Index: lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
===================================================================
--- lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
+++ lib/Target/PowerPC/Disassembler/PPCDisassembler.cpp
@@ -204,6 +204,17 @@
   PPC::X28, PPC::X29, PPC::X30, PPC::X31
 };
 
+static const unsigned G80Regs[] = {
+  PPC::ZERO8, PPC::X1, PPC::X2, PPC::X3,
+  PPC::X4, PPC::X5, PPC::X6, PPC::X7,
+  PPC::X8, PPC::X9, PPC::X10, PPC::X11,
+  PPC::X12, PPC::X13, PPC::X14, PPC::X15,
+  PPC::X16, PPC::X17, PPC::X18, PPC::X19,
+  PPC::X20, PPC::X21, PPC::X22, PPC::X23,
+  PPC::X24, PPC::X25, PPC::X26, PPC::X27,
+  PPC::X28, PPC::X29, PPC::X30, PPC::X31
+};
+
 static const unsigned QFRegs[] = {
   PPC::QF0, PPC::QF1, PPC::QF2, PPC::QF3,
   PPC::QF4, PPC::QF5, PPC::QF6, PPC::QF7,
@@ -301,6 +312,12 @@
   return decodeRegisterClass(Inst, RegNo, G8Regs);
 }
 
+static DecodeStatus DecodeG8RC_NOX0RegisterClass(MCInst &Inst, uint64_t RegNo,
+                                            uint64_t Address,
+                                            const void *Decoder) {
+  return decodeRegisterClass(Inst, RegNo, G80Regs);
+}
+
 #define DecodePointerLikeRegClass0 DecodeGPRCRegisterClass
 #define DecodePointerLikeRegClass1 DecodeGPRC_NOR0RegisterClass
 
Index: lib/Target/PowerPC/PPCInstrVSX.td
===================================================================
--- lib/Target/PowerPC/PPCInstrVSX.td
+++ lib/Target/PowerPC/PPCInstrVSX.td
@@ -1436,7 +1436,7 @@
   def MTVSRWS: XX1_RS6_RD5_XO<31, 403, (outs vsrc:$XT), (ins gprc:$rA),
                               "mtvsrws $XT, $rA", IIC_VecGeneral, []>;
 
-  def MTVSRDD: XX1Form<31, 435, (outs vsrc:$XT), (ins g8rc:$rA, g8rc:$rB),
+  def MTVSRDD: XX1Form<31, 435, (outs vsrc:$XT), (ins g8rc_nox0:$rA, g8rc:$rB),
                        "mtvsrdd $XT, $rA, $rB", IIC_VecGeneral,
                        []>, Requires<[In64BitMode]>;
 
Index: test/MC/Disassembler/PowerPC/ppc64-encoding-p9vector.txt
===================================================================
--- test/MC/Disassembler/PowerPC/ppc64-encoding-p9vector.txt
+++ test/MC/Disassembler/PowerPC/ppc64-encoding-p9vector.txt
@@ -0,0 +1,4 @@
+# RUN: llvm-mc --disassemble %s -triple powerpc64le-unknown-unknown -mcpu=pwr9 | FileCheck %s
+
+# CHECK: mtvsrdd 6, 0, 3
+0x66 0x1b 0xc0 0x7c