[wasm] Rework encoding of local declarations.

Local declarations were previously encoded as an optional set of
4 uint16 values as part of the function declaration. This CL
implements the current design of moving these declarations to
a list of pairs of (type, count) that is part of the body.

R=bradnelson@chromium.org,binji@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1763433002

Cr-Commit-Position: refs/heads/master@{#34564}

src/compiler/wasm-compiler.cc

@@ -2409,15 +2409,6 @@ Handle<Code> CompileWasmFunction(wasm::ErrorThrower& thrower, Isolate* isolate,
        << wasm::WasmFunctionName(&function, module_env) << std::endl;
     os << std::endl;
   }
-  // Initialize the function environment for decoding.
-  wasm::FunctionEnv env;
-  env.module = module_env;
-  env.sig = function.sig;
-  env.local_i32_count = function.local_i32_count;
-  env.local_i64_count = function.local_i64_count;
-  env.local_f32_count = function.local_f32_count;
-  env.local_f64_count = function.local_f64_count;
-  env.SumLocals();
 
   // Create a TF graph during decoding.
   Zone zone;
@@ -2428,11 +2419,11 @@ Handle<Code> CompileWasmFunction(wasm::ErrorThrower& thrower, Isolate* isolate,
       InstructionSelector::SupportedMachineOperatorFlags());
   JSGraph jsgraph(isolate, &graph, &common, nullptr, nullptr, &machine);
   WasmGraphBuilder builder(&zone, &jsgraph, function.sig);
-  wasm::TreeResult result = wasm::BuildTFGraph(
-      &builder, &env,                                                 // --
-      module_env->module->module_start,                               // --
-      module_env->module->module_start + function.code_start_offset,  // --
-      module_env->module->module_start + function.code_end_offset);   // --
+  wasm::FunctionBody body = {
+      module_env, function.sig, module_env->module->module_start,
+      module_env->module->module_start + function.code_start_offset,
+      module_env->module->module_start + function.code_end_offset};
+  wasm::TreeResult result = wasm::BuildTFGraph(&builder, body);
 
   if (result.failed()) {
     if (FLAG_trace_wasm_compiler) {

src/wasm/ast-decoder.h

@@ -183,61 +183,13 @@ struct MemoryAccessOperand {
 typedef compiler::WasmGraphBuilder TFBuilder;
 struct ModuleEnv;  // forward declaration of module interface.
 
-// Interface the function environment during decoding, include the signature
-// and number of locals.
-struct FunctionEnv {
-  ModuleEnv* module;             // module environment
-  FunctionSig* sig;              // signature of this function
-  uint32_t local_i32_count;      // number of int32 locals
-  uint32_t local_i64_count;      // number of int64 locals
-  uint32_t local_f32_count;      // number of float32 locals
-  uint32_t local_f64_count;      // number of float64 locals
-  uint32_t total_locals;         // sum of parameters and all locals
-
-  uint32_t GetLocalCount() { return total_locals; }
-  LocalType GetLocalType(uint32_t index) {
-    if (index < static_cast<uint32_t>(sig->parameter_count())) {
-      return sig->GetParam(index);
-    }
-    index -= static_cast<uint32_t>(sig->parameter_count());
-    if (index < local_i32_count) return kAstI32;
-    index -= local_i32_count;
-    if (index < local_i64_count) return kAstI64;
-    index -= local_i64_count;
-    if (index < local_f32_count) return kAstF32;
-    index -= local_f32_count;
-    if (index < local_f64_count) return kAstF64;
-    return kAstStmt;
-  }
-
-  void AddLocals(LocalType type, uint32_t count) {
-    switch (type) {
-      case kAstI32:
-        local_i32_count += count;
-        break;
-      case kAstI64:
-        local_i64_count += count;
-        break;
-      case kAstF32:
-        local_f32_count += count;
-        break;
-      case kAstF64:
-        local_f64_count += count;
-        break;
-      default:
-        UNREACHABLE();
-    }
-    total_locals += count;
-    DCHECK_EQ(total_locals,
-              (sig->parameter_count() + local_i32_count + local_i64_count +
-               local_f32_count + local_f64_count));
-  }
-
-  void SumLocals() {
-    total_locals = static_cast<uint32_t>(sig->parameter_count()) +
-                   local_i32_count + local_i64_count + local_f32_count +
-                   local_f64_count;
-  }
+// All of the various data structures necessary to decode a function body.
+struct FunctionBody {
+  ModuleEnv* module;  // module environment
+  FunctionSig* sig;   // function signature
+  const byte* base;   // base of the module bytes, for error reporting
+  const byte* start;  // start of the function body
+  const byte* end;    // end of the function body
 };
 
 struct Tree;
@@ -245,21 +197,21 @@ typedef Result<Tree*> TreeResult;
 
 std::ostream& operator<<(std::ostream& os, const Tree& tree);
 
-TreeResult VerifyWasmCode(FunctionEnv* env, const byte* base, const byte* start,
-                          const byte* end);
-TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env, const byte* base,
-                        const byte* start, const byte* end);
-
-void PrintAst(FunctionEnv* env, const byte* start, const byte* end);
+TreeResult VerifyWasmCode(FunctionBody& body);
+TreeResult BuildTFGraph(TFBuilder* builder, FunctionBody& body);
+void PrintAst(FunctionBody& body);
 
