Extend error messages for blob or isolate verification failures

Bug: v8:7777
Change-Id: I781ac51ba740655c644e19388c6cadad7267b18c
Reviewed-on: https://chromium-review.googlesource.com/c/1478209
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59765}

src/isolate.cc

@@ -218,7 +218,12 @@ void Isolate::SetEmbeddedBlob(const uint8_t* blob, uint32_t blob_size) {
   // Verify that the contents of the embedded blob are unchanged from
   // serialization-time, just to ensure the compiler isn't messing with us.
   EmbeddedData d = EmbeddedData::FromBlob();
-  CHECK_EQ(d.EmbeddedBlobHash(), d.CreateEmbeddedBlobHash());
+  if (d.EmbeddedBlobHash() != d.CreateEmbeddedBlobHash()) {
+    FATAL(
+        "Embedded blob checksum verification failed. This indicates that the "
+        "embedded blob has been modified since compilation time. A common "
+        "cause is a debugging breakpoint set within builtin code.");
+  }
 #endif  // DEBUG
 }
 
@@ -3407,12 +3412,20 @@ bool Isolate::Init(StartupDeserializer* des) {
   // Initialize the builtin entry table.
   Builtins::UpdateBuiltinEntryTable(this);
 
+#ifdef DEBUG
   // Verify that the current heap state (usually deserialized from the snapshot)
   // is compatible with the embedded blob. If this DCHECK fails, we've likely
   // loaded a snapshot generated by a different V8 version or build-time
   // configuration.
-  DCHECK(IsolateIsCompatibleWithEmbeddedBlob(this));
+  if (!IsolateIsCompatibleWithEmbeddedBlob(this)) {
+    FATAL(
+        "The Isolate is incompatible with the embedded blob. This is usually "
+        "caused by incorrect usage of mksnapshot. When generating custom "
+        "snapshots, embedders must ensure they pass the same flags as during "
+        "the V8 build process (e.g.: --turbo-instruction-scheduling).");
+  }
   DCHECK_IMPLIES(FLAG_jitless, FLAG_embedded_builtins);
+#endif  // DEBUG
 
 #ifndef V8_TARGET_ARCH_ARM
   // The IET for profiling should always be a full on-heap Code object.