[api] Add v8::ScriptCompiler::CachedData::CompatibilityCheck()

This patch adds a new API v8::ScriptCompiler::CachedData::CompatibilityCheck()
in order to allow embedders to check if the code cache can be used in
the current isolate without looking up for the source code. It also returns more detailed reasons about why the code cache cannot be used
when it's bound to be rejected. This makes it possible to enforce
portability checks in case code code becomes CPU-dependent in the
future.

Refs: nodejs/node#42566 (comment)

Change-Id: Ia1d677b949050add961af6fbf62c44342c061312
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4905290
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Joyee Cheung <joyee@igalia.com>
Cr-Commit-Position: refs/heads/main@{#90833}

include/v8-script.h

@@ -405,6 +405,27 @@ class V8_EXPORT ScriptCompiler {
     CachedData(const uint8_t* data, int length,
                BufferPolicy buffer_policy = BufferNotOwned);
     ~CachedData();
+
+    enum CompatibilityCheckResult {
+      // Don't change order/existing values of this enum since it keys into the
+      // `code_cache_reject_reason` histogram. Append-only!
+      kSuccess = 0,
+      kMagicNumberMismatch = 1,
+      kVersionMismatch = 2,
+      kSourceMismatch = 3,
+      kFlagsMismatch = 5,
+      kChecksumMismatch = 6,
+      kInvalidHeader = 7,
+      kLengthMismatch = 8,
+      kReadOnlySnapshotChecksumMismatch = 9,
+
+      // This should always point at the last real enum value.
+      kLast = kReadOnlySnapshotChecksumMismatch
+    };
+
+    // Check if the CachedData can be loaded in the given isolate.
+    CompatibilityCheckResult CompatibilityCheck(Isolate* isolate);
+
     // TODO(marja): Async compilation; add constructors which take a callback
     // which will be called when V8 no longer needs the data.
     const uint8_t* data;

src/api/api.cc

@@ -1963,6 +1963,18 @@ ScriptCompiler::CachedData::~CachedData() {
   }
 }
 
+ScriptCompiler::CachedData::CompatibilityCheckResult
+ScriptCompiler::CachedData::CompatibilityCheck(Isolate* isolate) {
+  i::AlignedCachedData aligned(data, length);
+  i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
+  i::SerializedCodeSanityCheckResult result;
+  i::SerializedCodeData scd =
+      i::SerializedCodeData::FromCachedDataWithoutSource(
+          i_isolate->AsLocalIsolate(), &aligned, &result);
+  return static_cast<ScriptCompiler::CachedData::CompatibilityCheckResult>(
+      result);
+}
+
 ScriptCompiler::StreamedSource::StreamedSource(
     std::unique_ptr<ExternalSourceStream> stream, Encoding encoding)
     : impl_(new i::ScriptStreamingData(std::move(stream), encoding)) {}

src/snapshot/code-serializer.h

@@ -49,22 +49,9 @@ class V8_EXPORT_PRIVATE AlignedCachedData {
   int length_;
 };
 
-enum class SerializedCodeSanityCheckResult {
-  // Don't change order/existing values of this enum since it keys into the
-  // `code_cache_reject_reason` histogram. Append-only!
-  kSuccess = 0,
-  kMagicNumberMismatch = 1,
-  kVersionMismatch = 2,
-  kSourceMismatch = 3,
-  kFlagsMismatch = 5,
-  kChecksumMismatch = 6,
-  kInvalidHeader = 7,
-  kLengthMismatch = 8,
-  kReadOnlySnapshotChecksumMismatch = 9,
-
-  // This should always point at the last real enum value.
-  kLast = kReadOnlySnapshotChecksumMismatch
-};
+typedef v8::ScriptCompiler::CachedData::CompatibilityCheckResult
+    SerializedCodeSanityCheckResult;
+
 // If this fails, update the static_assert AND the code_cache_reject_reason
 // histogram definition.
 static_assert(static_cast<int>(SerializedCodeSanityCheckResult::kLast) == 9);

test/cctest/test-serialize.cc

@@ -2799,6 +2799,78 @@ TEST(CodeSerializerFlagChange) {
   isolate2->Dispose();
 }
 
+TEST(CachedDataCompatibilityCheck) {
+  {
+    v8::Isolate::CreateParams create_params;
+    create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+    v8::Isolate* isolate = v8::Isolate::New(create_params);
+    // Hand-craft a zero-filled cached data which cannot be valid.
+    int length = 64;
+    uint8_t* payload = new uint8_t[length];
+    memset(payload, 0, length);
+    v8::ScriptCompiler::CachedData cache(
+        payload, length, v8::ScriptCompiler::CachedData::BufferOwned);
+    {
+      v8::Isolate::Scope iscope(isolate);
+      v8::ScriptCompiler::CachedData::CompatibilityCheckResult result =
+          cache.CompatibilityCheck(isolate);
+      CHECK_NE(result, v8::ScriptCompiler::CachedData::kSuccess);
+    }
+    isolate->Dispose();
+  }
+
+  const char* js_source = "function f() { return 'abc'; }; f() + 'def'";
+  std::unique_ptr<v8::ScriptCompiler::CachedData> cache;
+  {
+    v8::Isolate::CreateParams create_params;
+    create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+    v8::Isolate* isolate = v8::Isolate::New(create_params);
+    {
+      v8::Isolate::Scope iscope(isolate);
+      v8::HandleScope scope(isolate);
+      v8::Local<v8::Context> context = v8::Context::New(isolate);
+      v8::Context::Scope context_scope(context);
+      v8::ScriptCompiler::Source source(v8_str(js_source),
+                                        {isolate, v8_str("test")});
+      v8::Local<v8::UnboundScript> script =
+          v8::ScriptCompiler::CompileUnboundScript(
+              isolate, &source, v8::ScriptCompiler::kEagerCompile)
+              .ToLocalChecked();
+      cache.reset(ScriptCompiler::CreateCodeCache(script));
+    }
+    isolate->Dispose();
+  }
+
+  {
+    v8::Isolate::CreateParams create_params;
+    create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+    v8::Isolate* isolate = v8::Isolate::New(create_params);
+    {
+      v8::Isolate::Scope iscope(isolate);
+      v8::ScriptCompiler::CachedData::CompatibilityCheckResult result =
+          cache->CompatibilityCheck(isolate);
+      CHECK_EQ(result, v8::ScriptCompiler::CachedData::kSuccess);
+    }
+    isolate->Dispose();
+  }
+
+  {
+    v8_flags.allow_natives_syntax =
+        true;  // Flag change should trigger cache reject.
+    FlagList::EnforceFlagImplications();
+    v8::Isolate::CreateParams create_params;
+    create_params.array_buffer_allocator = CcTest::array_buffer_allocator();
+    v8::Isolate* isolate = v8::Isolate::New(create_params);
+    {
+      v8::Isolate::Scope iscope(isolate);
+      v8::ScriptCompiler::CachedData::CompatibilityCheckResult result =
+          cache->CompatibilityCheck(isolate);
+      CHECK_EQ(result, v8::ScriptCompiler::CachedData::kFlagsMismatch);
+    }
+    isolate->Dispose();
+  }
+}
+
 TEST(CodeSerializerBitFlip) {
   i::v8_flags.verify_snapshot_checksum = true;
   const char* js_source = "function f() { return 'abc'; }; f() + 'def'";