Allow the MCDisassembler to return a "soft fail" status code, indicating an instruction that is disassemblable, but invalid.  Only used for ARM UNPREDICTABLE instructions at the moment.
Patch by James Molloy.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137830 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index cb7a45a..98cdc64 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -24,188 +24,201 @@
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 
+// Pull DecodeStatus and its enum values into the global namespace.
+typedef llvm::MCDisassembler::DecodeStatus DecodeStatus;
+#define Success llvm::MCDisassembler::Success
+#define Unpredictable llvm::MCDisassembler::SoftFail
+#define Fail llvm::MCDisassembler::Fail
+
+// Helper macro to perform setwise reduction of the current running status
+// and another status, and return if the new status is Fail.
+#define CHECK(S,X) do {                           \
+    S = (DecodeStatus) ((int)S & (X));            \
+    if (S == Fail) return Fail;                   \
+  } while(0)
+
 // Forward declare these because the autogenerated code will reference them.
 // Definitions are further down.
-static bool DecodeGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeGPRnopcRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeGPRnopcRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodetGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodetGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodetcGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodetcGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecoderGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecoderGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeSPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeSPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeDPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeDPR_8RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPR_8RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeDPR_VFP2RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPR_VFP2RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
-static bool DecodeQPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeQPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder);
 
-static bool DecodePredicateOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodePredicateOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeCCOutOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeCCOutOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSOImmOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSOImmOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeDPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeDPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
 
-static bool DecodeBitfieldMaskOperand(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeBitfieldMaskOperand(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeCopMemInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeCopMemInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrMode2IdxInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeAddrMode2IdxInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSORegMemOperand(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSORegMemOperand(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrMode3Instruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeAddrMode3Instruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSORegImmOperand(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSORegImmOperand(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSORegRegOperand(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSORegRegOperand(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
 
-static bool DecodeMemMultipleWritebackInstruction(llvm::MCInst & Inst,
+static DecodeStatus DecodeMemMultipleWritebackInstruction(llvm::MCInst & Inst,
                                                   unsigned Insn,
                                                   uint64_t Adddress,
                                                   const void *Decoder);
-static bool DecodeSMLAInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSMLAInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeCPSInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeCPSInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrModeImm12Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrModeImm12Operand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrMode5Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode5Operand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrMode7Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode7Operand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeBranchImmInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeBranchImmInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVCVTImmOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVCVTImmOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeAddrMode6Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode6Operand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLDInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVLDInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVSTInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVSTInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD1DupInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVLD1DupInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD2DupInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVLD2DupInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD3DupInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVLD3DupInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD4DupInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVLD4DupInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeNEONModImmInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeNEONModImmInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVSHLMaxInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVSHLMaxInstruction(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeShiftRight8Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight8Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeShiftRight16Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight16Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeShiftRight32Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight32Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeShiftRight64Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight64Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeTBLInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeTBLInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVFPfpImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVFPfpImm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodePostIdxReg(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodePostIdxReg(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeCoprocessor(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeCoprocessor(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeMemBarrierOption(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeMemBarrierOption(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeMSRMask(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeMSRMask(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeDoubleRegLoad(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeDoubleRegLoad(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeDoubleRegStore(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeDoubleRegStore(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSTRPreImm(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSTRPreImm(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeSTRPreReg(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSTRPreReg(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD1LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD1LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD2LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD2LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD3LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD3LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVLD4LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD4LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVST1LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST1LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVST2LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST2LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVST3LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST3LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeVST4LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST4LN(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
 
 
-static bool DecodeThumbAddSpecialReg(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbAddSpecialReg(llvm::MCInst &Inst, uint16_t Insn,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbBROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBROperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2BROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2BROperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbCmpBROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbCmpBROperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddrModeRR(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeRR(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddrModeIS(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeIS(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddrModePC(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModePC(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddrModeSP(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeSP(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2AddrModeSOReg(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeSOReg(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2LoadShift(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2LoadShift(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2Imm8S4(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2Imm8S4(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2AddrModeImm8s4(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm8s4(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2Imm8(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2Imm8(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeT2AddrModeImm8(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm8(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddSPImm(llvm::MCInst &Inst, uint16_t Val,
+static DecodeStatus DecodeThumbAddSPImm(llvm::MCInst &Inst, uint16_t Val,
                                uint64_t Address, const void *Decoder);
-static bool DecodeThumbAddSPReg(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbAddSPReg(llvm::MCInst &Inst, uint16_t Insn,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumbCPS(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbCPS(llvm::MCInst &Inst, uint16_t Insn,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumbBLXOffset(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeThumbBLXOffset(llvm::MCInst &Inst, unsigned Insn,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeT2AddrModeImm12(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm12(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumbSRImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbSRImm(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumb2BCCInstruction(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumb2BCCInstruction(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeT2SOImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2SOImm(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumbBCCTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBCCTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
-static bool DecodeThumbBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                 uint64_t Address, const void *Decoder);
 
 #include "ARMGenDisassemblerTables.inc"
@@ -230,15 +243,14 @@
   return instInfoARM;
 }
 
-
-bool ARMDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
-                                     const MemoryObject &Region,
-                                     uint64_t Address,raw_ostream &os) const {
+DecodeStatus ARMDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
+                                             const MemoryObject &Region,
+                                             uint64_t Address,raw_ostream &os) const {
   uint8_t bytes[4];
 
   // We want to read exactly 4 bytes of data.
   if (Region.readBytes(Address, 4, (uint8_t*)bytes, NULL) == -1)
-    return false;
+    return Fail;
 
   // Encoded as a small-endian 32-bit word in the stream.
   uint32_t insn = (bytes[3] << 24) |
@@ -247,10 +259,10 @@
                   (bytes[0] <<  0);
 
   // Calling the auto-generated decoder function.
-  bool result = decodeARMInstruction32(MI, insn, Address, this);
-  if (result) {
+  DecodeStatus result = decodeARMInstruction32(MI, insn, Address, this);
+  if (result != Fail) {
     Size = 4;
-    return true;
+    return result;
   }
 
   // Instructions that are shared between ARM and Thumb modes.
@@ -258,53 +270,53 @@
   // fact that we fail to encode a few instructions properly for Thumb.
   MI.clear();
   result = decodeCommonInstruction32(MI, insn, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
-    return true;
+    return result;
   }
 
   // VFP and NEON instructions, similarly, are shared between ARM
   // and Thumb modes.
   MI.clear();
   result = decodeVFPInstruction32(MI, insn, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeNEONDataInstruction32(MI, insn, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     // Add a fake predicate operand, because we share these instruction
     // definitions with Thumb2 where these instructions are predicable.
-    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return false;
-    return true;
+    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return Fail;
+    return result;
   }
 
