[wasm][fuzzer] Generate correct tests with locals

The tests generated by --wasm-fuzzer-gen-test did not encode the locals
of functions yet. This CL fixes that.
A bit of care has to be taken to ensure that the locals are generated
in exactly the same order as in the module generated by the fuzzer.
This requires calling {addLocals} several times.

R=ahaas@chromium.org

Change-Id: I95237b0baef0731b6c164fddc8f12fa6f478e220
Reviewed-on: https://chromium-review.googlesource.com/848832
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50402}

test/fuzzer/wasm-fuzzer-common.cc

@@ -165,8 +165,26 @@ void GenerateTestCase(Isolate* isolate, ModuleWireBytes wire_bytes,
        << PrintParameters(func.sig) << ", " << PrintReturns(func.sig) << ");\n";
 
     // Add function.
-    os << "  builder.addFunction(undefined, sig" << func.func_index << ")\n"
-       << "    .addBodyWithEnd([\n";
+    os << "  builder.addFunction(undefined, sig" << func.func_index << ")\n";
+
+    // Add locals.
+    BodyLocalDecls decls(&tmp_zone);
+    DecodeLocalDecls(&decls, func_code.start(), func_code.end());
+    if (!decls.type_list.empty()) {
+      os << "    ";
+      for (size_t pos = 0, count = 1, locals = decls.type_list.size();
+           pos < locals; pos += count, count = 1) {
+        ValueType type = decls.type_list[pos];
+        while (pos + count < locals && decls.type_list[pos + count] == type)
+          ++count;
+        os << ".addLocals({" << WasmOpcodes::TypeName(type)
+           << "_count: " << count << "})";
+      }
+      os << "\n";
+    }
+
+    // Add body.
+    os << "    .addBodyWithEnd([\n";
 
     FunctionBody func_body(func.sig, func.code.offset(), func_code.start(),
                            func_code.end());

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

@@ -121,9 +121,25 @@ class WasmFunctionBuilder {
     return this;
   }
 
+  getNumLocals() {
+    let total_locals = 0;
+    for (let l of this.locals || []) {
+      for (let type of ["i32", "i64", "f32", "f64", "s128"]) {
+        total_locals += l[type + "_count"] || 0;
+      }
+    }
+    return total_locals;
+  }
+
   addLocals(locals, names) {
-    this.locals = locals;
-    this.local_names = names;
+    const old_num_locals = this.getNumLocals();
+    if (!this.locals) this.locals = []
+    this.locals.push(locals);
+    if (names) {
+      if (!this.local_names) this.local_names = [];
+      const missing_names = old_num_locals - this.local_names.length;
+      this.local_names.push(...new Array(missing_names), ...names);
+    }
     return this;
   }
 
@@ -537,9 +553,7 @@ class WasmModuleBuilder {
         for (let func of wasm.functions) {
           // Function body length will be patched later.
           let local_decls = [];
-          let l = func.locals;
-          if (l !== undefined) {
-            let local_decls_count = 0;
+          for (let l of func.locals || []) {
             if (l.i32_count > 0) {
               local_decls.push({count: l.i32_count, type: kWasmI32});
             }