[turbofan] Validation for deferred->hot transition edges

src/compiler/instruction.cc

Index: src/compiler/instruction.cc
diff --git a/src/compiler/instruction.cc b/src/compiler/instruction.cc
index 1d28a1bf36cb8024d61ba40eafb525afbd450801..c757557a0d750e97fa3ef9439679e09d280e1766 100644
--- a/src/compiler/instruction.cc
+++ b/src/compiler/instruction.cc
@@ -635,6 +635,17 @@ void InstructionSequence::ValidateEdgeSplitForm() {
   }
 }
 
+void InstructionSequence::ValidateDeferredBlockExitPaths() {
+  // A deferred block with more than one successor must have all its successors
+  // deferred.
+  for (const InstructionBlock* block : instruction_blocks()) {
+    if (!block->IsDeferred() || block->SuccessorCount() <= 1) continue;
+    for (RpoNumber successor_id : block->successors()) {
+      CHECK(InstructionBlockAt(successor_id)->IsDeferred());
+    }
+  }
+}
+
 void InstructionSequence::ValidateSSA() {
   // TODO(mtrofin): We could use a local zone here instead.
   BitVector definitions(VirtualRegisterCount(), zone());