   MI.clear();
   result = decodeNEONLoadStoreInstruction32(MI, insn, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     // Add a fake predicate operand, because we share these instruction
     // definitions with Thumb2 where these instructions are predicable.
-    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return false;
-    return true;
+    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return Fail;
+    return result;
   }
 
   MI.clear();
   result = decodeNEONDupInstruction32(MI, insn, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     // Add a fake predicate operand, because we share these instruction
     // definitions with Thumb2 where these instructions are predicable.
-    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return false;
-    return true;
+    if (!DecodePredicateOperand(MI, 0xE, Address, this)) return Fail;
+    return result;
   }
 
   MI.clear();
 
-  return false;
+  return Fail;
 }
 
 namespace llvm {
@@ -403,22 +415,21 @@
   }
 }
 
-
-bool ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
-                                       const MemoryObject &Region,
-                                       uint64_t Address,raw_ostream &os) const {
+DecodeStatus ThumbDisassembler::getInstruction(MCInst &MI, uint64_t &Size,
+                                               const MemoryObject &Region,
+                                               uint64_t Address,raw_ostream &os) const {
   uint8_t bytes[4];
 
   // We want to read exactly 2 bytes of data.
   if (Region.readBytes(Address, 2, (uint8_t*)bytes, NULL) == -1)
-    return false;
+    return Fail;
 
   uint16_t insn16 = (bytes[1] << 8) | bytes[0];
-  bool result = decodeThumbInstruction16(MI, insn16, Address, this);
-  if (result) {
+  DecodeStatus result = decodeThumbInstruction16(MI, insn16, Address, this);
+  if (result != Fail) {
     Size = 2;
     AddThumbPredicate(MI);
-    return true;
+    return result;
   }
 
   MI.clear();
@@ -428,12 +439,12 @@
     bool InITBlock = !ITBlock.empty();
     AddThumbPredicate(MI);
     AddThumb1SBit(MI, InITBlock);
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeThumb2Instruction16(MI, insn16, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 2;
     AddThumbPredicate(MI);
 
@@ -456,12 +467,12 @@
       ITBlock.push_back(firstcond);
     }
 
-    return true;
+    return result;
   }
 
   // We want to read exactly 4 bytes of data.
   if (Region.readBytes(Address, 4, (uint8_t*)bytes, NULL) == -1)
-    return false;
+    return Fail;
 
   uint32_t insn32 = (bytes[3] <<  8) |
                     (bytes[2] <<  0) |
@@ -469,44 +480,44 @@
                     (bytes[0] << 16);
   MI.clear();
   result = decodeThumbInstruction32(MI, insn32, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     bool InITBlock = ITBlock.size();
     AddThumbPredicate(MI);
     AddThumb1SBit(MI, InITBlock);
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeThumb2Instruction32(MI, insn32, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     AddThumbPredicate(MI);
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeCommonInstruction32(MI, insn32, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     AddThumbPredicate(MI);
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeVFPInstruction32(MI, insn32, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     UpdateThumbVFPPredicate(MI);
-    return true;
+    return result;
   }
 
   MI.clear();
   result = decodeNEONDupInstruction32(MI, insn32, Address, this);
-  if (result) {
+  if (result != Fail) {
     Size = 4;
     AddThumbPredicate(MI);
-    return true;
+    return result;
   }
 
   if (fieldFromInstruction32(insn32, 24, 8) == 0xF9) {
@@ -515,10 +526,10 @@
     NEONLdStInsn &= 0xF0FFFFFF;
     NEONLdStInsn |= 0x04000000;
     result = decodeNEONLoadStoreInstruction32(MI, NEONLdStInsn, Address, this);
-    if (result) {
+    if (result != Fail) {
       Size = 4;
       AddThumbPredicate(MI);
-      return true;
+      return result;
     }
   }
 
@@ -529,14 +540,14 @@
     NEONDataInsn |= (NEONDataInsn & 0x10000000) >> 4; // Move bit 28 to bit 24
     NEONDataInsn |= 0x12000000; // Set bits 28 and 25
     result = decodeNEONDataInstruction32(MI, NEONDataInsn, Address, this);
-    if (result) {
+    if (result != Fail) {
       Size = 4;
       AddThumbPredicate(MI);
-      return true;
+      return result;
     }
   }
 
-  return false;
+  return Fail;
 }
 
 
@@ -554,30 +565,30 @@
   ARM::R12, ARM::SP, ARM::LR, ARM::PC
 };
 
-static bool DecodeGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 15)
-    return false;
+    return Fail;
 
   unsigned Register = GPRDecoderTable[RegNo];
   Inst.addOperand(MCOperand::CreateReg(Register));
-  return true;
+  return Success;
 }
 
-static bool DecodeGPRnopcRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeGPRnopcRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                        uint64_t Address, const void *Decoder) {
-  if (RegNo == 15) return false;
+  if (RegNo == 15) return Fail;
   return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
 }
 
-static bool DecodetGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodetGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 7)
-    return false;
+    return Fail;
   return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
 }
 
-static bool DecodetcGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodetcGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   unsigned Register = 0;
   switch (RegNo) {
@@ -600,16 +611,16 @@
       Register = ARM::R12;
       break;
     default:
-      return false;
+      return Fail;
     }
 
   Inst.addOperand(MCOperand::CreateReg(Register));
-  return true;
+  return Success;
 }
 
-static bool DecoderGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecoderGPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
-  if (RegNo == 13 || RegNo == 15) return false;
+  if (RegNo == 13 || RegNo == 15) return Fail;
   return DecodeGPRRegisterClass(Inst, RegNo, Address, Decoder);
 }
 
@@ -624,14 +635,14 @@
     ARM::S28, ARM::S29, ARM::S30, ARM::S31
 };
 
-static bool DecodeSPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeSPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 31)
-    return false;
+    return Fail;
 
   unsigned Register = SPRDecoderTable[RegNo];
   Inst.addOperand(MCOperand::CreateReg(Register));
-  return true;
+  return Success;
 }
 
 static const unsigned DPRDecoderTable[] = { 
@@ -645,27 +656,27 @@
     ARM::D28, ARM::D29, ARM::D30, ARM::D31
 };
 
-static bool DecodeDPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 31)
-    return false;
+    return Fail;
 
   unsigned Register = DPRDecoderTable[RegNo];
   Inst.addOperand(MCOperand::CreateReg(Register));
-  return true;
+  return Success;
 }
 
-static bool DecodeDPR_8RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPR_8RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 7)
-    return false;
+    return Fail;
   return DecodeDPRRegisterClass(Inst, RegNo, Address, Decoder);
 }
 
-static bool DecodeDPR_VFP2RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeDPR_VFP2RegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 15)
-    return false;
+    return Fail;
   return DecodeDPRRegisterClass(Inst, RegNo, Address, Decoder);
 }
 
