[csa] add utilities for printf-style debugging

src/code-stub-assembler.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 "src/code-stub-assembler.h"
 #include "src/code-factory.h"
 #include "src/frames-inl.h"
 #include "src/frames.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 8380 matching lines @@
   StoreObjectFieldNoWriteBarrier(
       result, PromiseReactionJobInfo::kDeferredOnRejectOffset,
       deferred_on_reject);
   StoreObjectFieldNoWriteBarrier(result, PromiseReactionJobInfo::kDebugIdOffset,
                                  SmiConstant(kDebugPromiseNoID));
   StoreObjectFieldNoWriteBarrier(result, PromiseReactionJobInfo::kContextOffset,
                                  context);
   return result;
 }
 
+void CodeStubAssembler::Print(const char* s) {
+#ifdef DEBUG
+  std::string formatted(s);
+  formatted += "\n";
+  Handle<String> string = isolate()->factory()->NewStringFromAsciiChecked(
+      formatted.c_str(), TENURED);
+  CallRuntime(Runtime::kGlobalPrint, NoContextConstant(), HeapConstant(string));
+#endif
+}
+
+void CodeStubAssembler::Print(const char* prefix, Node* tagged_value) {
+#ifdef DEBUG
+  if (prefix != nullptr) {
+    std::string formatted(prefix);
+    formatted += ": ";
+    Handle<String> string = isolate()->factory()->NewStringFromAsciiChecked(
+        formatted.c_str(), TENURED);
+    CallRuntime(Runtime::kGlobalPrint, NoContextConstant(),
+                HeapConstant(string));
+  }
+  CallRuntime(Runtime::kGlobalPrint, NoContextConstant(), tagged_value);

[caitp, 2017/01/24 13:30:37]

Is there any way to assert that the value outputs from the `tagged_value` node
have a tagged representation during graph generation?

+#endif
+}
+
 }  // namespace internal
 }  // namespace v8