Issue #1691 - Part 5: Don't pre-create module metadata object when compiling. https://bugzilla.mozilla.org/show_bug.cgi?id=1489477

(cherry picked from commit d83bad49f6b03894548fbf85fc18ad7e8cc19a93)

js/src/jit/MIR.h

@@ -8379,6 +8379,33 @@ class MSubstr
     }
 };
 
+class MModuleMetadata : public MNullaryInstruction
+{
+    CompilerObject module_;
+
+    explicit MModuleMetadata(JSObject* module)
+      : module_(module)
+    {
+        setResultType(MIRType::Object);
+    }
+
+  public:
+    INSTRUCTION_HEADER(ModuleMetadata)
+    TRIVIAL_NEW_WRAPPERS
+
+    JSObject* module() const {
+      return module_;
+    }
+
+    AliasSet getAliasSet() const override {
+        return AliasSet::None();
+    }
+
+    bool appendRoots(MRootList& roots) const override {
+        return roots.append(module_);
+    }
+};
+
 class MDynamicImport : public MBinaryInstruction,
                        public BoxInputsPolicy::Data
 {