diff --git a/include/llvm/IntrinsicsX86.td b/include/llvm/IntrinsicsX86.td
index 6187618..912307b 100644
--- a/include/llvm/IntrinsicsX86.td
+++ b/include/llvm/IntrinsicsX86.td
@@ -1651,3 +1651,25 @@
   def int_x86_bmi_pext_64 : GCCBuiltin<"__builtin_ia32_pext_di">,
               Intrinsic<[llvm_i64_ty], [llvm_i64_ty, llvm_i64_ty], [IntrNoMem]>;
 }
+
+//===----------------------------------------------------------------------===//
+// FS/GS Base
+
+let TargetPrefix = "x86" in {  // All intrinsics start with "llvm.x86.".
+  def int_x86_rdfsbase_32 : GCCBuiltin<"__builtin_ia32_rdfsbase32">,
+              Intrinsic<[llvm_i32_ty], []>;
+  def int_x86_rdgsbase_32 : GCCBuiltin<"__builtin_ia32_rdgsbase32">,
+              Intrinsic<[llvm_i32_ty], []>;
+  def int_x86_rdfsbase_64 : GCCBuiltin<"__builtin_ia32_rdfsbase64">,
+              Intrinsic<[llvm_i64_ty], []>;
+  def int_x86_rdgsbase_64 : GCCBuiltin<"__builtin_ia32_rdgsbase64">,
+              Intrinsic<[llvm_i64_ty], []>;
+  def int_x86_wrfsbase_32 : GCCBuiltin<"__builtin_ia32_wrfsbase32">,
+              Intrinsic<[], [llvm_i32_ty]>;
+  def int_x86_wrgsbase_32 : GCCBuiltin<"__builtin_ia32_wrgsbase32">,
+              Intrinsic<[], [llvm_i32_ty]>;
+  def int_x86_wrfsbase_64 : GCCBuiltin<"__builtin_ia32_wrfsbase64">,
+              Intrinsic<[], [llvm_i64_ty]>;
+  def int_x86_wrgsbase_64 : GCCBuiltin<"__builtin_ia32_wrgsbase64">,
+              Intrinsic<[], [llvm_i64_ty]>;
+}
diff --git a/lib/Target/X86/X86.td b/lib/Target/X86/X86.td
index 9861960..62a7016 100644
--- a/lib/Target/X86/X86.td
+++ b/lib/Target/X86/X86.td
@@ -82,6 +82,9 @@
 
 def FeatureAVX     : SubtargetFeature<"avx", "HasAVX", "true",
                                       "Enable AVX instructions">;
+def FeatureAVX2    : SubtargetFeature<"avx2", "HasAVX2", "true",
+                                      "Enable AVX2 instructions",
+                                      [FeatureAVX]>;
 def FeatureCLMUL   : SubtargetFeature<"clmul", "HasCLMUL", "true",
                                "Enable carry-less multiplication instructions">;
 def FeatureFMA3    : SubtargetFeature<"fma3", "HasFMA3", "true",
@@ -99,6 +102,8 @@
                                       "Support RDRAND instruction">;
 def FeatureF16C    : SubtargetFeature<"f16c", "HasF16C", "true",
                        "Support 16-bit floating point conversion instructions">;
+def FeatureFSGSBase : SubtargetFeature<"fsgsbase", "HasFSGSBase", "true",
+                                       "Support FS/GS Base instructions">;
 def FeatureLZCNT   : SubtargetFeature<"lzcnt", "HasLZCNT", "true",
                                       "Support LZCNT instruction">;
 def FeatureBMI     : SubtargetFeature<"bmi", "HasBMI", "true",
@@ -157,13 +162,14 @@
 // Ivy Bridge
 def : Proc<"core-avx-i",      [FeatureSSE42, FeatureCMPXCHG16B,
                                FeatureAES, FeatureCLMUL,
-                               FeatureRDRAND, FeatureF16C]>;
+                               FeatureRDRAND, FeatureF16C, FeatureFSGSBase]>;
 
