[wasm] factor lower level utilties out of WasmFullDecoder

src/wasm/function-body-decoder.cc

Index: src/wasm/function-body-decoder.cc
diff --git a/src/wasm/function-body-decoder.cc b/src/wasm/function-body-decoder.cc
index 419b4999ad1e487eff38f5e144ea4b6187d0e458..a24087aafada55f77da7b216595ac63e8abda350 100644
--- a/src/wasm/function-body-decoder.cc
+++ b/src/wasm/function-body-decoder.cc
@@ -169,15 +169,114 @@ class WasmDecoder : public Decoder {
       : Decoder(start, end),
         module_(module),
         sig_(sig),
-        total_locals_(0),
         local_types_(nullptr) {}
   const WasmModule* module_;
   FunctionSig* sig_;
-  size_t total_locals_;
+
   ZoneVector<ValueType>* local_types_;
 
+  size_t total_locals() const {
+    return local_types_ == nullptr ? 0 : local_types_->size();
+  }
+
+  static bool DecodeLocals(Decoder* decoder, const FunctionSig* sig,
+                           ZoneVector<ValueType>* type_list) {
+    DCHECK_NOT_NULL(type_list);
+    // Initialize from signature.
+    if (sig != nullptr) {
+      type_list->reserve(sig->parameter_count());
+      for (size_t i = 0; i < sig->parameter_count(); ++i) {
+        type_list->push_back(sig->GetParam(i));
+      }
+    }
+    // Decode local declarations, if any.
+    uint32_t entries = decoder->consume_u32v("local decls count");
+    if (decoder->failed()) return false;
+
+    TRACE("local decls count: %u\n", entries);
+    while (entries-- > 0 && decoder->ok() && decoder->more()) {
+      uint32_t count = decoder->consume_u32v("local count");
+      if (decoder->failed()) return false;
+
+      if ((count + type_list->size()) > kMaxNumWasmLocals) {
+        decoder->error(decoder->pc() - 1, "local count too large");
+        return false;
+      }
+      byte code = decoder->consume_u8("local type");
+      if (decoder->failed()) return false;
+
+      ValueType type;
+      switch (code) {
+        case kLocalI32:
+          type = kWasmI32;
+          break;
+        case kLocalI64:
+          type = kWasmI64;
+          break;
+        case kLocalF32:
+          type = kWasmF32;
+          break;
+        case kLocalF64:
+          type = kWasmF64;
+          break;
+        case kLocalS128:
+          type = kWasmS128;
+          break;
+        default:
+          decoder->error(decoder->pc() - 1, "invalid local type");
+          return false;
+      }
+      type_list->insert(type_list->end(), count, type);
+    }
+    DCHECK(decoder->ok());
+    return true;
+  }
+
+  static BitVector* AnalyzeLoopAssignment(Decoder* decoder, const byte* pc,
+                                          int locals_count, Zone* zone) {
+    if (pc >= decoder->end()) return nullptr;
+    if (*pc != kExprLoop) return nullptr;
+
+    BitVector* assigned = new (zone) BitVector(locals_count, zone);
+    int depth = 0;
+    // Iteratively process all AST nodes nested inside the loop.
+    while (pc < decoder->end() && decoder->ok()) {
+      WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
+      unsigned length = 1;
+      switch (opcode) {
+        case kExprLoop:
+        case kExprIf:
+        case kExprBlock:
+        case kExprTry:
+          length = OpcodeLength(decoder, pc);
+          depth++;
+          break;
+        case kExprSetLocal:  // fallthru
+        case kExprTeeLocal: {
+          LocalIndexOperand operand(decoder, pc);
+          if (assigned->length() > 0 &&
+              operand.index < static_cast<uint32_t>(assigned->length())) {
+            // Unverified code might have an out-of-bounds index.
+            assigned->Add(operand.index);
+          }
+          length = 1 + operand.length;
+          break;
+        }
+        case kExprEnd:
+          depth--;
+          break;
+        default:
+          length = OpcodeLength(decoder, pc);
+          break;
+      }
+      if (depth <= 0) break;
+      pc += length;
+    }
+    return decoder->ok() ? assigned : nullptr;
+  }
+
   inline bool Validate(const byte* pc, LocalIndexOperand& operand) {
-    if (operand.index < total_locals_) {
+    if (operand.index < total_locals()) {
       if (local_types_) {
         operand.type = local_types_->at(operand.index);
       } else {
@@ -260,33 +359,33 @@ class WasmDecoder : public Decoder {
     }
   }
 