@@ -677,65 +688,66 @@
 };
 
 
-static bool DecodeQPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
+static DecodeStatus DecodeQPRRegisterClass(llvm::MCInst &Inst, unsigned RegNo,
                                    uint64_t Address, const void *Decoder) {
   if (RegNo > 31)
-    return false;
+    return Fail;
   RegNo >>= 1;
 
   unsigned Register = QPRDecoderTable[RegNo];
   Inst.addOperand(MCOperand::CreateReg(Register));
-  return true;
+  return Success;
 }
 
-static bool DecodePredicateOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodePredicateOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
-  if (Val == 0xF) return false;
+  if (Val == 0xF) return Fail;
   // AL predicate is not allowed on Thumb1 branches.
   if (Inst.getOpcode() == ARM::tBcc && Val == 0xE)
-    return false;
+    return Fail;
   Inst.addOperand(MCOperand::CreateImm(Val));
   if (Val == ARMCC::AL) {
     Inst.addOperand(MCOperand::CreateReg(0));
   } else
     Inst.addOperand(MCOperand::CreateReg(ARM::CPSR));
-  return true;
+  return Success;
 }
 
-static bool DecodeCCOutOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeCCOutOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   if (Val)
     Inst.addOperand(MCOperand::CreateReg(ARM::CPSR));
   else
     Inst.addOperand(MCOperand::CreateReg(0));
-  return true;
+  return Success;
 }
 
-static bool DecodeSOImmOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSOImmOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   uint32_t imm = Val & 0xFF;
   uint32_t rot = (Val & 0xF00) >> 7;
   uint32_t rot_imm = (imm >> rot) | (imm << (32-rot));
   Inst.addOperand(MCOperand::CreateImm(rot_imm));
-  return true;
+  return Success;
 }
 
-static bool DecodeBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   Val <<= 2;
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<26>(Val)));
-  return true;
+  return Success;
 }
 
-static bool DecodeSORegImmOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSORegImmOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
 
   unsigned Rm = fieldFromInstruction32(Val, 0, 4);
   unsigned type = fieldFromInstruction32(Val, 5, 2);
   unsigned imm = fieldFromInstruction32(Val, 7, 5);
 
   // Register-immediate
-  if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
 
   ARM_AM::ShiftOpc Shift = ARM_AM::lsl;
   switch (type) {
@@ -759,19 +771,20 @@
   unsigned Op = Shift | (imm << 3);
   Inst.addOperand(MCOperand::CreateImm(Op));
 
-  return true;
+  return S;
 }
 
-static bool DecodeSORegRegOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSORegRegOperand(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
 
   unsigned Rm = fieldFromInstruction32(Val, 0, 4);
   unsigned type = fieldFromInstruction32(Val, 5, 2);
   unsigned Rs = fieldFromInstruction32(Val, 8, 4);
 
   // Register-register
-  if (!DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder)) return false;
-  if (!DecodeGPRnopcRegisterClass(Inst, Rs, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder));
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rs, Address, Decoder));
 
   ARM_AM::ShiftOpc Shift = ARM_AM::lsl;
   switch (type) {
@@ -791,49 +804,55 @@
 
   Inst.addOperand(MCOperand::CreateImm(Shift));
 
-  return true;
+  return S;
 }
 
-static bool DecodeRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   // Empty register lists are not allowed.
-  if (CountPopulation_32(Val) == 0) return false;
+  if (CountPopulation_32(Val) == 0) return Fail;
   for (unsigned i = 0; i < 16; ++i) {
     if (Val & (1 << i)) {
-      if (!DecodeGPRRegisterClass(Inst, i, Address, Decoder)) return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, i, Address, Decoder));
     }
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeSPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Vd = fieldFromInstruction32(Val, 8, 4);
   unsigned regs = Val & 0xFF;
 
-  if (!DecodeSPRRegisterClass(Inst, Vd, Address, Decoder)) return false;
+  CHECK(S, DecodeSPRRegisterClass(Inst, Vd, Address, Decoder));
   for (unsigned i = 0; i < (regs - 1); ++i) {
-    if (!DecodeSPRRegisterClass(Inst, ++Vd, Address, Decoder)) return false;
+    CHECK(S, DecodeSPRRegisterClass(Inst, ++Vd, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeDPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeDPRRegListOperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Vd = fieldFromInstruction32(Val, 8, 4);
   unsigned regs = (Val & 0xFF) / 2;
 
-  if (!DecodeDPRRegisterClass(Inst, Vd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Vd, Address, Decoder));
   for (unsigned i = 0; i < (regs - 1); ++i) {
-    if (!DecodeDPRRegisterClass(Inst, ++Vd, Address, Decoder)) return false;
+    CHECK(S, DecodeDPRRegisterClass(Inst, ++Vd, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeBitfieldMaskOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeBitfieldMaskOperand(llvm::MCInst &Inst, unsigned Val,
                                       uint64_t Address, const void *Decoder) {
   // This operand encodes a mask of contiguous zeros between a specified MSB
   // and LSB.  To decode it, we create the mask of all bits MSB-and-lower,
@@ -845,11 +864,13 @@
   uint32_t msb_mask = (1 << (msb+1)) - 1;
   uint32_t lsb_mask = (1 << lsb) - 1;
   Inst.addOperand(MCOperand::CreateImm(~(msb_mask ^ lsb_mask)));
-  return true;
+  return Success;
 }
 
-static bool DecodeCopMemInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeCopMemInstruction(llvm::MCInst &Inst, unsigned Insn,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
   unsigned CRd = fieldFromInstruction32(Insn, 12, 4);
   unsigned coproc = fieldFromInstruction32(Insn, 8, 4);
@@ -875,7 +896,7 @@
     case ARM::STCL_POST:
     case ARM::STCL_OPTION:
       if (coproc == 0xA || coproc == 0xB)
-        return false;
+        return Fail;
       break;
     default:
       break;
@@ -883,7 +904,7 @@
 
   Inst.addOperand(MCOperand::CreateImm(coproc));
   Inst.addOperand(MCOperand::CreateImm(CRd));
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   switch (Inst.getOpcode()) {
     case ARM::LDC_OPTION:
     case ARM::LDCL_OPTION:
@@ -952,17 +973,19 @@
     case ARM::STCL_PRE:
     case ARM::STCL_POST:
     case ARM::STCL_OPTION:
-      if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+      CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
       break;
     default:
       break;
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeAddrMode2IdxInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeAddrMode2IdxInstruction(llvm::MCInst &Inst, unsigned Insn,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
@@ -982,13 +1005,13 @@
     case ARM::STRT_POST_IMM:
     case ARM::STRBT_POST_REG:
     case ARM::STRBT_POST_IMM:
-      if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
       break;
     default:
       break;
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
 