 // Haswell
+// FIXME: Disabling AVX/AVX2 for now since it's not ready.
 def : Proc<"core-avx2",       [FeatureSSE42, FeatureCMPXCHG16B, FeatureAES,
                                FeatureCLMUL, FeatureRDRAND, FeatureF16C,
-                               FeatureFMA3, FeatureMOVBE, FeatureLZCNT,
-                               FeatureBMI, FeatureBMI2]>;
+                               FeatureFSGSBase, FeatureFMA3, FeatureMOVBE,
+                               FeatureLZCNT, FeatureBMI, FeatureBMI2]>;
 
 def : Proc<"k6",              [FeatureMMX]>;
 def : Proc<"k6-2",            [Feature3DNow]>;
@@ -194,9 +200,8 @@
                                Feature3DNowA, FeatureCMPXCHG16B,
                                FeatureSlowBTMem]>;
 def : Proc<"istanbul",        [Feature3DNowA, FeatureCMPXCHG16B,
-                               FeatureSSE4A, Feature3DNowA]>;
-def : Proc<"shanghai",        [Feature3DNowA, FeatureCMPXCHG16B, FeatureSSE4A,
-                               Feature3DNowA]>;
+                               FeatureSSE4A]>;
+def : Proc<"shanghai",        [Feature3DNowA, FeatureCMPXCHG16B, FeatureSSE4A]>;
 
 def : Proc<"winchip-c6",      [FeatureMMX]>;
 def : Proc<"winchip2",        [Feature3DNow]>;
diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index 2a85ba1..79ce509 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -472,6 +472,7 @@
 def HasSSE4A     : Predicate<"Subtarget->hasSSE4A()">;
 
 def HasAVX       : Predicate<"Subtarget->hasAVX()">;
+def HasAVX2      : Predicate<"Subtarget->hasAVX2()">;
 def HasXMMInt    : Predicate<"Subtarget->hasXMMInt()">;
 
 def HasPOPCNT    : Predicate<"Subtarget->hasPOPCNT()">;
@@ -482,6 +483,7 @@
 def HasMOVBE     : Predicate<"Subtarget->hasMOVBE()">;
 def HasRDRAND    : Predicate<"Subtarget->hasRDRAND()">;
 def HasF16C      : Predicate<"Subtarget->hasF16C()">;
+def HasFSGSBase  : Predicate<"Subtarget->hasFSGSBase()">;
 def HasLZCNT     : Predicate<"Subtarget->hasLZCNT()">;
 def HasBMI       : Predicate<"Subtarget->hasBMI()">;
 def HasBMI2      : Predicate<"Subtarget->hasBMI2()">;
diff --git a/lib/Target/X86/X86InstrSystem.td b/lib/Target/X86/X86InstrSystem.td
index be3500a..1b43838 100644
--- a/lib/Target/X86/X86InstrSystem.td
+++ b/lib/Target/X86/X86InstrSystem.td
@@ -446,23 +446,31 @@
 
 //===----------------------------------------------------------------------===//
 // FS/GS Base Instructions
-let Predicates = [In64BitMode] in {
+let Predicates = [HasFSGSBase, In64BitMode] in {
   def RDFSBASE : I<0xAE, MRM0r, (outs GR32:$dst), (ins),
-                   "rdfsbase{l}\t$dst", []>, TB, XS;
+                   "rdfsbase{l}\t$dst",
+                   [(set GR32:$dst, (int_x86_rdfsbase_32))]>, TB, XS;
   def RDFSBASE64 : RI<0xAE, MRM0r, (outs GR64:$dst), (ins),
-                     "rdfsbase{q}\t$dst", []>, TB, XS;
+                     "rdfsbase{q}\t$dst",
+                     [(set GR64:$dst, (int_x86_rdfsbase_64))]>, TB, XS;
   def RDGSBASE : I<0xAE, MRM1r, (outs GR32:$dst), (ins),
-                   "rdgsbase{l}\t$dst", []>, TB, XS;
+                   "rdgsbase{l}\t$dst",
+                   [(set GR32:$dst, (int_x86_rdgsbase_32))]>, TB, XS;
   def RDGSBASE64 : RI<0xAE, MRM1r, (outs GR64:$dst), (ins),
-                     "rdgsbase{q}\t$dst", []>, TB, XS;
-  def WRFSBASE : I<0xAE, MRM2r, (outs), (ins GR32:$dst),
-                   "wrfsbase{l}\t$dst", []>, TB, XS;
-  def WRFSBASE64 : RI<0xAE, MRM2r, (outs), (ins GR64:$dst),
-                   "wrfsbase{q}\t$dst", []>, TB, XS;
-  def WRGSBASE : I<0xAE, MRM3r, (outs), (ins GR32:$dst),
-                   "wrgsbase{l}\t$dst", []>, TB, XS;
-  def WRGSBASE64 : RI<0xAE, MRM3r, (outs), (ins GR64:$dst),
-                    "wrgsbase{q}\t$dst", []>, TB, XS;
+                     "rdgsbase{q}\t$dst",
+                     [(set GR64:$dst, (int_x86_rdgsbase_64))]>, TB, XS;
+  def WRFSBASE : I<0xAE, MRM2r, (outs), (ins GR32:$src),
+                   "wrfsbase{l}\t$src",
+                   [(int_x86_wrfsbase_32 GR32:$src)]>, TB, XS;
+  def WRFSBASE64 : RI<0xAE, MRM2r, (outs), (ins GR64:$src),
+                      "wrfsbase{q}\t$src",
+                      [(int_x86_wrfsbase_64 GR64:$src)]>, TB, XS;
+  def WRGSBASE : I<0xAE, MRM3r, (outs), (ins GR32:$src),
+                   "wrgsbase{l}\t$src",
+                   [(int_x86_wrgsbase_32 GR32:$src)]>, TB, XS;
+  def WRGSBASE64 : RI<0xAE, MRM3r, (outs), (ins GR64:$src),
+                      "wrgsbase{q}\t$src",
+                      [(int_x86_wrgsbase_64 GR64:$src)]>, TB, XS;
 }
 