-inline TreeResult VerifyWasmCode(FunctionEnv* env, const byte* start,
-                                 const byte* end) {
-  return VerifyWasmCode(env, nullptr, start, end);
+inline TreeResult VerifyWasmCode(ModuleEnv* module, FunctionSig* sig,
+                                 const byte* start, const byte* end) {
+  FunctionBody body = {module, sig, nullptr, start, end};
+  return VerifyWasmCode(body);
 }
 
-inline TreeResult BuildTFGraph(TFBuilder* builder, FunctionEnv* env,
-                               const byte* start, const byte* end) {
-  return BuildTFGraph(builder, env, nullptr, start, end);
+inline TreeResult BuildTFGraph(TFBuilder* builder, ModuleEnv* module,
+                               FunctionSig* sig, const byte* start,
+                               const byte* end) {
+  FunctionBody body = {module, sig, nullptr, start, end};
+  return BuildTFGraph(builder, body);
 }
 
 enum ReadUnsignedLEB128ErrorCode { kNoError, kInvalidLEB128, kMissingLEB128 };
@@ -267,14 +219,17 @@ enum ReadUnsignedLEB128ErrorCode { kNoError, kInvalidLEB128, kMissingLEB128 };
 ReadUnsignedLEB128ErrorCode ReadUnsignedLEB128Operand(const byte*, const byte*,
                                                       int*, uint32_t*);
 
-BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, FunctionEnv* env,
+std::vector<LocalType>* DecodeLocalDeclsForTesting(const byte* start,
+                                                   const byte* end);
+BitVector* AnalyzeLoopAssignmentForTesting(Zone* zone, size_t num_locals,
                                            const byte* start, const byte* end);
 
 // Computes the length of the opcode at the given address.
 int OpcodeLength(const byte* pc, const byte* end);
 
 // Computes the arity (number of sub-nodes) of the opcode at the given address.
-int OpcodeArity(FunctionEnv* env, const byte* pc, const byte* end);
+int OpcodeArity(ModuleEnv* module, FunctionSig* sig, const byte* pc,
+                const byte* end);
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8

src/wasm/decoder.h

@@ -327,6 +327,7 @@ class Decoder {
 
   bool ok() const { return error_pc_ == nullptr; }
   bool failed() const { return error_pc_ != nullptr; }
+  bool more() const { return pc_ < limit_; }
 
   const byte* start() { return start_; }
   const byte* pc() { return pc_; }

src/wasm/encoder.cc

@@ -10,6 +10,7 @@
 
 #include "src/wasm/ast-decoder.h"
 #include "src/wasm/encoder.h"
+#include "src/wasm/wasm-macro-gen.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-opcodes.h"
 
@@ -250,7 +251,6 @@ WasmFunctionEncoder::WasmFunctionEncoder(Zone* zone, LocalType return_type,
 
 uint32_t WasmFunctionEncoder::HeaderSize() const {
   uint32_t size = 3;
-  if (HasLocals()) size += 8;
   if (!external_) size += 2;
   if (HasName()) size += 4;
   return size;
@@ -258,7 +258,15 @@ uint32_t WasmFunctionEncoder::HeaderSize() const {
 
 
 uint32_t WasmFunctionEncoder::BodySize(void) const {
-  return external_ ? 0 : static_cast<uint32_t>(body_.size());
+  // TODO(titzer): embed a LocalDeclEncoder in the WasmFunctionEncoder
+  LocalDeclEncoder local_decl;
+  local_decl.AddLocals(local_i32_count_, kAstI32);
+  local_decl.AddLocals(local_i64_count_, kAstI64);
+  local_decl.AddLocals(local_f32_count_, kAstF32);
+  local_decl.AddLocals(local_f64_count_, kAstF64);
+
+  return external_ ? 0
+                   : static_cast<uint32_t>(body_.size() + local_decl.Size());
 }
 
 
@@ -271,7 +279,6 @@ void WasmFunctionEncoder::Serialize(byte* buffer, byte** header,
                                     byte** body) const {
   uint8_t decl_bits = (exported_ ? kDeclFunctionExport : 0) |
                       (external_ ? kDeclFunctionImport : 0) |
-                      (HasLocals() ? kDeclFunctionLocals : 0) |
                       (HasName() ? kDeclFunctionName : 0);
 
   EmitUint8(header, decl_bits);
@@ -284,15 +291,17 @@ void WasmFunctionEncoder::Serialize(byte* buffer, byte** header,
     (*body) += name_.size();
   }
 
-  if (HasLocals()) {
-    EmitUint16(header, local_i32_count_);
-    EmitUint16(header, local_i64_count_);
-    EmitUint16(header, local_f32_count_);
-    EmitUint16(header, local_f64_count_);
-  }
 
   if (!external_) {
-    EmitUint16(header, static_cast<uint16_t>(body_.size()));
+    // TODO(titzer): embed a LocalDeclEncoder in the WasmFunctionEncoder
+    LocalDeclEncoder local_decl;
+    local_decl.AddLocals(local_i32_count_, kAstI32);
+    local_decl.AddLocals(local_i64_count_, kAstI64);
+    local_decl.AddLocals(local_f32_count_, kAstF32);
+    local_decl.AddLocals(local_f64_count_, kAstF64);
+
+    EmitUint16(header, static_cast<uint16_t>(body_.size() + local_decl.Size()));
+    (*header) += local_decl.Emit(*header);
     if (body_.size() > 0) {
       std::memcpy(*header, &body_[0], body_.size());
       (*header) += body_.size();

src/wasm/encoder.h

@@ -42,11 +42,6 @@ class WasmFunctionEncoder : public ZoneObject {
   ZoneVector<uint8_t> body_;
   ZoneVector<char> name_;
 