   // On loads, the writeback operand comes after Rt.
   switch (Inst.getOpcode()) {
@@ -1002,14 +1025,13 @@
     case ARM::LDRBT_POST_IMM:
     case ARM::LDRT_POST_REG:
     case ARM::LDRT_POST_IMM:
-      if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-        return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
       break;
     default:
       break;
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
 
   ARM_AM::AddrOpc Op = ARM_AM::add;
   if (!fieldFromInstruction32(Insn, 23, 1))
@@ -1022,10 +1044,10 @@
   else if (!P && writeback)
     idx_mode = ARMII::IndexModePost;
 
-  if (writeback && (Rn == 15 || Rn == Rt)) return false; // UNPREDICTABLE
+  if (writeback && (Rn == 15 || Rn == Rt)) S = Unpredictable; // UNPREDICTABLE
 
   if (reg) {
-    if (!DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder));
     ARM_AM::ShiftOpc Opc = ARM_AM::lsl;
     switch( fieldFromInstruction32(Insn, 5, 2)) {
       case 0:
@@ -1041,7 +1063,7 @@
         Opc = ARM_AM::ror;
         break;
       default:
-        return false;
+        return Fail;
     }
     unsigned amt = fieldFromInstruction32(Insn, 7, 5);
     unsigned imm = ARM_AM::getAM2Opc(Op, amt, Opc, idx_mode);
@@ -1053,13 +1075,15 @@
     Inst.addOperand(MCOperand::CreateImm(tmp));
   }
 
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeSORegMemOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeSORegMemOperand(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 13, 4);
   unsigned Rm = fieldFromInstruction32(Val,  0, 4);
   unsigned type = fieldFromInstruction32(Val, 5, 2);
@@ -1082,8 +1106,8 @@
       break;
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   unsigned shift;
   if (U)
     shift = ARM_AM::getAM2Opc(ARM_AM::add, imm, ShOp);
@@ -1091,11 +1115,13 @@
     shift = ARM_AM::getAM2Opc(ARM_AM::sub, imm, ShOp);
   Inst.addOperand(MCOperand::CreateImm(shift));
 
-  return true;
+  return S;
 }
 
-static bool DecodeAddrMode3Instruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeAddrMode3Instruction(llvm::MCInst &Inst, unsigned Insn,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
@@ -1116,7 +1142,7 @@
     case ARM::LDRD:
     case ARM::LDRD_PRE:
     case ARM::LDRD_POST:
-      if (Rt & 0x1) return false;
+      if (Rt & 0x1) return Fail;
       break;
   default:
     break;
@@ -1136,16 +1162,14 @@
     case ARM::STRH:
     case ARM::STRH_PRE:
     case ARM::STRH_POST:
-      if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-        return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
       break;
     default:
       break;
     }
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
   switch (Inst.getOpcode()) {
     case ARM::STRD:
     case ARM::STRD_PRE:
@@ -1153,8 +1177,7 @@
     case ARM::LDRD:
     case ARM::LDRD_PRE:
     case ARM::LDRD_POST:
-      if (!DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder))
-        return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder));
       break;
     default:
       break;
@@ -1177,33 +1200,32 @@
     case ARM::LDRSB_POST:
     case ARM::LDRHTr:
     case ARM::LDRSBTr:
-      if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-        return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
       break;
     default:
       break;
     }
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
 
   if (type) {
     Inst.addOperand(MCOperand::CreateReg(0));
     Inst.addOperand(MCOperand::CreateImm(U | (imm << 4) | Rm));
   } else {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
     Inst.addOperand(MCOperand::CreateImm(U));
   }
 
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeRFEInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeRFEInstruction(llvm::MCInst &Inst, unsigned Insn,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned mode = fieldFromInstruction32(Insn, 23, 2);
 
@@ -1223,14 +1245,16 @@
   }
 
   Inst.addOperand(MCOperand::CreateImm(mode));
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeMemMultipleWritebackInstruction(llvm::MCInst &Inst,
+static DecodeStatus DecodeMemMultipleWritebackInstruction(llvm::MCInst &Inst,
                                   unsigned Insn,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
   unsigned reglist = fieldFromInstruction32(Insn, 0, 16);
@@ -1265,16 +1289,15 @@
     return DecodeRFEInstruction(Inst, Insn, Address, Decoder);
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)   ||
-      !DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)   || // Tied
-      !DecodePredicateOperand(Inst, pred, Address, Decoder) ||
-      !DecodeRegListOperand(Inst, reglist, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)); // Tied
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
+  CHECK(S, DecodeRegListOperand(Inst, reglist, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeCPSInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeCPSInstruction(llvm::MCInst &Inst, unsigned Insn,
                                  uint64_t Address, const void *Decoder) {
   unsigned imod = fieldFromInstruction32(Insn, 18, 2);
   unsigned M = fieldFromInstruction32(Insn, 17, 1);
@@ -1282,30 +1305,32 @@
   unsigned mode = fieldFromInstruction32(Insn, 0, 5);
 
   // imod == '01' --> UNPREDICTABLE
-  if (imod == 1) return false;
+  if (imod == 1) return Fail;
 
   if (M && mode && imod && iflags) {
     Inst.setOpcode(ARM::CPS3p);
     Inst.addOperand(MCOperand::CreateImm(imod));
     Inst.addOperand(MCOperand::CreateImm(iflags));
     Inst.addOperand(MCOperand::CreateImm(mode));
-    return true;
+    return Success;
   } else if (!mode && !M) {
     Inst.setOpcode(ARM::CPS2p);
     Inst.addOperand(MCOperand::CreateImm(imod));
     Inst.addOperand(MCOperand::CreateImm(iflags));
-    return true;
+    return Success;
   } else if (!imod && !iflags && M) {
     Inst.setOpcode(ARM::CPS1p);
     Inst.addOperand(MCOperand::CreateImm(mode));
-    return true;
+    return Success;
   }
 
-  return false;
+  return Fail;
 }
 
-static bool DecodeSMLAInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSMLAInstruction(llvm::MCInst &Inst, unsigned Insn,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rn = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 8, 4);
@@ -1315,57 +1340,60 @@
   if (pred == 0xF)
     return DecodeCPSInstruction(Inst, Insn, Address, Decoder);
 
-  if (!DecodeGPRnopcRegisterClass(Inst, Rd, Address, Decoder) ||
-      !DecodeGPRnopcRegisterClass(Inst, Rn, Address, Decoder) ||
-      !DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder) ||
-      !DecodeGPRnopcRegisterClass(Inst, Ra, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Rm, Address, Decoder));
+  CHECK(S, DecodeGPRnopcRegisterClass(Inst, Ra, Address, Decoder));
 
