Index: lld/COFF/Driver.cpp
===================================================================
--- lld/COFF/Driver.cpp
+++ lld/COFF/Driver.cpp
@@ -1739,6 +1739,20 @@
     config->incremental = false;
   }
 
+  // Print a warning message for those flags that aren't supported by LLD
+  // but can be ignored due to MS-LINK
+  for (auto *arg : args) {
+
+    auto argOption = arg->getOption();
+    if (!argOption.isValid())
+      continue;
+
+    auto argOptionGroup = argOption.getGroup();
+    if (argOptionGroup.isValid() &&
+        argOptionGroup.getID() == OPT_lldWarnMessageGroup)
+      warn("ignoring unknown argument \'" + argOption.getPrefixedName() + "\'");
+  }
+
   if (errorCount())
     return;
 
Index: lld/COFF/Options.td
===================================================================
--- lld/COFF/Options.td
+++ lld/COFF/Options.td
@@ -285,3 +285,33 @@
 def tlbout : QF<"tlbout">;
 def verbose_all : QF<"verbose">;
 def guardsym : QF<"guardsym">;
+
+//=============================================================================
+// Using the flags below will cause a warning to be printed saying that they
+// will be ignored. This is for compatibility with MS LINK.
+//
+//   If the flag doesn't need an extra arguments
+//     def NAME_OF_OPTION : lldWarnMessage<"NAME_OF_OPTION">
+//
+//   If the flag does need an extra argument
+//     def NAME_OF_OPTION :  lldWarnMessageArgs<"NAME_OF_OPTION">
+//
+// If the flag has both options (with and without extra arguments) then both
+// forms need to be added.
+//=============================================================================
+
+// Define the lldWarnMessageGroup group. This group is used to identify
+// all the flags that we want to print the warning message.
+def lldWarnMessageGroup : OptionGroup<"lldWarnMessageGroup">;
+
+// Class for options that won't require extra arguments
+class lldWarnMessage<string name> : F<name> {
+  OptionGroup Group = lldWarnMessageGroup;
+}
+
+// Class for options that require an extra argument
+class lldWarnMessageArgs<string name> : QF<name> {
+  OptionGroup Group = lldWarnMessageGroup;
+}
+
+def assemblydebug : lldWarnMessage<"assemblydebug">;
Index: lld/test/COFF/ignore-option-message.ll
===================================================================
--- /dev/null
+++ lld/test/COFF/ignore-option-message.ll
@@ -0,0 +1,23 @@
+; This test checks that the option /ASSEMBLYDEBUG causes a warning to be
+; printed and is then ignored.
+
+; RUN: llc %s -o %t.obj -filetype=obj
+
+; Check that the /ASSEMBLYDEBUG flag is ignored
+; RUN: not lld-link /subsystem:console /ASSEMBLYDEBUG %t.obj 2>&1 | FileCheck -check-prefix=CHECKAD -allow-empty %s
+; CHECKAD:     warning: ignoring unknown argument '/assemblydebug'
+; CHECKAD-NOT: could not open '/ASSEMBLYDEBUG'
+
+; Check that the /assemblydebug flag is ignored
+; RUN: not lld-link /subsystem:console /assemblydebug %t.obj 2>&1 | FileCheck -check-prefix=CHECKAD2 -allow-empty %s
+; CHECKAD2:     warning: ignoring unknown argument '/assemblydebug'
+; CHECKAD2-NOT: could not open '/assemblydebug'
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define internal i32 @add(i32 %a) {
+entry:
+  %add = add nsw i32 %a, 2
+  ret i32 %add
+}