-  bool HasLocals() const {
-    return (local_i32_count_ + local_i64_count_ + local_f32_count_ +
-            local_f64_count_) > 0;
-  }
-
   bool HasName() const { return (exported_ || external_) && name_.size() > 0; }
 };
 

src/wasm/module-decoder.cc

@@ -338,14 +338,10 @@ class ModuleDecoder : public Decoder {
   FunctionResult DecodeSingleFunction(ModuleEnv* module_env,
                                       WasmFunction* function) {
     pc_ = start_;
-    function->sig = consume_sig();                  // read signature
+    function->sig = consume_sig();               // read signature
     function->name_offset = 0;                   // ---- name
-    function->code_start_offset = off(pc_ + 8);  // ---- code start
+    function->code_start_offset = off(pc_);      // ---- code start
     function->code_end_offset = off(limit_);     // ---- code end
-    function->local_i32_count = consume_u16();      // read u16
-    function->local_i64_count = consume_u16();      // read u16
-    function->local_f32_count = consume_u16();      // read u16
-    function->local_f64_count = consume_u16();      // read u16
     function->exported = false;                  // ---- exported
     function->external = false;                  // ---- external
 
@@ -473,18 +469,10 @@ class ModuleDecoder : public Decoder {
          << std::endl;
       os << std::endl;
     }
-    FunctionEnv fenv;
-    fenv.module = menv;
-    fenv.sig = function->sig;
-    fenv.local_i32_count = function->local_i32_count;
-    fenv.local_i64_count = function->local_i64_count;
-    fenv.local_f32_count = function->local_f32_count;
-    fenv.local_f64_count = function->local_f64_count;
-    fenv.SumLocals();
-
-    TreeResult result =
-        VerifyWasmCode(&fenv, start_, start_ + function->code_start_offset,
-                       start_ + function->code_end_offset);
+    FunctionBody body = {menv, function->sig, start_,
+                         start_ + function->code_start_offset,
+                         start_ + function->code_end_offset};
+    TreeResult result = VerifyWasmCode(body);
     if (result.failed()) {
       // Wrap the error message from the function decoder.
       std::ostringstream str;

src/wasm/wasm-macro-gen.h

@@ -7,6 +7,43 @@
 
 #include "src/wasm/wasm-opcodes.h"
 
+#define U32_LE(v)                                    \
+  static_cast<byte>(v), static_cast<byte>((v) >> 8), \
+      static_cast<byte>((v) >> 16), static_cast<byte>((v) >> 24)
+
+#define U16_LE(v) static_cast<byte>(v), static_cast<byte>((v) >> 8)
+
+#define WASM_MODULE_HEADER U32_LE(kWasmMagic), U32_LE(kWasmVersion)
+
+#define SIG_INDEX(v) U16_LE(v)
+#define FUNC_INDEX(v) U16_LE(v)
+#define NAME_OFFSET(v) U32_LE(v)
+#define BR_TARGET(v) U16_LE(v)
+
+#define MASK_7 ((1 << 7) - 1)
+#define MASK_14 ((1 << 14) - 1)
+#define MASK_21 ((1 << 21) - 1)
+#define MASK_28 ((1 << 28) - 1)
+
+#define U32V_1(x) static_cast<byte>((x)&MASK_7)
+#define U32V_2(x) \
+  static_cast<byte>(((x)&MASK_7) | 0x80), static_cast<byte>(((x) >> 7) & MASK_7)
+#define U32V_3(x)                                      \
+  static_cast<byte>((((x)) & MASK_7) | 0x80),          \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 14) & MASK_7)
+#define U32V_4(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>(((x) >> 21) & MASK_7)
+#define U32V_5(x)                                       \
+  static_cast<byte>(((x)&MASK_7) | 0x80),               \
+      static_cast<byte>((((x) >> 7) & MASK_7) | 0x80),  \
+      static_cast<byte>((((x) >> 14) & MASK_7) | 0x80), \
+      static_cast<byte>((((x) >> 21) & MASK_7) | 0x80), \
+      static_cast<byte>((((x) >> 28) & MASK_7))
+
 // Convenience macros for building Wasm bytecode directly into a byte array.
 