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeAddrModeImm12Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrModeImm12Operand(llvm::MCInst &Inst, unsigned Val,
                            uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned add = fieldFromInstruction32(Val, 12, 1);
   unsigned imm = fieldFromInstruction32(Val, 0, 12);
   unsigned Rn = fieldFromInstruction32(Val, 13, 4);
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
 
   if (!add) imm *= -1;
   if (imm == 0 && !add) imm = INT32_MIN;
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return S;
 }
 
-static bool DecodeAddrMode5Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode5Operand(llvm::MCInst &Inst, unsigned Val,
                                    uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 9, 4);
   unsigned U = fieldFromInstruction32(Val, 8, 1);
   unsigned imm = fieldFromInstruction32(Val, 0, 8);
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
 
   if (U)
     Inst.addOperand(MCOperand::CreateImm(ARM_AM::getAM5Opc(ARM_AM::add, imm)));
   else
     Inst.addOperand(MCOperand::CreateImm(ARM_AM::getAM5Opc(ARM_AM::sub, imm)));
 
-  return true;
+  return S;
 }
 
-static bool DecodeAddrMode7Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode7Operand(llvm::MCInst &Inst, unsigned Val,
                                    uint64_t Address, const void *Decoder) {
   return DecodeGPRRegisterClass(Inst, Val, Address, Decoder);
 }
 
-static bool DecodeBranchImmInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeBranchImmInstruction(llvm::MCInst &Inst, unsigned Insn,
                                    uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
   unsigned imm = fieldFromInstruction32(Insn, 0, 24) << 2;
 
@@ -1373,39 +1401,42 @@
     Inst.setOpcode(ARM::BLXi);
     imm |= fieldFromInstruction32(Insn, 24, 1) << 1;
     Inst.addOperand(MCOperand::CreateImm(SignExtend32<26>(imm)));
-    return true;
+    return S;
   }
 
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<26>(imm)));
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeVCVTImmOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVCVTImmOperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(64 - Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeAddrMode6Operand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeAddrMode6Operand(llvm::MCInst &Inst, unsigned Val,
                                    uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rm = fieldFromInstruction32(Val, 0, 4);
   unsigned align = fieldFromInstruction32(Val, 4, 2);
 
-  if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   if (!align)
     Inst.addOperand(MCOperand::CreateImm(0));
   else
     Inst.addOperand(MCOperand::CreateImm(4 << align));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLDInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLDInstruction(llvm::MCInst &Inst, unsigned Insn,
                                    uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned wb = fieldFromInstruction32(Insn, 16, 4);
@@ -1414,7 +1445,7 @@
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
 
   // First output register
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
 
   // Second output register
   switch (Inst.getOpcode()) {
@@ -1466,7 +1497,7 @@
     case ARM::VLD4d8_UPD:
     case ARM::VLD4d16_UPD:
     case ARM::VLD4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder));
       break;
     case ARM::VLD2b8:
     case ARM::VLD2b16:
@@ -1486,7 +1517,7 @@
     case ARM::VLD4q8_UPD:
     case ARM::VLD4q16_UPD:
     case ARM::VLD4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder));
     default:
       break;
   }
@@ -1527,7 +1558,7 @@
     case ARM::VLD4d8_UPD:
     case ARM::VLD4d16_UPD:
     case ARM::VLD4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder));
       break;
     case ARM::VLD3q8:
     case ARM::VLD3q16:
@@ -1541,7 +1572,7 @@
     case ARM::VLD4q8_UPD:
     case ARM::VLD4q16_UPD:
     case ARM::VLD4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+4)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+4)%32, Address, Decoder));
       break;
     default:
       break;
@@ -1569,7 +1600,7 @@
     case ARM::VLD4d8_UPD:
     case ARM::VLD4d16_UPD:
     case ARM::VLD4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+3)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+3)%32, Address, Decoder));
       break;
     case ARM::VLD4q8:
     case ARM::VLD4q16:
@@ -1577,7 +1608,7 @@
     case ARM::VLD4q8_UPD:
     case ARM::VLD4q16_UPD:
     case ARM::VLD4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+6)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+6)%32, Address, Decoder));
       break;
     default:
       break;
@@ -1622,28 +1653,29 @@
     case ARM::VLD4q8_UPD:
     case ARM::VLD4q16_UPD:
     case ARM::VLD4q32_UPD:
-      if (!DecodeGPRRegisterClass(Inst, wb, Address, Decoder)) return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, wb, Address, Decoder));
       break;
     default:
       break;
   }
 
   // AddrMode6 Base (register+alignment)
-  if (!DecodeAddrMode6Operand(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeAddrMode6Operand(Inst, Rn, Address, Decoder));
 
   // AddrMode6 Offset (register)
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVSTInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVSTInstruction(llvm::MCInst &Inst, unsigned Insn,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned wb = fieldFromInstruction32(Insn, 16, 4);
@@ -1690,25 +1722,24 @@
     case ARM::VST4q8_UPD:
     case ARM::VST4q16_UPD:
     case ARM::VST4q32_UPD:
-      if (!DecodeGPRRegisterClass(Inst, wb, Address, Decoder))
-        return false;
+      CHECK(S, DecodeGPRRegisterClass(Inst, wb, Address, Decoder));
       break;
     default:
       break;
   }
 
   // AddrMode6 Base (register+alignment)
-  if (!DecodeAddrMode6Operand(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeAddrMode6Operand(Inst, Rn, Address, Decoder));
 
   // AddrMode6 Offset (register)
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
   // First input register
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
 
   // Second input register
   switch (Inst.getOpcode()) {
@@ -1760,7 +1791,7 @@
     case ARM::VST4d8_UPD:
     case ARM::VST4d16_UPD:
     case ARM::VST4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder));
       break;
     case ARM::VST2b8:
     case ARM::VST2b16:
@@ -1780,7 +1811,7 @@
     case ARM::VST4q8_UPD:
     case ARM::VST4q16_UPD:
     case ARM::VST4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder));
       break;
     default:
       break;
@@ -1822,7 +1853,7 @@
     case ARM::VST4d8_UPD:
     case ARM::VST4d16_UPD:
     case ARM::VST4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2)%32, Address, Decoder));
       break;
     case ARM::VST3q8:
     case ARM::VST3q16:
@@ -1836,7 +1867,7 @@
     case ARM::VST4q8_UPD:
     case ARM::VST4q16_UPD:
     case ARM::VST4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+4)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+4)%32, Address, Decoder));
       break;
     default:
       break;
@@ -1864,7 +1895,7 @@
     case ARM::VST4d8_UPD:
     case ARM::VST4d16_UPD:
     case ARM::VST4d32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+3)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+3)%32, Address, Decoder));
       break;
     case ARM::VST4q8:
     case ARM::VST4q16:
@@ -1872,17 +1903,19 @@
     case ARM::VST4q8_UPD:
     case ARM::VST4q16_UPD:
     case ARM::VST4q32_UPD:
-      if (!DecodeDPRRegisterClass(Inst, (Rd+6)%32, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+6)%32, Address, Decoder));
       break;
     default:
       break;
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLD1DupInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD1DupInstruction(llvm::MCInst &Inst, unsigned Insn,
                                     uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
@@ -1893,28 +1926,30 @@
 
   align *= (1 << size);
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   if (regs == 2) {
-    if (!DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder)) return false;
+    CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+1)%32, Address, Decoder));
   }
   if (Rm == 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
 
