Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -4731,10 +4731,12 @@
 DILocalVariable
 """""""""""""""
 
-``DILocalVariable`` nodes represent local variables in the source language. If
-the ``arg:`` field is set to non-zero, then this variable is a subprogram
-parameter, and it will be included in the ``variables:`` field of its
-:ref:`DISubprogram`.
+``DILocalVariable`` nodes represent local variables in the source
+language. If the ``arg:`` field is set to non-zero, then this variable
+is a subprogram parameter, and it will be included in the
+``variables:`` field of its :ref:`DISubprogram`. If the flag
+``DIFlagConstant`` is set the variable is a named constant in the
+source language.
 
 .. code-block:: text
 
Index: llvm/include/llvm/BinaryFormat/Dwarf.def
===================================================================
--- llvm/include/llvm/BinaryFormat/Dwarf.def
+++ llvm/include/llvm/BinaryFormat/Dwarf.def
@@ -403,6 +403,7 @@
 HANDLE_DW_AT(0x3e01, LLVM_config_macros, 0, LLVM)
 HANDLE_DW_AT(0x3e02, LLVM_isysroot, 0, LLVM)
 HANDLE_DW_AT(0x3e03, LLVM_tag_offset, 0, LLVM)
+HANDLE_DW_AT(0x3e04, LLVM_constant, 0, LLVM)
 // Apple extensions.
 HANDLE_DW_AT(0x3fe1, APPLE_optimized, 0, APPLE)
 HANDLE_DW_AT(0x3fe2, APPLE_flags, 0, APPLE)
Index: llvm/include/llvm/IR/DebugInfoFlags.def
===================================================================
--- llvm/include/llvm/IR/DebugInfoFlags.def
+++ llvm/include/llvm/IR/DebugInfoFlags.def
@@ -31,8 +31,7 @@
 HANDLE_DI_FLAG(3, Public)
 HANDLE_DI_FLAG((1 << 2), FwdDecl)
 HANDLE_DI_FLAG((1 << 3), AppleBlock)
-// Used to be BlockByRef, can be reused for anything except DICompositeType.
-HANDLE_DI_FLAG((1 << 4), ReservedBit4)
+HANDLE_DI_FLAG((1 << 4), Constant)
 HANDLE_DI_FLAG((1 << 5), Virtual)
 HANDLE_DI_FLAG((1 << 6), Artificial)
 HANDLE_DI_FLAG((1 << 7), Explicit)
Index: llvm/include/llvm/IR/DebugInfoMetadata.h
===================================================================
--- llvm/include/llvm/IR/DebugInfoMetadata.h
+++ llvm/include/llvm/IR/DebugInfoMetadata.h
@@ -2806,6 +2806,7 @@
   unsigned getArg() const { return Arg; }
   DIFlags getFlags() const { return Flags; }
 
+  bool isConstant() const { return getFlags() & FlagConstant; }
   bool isArtificial() const { return getFlags() & FlagArtificial; }
   bool isObjectPointer() const { return getFlags() & FlagObjectPointer; }
 
Index: llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
@@ -1244,6 +1244,8 @@
   addType(VariableDie, Var.getType());
   if (Var.isArtificial())
     addFlag(VariableDie, dwarf::DW_AT_artificial);
+  if (Var.isConstant())
+    addFlag(VariableDie, dwarf::DW_AT_LLVM_constant);
 }
 
 void DwarfCompileUnit::applyLabelAttributes(const DbgLabel &Label,
Index: llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -181,12 +181,10 @@
   bool hasFrameIndexExprs() const { return !FrameIndexExprs.empty(); }
   void addMMIEntry(const DbgVariable &V);
 
-  // Translate tag to proper Dwarf tag.
+  /// Determine the appropriate tag for this variable.
   dwarf::Tag getTag() const {
-    // FIXME: Why don't we just infer this tag and store it all along?
     if (getVariable()->isParameter())
       return dwarf::DW_TAG_formal_parameter;
-
     return dwarf::DW_TAG_variable;
   }
 
@@ -199,6 +197,11 @@
     return false;
   }
 
+  /// Return true if the source variable is an immutable constant value.
+  bool isConstant() const {
+    return getVariable()->isConstant();
+  }
+
   bool isObjectPointer() const {
     if (getVariable()->isObjectPointer())
       return true;
Index: llvm/test/DebugInfo/Generic/constants.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/Generic/constants.ll
@@ -0,0 +1,34 @@
+; RUN: %llc_dwarf -O0 -filetype=obj -o - %s | llvm-dwarfdump - | FileCheck %s
+; REQUIRES: object-emission
+; CHECK: DW_TAG_variable
+; CHECK-NEXT: DW_AT_location
+; CHECK-NEXT: DW_AT_name {{.*}}"local_constant"
+; CHECK-NOT: DW_TAG
+; CHECK: DW_AT_LLVM_constant (true)
+
+; Function Attrs: noinline nounwind optnone ssp uwtable
+define void @foo() !dbg !14 {
+  %1 = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %1, metadata !17, metadata !DIExpression()), !dbg !18
+  store i32 23, i32* %1, align 4, !dbg !18
+  ret void, !dbg !18
+}
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+attributes #1 = { nounwind readnone speculatable }
+
+!llvm.module.flags = !{!9, !10}
+!llvm.dbg.cu = !{!2}
+
+!2 = distinct !DICompileUnit(language: DW_LANG_Swift, file: !3, producer: "handwritten", isOptimized: false, emissionKind: FullDebug)
+!3 = !DIFile(filename: "t.swift", directory: "/")
+!4 = !{}
+!7 = !DIBasicType(name: "Int32", size: 32, encoding: DW_ATE_signed)
+!9 = !{i32 2, !"Dwarf Version", i32 4}
+!10 = !{i32 2, !"Debug Info Version", i32 3}
+!14 = distinct !DISubprogram(name: "foo", scope: !3, file: !3, line: 2, type: !15, scopeLine: 2, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !4)
+!15 = !DISubroutineType(types: !16)
+!16 = !{null}
+!17 = !DILocalVariable(name: "local_constant", flags: DIFlagConstant, scope: !14, file: !3, line: 3, type: !7)
+!18 = !DILocation(line: 3, scope: !14)