Index: llvm/test/TableGen/Common/reg-with-subregs-common.td
===================================================================
--- llvm/test/TableGen/Common/reg-with-subregs-common.td
+++ llvm/test/TableGen/Common/reg-with-subregs-common.td
@@ -16,6 +16,9 @@
            !listconcat(acc, !if(!lt(cur, N), [cur], [])));
 }
 
+#ifdef USE_NAMESPACE
+  let Namespace = "TestNamespace" in {
+#endif
 foreach Index = 0-31 in {
   def sub#Index : SubRegIndex<32, !shl(Index, 5)>;
 }
@@ -35,6 +38,9 @@
 foreach Index = 0-255 in {
   def R#Index : Register <"r"#Index>;
 }
+#ifdef USE_NAMESPACE
+}
+#endif
 
 def GPR32 : RegisterClass<"TestTarget", [i32], 32,
                           (add (sequence "R%u", 0, 255))>;
@@ -124,5 +130,11 @@
                               (decimate (shl GPR32, 31), 1)
                              ]>;
 
+#ifdef USE_NAMESPACE
+  let Namespace = "TestNamespace" in {
+#endif
 def GPR_64 : RegisterClass<"", [v2i32], 64, (add GPR64)>;
 def GPR_1024 : RegisterClass<"", [v32i32], 1024, (add GPR1024)>;
+#ifdef USE_NAMESPACE
+}
+#endif
Index: llvm/test/TableGen/pset-enum.td
===================================================================
--- /dev/null
+++ llvm/test/TableGen/pset-enum.td
@@ -0,0 +1,11 @@
+// RUN: llvm-tblgen -gen-register-info -I %p/../../include -I %p/Common %s | FileCheck %s
+// RUN: llvm-tblgen -gen-register-info -I %p/../../include -I %p/Common -DUSE_NAMESPACE %s | FileCheck --check-prefixes=CHECK,NAMESPACE %s
+
+include "reg-with-subregs-common.td"
+
+// CHECK-LABEL:    // Register pressure sets enum.
+// NAMESPACE-NEXT: namespace TestNamespace {
+// CHECK-NEXT:     enum RegisterPressureSets {
+// CHECK-NEXT:       GPR32 = 0,
+// CHECK-NEXT:     };
+// NAMESPACE-NEXT: } // end namespace TestNamespace
Index: llvm/utils/TableGen/RegisterInfoEmitter.cpp
===================================================================
--- llvm/utils/TableGen/RegisterInfoEmitter.cpp
+++ llvm/utils/TableGen/RegisterInfoEmitter.cpp
@@ -190,11 +190,23 @@
   OS << Val;
 }
 
+static std::string getLegalCName(std::string Name) {
+  static const char legal_elements[] =
+    "_abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
+  std::string::size_type pos = 0;
+  while ((pos = Name.find_first_not_of(legal_elements, pos)) !=
+         std::string::npos)
+    Name.replace(pos, 1, "_");
+  return Name;
+}
+
 void RegisterInfoEmitter::
 EmitRegUnitPressure(raw_ostream &OS, const CodeGenRegBank &RegBank,
                     const std::string &ClassName) {
   unsigned NumRCs = RegBank.getRegClasses().size();
   unsigned NumSets = RegBank.getNumRegPressureSets();
+  StringRef Namespace = RegBank.getRegisters().front().TheDef->
+    getValueAsString("Namespace");
 
   OS << "/// Get the weight in units of pressure for this register class.\n"
      << "const RegClassWeight &" << ClassName << "::\n"
@@ -251,14 +263,27 @@
      << "unsigned " << ClassName << "::getNumRegPressureSets() const {\n"
      << "  return " << NumSets << ";\n}\n\n";
 
+  OS << "// Register pressure sets enum.\n";
+  if (!Namespace.empty())
+    OS << "namespace " << Namespace << " {\n";
+  OS << "enum RegisterPressureSets {\n";
+  unsigned MaxRegUnitWeight = 0;
+  for (unsigned i = 0; i < NumSets; ++i ) {
+    const RegUnitSet &RegUnits = RegBank.getRegSetAt(i);
+    MaxRegUnitWeight = std::max(MaxRegUnitWeight, RegUnits.Weight);
+    OS << "  " << getLegalCName(RegUnits.Name) << " = " << i << ",\n";
+  }
+  OS << "};\n";
+  if (!Namespace.empty())
+    OS << "} // end namespace " << Namespace << '\n';
+  OS << '\n';
+
   OS << "// Get the name of this register unit pressure set.\n"
      << "const char *" << ClassName << "::\n"
      << "getRegPressureSetName(unsigned Idx) const {\n"
      << "  static const char *const PressureNameTable[] = {\n";
-  unsigned MaxRegUnitWeight = 0;
   for (unsigned i = 0; i < NumSets; ++i ) {
     const RegUnitSet &RegUnits = RegBank.getRegSetAt(i);
-    MaxRegUnitWeight = std::max(MaxRegUnitWeight, RegUnits.Weight);
     OS << "    \"" << RegUnits.Name << "\",\n";
   }
   OS << "  };\n"