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLD2DupInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD2DupInstruction(llvm::MCInst &Inst, unsigned Insn,
                                     uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
@@ -1924,54 +1959,57 @@
   unsigned inc = fieldFromInstruction32(Insn, 5, 1) + 1;
   align *= 2*size;
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder));
   if (Rm == 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
 
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLD3DupInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD3DupInstruction(llvm::MCInst &Inst, unsigned Insn,
                                     uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned inc = fieldFromInstruction32(Insn, 5, 1) + 1;
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)          ||
-      !DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder) ||
-      !DecodeDPRRegisterClass(Inst, (Rd+2*inc)%32, Address, Decoder))
-    return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2*inc)%32, Address, Decoder));
   if (Rm == 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(0));
 
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLD4DupInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD4DupInstruction(llvm::MCInst &Inst, unsigned Insn,
                                     uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
@@ -1993,29 +2031,30 @@
     }
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)            ||
-      !DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder)   ||
-      !DecodeDPRRegisterClass(Inst, (Rd+2*inc)%32, Address, Decoder) ||
-      !DecodeDPRRegisterClass(Inst, (Rd+3*inc)%32, Address, Decoder))
-    return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+inc)%32, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+2*inc)%32, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, (Rd+3*inc)%32, Address, Decoder));
   if (Rm == 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
 
   if (Rm == 0xD)
     Inst.addOperand(MCOperand::CreateReg(0));
   else if (Rm != 0xF) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeNEONModImmInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeNEONModImmInstruction(llvm::MCInst &Inst, unsigned Insn,
                                         uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned imm = fieldFromInstruction32(Insn, 0, 4);
@@ -2026,9 +2065,9 @@
   unsigned Q = fieldFromInstruction32(Insn, 6, 1);
 
   if (Q) {
-    if (!DecodeQPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+    CHECK(S, DecodeQPRRegisterClass(Inst, Rd, Address, Decoder));
   } else {
-    if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+    CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   }
 
   Inst.addOperand(MCOperand::CreateImm(imm));
@@ -2038,62 +2077,66 @@
     case ARM::VORRiv2i32:
     case ARM::VBICiv4i16:
     case ARM::VBICiv2i32:
-      if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+      CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
       break;
     case ARM::VORRiv8i16:
     case ARM::VORRiv4i32:
     case ARM::VBICiv8i16:
     case ARM::VBICiv4i32:
-      if (!DecodeQPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+      CHECK(S, DecodeQPRRegisterClass(Inst, Rd, Address, Decoder));
       break;
     default:
       break;
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeVSHLMaxInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVSHLMaxInstruction(llvm::MCInst &Inst, unsigned Insn,
                                         uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   Rm |= fieldFromInstruction32(Insn, 5, 1) << 4;
   unsigned size = fieldFromInstruction32(Insn, 18, 2);
 
-  if (!DecodeQPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+  CHECK(S, DecodeQPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rm, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(8 << size));
 
-  return true;
+  return S;
 }
 
-static bool DecodeShiftRight8Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight8Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(8 - Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeShiftRight16Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight16Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(16 - Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeShiftRight32Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight32Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(32 - Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeShiftRight64Imm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeShiftRight64Imm(llvm::MCInst &Inst, unsigned Val,
                                uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(64 - Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeTBLInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeTBLInstruction(llvm::MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   Rd |= fieldFromInstruction32(Insn, 22, 1) << 4;
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
@@ -2103,21 +2146,21 @@
   unsigned op = fieldFromInstruction32(Insn, 6, 1);
   unsigned length = fieldFromInstruction32(Insn, 8, 2) + 1;
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   if (op) {
-    if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false; // Writeback
+    CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)); // Writeback
   }
 
   for (unsigned i = 0; i < length; ++i) {
-    if (!DecodeDPRRegisterClass(Inst, (Rn+i)%32, Address, Decoder)) return false;
+    CHECK(S, DecodeDPRRegisterClass(Inst, (Rn+i)%32, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rm, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVFPfpImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeVFPfpImm(llvm::MCInst &Inst, unsigned Val,
                             uint64_t Address, const void *Decoder) {
   // The immediate needs to be a fully instantiated float.  However, the
   // auto-generated decoder is only able to fill in some of the bits
@@ -2139,102 +2182,110 @@
   fp_conv.integer |= (~b & 0x1) << 30;
 
   Inst.addOperand(MCOperand::CreateFPImm(fp_conv.fp));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbAddSpecialReg(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbAddSpecialReg(llvm::MCInst &Inst, uint16_t Insn,
                                      uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned dst = fieldFromInstruction16(Insn, 8, 3);
   unsigned imm = fieldFromInstruction16(Insn, 0, 8);
 
-  if (!DecodetGPRRegisterClass(Inst, dst, Address, Decoder)) return false;
+  CHECK(S, DecodetGPRRegisterClass(Inst, dst, Address, Decoder));
 
   if (Inst.getOpcode() == ARM::tADR)
     Inst.addOperand(MCOperand::CreateReg(ARM::PC));
   else if (Inst.getOpcode() == ARM::tADDrSPi)
     Inst.addOperand(MCOperand::CreateReg(ARM::SP));
   else
-    return false;
+    return Fail;
 
   Inst.addOperand(MCOperand::CreateImm(imm));
-  return true;
+  return S;
 }
 
-static bool DecodeThumbBROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBROperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<12>(Val << 1)));
-  return true;
+  return Success;
 }
 
-static bool DecodeT2BROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2BROperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<21>(Val)));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbCmpBROperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbCmpBROperand(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<7>(Val << 1)));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbAddrModeRR(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeRR(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 0, 3);
   unsigned Rm = fieldFromInstruction32(Val, 3, 3);
 
-  if (!DecodetGPRRegisterClass(Inst, Rn, Address, Decoder) ||
-      !DecodetGPRRegisterClass(Inst, Rm, Address, Decoder))
-    return false;
+  CHECK(S, DecodetGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodetGPRRegisterClass(Inst, Rm, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeThumbAddrModeIS(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeIS(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 0, 3);
   unsigned imm = fieldFromInstruction32(Val, 3, 5);
 
-  if (!DecodetGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodetGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return S;
 }
 
-static bool DecodeThumbAddrModePC(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModePC(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(Val << 2));
 
