diff --git a/include/llvm/ADT/Triple.h b/include/llvm/ADT/Triple.h
index 0b80bb5a33a..60f622d2dea 100644
--- a/include/llvm/ADT/Triple.h
+++ b/include/llvm/ADT/Triple.h
@@ -95,6 +95,9 @@ public:
     Haiku,
     Minix
   };
+  enum EnvironmentType {
+    UnknownEnvironment
+  };
   
 private:
   std::string Data;
@@ -108,10 +111,14 @@ private:
   /// The parsed OS type.
   mutable OSType OS;
 
+  /// The parsed Environment type.
+  mutable EnvironmentType Environment;
+
   bool isInitialized() const { return Arch != InvalidArch; }
   static ArchType ParseArch(StringRef ArchName);
   static VendorType ParseVendor(StringRef VendorName);
   static OSType ParseOS(StringRef OSName);
+  static EnvironmentType ParseEnvironment(StringRef EnvironmentName);
   void Parse() const;
 
 public:
@@ -128,6 +135,17 @@ public:
     Data += OSStr;
   }
 
+  explicit Triple(StringRef ArchStr, StringRef VendorStr, StringRef OSStr,
+    StringRef EnvironmentStr)
+    : Data(ArchStr), Arch(InvalidArch) {
+    Data += '-';
+    Data += VendorStr;
+    Data += '-';
+    Data += OSStr;
+    Data += '-';
+    Data += EnvironmentStr;
+  }
+
   /// @}
   /// @name Normalization
   /// @{
@@ -166,6 +184,12 @@ public:
     return getEnvironmentName() != "";
   }
 
+  /// getEnvironment - Get the parsed environment type of this triple.
+  EnvironmentType getEnvironment() const { 
+    if (!isInitialized()) Parse(); 
+    return Environment;
+  }
+
   /// @}
   /// @name Direct Component Access
   /// @{
@@ -225,6 +249,10 @@ public:
   /// to a known type.
   void setOS(OSType Kind);
 
+  /// setEnvironment - Set the environment (fourth) component of the triple
+  /// to a known type.
+  void setEnvironment(EnvironmentType Kind);
+
   /// setTriple - Set all components to the new triple \arg Str.
   void setTriple(const Twine &Str);
 
@@ -272,9 +300,14 @@ public:
   /// vendor.
   static const char *getVendorTypeName(VendorType Kind);
 
-  /// getOSTypeName - Get the canonical name for the \arg Kind vendor.
+  /// getOSTypeName - Get the canonical name for the \arg Kind operating
+  /// system.
   static const char *getOSTypeName(OSType Kind);
 
+  /// getEnvironmentTypeName - Get the canonical name for the \arg Kind
+  /// environment.
+  static const char *getEnvironmentTypeName(EnvironmentType Kind);
+
   /// @}
   /// @name Static helpers for converting alternate architecture names.
   /// @{
diff --git a/lib/Support/Triple.cpp b/lib/Support/Triple.cpp
index 365c0836953..24f83e2f6fb 100644
--- a/lib/Support/Triple.cpp
+++ b/lib/Support/Triple.cpp
@@ -10,6 +10,7 @@
 #include "llvm/ADT/Triple.h"
 
 #include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Twine.h"
 #include <cassert>
 #include <cstring>
@@ -114,6 +115,14 @@ const char *Triple::getOSTypeName(OSType Kind) {
   return "<invalid>";
 }
 
+const char *Triple::getEnvironmentTypeName(EnvironmentType Kind) {
+  switch (Kind) {
+  case UnknownEnvironment: return "unknown";
+  }
+
+  return "<invalid>";
+}
+
 Triple::ArchType Triple::getArchTypeForLLVMName(StringRef Name) {
   if (Name == "alpha")
     return alpha;
@@ -329,12 +338,17 @@ Triple::OSType Triple::ParseOS(StringRef OSName) {
     return UnknownOS;
 }
 
+Triple::EnvironmentType Triple::ParseEnvironment(StringRef EnvironmentName) {
+  return UnknownEnvironment;
+}
+
 void Triple::Parse() const {
   assert(!isInitialized() && "Invalid parse call.");
 
   Arch = ParseArch(getArchName());
   Vendor = ParseVendor(getVendorName());
   OS = ParseOS(getOSName());
+  Environment = ParseEnvironment(getEnvironmentName());
 
   assert(isInitialized() && "Failed to initialize!");
 }
@@ -361,24 +375,28 @@ std::string Triple::normalize(StringRef Str) {
   OSType OS = UnknownOS;
   if (Components.size() > 2)
     OS = ParseOS(Components[2]);
+  EnvironmentType Environment = UnknownEnvironment;
+  if (Components.size() > 3)
+    Environment = ParseEnvironment(Components[3]);
 
   // Note which components are already in their final position.  These will not
   // be moved.
-  bool Found[3];
+  bool Found[4];
   Found[0] = Arch != UnknownArch;
   Found[1] = Vendor != UnknownVendor;
   Found[2] = OS != UnknownOS;
+  Found[3] = Environment != UnknownEnvironment;
 
   // If they are not there already, permute the components into their canonical
   // positions by seeing if they parse as a valid architecture, and if so moving
   // the component to the architecture position etc.
-  for (unsigned Pos = 0; Pos != 3; ++Pos) {
+  for (unsigned Pos = 0; Pos != array_lengthof(Found); ++Pos) {
     if (Found[Pos])
       continue; // Already in the canonical position.
 