-  unsigned OpcodeLength(const byte* pc) {
+  static unsigned OpcodeLength(Decoder* decoder, const byte* pc) {
     switch (static_cast<byte>(*pc)) {
 #define DECLARE_OPCODE_CASE(name, opcode, sig) case kExpr##name:
       FOREACH_LOAD_MEM_OPCODE(DECLARE_OPCODE_CASE)
       FOREACH_STORE_MEM_OPCODE(DECLARE_OPCODE_CASE)
 #undef DECLARE_OPCODE_CASE
       {
-        MemoryAccessOperand operand(this, pc, UINT32_MAX);
+        MemoryAccessOperand operand(decoder, pc, UINT32_MAX);
         return 1 + operand.length;
       }
       case kExprBr:
       case kExprBrIf: {
-        BreakDepthOperand operand(this, pc);
+        BreakDepthOperand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprSetGlobal:
       case kExprGetGlobal: {
-        GlobalIndexOperand operand(this, pc);
+        GlobalIndexOperand operand(decoder, pc);
         return 1 + operand.length;
       }
 
       case kExprCallFunction: {
-        CallFunctionOperand operand(this, pc);
+        CallFunctionOperand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprCallIndirect: {
-        CallIndirectOperand operand(this, pc);
+        CallIndirectOperand operand(decoder, pc);
         return 1 + operand.length;
       }
 
@@ -294,7 +393,7 @@ class WasmDecoder : public Decoder {
       case kExprIf:  // fall thru
       case kExprLoop:
       case kExprBlock: {
-        BlockTypeOperand operand(this, pc);
+        BlockTypeOperand operand(decoder, pc);
         return 1 + operand.length;
       }
 
@@ -302,25 +401,25 @@ class WasmDecoder : public Decoder {
       case kExprTeeLocal:
       case kExprGetLocal:
       case kExprCatch: {
-        LocalIndexOperand operand(this, pc);
+        LocalIndexOperand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprBrTable: {
-        BranchTableOperand operand(this, pc);
-        BranchTableIterator iterator(this, operand);
+        BranchTableOperand operand(decoder, pc);
+        BranchTableIterator iterator(decoder, operand);
         return 1 + iterator.length();
       }
       case kExprI32Const: {
-        ImmI32Operand operand(this, pc);
+        ImmI32Operand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprI64Const: {
-        ImmI64Operand operand(this, pc);
+        ImmI64Operand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprGrowMemory:
       case kExprMemorySize: {
-        MemoryIndexOperand operand(this, pc);
+        MemoryIndexOperand operand(decoder, pc);
         return 1 + operand.length;
       }
       case kExprI8Const:
@@ -330,7 +429,7 @@ class WasmDecoder : public Decoder {
       case kExprF64Const:
         return 9;
       case kSimdPrefix: {
-        byte simd_index = checked_read_u8(pc, 1, "simd_index");
+        byte simd_index = decoder->checked_read_u8(pc, 1, "simd_index");
         WasmOpcode opcode =
             static_cast<WasmOpcode>(kSimdPrefix << 8 | simd_index);
         switch (opcode) {
@@ -347,7 +446,7 @@ class WasmDecoder : public Decoder {
             return 3;
           }
           default:
-            error("invalid SIMD opcode");
+            decoder->error(pc, "invalid SIMD opcode");
             return 2;
         }
       }
@@ -363,9 +462,6 @@ static const int32_t kNullCatch = -1;
 // generates a TurboFan IR graph.
 class WasmFullDecoder : public WasmDecoder {
  public:
-  WasmFullDecoder(Zone* zone, const FunctionBody& body)
-      : WasmFullDecoder(zone, nullptr, nullptr, body) {}
-
   WasmFullDecoder(Zone* zone, const wasm::WasmModule* module,
                   const FunctionBody& body)
       : WasmFullDecoder(zone, module, nullptr, body) {}
@@ -392,7 +488,8 @@ class WasmFullDecoder : public WasmDecoder {
       return false;
     }
 
-    DecodeLocalDecls();
+    DCHECK_EQ(0, local_types_->size());
+    WasmDecoder::DecodeLocals(this, sig_, local_types_);
     InitSsaEnv();
     DecodeFunctionBody();
 
@@ -458,35 +555,6 @@ class WasmFullDecoder : public WasmDecoder {
     return false;
   }
 