 //===----------------------------------------------------------------------===//
diff --git a/lib/Target/X86/X86Subtarget.cpp b/lib/Target/X86/X86Subtarget.cpp
index fd8ef19..e7bcbf8 100644
--- a/lib/Target/X86/X86Subtarget.cpp
+++ b/lib/Target/X86/X86Subtarget.cpp
@@ -279,10 +279,19 @@
 
   if (IsIntel && MaxLevel >= 7) {
     if (!X86_MC::GetCpuIDAndInfoEx(0x7, 0x0, &EAX, &EBX, &ECX, &EDX)) {
+      if (EBX & 0x1) {
+        HasFSGSBase = true;
+        ToggleFeature(X86::FeatureFSGSBase);
+      }
       if ((EBX >> 3) & 0x1) {
         HasBMI = true;
         ToggleFeature(X86::FeatureBMI);
       }
+      // FIXME: AVX2 codegen support is not ready.
+      //if ((EBX >> 5) & 0x1) {
+      //  HasAVX2 = true;
+      //  ToggleFeature(X86::FeatureAVX2);
+      //}
       if ((EBX >> 8) & 0x1) {
         HasBMI2 = true;
         ToggleFeature(X86::FeatureBMI2);
@@ -303,6 +312,7 @@
   , HasPOPCNT(false)
   , HasSSE4A(false)
   , HasAVX(false)
+  , HasAVX2(false)
   , HasAES(false)
   , HasCLMUL(false)
   , HasFMA3(false)
@@ -310,6 +320,7 @@
   , HasMOVBE(false)
   , HasRDRAND(false)
   , HasF16C(false)
+  , HasFSGSBase(false)
   , HasLZCNT(false)
   , HasBMI(false)
   , HasBMI2(false)
diff --git a/lib/Target/X86/X86Subtarget.h b/lib/Target/X86/X86Subtarget.h
index 5e08f01..763fb43 100644
--- a/lib/Target/X86/X86Subtarget.h
+++ b/lib/Target/X86/X86Subtarget.h
@@ -78,6 +78,9 @@
   /// HasAVX - Target has AVX instructions
   bool HasAVX;
 
+  /// HasAVX2 - Target has AVX2 instructions
+  bool HasAVX2;
+
   /// HasAES - Target has AES instructions
   bool HasAES;
 
@@ -99,6 +102,9 @@
   /// HasF16C - Processor has 16-bit floating point conversion instructions.
   bool HasF16C;
 
+  /// HasFSGSBase - Processor has FS/GS base insturctions.
+  bool HasFSGSBase;
+
   /// HasLZCNT - Processor has LZCNT instruction.
   bool HasLZCNT;
 
@@ -181,6 +187,7 @@
   bool has3DNowA() const { return X863DNowLevel >= ThreeDNowA; }
   bool hasPOPCNT() const { return HasPOPCNT; }
   bool hasAVX() const { return HasAVX; }
+  bool hasAVX2() const { return HasAVX2; }
   bool hasXMM() const { return hasSSE1() || hasAVX(); }
   bool hasXMMInt() const { return hasSSE2() || hasAVX(); }
   bool hasAES() const { return HasAES; }
@@ -190,6 +197,7 @@
   bool hasMOVBE() const { return HasMOVBE; }
   bool hasRDRAND() const { return HasRDRAND; }
   bool hasF16C() const { return HasF16C; }
+  bool hasFSGSBase() const { return HasFSGSBase; }
   bool hasLZCNT() const { return HasLZCNT; }
   bool hasBMI() const { return HasBMI; }
   bool hasBMI2() const { return HasBMI2; }