Index: lib/Target/ARM/Disassembler/ARMDisassembler.cpp
===================================================================
--- lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -966,8 +966,13 @@
 static DecodeStatus DecoderGPRRegisterClass(MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   DecodeStatus S = MCDisassembler::Success;
-  if (RegNo == 13 || RegNo == 15)
+
+  const FeatureBitset &featureBits =
+    ((const MCDisassembler*)Decoder)->getSubtargetInfo().getFeatureBits();
+
+  if ((RegNo == 13 && !featureBits[ARM::HasV8Ops]) || RegNo == 15)
     S = MCDisassembler::SoftFail;
+
   Check(S, DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder));
   return S;
 }
@@ -1127,7 +1132,7 @@
   unsigned imm = fieldFromInstruction(Val, 7, 5);
 
   // Register-immediate
-  if (!Check(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)))
+  if (!Check(S, DecoderGPRRegisterClass(Inst, Rm, Address, Decoder)))
     return MCDisassembler::Fail;
 
   ARM_AM::ShiftOpc Shift = ARM_AM::lsl;
Index: test/MC/Disassembler/ARM/invalid-thumbv7.txt
===================================================================
--- test/MC/Disassembler/ARM/invalid-thumbv7.txt
+++ test/MC/Disassembler/ARM/invalid-thumbv7.txt
@@ -1,4 +1,5 @@
-# RUN: not llvm-mc -disassemble %s -mcpu cortex-a8 -triple thumbv7 2>&1 | FileCheck %s
+# RUN: not llvm-mc -disassemble %s -mcpu cortex-a8 -triple thumbv7 2>&1 | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-V7
+# RUN: not llvm-mc -disassemble %s -mcpu cortex-a53 -triple thumbv8 2>&1 | FileCheck %s
 
 # This file is checking Thumbv7 encodings which are globally invalid, usually due
 # to the constraints of the instructions not being met. For example invalid
@@ -359,10 +360,22 @@
 # 32-bit Thumb STM instructions cannot have a writeback register which appears
 # in the list.
 
-[0xa1,0xe8,0x07,0x04]
+[0xa1 0xe8 0x07 0x04]
 # CHECK: warning: potentially undefined instruction encoding
-# CHECK-NEXT: [0xa1,0xe8,0x07,0x04]
+# CHECK-NEXT: [0xa1 0xe8 0x07 0x04]
 
-[0x21,0xe9,0x07,0x04]
+[0x21 0xe9 0x07 0x04]
 # CHECK: warning: potentially undefined instruction encoding
-# CHECK-NEXT: [0x21,0xe9,0x07,0x04]
+# CHECK-NEXT: [0x21 0xe9 0x07 0x04]
+
+#------------------------------------------------------------------------------
+# SP is invalid as rGPR before ARMv8
+#------------------------------------------------------------------------------
+
+[0x00 0xf0 0x00 0x0d]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x00 0xf0 0x00 0x0d]
+
+[0x63 0xeb 0x2d 0x46]
+# CHECK-V7: warning: potentially undefined instruction encoding
+# CHECK-V7-NEXT: [0x63 0xeb 0x2d 0x46]
Index: test/MC/Disassembler/ARM/thumb-v8.txt
===================================================================
--- test/MC/Disassembler/ARM/thumb-v8.txt
+++ test/MC/Disassembler/ARM/thumb-v8.txt
@@ -1,4 +1,5 @@
-# RUN: llvm-mc -disassemble -triple thumbv8 -mattr=+db -show-encoding < %s | FileCheck %s
+# RUN: llvm-mc -disassemble -triple thumbv8 -mattr=+db -show-encoding 2>%t < %s | FileCheck %s
+# RUN: FileCheck -allow-empty -check-prefix=STDERR < %t %s
 
 0x80 0xba
 # CHECK: hlt #0
@@ -26,3 +27,10 @@
 # CHECK: dmb oshld
 # CHECK: dmb nshld
 # CHECK: dmb ld
+
+[0x00 0xf0 0x00 0x0d]
+[0x63 0xeb 0x2d 0x46]
+# CHECK: and sp, r0, #0
+# CHECK: sbc.w r6, r3, sp, asr #16
+
+# STDERR-NOT: warning