     for (unsigned Idx = 0; Idx != Components.size(); ++Idx) {
       // Do not reparse any components that already matched.
-      if (Idx < 3 && Found[Idx])
+      if (Idx < array_lengthof(Found) && Found[Idx])
         continue;
 
       // Does this component parse as valid for the target position?
@@ -399,6 +417,10 @@ std::string Triple::normalize(StringRef Str) {
         OS = ParseOS(Comp);
         Valid = OS != UnknownOS;
         break;
+      case 3:
+        Environment = ParseEnvironment(Comp);
+        Valid = Environment != UnknownEnvironment;
+        break;
       }
       if (!Valid)
         continue; // Nope, try the next component.
@@ -417,7 +439,7 @@ std::string Triple::normalize(StringRef Str) {
         // components to the right.
         for (unsigned i = Pos; !CurrentComponent.empty(); ++i) {
           // Skip over any fixed components.
-          while (i < 3 && Found[i]) ++i;
+          while (i < array_lengthof(Found) && Found[i]) ++i;
           // Place the component at the new position, getting the component
           // that was at this position - it will be moved right.
           std::swap(CurrentComponent, Components[i]);
@@ -431,7 +453,7 @@ std::string Triple::normalize(StringRef Str) {
           StringRef CurrentComponent(""); // The empty component.
           for (unsigned i = Idx; i < Components.size(); ++i) {
             // Skip over any fixed components.
-            while (i < 3 && Found[i]) ++i;
+            while (i < array_lengthof(Found) && Found[i]) ++i;
             // Place the component at the new position, getting the component
             // that was at this position - it will be moved right.
             std::swap(CurrentComponent, Components[i]);
@@ -444,7 +466,7 @@ std::string Triple::normalize(StringRef Str) {
             Components.push_back(CurrentComponent);
 
           // Advance Idx to the component's new position.
-          while (++Idx < 3 && Found[Idx]) {}
+          while (++Idx < array_lengthof(Found) && Found[Idx]) {}
         } while (Idx < Pos); // Add more until the final position is reached.
       }
       assert(Pos < Components.size() && Components[Pos] == Comp &&
@@ -574,6 +596,10 @@ void Triple::setOS(OSType Kind) {
   setOSName(getOSTypeName(Kind));
 }
 
+void Triple::setEnvironment(EnvironmentType Kind) {
+  setEnvironmentName(getEnvironmentTypeName(Kind));
+}
+
 void Triple::setArchName(StringRef Str) {
   // Work around a miscompilation bug for Twines in gcc 4.0.3.
   SmallString<64> Triple;
diff --git a/unittests/ADT/TripleTest.cpp b/unittests/ADT/TripleTest.cpp
index 067f5e5116c..bcc71968fe2 100644
--- a/unittests/ADT/TripleTest.cpp
+++ b/unittests/ADT/TripleTest.cpp
@@ -79,16 +79,21 @@ TEST(TripleTest, ParsedIDs) {
   EXPECT_EQ(Triple::x86, T.getArch());
   EXPECT_EQ(Triple::Apple, T.getVendor());
   EXPECT_EQ(Triple::Darwin, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
 
   T = Triple("x86_64-pc-linux-gnu");
   EXPECT_EQ(Triple::x86_64, T.getArch());
   EXPECT_EQ(Triple::PC, T.getVendor());
   EXPECT_EQ(Triple::Linux, T.getOS());
+  // When environments are defined, change this test to verify the "gnu"
+  // environment.
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
 
   T = Triple("powerpc-dunno-notsure");
   EXPECT_EQ(Triple::ppc, T.getArch());
   EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
   EXPECT_EQ(Triple::UnknownOS, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
 
   T = Triple("huh");
   EXPECT_EQ(Triple::UnknownArch, T.getArch());
@@ -119,10 +124,12 @@ TEST(TripleTest, Normalization) {
   EXPECT_EQ("i386-b-c", Triple::normalize("i386-b-c"));
   EXPECT_EQ("i386-a-c", Triple::normalize("a-i386-c"));
   EXPECT_EQ("i386-a-b", Triple::normalize("a-b-i386"));
+  EXPECT_EQ("i386-a-b-c", Triple::normalize("a-b-c-i386"));
 
   EXPECT_EQ("a-pc-c", Triple::normalize("a-pc-c"));
   EXPECT_EQ("-pc-b-c", Triple::normalize("pc-b-c"));
   EXPECT_EQ("a-pc-b", Triple::normalize("a-b-pc"));
+  EXPECT_EQ("a-pc-b-c", Triple::normalize("a-b-c-pc"));
 
   EXPECT_EQ("a-b-linux", Triple::normalize("a-b-linux"));
   EXPECT_EQ("--linux-b-c", Triple::normalize("linux-b-c"));
@@ -210,6 +217,7 @@ TEST(TripleTest, MutateName) {
   EXPECT_EQ(Triple::UnknownArch, T.getArch());
   EXPECT_EQ(Triple::UnknownVendor, T.getVendor());
   EXPECT_EQ(Triple::UnknownOS, T.getOS());
+  EXPECT_EQ(Triple::UnknownEnvironment, T.getEnvironment());
 
   T.setArchName("i386");
   EXPECT_EQ(Triple::x86, T.getArch());