[turbofan] Add comments to CodeAssembler

src/compiler/machine-operator.cc

Index: src/compiler/machine-operator.cc
diff --git a/src/compiler/machine-operator.cc b/src/compiler/machine-operator.cc
index 2fa550b623b1fe44cc134e9838f4b0499b07a38f..0cfa671e6b10c50d872f1cb032cb5b4a39a3af3f 100644
--- a/src/compiler/machine-operator.cc
+++ b/src/compiler/machine-operator.cc
@@ -537,6 +537,11 @@ struct MachineOperatorGlobalCache {
   DebugBreakOperator kDebugBreak;
 };
 
+struct CommentOperator : public Operator1<const char*> {
+  explicit CommentOperator(const char* msg)
+      : Operator1<const char*>(IrOpcode::kComment, Operator::kNoThrow,
+                               "Comment", 0, 0, 0, 0, 0, 0, msg) {}
+};
 
 static base::LazyInstance<MachineOperatorGlobalCache>::type kCache =
     LAZY_INSTANCE_INITIALIZER;
@@ -544,7 +549,8 @@ static base::LazyInstance<MachineOperatorGlobalCache>::type kCache =
 MachineOperatorBuilder::MachineOperatorBuilder(
     Zone* zone, MachineRepresentation word, Flags flags,
     AlignmentRequirements alignmentRequirements)
-    : cache_(kCache.Get()),
+    : zone_(zone),
+      cache_(kCache.Get()),
       word_(word),
       flags_(flags),
       alignment_requirements_(alignmentRequirements) {
@@ -619,6 +625,10 @@ const Operator* MachineOperatorBuilder::DebugBreak() {
   return &cache_.kDebugBreak;
 }
 
+const Operator* MachineOperatorBuilder::Comment(const char* msg) {
+  return new (zone_) CommentOperator(msg);
+}
+
 const Operator* MachineOperatorBuilder::CheckedLoad(
     CheckedLoadRepresentation rep) {
 #define LOAD(Type)                     \