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbAddrModeSP(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbAddrModeSP(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateReg(ARM::SP));
   Inst.addOperand(MCOperand::CreateImm(Val << 2));
 
-  return true;
+  return Success;
 }
 
-static bool DecodeT2AddrModeSOReg(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeSOReg(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 6, 4);
   unsigned Rm = fieldFromInstruction32(Val, 2, 4);
   unsigned imm = fieldFromInstruction32(Val, 0, 2);
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder) ||
-      !DecoderGPRRegisterClass(Inst, Rm, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecoderGPRRegisterClass(Inst, Rm, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return S;
 }
 
-static bool DecodeT2LoadShift(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeT2LoadShift(llvm::MCInst &Inst, unsigned Insn,
                               uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   if (Inst.getOpcode() != ARM::t2PLDs) {
     unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
-    if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
   }
 
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
@@ -2257,57 +2308,60 @@
         Inst.addOperand(MCOperand::CreateReg(ARM::PC));
         break;
       default:
-        return false;
+        return Fail;
     }
 
     int imm = fieldFromInstruction32(Insn, 0, 12);
     if (!fieldFromInstruction32(Insn, 23, 1)) imm *= -1;
     Inst.addOperand(MCOperand::CreateImm(imm));
 
-    return true;
+    return S;
   }
 
   unsigned addrmode = fieldFromInstruction32(Insn, 4, 2);
   addrmode |= fieldFromInstruction32(Insn, 0, 4) << 2;
   addrmode |= fieldFromInstruction32(Insn, 16, 4) << 6;
-  DecodeT2AddrModeSOReg(Inst, addrmode, Address, Decoder);
+  CHECK(S, DecodeT2AddrModeSOReg(Inst, addrmode, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeT2Imm8S4(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2Imm8S4(llvm::MCInst &Inst, unsigned Val,
                            uint64_t Address, const void *Decoder) {
   int imm = Val & 0xFF;
   if (!(Val & 0x100)) imm *= -1;
   Inst.addOperand(MCOperand::CreateImm(imm << 2));
 
-  return true;
+  return Success;
 }
 
-static bool DecodeT2AddrModeImm8s4(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm8s4(llvm::MCInst &Inst, unsigned Val,
                                    uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 9, 4);
   unsigned imm = fieldFromInstruction32(Val, 0, 9);
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder) ||
-      !DecodeT2Imm8S4(Inst, imm, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeT2Imm8S4(Inst, imm, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeT2Imm8(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2Imm8(llvm::MCInst &Inst, unsigned Val,
                          uint64_t Address, const void *Decoder) {
   int imm = Val & 0xFF;
   if (!(Val & 0x100)) imm *= -1;
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return Success;
 }
 
 
-static bool DecodeT2AddrModeImm8(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm8(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 9, 4);
   unsigned imm = fieldFromInstruction32(Val, 0, 9);
 
@@ -2324,27 +2378,28 @@
       break;
   }
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder) ||
-      !DecodeT2Imm8(Inst, imm, Address, Decoder))
-    return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeT2Imm8(Inst, imm, Address, Decoder));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeT2AddrModeImm12(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2AddrModeImm12(llvm::MCInst &Inst, unsigned Val,
                                   uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Val, 13, 4);
   unsigned imm = fieldFromInstruction32(Val, 0, 12);
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeThumbAddSPImm(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbAddSPImm(llvm::MCInst &Inst, uint16_t Insn,
                                 uint64_t Address, const void *Decoder) {
   unsigned imm = fieldFromInstruction16(Insn, 0, 7);
 
@@ -2352,30 +2407,32 @@
   Inst.addOperand(MCOperand::CreateReg(ARM::SP));
   Inst.addOperand(MCOperand::CreateImm(imm));
 
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbAddSPReg(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbAddSPReg(llvm::MCInst &Inst, uint16_t Insn,
                                 uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   if (Inst.getOpcode() == ARM::tADDrSP) {
     unsigned Rdm = fieldFromInstruction16(Insn, 0, 3);
     Rdm |= fieldFromInstruction16(Insn, 7, 1) << 3;
 
-    if (!DecodeGPRRegisterClass(Inst, Rdm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rdm, Address, Decoder));
     Inst.addOperand(MCOperand::CreateReg(ARM::SP));
-    if (!DecodeGPRRegisterClass(Inst, Rdm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rdm, Address, Decoder));
   } else if (Inst.getOpcode() == ARM::tADDspr) {
     unsigned Rm = fieldFromInstruction16(Insn, 3, 4);
 
     Inst.addOperand(MCOperand::CreateReg(ARM::SP));
     Inst.addOperand(MCOperand::CreateReg(ARM::SP));
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  return true;
+  return S;
 }
 
-static bool DecodeThumbCPS(llvm::MCInst &Inst, uint16_t Insn,
+static DecodeStatus DecodeThumbCPS(llvm::MCInst &Inst, uint16_t Insn,
                            uint64_t Address, const void *Decoder) {
   unsigned imod = fieldFromInstruction16(Insn, 4, 1) | 0x2;
   unsigned flags = fieldFromInstruction16(Insn, 0, 3);
@@ -2383,52 +2440,55 @@
   Inst.addOperand(MCOperand::CreateImm(imod));
   Inst.addOperand(MCOperand::CreateImm(flags));
 
-  return true;
+  return Success;
 }
 
-static bool DecodePostIdxReg(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodePostIdxReg(llvm::MCInst &Inst, unsigned Insn,
                              uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned add = fieldFromInstruction32(Insn, 4, 1);
 
-  if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder)) ;
   Inst.addOperand(MCOperand::CreateImm(add));
 
-  return true;
+  return S;
 }
 
-static bool DecodeThumbBLXOffset(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBLXOffset(llvm::MCInst &Inst, unsigned Val,
                                  uint64_t Address, const void *Decoder) {
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<22>(Val << 1)));
-  return true;
+  return Success;
 }
 
-static bool DecodeCoprocessor(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeCoprocessor(llvm::MCInst &Inst, unsigned Val,
                               uint64_t Address, const void *Decoder) {
   if (Val == 0xA || Val == 0xB)
-    return false;
+    return Fail;
 
   Inst.addOperand(MCOperand::CreateImm(Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbSRImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbSRImm(llvm::MCInst &Inst, unsigned Val,
                              uint64_t Address, const void *Decoder) {
   if (Val == 0)
     Inst.addOperand(MCOperand::CreateImm(32));
   else
     Inst.addOperand(MCOperand::CreateImm(Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumb2BCCInstruction(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeThumb2BCCInstruction(llvm::MCInst &Inst, unsigned Insn,
                                        uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned pred = fieldFromInstruction32(Insn, 22, 4);
   if (pred == 0xE || pred == 0xF) {
     unsigned opc = fieldFromInstruction32(Insn, 4, 2);
     switch (opc) {
       default:
-        return false;
+        return Fail;
       case 0:
         Inst.setOpcode(ARM::t2DSB);
         break;
@@ -2437,7 +2497,7 @@
         break;
       case 2:
         Inst.setOpcode(ARM::t2ISB);
-        return true;
+        return Success;
     }
 
     unsigned imm = fieldFromInstruction32(Insn, 0, 4);
@@ -2450,17 +2510,16 @@
   brtarget |= fieldFromInstruction32(Insn, 16, 6) << 12;
   brtarget |= fieldFromInstruction32(Insn, 26, 1) << 20;
 
