[asm.js] [wasm] Store function start position for stack check

src/wasm/wasm-module-builder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/signature.h"
 
 #include "src/handles.h"
 #include "src/v8.h"
 #include "src/zone/zone-containers.h"
 
@@ skipping 134 matching lines @@
       name.start(), name.start() + name.length(), builder_->zone()));
 }
 
 void WasmFunctionBuilder::SetName(Vector<const char> name) {
   name_.resize(name.length());
   memcpy(name_.data(), name.start(), name.length());
 }
 
 void WasmFunctionBuilder::AddAsmWasmOffset(int call_position,
                                            int to_number_position) {
-  // We only want to emit one mapping per byte offset:
+  // We only want to emit one mapping per byte offset.
   DCHECK(asm_offsets_.size() == 0 || body_.size() > last_asm_byte_offset_);
 
   DCHECK_LE(body_.size(), kMaxUInt32);
   uint32_t byte_offset = static_cast<uint32_t>(body_.size());
   asm_offsets_.write_u32v(byte_offset - last_asm_byte_offset_);
   last_asm_byte_offset_ = byte_offset;
 
   DCHECK_GE(call_position, 0);
   asm_offsets_.write_i32v(call_position - last_asm_source_position_);
 
   DCHECK_GE(to_number_position, 0);
   asm_offsets_.write_i32v(to_number_position - call_position);
   last_asm_source_position_ = to_number_position;
 }
 
+void WasmFunctionBuilder::SetAsmFunctionStartPosition(int position) {
+  DCHECK_EQ(0, asm_func_start_source_position_);
+  DCHECK_LE(0, position);
+  // Must be called before emitting any asm.js source position.
+  DCHECK_EQ(0, asm_offsets_.size());
+  asm_func_start_source_position_ = position;
+  last_asm_source_position_ = position;
+}
+
 void WasmFunctionBuilder::WriteSignature(ZoneBuffer& buffer) const {
   buffer.write_u32v(signature_index_);
 }
 
 void WasmFunctionBuilder::WriteExports(ZoneBuffer& buffer) const {
   for (auto name : exported_names_) {
     buffer.write_size(name.size());
     buffer.write(reinterpret_cast<const byte*>(name.data()), name.size());
     buffer.write_u8(kExternalFunction);
     buffer.write_u32v(func_index_ +
@@ skipping 13 matching lines @@
     buffer.write(&body_[0], body_.size());
     for (DirectCallIndex call : direct_calls_) {
       buffer.patch_u32v(
           base + call.offset,
           call.direct_index + static_cast<uint32_t>(builder_->imports_.size()));
     }
   }
 }
 
 void WasmFunctionBuilder::WriteAsmWasmOffsetTable(ZoneBuffer& buffer) const {
-  if (asm_offsets_.size() == 0) {
+  if (asm_func_start_source_position_ == 0 && asm_offsets_.size() == 0) {
     buffer.write_size(0);
     return;
   }
-  buffer.write_size(asm_offsets_.size() + kInt32Size);
+  size_t locals_enc_size = LEBHelper::sizeof_u32v(locals_.Size());
+  size_t func_start_size =
+      LEBHelper::sizeof_u32v(asm_func_start_source_position_);
+  buffer.write_size(asm_offsets_.size() + locals_enc_size + func_start_size);
   // Offset of the recorded byte offsets.
   DCHECK_GE(kMaxUInt32, locals_.Size());
-  buffer.write_u32(static_cast<uint32_t>(locals_.Size()));
+  buffer.write_u32v(static_cast<uint32_t>(locals_.Size()));
+  // Start position of the function.
+  buffer.write_u32v(asm_func_start_source_position_);
   buffer.write(asm_offsets_.begin(), asm_offsets_.size());
 }
 
 WasmModuleBuilder::WasmModuleBuilder(Zone* zone)
     : zone_(zone),
       signatures_(zone),
       imports_(zone),
       functions_(zone),
       data_segments_(zone),
       indirect_functions_(zone),
@@ skipping 313 matching lines @@
   // Emit the offset table per function.
   for (auto function : functions_) {
     function->WriteAsmWasmOffsetTable(buffer);
   }
   // Append a 0 to indicate that this is an encoded table.
   buffer.write_u8(0);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8