-  bool DecodeLocalDecls(BodyLocalDecls& decls) {
-    DecodeLocalDecls();
-    if (failed()) return false;
-    decls.decls_encoded_size = pc_offset();
-    decls.local_types.reserve(local_type_vec_.size());
-    for (size_t pos = 0; pos < local_type_vec_.size();) {
-      uint32_t count = 0;
-      ValueType type = local_type_vec_[pos];
-      while (pos < local_type_vec_.size() && local_type_vec_[pos] == type) {
-        pos++;
-        count++;
-      }
-      decls.local_types.push_back(std::pair<ValueType, uint32_t>(type, count));
-    }
-    decls.total_local_count = static_cast<uint32_t>(local_type_vec_.size());
-    return true;
-  }
-
-  BitVector* AnalyzeLoopAssignmentForTesting(const byte* pc,
-                                             size_t num_locals) {
-    total_locals_ = num_locals;
-    local_type_vec_.reserve(num_locals);
-    if (num_locals > local_type_vec_.size()) {
-      local_type_vec_.insert(local_type_vec_.end(),
-                             num_locals - local_type_vec_.size(), kWasmI32);
-    }
-    return AnalyzeLoopAssignment(pc);
-  }
-
  private:
   WasmFullDecoder(Zone* zone, const wasm::WasmModule* module,
                   TFBuilder* builder, const FunctionBody& body)
@@ -584,52 +652,6 @@ class WasmFullDecoder : public WasmDecoder {
     return bytes;
   }
 
-  // Decodes the locals declarations, if any, populating {local_type_vec_}.
-  void DecodeLocalDecls() {
-    DCHECK_EQ(0, local_type_vec_.size());
-    // Initialize {local_type_vec} from signature.
-    if (sig_) {
-      local_type_vec_.reserve(sig_->parameter_count());
-      for (size_t i = 0; i < sig_->parameter_count(); ++i) {
-        local_type_vec_.push_back(sig_->GetParam(i));
-      }
-    }
-    // Decode local declarations, if any.
-    uint32_t entries = consume_u32v("local decls count");
-    TRACE("local decls count: %u\n", entries);
-    while (entries-- > 0 && pc_ < end_) {
-      uint32_t count = consume_u32v("local count");
-      if ((count + local_type_vec_.size()) > kMaxNumWasmLocals) {
-        error(pc_ - 1, "local count too large");
-        return;
-      }
-      byte code = consume_u8("local type");
-      ValueType type;
-      switch (code) {
-        case kLocalI32:
-          type = kWasmI32;
-          break;
-        case kLocalI64:
-          type = kWasmI64;
-          break;
-        case kLocalF32:
-          type = kWasmF32;
-          break;
-        case kLocalF64:
-          type = kWasmF64;
-          break;
-        case kLocalS128:
-          type = kWasmS128;
-          break;
-        default:
-          error(pc_ - 1, "invalid local type");
-          return;
-      }
-      local_type_vec_.insert(local_type_vec_.end(), count, type);
-    }
-    total_locals_ = local_type_vec_.size();
-  }
-
   // Decodes the body of a function.
   void DecodeFunctionBody() {
     TRACE("wasm-decode %p...%p (module+%d, %d bytes) %s\n",
@@ -1744,7 +1766,8 @@ class WasmFullDecoder : public WasmDecoder {
     env->effect = builder_->EffectPhi(1, &env->effect, env->control);
     builder_->Terminate(env->effect, env->control);
     if (FLAG_wasm_loop_assignment_analysis) {
-      BitVector* assigned = AnalyzeLoopAssignment(pc);
+      BitVector* assigned = AnalyzeLoopAssignment(
+          this, pc, static_cast<int>(total_locals()), zone_);
       if (failed()) return env;
       if (assigned != nullptr) {
         // Only introduce phis for variables assigned in this loop.
@@ -1827,48 +1850,6 @@ class WasmFullDecoder : public WasmDecoder {
     builder_ = nullptr;  // Don't build any more nodes.
     TRACE(" !%s\n", error_msg_.get());
   }
-  BitVector* AnalyzeLoopAssignment(const byte* pc) {
-    if (pc >= end_) return nullptr;
-    if (*pc != kExprLoop) return nullptr;
-
-    BitVector* assigned =
-        new (zone_) BitVector(static_cast<int>(local_type_vec_.size()), zone_);
-    int depth = 0;
-    // Iteratively process all AST nodes nested inside the loop.
-    while (pc < end_ && ok()) {
-      WasmOpcode opcode = static_cast<WasmOpcode>(*pc);
-      unsigned length = 1;
-      switch (opcode) {
-        case kExprLoop:
-        case kExprIf:
-        case kExprBlock:
-        case kExprTry:
-          length = OpcodeLength(pc);
-          depth++;
-          break;
-        case kExprSetLocal:  // fallthru
-        case kExprTeeLocal: {
-          LocalIndexOperand operand(this, pc);
-          if (assigned->length() > 0 &&
-              operand.index < static_cast<uint32_t>(assigned->length())) {
-            // Unverified code might have an out-of-bounds index.
-            assigned->Add(operand.index);
-          }
-          length = 1 + operand.length;
-          break;
-        }
-        case kExprEnd:
-          depth--;
-          break;
-        default:
-          length = OpcodeLength(pc);
-          break;
-      }
-      if (depth <= 0) break;
-      pc += length;
-    }
-    return ok() ? assigned : nullptr;
-  }
 