 //------------------------------------------------------------------------------
@@ -57,6 +94,8 @@
 #define I64V_IN_RANGE(value, length) \
   ((value) >= I64V_MIN(length) && (value) <= I64V_MAX(length))
 
+#define WASM_NO_LOCALS 0
+
 namespace v8 {
 namespace internal {
 namespace wasm {
@@ -73,6 +112,83 @@ inline void CheckI64v(int64_t value, int length) {
   DCHECK(length == 1 || !I64V_IN_RANGE(value, length - 1));
 }
 
+// A helper for encoding local declarations prepended to the body of a
+// function.
+class LocalDeclEncoder {
+ public:
+  // Prepend local declarations by creating a new buffer and copying data
+  // over. The new buffer must be delete[]'d by the caller.
+  void Prepend(const byte** start, const byte** end) const {
+    size_t size = (*end - *start);
+    byte* buffer = new byte[Size() + size];
+    size_t pos = Emit(buffer);
+    memcpy(buffer + pos, *start, size);
+    pos += size;
+    *start = buffer;
+    *end = buffer + pos;
+  }
+
+  size_t Emit(byte* buffer) const {
+    size_t pos = 0;
+    pos = WriteUint32v(buffer, pos, static_cast<uint32_t>(local_decls.size()));
+    for (size_t i = 0; i < local_decls.size(); i++) {
+      pos = WriteUint32v(buffer, pos, local_decls[i].first);
+      buffer[pos++] = WasmOpcodes::LocalTypeCodeFor(local_decls[i].second);
+    }
+    DCHECK_EQ(Size(), pos);
+    return pos;
+  }
+
+  // Add locals declarations to this helper. Return the index of the newly added
+  // local(s), with an optional adjustment for the parameters.
+  uint32_t AddLocals(uint32_t count, LocalType type,
+                     FunctionSig* sig = nullptr) {
+    if (count == 0) {
+      return static_cast<uint32_t>((sig ? sig->parameter_count() : 0) +
+                                   local_decls.size());
+    }
+    size_t pos = local_decls.size();
+    if (local_decls.size() > 0 && local_decls.back().second == type) {
+      count += local_decls.back().first;
+      local_decls.pop_back();
+    }
+    local_decls.push_back(std::pair<uint32_t, LocalType>(count, type));
+    return static_cast<uint32_t>(pos + (sig ? sig->parameter_count() : 0));
+  }
+
+  size_t Size() const {
+    size_t size = SizeofUint32v(static_cast<uint32_t>(local_decls.size()));
+    for (auto p : local_decls) size += 1 + SizeofUint32v(p.first);
+    return size;
+  }
+
+ private:
+  std::vector<std::pair<uint32_t, LocalType>> local_decls;
+
+  size_t SizeofUint32v(uint32_t val) const {
+    size_t size = 1;
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) return size;
+      size++;
+      val = val >> 7;
+    }
+  }
+
+  // TODO(titzer): lift encoding of u32v to a common place.
+  size_t WriteUint32v(byte* buffer, size_t pos, uint32_t val) const {
+    while (true) {
+      byte b = val & MASK_7;
+      if (b == val) {
+        buffer[pos++] = b;
+        break;
+      }
+      buffer[pos++] = 0x80 | b;
+      val = val >> 7;
+    }
+    return pos;
+  }
+};
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
@@ -390,41 +506,4 @@ inline void CheckI64v(int64_t value, int length) {
 #define WASM_I32_REINTERPRET_F32(x) kExprI32ReinterpretF32, x
 #define WASM_I64_REINTERPRET_F64(x) kExprI64ReinterpretF64, x
 
-#define U32_LE(v)                                    \
-  static_cast<byte>(v), static_cast<byte>((v) >> 8), \
-      static_cast<byte>((v) >> 16), static_cast<byte>((v) >> 24)
-
-#define U16_LE(v) static_cast<byte>(v), static_cast<byte>((v) >> 8)
-
-#define WASM_MODULE_HEADER U32_LE(kWasmMagic), U32_LE(kWasmVersion)
-
-#define SIG_INDEX(v) U16_LE(v)
-#define FUNC_INDEX(v) U16_LE(v)
-#define NAME_OFFSET(v) U32_LE(v)
-#define BR_TARGET(v) U16_LE(v)
-
-#define MASK_7 ((1 << 7) - 1)
-#define MASK_14 ((1 << 14) - 1)
-#define MASK_21 ((1 << 21) - 1)
-#define MASK_28 ((1 << 28) - 1)
-
-#define U32V_1(x) static_cast<byte>(x & MASK_7)
-#define U32V_2(x) \
-  static_cast<byte>((x & MASK_7) | 0x80), static_cast<byte>((x >> 7) & MASK_7)
-#define U32V_3(x)                                    \
-  static_cast<byte>((x & MASK_7) | 0x80),            \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 14) & MASK_7)
-#define U32V_4(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>((x >> 21) & MASK_7)
-#define U32V_5(x)                                     \
-  static_cast<byte>((x & MASK_7) | 0x80),             \
-      static_cast<byte>(((x >> 7) & MASK_7) | 0x80),  \
-      static_cast<byte>(((x >> 14) & MASK_7) | 0x80), \
-      static_cast<byte>(((x >> 21) & MASK_7) | 0x80), \
-      static_cast<byte>(((x >> 28) & MASK_7))
-
 #endif  // V8_WASM_MACRO_GEN_H_

src/wasm/wasm-opcodes.h

@@ -97,7 +97,8 @@ std::ostream& operator<<(std::ostream& os, const FunctionSig& function);
   V(StoreGlobal, 0x11, _)      \
   V(CallFunction, 0x12, _)     \
   V(CallIndirect, 0x13, _)     \
-  V(CallImport, 0x1F, _)
+  V(CallImport, 0x1F, _)       \
+  V(DeclLocals, 0x1E, _)
 
