[wasm] Rework encoding of local declarations.

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

 // Copyright 2016 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.
 
 function StringRef(string) {
     this.pos = -1;
     this.string = string;
 }
 
 function DataRef(data) {
@@ skipping 172 matching lines @@
     if (this.functions.length > 0) {
         if (debug) print("emitting functions @ " + bytes.length);
         emit_u8(bytes, kDeclFunctions);
         emit_varint(bytes, this.functions.length);
         var index = 0;
         for (func of this.functions) {
             var flags = 0;
             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++;
         }
     }
 
     // Add start function section.
     if (this.start_index != undefined) {
         if (debug) print("emitting start function @ " + bytes.length);
       emit_u8(bytes, kDeclStartFunction);
       emit_varint(bytes, this.start_index);
@@ skipping 114 matching lines @@
 }
 
 WasmModuleBuilder.prototype.instantiate = function(ffi, memory) {
     var buffer = this.toBuffer();
     if (memory != undefined) {
       return _WASMEXP_.instantiateModule(buffer, ffi, memory);
     } else {
       return _WASMEXP_.instantiateModule(buffer, ffi);
     }
 }