   inline wasm::WasmCodePosition position() {
     int offset = static_cast<int>(pc_ - start_);
@@ -1899,21 +1880,23 @@ class WasmFullDecoder : public WasmDecoder {
   }
 };
 
-bool DecodeLocalDecls(BodyLocalDecls& decls, const byte* start,
+bool DecodeLocalDecls(BodyLocalDecls* decls, const byte* start,
                       const byte* end) {
-  AccountingAllocator allocator;
-  Zone tmp(&allocator, ZONE_NAME);
-  FunctionBody body = {nullptr, nullptr, start, end};
-  WasmFullDecoder decoder(&tmp, body);
-  return decoder.DecodeLocalDecls(decls);
+  Decoder decoder(start, end);
+  if (WasmDecoder::DecodeLocals(&decoder, nullptr, &decls->type_list)) {
+    DCHECK(decoder.ok());
+    decls->encoded_size = decoder.pc_offset();
+    return true;
+  }
+  return false;
 }
 
 BytecodeIterator::BytecodeIterator(const byte* start, const byte* end,
                                    BodyLocalDecls* decls)
     : Decoder(start, end) {
   if (decls != nullptr) {
-    if (DecodeLocalDecls(*decls, start, end)) {
-      pc_ += decls->decls_encoded_size;
+    if (DecodeLocalDecls(decls, start, end)) {
+      pc_ += decls->encoded_size;
       if (pc_ > end_) pc_ = end_;
     }
   }
@@ -1937,8 +1920,8 @@ DecodeResult BuildTFGraph(AccountingAllocator* allocator, TFBuilder* builder,
 }
 
 unsigned OpcodeLength(const byte* pc, const byte* end) {
-  WasmDecoder decoder(nullptr, nullptr, pc, end);
-  return decoder.OpcodeLength(pc);
+  Decoder decoder(pc, end);
+  return WasmDecoder::OpcodeLength(&decoder, pc);
 }
 
 void PrintWasmCodeForDebugging(const byte* start, const byte* end) {
@@ -1966,10 +1949,18 @@ bool PrintWasmCode(AccountingAllocator* allocator, const FunctionBody& body,
   BytecodeIterator i(body.start, body.end, &decls);
   if (body.start != i.pc() && !FLAG_wasm_code_fuzzer_gen_test) {
     os << "// locals: ";
-    for (auto p : decls.local_types) {
-      ValueType type = p.first;
-      uint32_t count = p.second;
-      os << " " << count << " " << WasmOpcodes::TypeName(type);
+    if (!decls.type_list.empty()) {
+      ValueType type = decls.type_list[0];
+      uint32_t count = 0;
+      for (size_t pos = 0; pos < decls.type_list.size(); ++pos) {
+        if (decls.type_list[pos] == type) {
+          ++count;
+        } else {
+          os << " " << count << " " << WasmOpcodes::TypeName(type);
+          type = decls.type_list[pos];
+          count = 1;
+        }
+      }
     }
     os << std::endl;
     ++line_nr;
@@ -1985,7 +1976,7 @@ bool PrintWasmCode(AccountingAllocator* allocator, const FunctionBody& body,
   ++line_nr;
   unsigned control_depth = 0;
   for (; i.has_next(); i.next()) {
-    unsigned length = decoder.OpcodeLength(i.pc());
+    unsigned length = WasmDecoder::OpcodeLength(&decoder, i.pc());
 
     WasmOpcode opcode = i.current();
     if (opcode == kExprElse) control_depth--;
@@ -2070,9 +2061,9 @@ bool PrintWasmCode(AccountingAllocator* allocator, const FunctionBody& body,
 
 BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end) {
-  FunctionBody body = {nullptr, nullptr, start, end};
-  WasmFullDecoder decoder(zone, body);
-  return decoder.AnalyzeLoopAssignmentForTesting(start, num_locals);
+  Decoder decoder(start, end);
+  return WasmDecoder::AnalyzeLoopAssignment(&decoder, start,
+                                            static_cast<int>(num_locals), zone);
 }
 
 }  // namespace wasm