 // Load memory expressions.
 #define FOREACH_LOAD_MEM_OPCODE(V) \

test/cctest/wasm/test-run-wasm-64.cc

@@ -206,8 +206,7 @@ TEST(Run_WasmCallI64Parameter) {
     uint32_t index = t.CompileAndAdd();
 
     // Build the calling function.
-    WasmRunner<int32_t> r;
-    r.env()->module = &module;
+    WasmRunner<int32_t> r(&module);
     BUILD(
         r,
         WASM_I32_CONVERT_I64(WASM_CALL_FUNCTION(

test/cctest/wasm/test-run-wasm-module.cc

@@ -42,14 +42,16 @@ TEST(Run_WasmModule_CallAdd_rev) {
       2, kLocalI32, kLocalI32, kLocalI32,  // int,int -> int
       // func#0 (main) ----------------------------------
       kDeclFunctions, 2, kDeclFunctionExport, 0, 0,  // sig index
-      6, 0,                                          // body size
+      7, 0,                                          // body size
+      0,                                             // locals
       kExprCallFunction, 1,                          // --
       kExprI8Const, 77,                              // --
       kExprI8Const, 22,                              // --
       // func#1 -----------------------------------------
       0,                 // no name, not exported
       1, 0,              // sig index
-      5, 0,              // body size
+      6, 0,              // body size
+      0,                 // locals
       kExprI32Add,       // --
       kExprGetLocal, 0,  // --
       kExprGetLocal, 1,  // --

test/cctest/wasm/test-run-wasm.cc

@@ -973,7 +973,8 @@ TEST(Run_Wasm_Select_strict1) {
 
 TEST(Run_Wasm_Select_strict2) {
   WasmRunner<int32_t> r(MachineType::Int32());
-  r.env()->AddLocals(kAstI32, 2);
+  r.AllocateLocal(kAstI32);
+  r.AllocateLocal(kAstI32);
   // select(b=5, c=6, a)
   BUILD(r, WASM_SELECT(WASM_SET_LOCAL(1, WASM_I8(5)),
                        WASM_SET_LOCAL(2, WASM_I8(6)), WASM_GET_LOCAL(0)));
@@ -985,7 +986,8 @@ TEST(Run_Wasm_Select_strict2) {
 
 TEST(Run_Wasm_Select_strict3) {
   WasmRunner<int32_t> r(MachineType::Int32());
-  r.env()->AddLocals(kAstI32, 2);
+  r.AllocateLocal(kAstI32);
+  r.AllocateLocal(kAstI32);
   // select(b=5, c=6, a=b)
   BUILD(r, WASM_SELECT(WASM_SET_LOCAL(1, WASM_I8(5)),
                        WASM_SET_LOCAL(2, WASM_I8(6)),
@@ -1232,8 +1234,7 @@ TEST(Run_Wasm_VoidReturn1) {
 
   const int32_t kExpected = -414444;
   // Build the calling function.
-  WasmRunner<int32_t> r;
-  r.env()->module = &module;
+  WasmRunner<int32_t> r(&module);
   BUILD(r, B2(WASM_CALL_FUNCTION0(index), WASM_I32V_3(kExpected)));
 
   int32_t result = r.Call();
@@ -1252,8 +1253,7 @@ TEST(Run_Wasm_VoidReturn2) {
 
   const int32_t kExpected = -414444;
   // Build the calling function.
-  WasmRunner<int32_t> r;
-  r.env()->module = &module;
+  WasmRunner<int32_t> r(&module);
   BUILD(r, B2(WASM_CALL_FUNCTION0(index), WASM_I32V_3(kExpected)));
 
   int32_t result = r.Call();
@@ -2006,18 +2006,19 @@ static void TestBuildGraphForSimpleExpression(WasmOpcode opcode) {
                                  MachineOperatorBuilder::kAllOptionalOps);
   Graph graph(&zone);
   JSGraph jsgraph(isolate, &graph, &common, nullptr, nullptr, &machine);
-  FunctionEnv env;
   FunctionSig* sig = WasmOpcodes::Signature(opcode);
-  init_env(&env, sig);
 
   if (sig->parameter_count() == 1) {
-    byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0};
-    TestBuildingGraph(&zone, &jsgraph, &env, code, code + arraysize(code));
+    byte code[] = {WASM_NO_LOCALS, static_cast<byte>(opcode), kExprGetLocal, 0};
+    TestBuildingGraph(&zone, &jsgraph, nullptr, sig, code,
+                      code + arraysize(code));
   } else {
     CHECK_EQ(2, sig->parameter_count());
-    byte code[] = {static_cast<byte>(opcode), kExprGetLocal, 0, kExprGetLocal,
-                   1};
-    TestBuildingGraph(&zone, &jsgraph, &env, code, code + arraysize(code));
+    byte code[] = {WASM_NO_LOCALS, static_cast<byte>(opcode),
+                   kExprGetLocal,  0,
+                   kExprGetLocal,  1};
+    TestBuildingGraph(&zone, &jsgraph, nullptr, sig, code,
+                      code + arraysize(code));
   }
 }
 

test/cctest/wasm/wasm-run-utils.h

@@ -63,16 +63,6 @@ using namespace v8::internal;
 using namespace v8::internal::compiler;
 using namespace v8::internal::wasm;
 
