@@ -75,12 +75,6 @@ V8_EXPORT_PRIVATE FunctionResult DecodeWasmFunction(Isolate* isolate,
                                                     const byte* function_start,
                                                     const byte* function_end);
 
-// Extracts the function offset table from the wasm module bytes.
-// Returns a vector with <offset, length> entries, or failure if the wasm bytes
-// are detected as invalid. Note that this validation is not complete.
-FunctionOffsetsResult DecodeWasmFunctionOffsets(const byte* module_start,
-                                                const byte* module_end);
-
 V8_EXPORT_PRIVATE WasmInitExpr DecodeWasmInitExprForTesting(const byte* start,
                                                             const byte* end);