Index: clang/include/clang/Basic/CodeGenOptions.def
===================================================================
--- clang/include/clang/Basic/CodeGenOptions.def
+++ clang/include/clang/Basic/CodeGenOptions.def
@@ -316,6 +316,9 @@
 VALUE_CODEGENOPT(WarnStackSize     , 32, UINT_MAX) ///< Set via -fwarn-stack-size.
 CODEGENOPT(NoStackArgProbe, 1, 0) ///< Set when -mno-stack-arg-probe is used
 CODEGENOPT(DebugStrictDwarf, 1, 1) ///< Whether or not to use strict DWARF info.
+
+CODEGENOPT(EnableAssignmentTracking, 1,0)
+
 CODEGENOPT(DebugColumnInfo, 1, 0) ///< Whether or not to use column information
                                   ///< in debug info.
 
Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -5283,6 +5283,11 @@
 def fdenormal_fp_math_f32_EQ : Joined<["-"], "fdenormal-fp-math-f32=">,
    Group<f_Group>;
 
+def fexperimental_assignment_tracking :
+  Flag<["-"], "fexperimental-assignment-tracking">, Group<f_Group>,
+  HelpText<"Enable assignment tracking debug info">,
+  MarshallingInfoFlag<CodeGenOpts<"EnableAssignmentTracking">>;
+
 //===----------------------------------------------------------------------===//
 // Dependency Output Options
 //===----------------------------------------------------------------------===//
Index: clang/lib/Driver/ToolChains/Clang.cpp
===================================================================
--- clang/lib/Driver/ToolChains/Clang.cpp
+++ clang/lib/Driver/ToolChains/Clang.cpp
@@ -6761,18 +6761,21 @@
 
   // Forward -Xclang arguments to -cc1, and -mllvm arguments to the LLVM option
   // parser.
-  // -finclude-default-header flag is for preprocessor,
-  // do not pass it to other cc1 commands when save-temps is enabled
-  if (C.getDriver().isSaveTempsEnabled() &&
-      !isa<PreprocessJobAction>(JA)) {
-    for (auto Arg : Args.filtered(options::OPT_Xclang)) {
-      Arg->claim();
-      if (StringRef(Arg->getValue()) != "-finclude-default-header")
-        CmdArgs.push_back(Arg->getValue());
+  for (auto Arg : Args.filtered(options::OPT_Xclang)) {
+    Arg->claim();
+    // -finclude-default-header flag is for preprocessor,
+    // do not pass it to other cc1 commands when save-temps is enabled
+    if (C.getDriver().isSaveTempsEnabled() &&
+        !isa<PreprocessJobAction>(JA)) {
+      if (StringRef(Arg->getValue()) == "-finclude-default-header")
+        continue;
     }
-  }
-  else {
-    Args.AddAllArgValues(CmdArgs, options::OPT_Xclang);
+    if (StringRef(Arg->getValue()) == "-fexperimental-assignment-tracking") {
+      // Add the llvm version of this flag too.
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back("-experimental-assignment-tracking");
+    }
+    CmdArgs.push_back(Arg->getValue());
   }
   for (const Arg *A : Args.filtered(options::OPT_mllvm)) {
     A->claim();
Index: llvm/include/llvm/IR/DebugInfo.h
===================================================================
--- llvm/include/llvm/IR/DebugInfo.h
+++ llvm/include/llvm/IR/DebugInfo.h
@@ -159,6 +159,8 @@
   SmallPtrSet<const MDNode *, 32> NodesSeen;
 };
 
+/// Return true if assignment tracking is enabled.
+bool getEnableAssignmentTracking();
 } // end namespace llvm
 
 #endif // LLVM_IR_DEBUGINFO_H
Index: llvm/lib/IR/DebugInfo.cpp
===================================================================
--- llvm/lib/IR/DebugInfo.cpp
+++ llvm/lib/IR/DebugInfo.cpp
@@ -39,6 +39,13 @@
 using namespace llvm;
 using namespace llvm::dwarf;
 
+static cl::opt<bool>
+    ExperimentalAssignmentTracking("experimental-assignment-tracking",
+                                   cl::init(false));
+bool llvm::getEnableAssignmentTracking() {
+  return ExperimentalAssignmentTracking;
+}
+
 /// Finds all intrinsics declaring local variables as living in the memory that
 /// 'V' points to. This may include a mix of dbg.declare and
 /// dbg.addr intrinsics.