-inline void init_env(FunctionEnv* env, FunctionSig* sig) {
-  env->module = nullptr;
-  env->sig = sig;
-  env->local_i32_count = 0;
-  env->local_i64_count = 0;
-  env->local_f32_count = 0;
-  env->local_f64_count = 0;
-  env->SumLocals();
-}
-
 const uint32_t kMaxGlobalsSize = 128;
 
 // A helper for module environments that adds the ability to allocate memory
@@ -227,11 +217,11 @@ class TestingModule : public ModuleEnv {
   }
 };
 
-
-inline void TestBuildingGraph(Zone* zone, JSGraph* jsgraph, FunctionEnv* env,
-                              const byte* start, const byte* end) {
-  compiler::WasmGraphBuilder builder(zone, jsgraph, env->sig);
-  TreeResult result = BuildTFGraph(&builder, env, start, end);
+inline void TestBuildingGraph(Zone* zone, JSGraph* jsgraph, ModuleEnv* module,
+                              FunctionSig* sig, const byte* start,
+                              const byte* end) {
+  compiler::WasmGraphBuilder builder(zone, jsgraph, sig);
+  TreeResult result = BuildTFGraph(&builder, module, sig, start, end);
   if (result.failed()) {
     ptrdiff_t pc = result.error_pc - result.start;
     ptrdiff_t pt = result.error_pt - result.start;
@@ -399,10 +389,9 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
       : GraphAndBuilders(main_zone()),
         jsgraph(this->isolate(), this->graph(), this->common(), nullptr,
                 nullptr, this->machine()),
+        sig(sig),
         descriptor_(nullptr),
         testing_module_(module) {
-    init_env(&env, sig);
-    env.module = module;
     if (module) {
       // Get a new function from the testing module.
       function_ = nullptr;
@@ -420,12 +409,13 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
   }
 
   JSGraph jsgraph;
-  FunctionEnv env;
+  FunctionSig* sig;
   // The call descriptor is initialized when the function is compiled.
   CallDescriptor* descriptor_;
   TestingModule* testing_module_;
   WasmFunction* function_;
   int function_index_;
+  LocalDeclEncoder local_decls;
 
   Isolate* isolate() { return main_isolate(); }
   Graph* graph() const { return main_graph_; }
@@ -434,28 +424,23 @@ class WasmFunctionCompiler : public HandleAndZoneScope,
   MachineOperatorBuilder* machine() { return &main_machine_; }
   void InitializeDescriptor() {
     if (descriptor_ == nullptr) {
-      descriptor_ = env.module->GetWasmCallDescriptor(main_zone(), env.sig);
+      descriptor_ = testing_module_->GetWasmCallDescriptor(main_zone(), sig);
     }
   }
   CallDescriptor* descriptor() { return descriptor_; }
 
   void Build(const byte* start, const byte* end) {
-    // Transfer local counts before compiling.
-    function()->local_i32_count = env.local_i32_count;
-    function()->local_i64_count = env.local_i64_count;
-    function()->local_f32_count = env.local_f32_count;
-    function()->local_f64_count = env.local_f64_count;
-
     // Build the TurboFan graph.
-    TestBuildingGraph(main_zone(), &jsgraph, &env, start, end);
+    local_decls.Prepend(&start, &end);
+    TestBuildingGraph(main_zone(), &jsgraph, testing_module_, sig, start, end);
+    delete[] start;
   }
 
   byte AllocateLocal(LocalType type) {
-    int result = static_cast<int>(env.total_locals);
-    env.AddLocals(type, 1);
-    byte b = static_cast<byte>(result);
-    CHECK_EQ(result, b);
-    return b;
+    uint32_t index = local_decls.AddLocals(1, type, sig);
+    byte result = static_cast<byte>(index);
+    DCHECK_EQ(index, result);
+    return result;
   }
 
   // TODO(titzer): remove me.
@@ -542,8 +527,6 @@ class WasmRunner {
     wrapper_.Init(compiler_.descriptor(), p0, p1, p2, p3);
   }
 
-  FunctionEnv* env() { return &compiler_.env; }
-
   // Builds a graph from the given Wasm code and generates the machine
   // code and call wrapper for that graph. This method must not be called
   // more than once.
@@ -593,13 +576,7 @@ class WasmRunner {
     return return_value;
   }
 
-  byte AllocateLocal(LocalType type) {
-    int result = static_cast<int>(env()->total_locals);
-    env()->AddLocals(type, 1);
-    byte b = static_cast<byte>(result);
-    CHECK_EQ(result, b);
-    return b;
-  }
+  byte AllocateLocal(LocalType type) { return compiler_.AllocateLocal(type); }
 
  protected:
   Zone zone;

test/mjsunit/wasm/test-wasm-module-builder.js

@@ -47,6 +47,29 @@ var debug = false;
     assertEquals(27777, instance.exports.main(27777));
 })();
 
