[wasm][fuzzer] Small fixes in the correctness fuzzer result comparison.

R=eholk@chromium.org

Change-Id: Ieb88f807275e1cc31cc7715270e316c427b212d4
Reviewed-on: https://chromium-review.googlesource.com/442425
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#43243}

test/fuzzer/wasm-call.cc

@@ -169,15 +169,19 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
         i_isolate, instance, &compiler_thrower, "main", argc, compiled_args,
         v8::internal::wasm::ModuleOrigin::kWasmOrigin);
   }
+
+  // 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) return 0;
+
   if (result_interpreted == bit_cast<int32_t>(0xdeadbeef)) {
     CHECK(i_isolate->has_pending_exception());
     i_isolate->clear_pending_exception();
   } else {
-    // 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)) {
+    CHECK(!i_isolate->has_pending_exception());
+    if (result_interpreted != result_compiled) {
       V8_Fatal(__FILE__, __LINE__, "WasmCodeFuzzerHash=%x",
                v8::internal::StringHasher::HashSequentialString(
                    data, static_cast<int>(size), WASM_CODE_FUZZER_HASH_SEED));

test/fuzzer/wasm-code.cc

@@ -137,16 +137,23 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
         i_isolate, instance, &compiler_thrower, "main", arraysize(arguments),
         arguments, v8::internal::wasm::ModuleOrigin::kWasmOrigin);
   }
-  if (result_interpreted == bit_cast<int32_t>(0xdeadbeef) &&
-      !possible_nondeterminism) {
+
+  // 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) return 0;
+
+  if (result_interpreted == bit_cast<int32_t>(0xdeadbeef)) {
     CHECK(i_isolate->has_pending_exception());
     i_isolate->clear_pending_exception();
   } else {
+    CHECK(!i_isolate->has_pending_exception());
     // 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)) {
+    if (result_interpreted != result_compiled) {
       V8_Fatal(__FILE__, __LINE__, "WasmCodeFuzzerHash=%x",
                v8::internal::StringHasher::HashSequentialString(
                    data, static_cast<int>(size), WASM_CODE_FUZZER_HASH_SEED));