diff --git a/lib/Target/X86/X86InstrFPStack.td b/lib/Target/X86/X86InstrFPStack.td
index a4ab0eaded2..b506f5e0b81 100644
--- a/lib/Target/X86/X86InstrFPStack.td
+++ b/lib/Target/X86/X86InstrFPStack.td
@@ -625,8 +625,12 @@ def FCOMPP : I<0xD9, RawFrm, (outs), (ins), "fcompp", []>, DE;
 
 def FXSAVE : I<0xAE, MRM0m, (outs opaque512mem:$dst), (ins),
                "fxsave\t$dst", []>, TB;
+def FXSAVE64 : I<0xAE, MRM0m, (outs opaque512mem:$dst), (ins),
+                 "fxsaveq\t$dst", []>, TB, REX_W, Requires<[In64BitMode]>;
 def FXRSTOR : I<0xAE, MRM1m, (outs), (ins opaque512mem:$src),
                 "fxrstor\t$src", []>, TB;
+def FXRSTOR64 : I<0xAE, MRM1m, (outs), (ins opaque512mem:$src),
+                  "fxrstorq\t$src", []>, TB, REX_W, Requires<[In64BitMode]>;
 
 //===----------------------------------------------------------------------===//
 // Non-Instruction Patterns
diff --git a/test/MC/X86/x86_64-encoding.s b/test/MC/X86/x86_64-encoding.s
index f45b0a23d5e..c071a1b765e 100644
--- a/test/MC/X86/x86_64-encoding.s
+++ b/test/MC/X86/x86_64-encoding.s
@@ -140,3 +140,11 @@ pshufb	CPI1_0(%rip), %xmm1
 // CHECK: encoding: [0x48,0x8b,0x04,0xe1]
           movq  (%rcx,%riz,8), %rax
 
+// CHECK: fxsaveq (%rax)
+// CHECK: encoding: [0x48,0x0f,0xae,0x00]
+          fxsaveq (%rax)
+
+// CHECK: fxrstorq (%rax)
+// CHECK: encoding: [0x48,0x0f,0xae,0x08]
+          fxrstorq (%rax)
+