+(function LocalsTest2() {
+    // TODO(titzer): i64 only works on 64-bit platforms.
+    var types = [
+      {locals: {i32_count: 1}, type: kAstI32},
+//      {locals: {i64_count: 1}, type: kAstI64},
+      {locals: {f32_count: 1}, type: kAstF32},
+      {locals: {f64_count: 1}, type: kAstF64},
+    ];
+
+    for (p of types) {
+      var module = new WasmModuleBuilder();
+      module.addFunction(undefined, [p.type, p.type])
+        .addLocals(p.locals)
+        .addBody([kExprSetLocal, 1, kExprGetLocal, 0])
+        .exportAs("main");
+
+      var buffer = module.toBuffer(debug);
+      var instance = _WASMEXP_.instantiateModule(buffer);
+      assertEquals(19, instance.exports.main(19));
+      assertEquals(27777, instance.exports.main(27777));
+    }
+})();
+
 (function CallTest() {
     var module = new WasmModuleBuilder();
     module.addFunction("add", [kAstI32, kAstI32, kAstI32])

test/mjsunit/wasm/verify-function-simple.js

@@ -9,10 +9,7 @@ load("test/mjsunit/wasm/wasm-constants.js");
 try {
   var data = bytes(
       0,       kAstStmt,  // signature
-      3,       0,         // local int32 count
-      4,       0,         // local int64 count
-      5,       0,         // local float32 count
-      6,       0,         // local float64 count
+      kDeclNoLocals,      // --
       kExprNop            // body
   );
 
@@ -27,10 +24,7 @@ var threw = false;
 try {
   var data = bytes(
       0,       kAstI32,   // signature
-      2,       0,         // local int32 count
-      3,       0,         // local int64 count
-      4,       0,         // local float32 count
-      5,       0,         // local float64 count
+      kDeclNoLocals,      // --
       kExprBlock, 2, kExprNop, kExprNop  // body
   );
 

test/mjsunit/wasm/wasm-constants.js

@@ -48,6 +48,8 @@ function bytesWithHeader() {
   return buffer;
 }
 
+var kDeclNoLocals = 0;
+
 // Section declaration constants
 var kDeclMemory = 0x00;
 var kDeclSignatures = 0x01;

test/mjsunit/wasm/wasm-module-builder.js

@@ -190,25 +190,46 @@ WasmModuleBuilder.prototype.toArray = function(debug) {
             var hasName = func.name != undefined && func.name.length > 0;
             names = names || hasName;
             if (hasName) flags |= kDeclFunctionName;
-            if (func.locals != undefined) flags |= kDeclFunctionLocals;
             exports += func.exports.length;
 
             emit_u8(bytes, flags);
             emit_u16(bytes, func.sig_index);
 
-            if (hasName) {
-                emit_string(bytes, func.name);
+            if (hasName) emit_string(bytes, func.name);
+
+            // Function body length will be patched later.
+            var length_pos = bytes.length;
+            emit_u16(bytes, 0);
+
+            var local_decls = [];
+            var l = func.locals;
+            if (l != undefined) {
+              var local_decls_count = 0;
+              if (l.i32_count > 0) {
+                local_decls.push({count: l.i32_count, type: kAstI32});
+              }
+              if (l.i64_count > 0) {
+                local_decls.push({count: l.i64_count, type: kAstI64});
+              }
+              if (l.f32_count > 0) {
+                local_decls.push({count: l.f32_count, type: kAstF32});
+              }
+              if (l.f64_count > 0) {
+                local_decls.push({count: l.f64_count, type: kAstF64});
+              }
             }
-            if (func.locals != undefined) {
-                emit_u16(bytes, func.locals.i32_count);
-                emit_u16(bytes, func.locals.i64_count);
-                emit_u16(bytes, func.locals.f32_count);
-                emit_u16(bytes, func.locals.f64_count);
+            emit_u8(bytes, local_decls.length);
+            for (decl of local_decls) {
+              emit_varint(bytes, decl.count);
+              emit_u8(bytes, decl.type);
             }
-            emit_u16(bytes, func.body.length);
+
             for (var i = 0; i < func.body.length; i++) {
                 emit_u8(bytes, func.body[i]);
             }
+            var length = bytes.length - length_pos - 2;
+            bytes[length_pos] = length & 0xff;
+            bytes[length_pos + 1] = (length >> 8) & 0xff;
 
             index++;
         }

test/unittests/wasm/encoder-unittest.cc

@@ -86,9 +86,6 @@ TEST_F(EncoderTest, Function_Builder_Variable_Indexing) {
   byte* header = buffer;
   byte* body = buffer + f->HeaderSize();
   f->Serialize(buffer, &header, &body);
-  for (size_t i = 0; i < 7; i++) {
-    CHECK_EQ(i, static_cast<size_t>(*(buffer + 2 * i + f->HeaderSize() + 1)));
-  }
 }
 
 
@@ -109,15 +106,6 @@ TEST_F(EncoderTest, Function_Builder_Indexing_Variable_Width) {
   byte* body = buffer + f->HeaderSize();
   f->Serialize(buffer, &header, &body);
   body = buffer + f->HeaderSize();
-  for (size_t i = 0; i < 127; i++) {
-    CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * i)));
-    CHECK_EQ(i + 1, static_cast<size_t>(*(body + 2 * i + 1)));
-  }
-  CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * 127)));
-  CHECK_EQ(0x80, static_cast<size_t>(*(body + 2 * 127 + 1)));
-  CHECK_EQ(0x01, static_cast<size_t>(*(body + 2 * 127 + 2)));
-  CHECK_EQ(kExprGetLocal, static_cast<size_t>(*(body + 2 * 127 + 3)));
-  CHECK_EQ(0x00, static_cast<size_t>(*(body + 2 * 127 + 4)));
 }
 
