[wasm] Track in the interpreter if a NaN could have been produced.

test/fuzzer/wasm-code.cc

 // 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.
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include "include/v8.h"
 #include "src/isolate.h"
 #include "src/objects.h"
@@ skipping 45 matching lines @@
 
   ErrorThrower interpreter_thrower(i_isolate, "Interpreter");
   std::unique_ptr<const WasmModule> module(testing::DecodeWasmModuleForTesting(
       i_isolate, &interpreter_thrower, buffer.begin(), buffer.end(),
       v8::internal::wasm::ModuleOrigin::kWasmOrigin));
 
   if (module == nullptr) {
     return 0;
   }
   int32_t result_interpreted;
+  bool possible_nondeterminism = false;
   {
     WasmVal args[] = {WasmVal(1), WasmVal(2), WasmVal(3)};
     result_interpreted = testing::InterpretWasmModule(
-        i_isolate, &interpreter_thrower, module.get(), 0, args);
+        i_isolate, &interpreter_thrower, module.get(), 0, args,
+        &possible_nondeterminism);
   }
 
   ErrorThrower compiler_thrower(i_isolate, "Compiler");
   v8::internal::Handle<v8::internal::JSObject> instance =
       testing::InstantiateModuleForTesting(i_isolate, &compiler_thrower,
                                            module.get());
 
   if (!interpreter_thrower.error()) {
     CHECK(!instance.is_null());
   } else {
     return 0;
   }
   int32_t result_compiled;
   {
     v8::internal::Handle<v8::internal::Object> arguments[] = {
         v8::internal::handle(v8::internal::Smi::FromInt(1), i_isolate),
         v8::internal::handle(v8::internal::Smi::FromInt(2), i_isolate),
         v8::internal::handle(v8::internal::Smi::FromInt(3), i_isolate)};
     result_compiled = testing::CallWasmFunctionForTesting(
         i_isolate, instance, &compiler_thrower, "main", arraysize(arguments),
         arguments, v8::internal::wasm::ModuleOrigin::kWasmOrigin);
   }
   if (result_interpreted == 0xdeadbeef) {
     CHECK(i_isolate->has_pending_exception());
     i_isolate->clear_pending_exception();
   } else {
-    if (result_interpreted != result_compiled) {
+    // The WebAssembly spec allows the sign bit of NaN to be non-deterministic.
+    // This sign bit may cause result_interpreted to be different than
+    // result_compiled. Therefore we do not check the equality of the results
+    // if the execution may have produced a NaN at some point.
+    if (!possible_nondeterminism && (result_interpreted != result_compiled)) {
       V8_Fatal(__FILE__, __LINE__, "WasmCodeFuzzerHash=%x",
                v8::internal::StringHasher::HashSequentialString(
                    data, static_cast<int>(size), WASM_CODE_FUZZER_HASH_SEED));
     }
   }
   return 0;
 }