 

test/unittests/wasm/loop-assignment-analysis-unittest.cc

@@ -23,25 +23,12 @@ namespace wasm {
 
 class WasmLoopAssignmentAnalyzerTest : public TestWithZone {
  public:
-  WasmLoopAssignmentAnalyzerTest() : TestWithZone(), sigs() {
-    init_env(&env, sigs.v_v());
-  }
-
+  WasmLoopAssignmentAnalyzerTest() : num_locals(0) {}
   TestSignatures sigs;
-  FunctionEnv env;
-
-  static void init_env(FunctionEnv* env, FunctionSig* sig) {
-    env->module = nullptr;
-    env->sig = sig;
-    env->local_i32_count = 0;
-    env->local_i64_count = 0;
-    env->local_f32_count = 0;
-    env->local_f64_count = 0;
-    env->SumLocals();
-  }
+  uint32_t num_locals;
 
   BitVector* Analyze(const byte* start, const byte* end) {
-    return AnalyzeLoopAssignmentForTesting(zone(), &env, start, end);
+    return AnalyzeLoopAssignmentForTesting(zone(), num_locals, start, end);
   }
 };
 
@@ -60,13 +47,13 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Empty1) {
     for (int j = 0; j < assigned->length(); j++) {
       CHECK_EQ(false, assigned->Contains(j));
     }
-    env.AddLocals(kAstI32, 1);
+    num_locals++;
   }
 }
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, One) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(1, WASM_SET_ZERO(i))};
     BitVector* assigned = Analyze(code, code + arraysize(code));
@@ -78,7 +65,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, One) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, OneBeyond) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(1, WASM_SET_ZERO(i)), WASM_SET_ZERO(1)};
     BitVector* assigned = Analyze(code, code + arraysize(code));
@@ -90,7 +77,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, OneBeyond) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Two) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     for (int j = 0; j < 5; j++) {
       byte code[] = {WASM_LOOP(2, WASM_SET_ZERO(i), WASM_SET_ZERO(j))};
@@ -105,7 +92,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Two) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, NestedIf) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   for (int i = 0; i < 5; i++) {
     byte code[] = {WASM_LOOP(
         1, WASM_IF_ELSE(WASM_SET_ZERO(0), WASM_SET_ZERO(i), WASM_SET_ZERO(1)))};
@@ -126,7 +113,7 @@ static byte LEBByte(uint32_t val, byte which) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, BigLocal) {
-  env.AddLocals(kAstI32, 65000);
+  num_locals = 65000;
   for (int i = 13; i < 65000; i = static_cast<int>(i * 1.5)) {
     byte code[] = {kExprLoop,
                    1,
@@ -148,7 +135,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, BigLocal) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Break) {
-  env.AddLocals(kAstI32, 3);
+  num_locals = 3;
   byte code[] = {
       WASM_LOOP(1, WASM_IF(WASM_GET_LOCAL(0), WASM_BRV(1, WASM_SET_ZERO(1)))),
       WASM_SET_ZERO(0)};
@@ -162,7 +149,7 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Break) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Loop1) {
-  env.AddLocals(kAstI32, 5);
+  num_locals = 5;
   byte code[] = {
       WASM_LOOP(1, WASM_IF(WASM_GET_LOCAL(0),
                            WASM_BRV(0, WASM_SET_LOCAL(
@@ -179,9 +166,8 @@ TEST_F(WasmLoopAssignmentAnalyzerTest, Loop1) {
 
 
 TEST_F(WasmLoopAssignmentAnalyzerTest, Loop2) {
-  env.AddLocals(kAstI32, 3);
+  num_locals = 6;
   const byte kIter = 0;
-  env.AddLocals(kAstF32, 3);
   const byte kSum = 3;
 
   byte code[] = {WASM_BLOCK(

test/unittests/wasm/module-decoder-unittest.cc

@@ -903,10 +903,11 @@ class WasmFunctionVerifyTest : public TestWithZone {};
 TEST_F(WasmFunctionVerifyTest, Ok_v_v_empty) {
   static const byte data[] = {
       0,       kLocalVoid,  // signature
-      3,       0,           // local int32 count
-      4,       0,           // local int64 count
-      5,       0,           // local float32 count
-      6,       0,           // local float64 count
+      4,                    // locals
+      3,       kLocalI32,   // --
+      4,       kLocalI64,   // --
+      5,       kLocalF32,   // --
+      6,       kLocalF64,   // --
       kExprNop              // body
   };
 
@@ -919,12 +920,9 @@ TEST_F(WasmFunctionVerifyTest, Ok_v_v_empty) {
     EXPECT_EQ(0, function->sig->parameter_count());
     EXPECT_EQ(0, function->sig->return_count());
     EXPECT_EQ(0, function->name_offset);
-    EXPECT_EQ(arraysize(data) - 1, function->code_start_offset);
+    EXPECT_EQ(2, function->code_start_offset);
     EXPECT_EQ(arraysize(data), function->code_end_offset);
-    EXPECT_EQ(3, function->local_i32_count);
-    EXPECT_EQ(4, function->local_i64_count);
-    EXPECT_EQ(5, function->local_f32_count);
-    EXPECT_EQ(6, function->local_f64_count);
+    // TODO(titzer): verify encoding of local declarations
     EXPECT_FALSE(function->external);
     EXPECT_FALSE(function->exported);
   }