-  if (!DecodeT2BROperand(Inst, brtarget, Address, Decoder) ||
-      !DecodePredicateOperand(Inst, pred, Address, Decoder))
-    return false;
+  CHECK(S, DecodeT2BROperand(Inst, brtarget, Address, Decoder));
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
 // Decode a shifted immediate operand.  These basically consist
 // of an 8-bit value, and a 4-bit directive that specifies either
 // a splat operation or a rotation.
-static bool DecodeT2SOImm(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeT2SOImm(llvm::MCInst &Inst, unsigned Val,
                           uint64_t Address, const void *Decoder) {
   unsigned ctrl = fieldFromInstruction32(Val, 10, 2);
   if (ctrl == 0) {
@@ -2488,26 +2547,26 @@
     Inst.addOperand(MCOperand::CreateImm(imm));
   }
 
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbBCCTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBCCTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                         uint64_t Address, const void *Decoder){
   Inst.addOperand(MCOperand::CreateImm(Val << 1));
-  return true;
+  return Success;
 }
 
-static bool DecodeThumbBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeThumbBLTargetOperand(llvm::MCInst &Inst, unsigned Val,
                                        uint64_t Address, const void *Decoder){
   Inst.addOperand(MCOperand::CreateImm(SignExtend32<22>(Val << 1)));
-  return true;
+  return Success;
 }
 
-static bool DecodeMemBarrierOption(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeMemBarrierOption(llvm::MCInst &Inst, unsigned Val,
                                    uint64_t Address, const void *Decoder) {
   switch (Val) {
   default:
-    return false;
+    return Fail;
   case 0xF: // SY
   case 0xE: // ST
   case 0xB: // ISH
@@ -2520,55 +2579,61 @@
   }
 
   Inst.addOperand(MCOperand::CreateImm(Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeMSRMask(llvm::MCInst &Inst, unsigned Val,
+static DecodeStatus DecodeMSRMask(llvm::MCInst &Inst, unsigned Val,
                           uint64_t Address, const void *Decoder) {
-  if (!Val) return false;
+  if (!Val) return Fail;
   Inst.addOperand(MCOperand::CreateImm(Val));
-  return true;
+  return Success;
 }
 
-static bool DecodeDoubleRegLoad(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeDoubleRegLoad(llvm::MCInst &Inst, unsigned Insn,
                                           uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
 
-  if ((Rt & 1) || Rt == 0xE || Rn == 0xF) return false;
+  if ((Rt & 1) || Rt == 0xE || Rn == 0xF) return Fail;
 
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeDoubleRegStore(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeDoubleRegStore(llvm::MCInst &Inst, unsigned Insn,
                                           uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
   unsigned Rt = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
 
-  if (!DecoderGPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecoderGPRRegisterClass(Inst, Rd, Address, Decoder));
 
-  if ((Rt & 1) || Rt == 0xE || Rn == 0xF) return false;
-  if (Rd == Rn || Rd == Rt || Rd == Rt+1) return false;
+  if ((Rt & 1) || Rt == 0xE || Rn == 0xF) return Fail;
+  if (Rd == Rn || Rd == Rt || Rd == Rt+1) return Fail;
 
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt+1, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeSTRPreImm(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSTRPreImm(llvm::MCInst &Inst, unsigned Insn,
                             uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
   unsigned imm = fieldFromInstruction32(Insn, 0, 12);
@@ -2576,18 +2641,20 @@
   imm |= fieldFromInstruction32(Insn, 23, 1) << 12;
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
 
-  if (Rn == 0xF || Rn == Rt) return false; // UNPREDICTABLE
+  if (Rn == 0xF || Rn == Rt) return Unpredictable; // UNPREDICTABLE
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
-  if (!DecodeAddrModeImm12Operand(Inst, imm, Address, Decoder)) return false;
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
+  CHECK(S, DecodeAddrModeImm12Operand(Inst, imm, Address, Decoder));
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeSTRPreReg(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeSTRPreReg(llvm::MCInst &Inst, unsigned Insn,
                             uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rt = fieldFromInstruction32(Insn, 12, 4);
   unsigned imm = fieldFromInstruction32(Insn, 0, 12);
@@ -2595,18 +2662,20 @@
   imm |= fieldFromInstruction32(Insn, 23, 1) << 12;
   unsigned pred = fieldFromInstruction32(Insn, 28, 4);
 
-  if (Rn == 0xF || Rn == Rt) return false; // UNPREDICTABLE
+  if (Rn == 0xF || Rn == Rt) return Unpredictable; // UNPREDICTABLE
 
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
-  if (!DecodeGPRRegisterClass(Inst, Rt, Address, Decoder)) return false;
-  if (!DecodeSORegMemOperand(Inst, imm, Address, Decoder)) return false;
-  if (!DecodePredicateOperand(Inst, pred, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rt, Address, Decoder));
+  CHECK(S, DecodeSORegMemOperand(Inst, imm, Address, Decoder));
+  CHECK(S, DecodePredicateOperand(Inst, pred, Address, Decoder));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVLD1LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD1LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2617,47 +2686,47 @@
   unsigned index = 0;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 5, 3);
       break;
     case 1:
       if (fieldFromInstruction32(Insn, 5, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 6, 2);
       if (fieldFromInstruction32(Insn, 4, 1))
         align = 2;
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 6, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 4, 2) != 0)
         align = 4;
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVST1LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST1LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2668,47 +2737,47 @@
   unsigned index = 0;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 5, 3);
       break;
     case 1:
       if (fieldFromInstruction32(Insn, 5, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 6, 2);
       if (fieldFromInstruction32(Insn, 4, 1))
         align = 2;
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 6, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 4, 2) != 0)
         align = 4;
   }
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeVLD2LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD2LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2720,7 +2789,7 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       index = fieldFromInstruction32(Insn, 5, 3);
       if (fieldFromInstruction32(Insn, 4, 1))
@@ -2735,7 +2804,7 @@
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 5, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 4, 1) != 0)
         align = 8;
@@ -2744,28 +2813,28 @@
       break;
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVST2LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST2LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2777,7 +2846,7 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       index = fieldFromInstruction32(Insn, 5, 3);
       if (fieldFromInstruction32(Insn, 4, 1))
@@ -2792,7 +2861,7 @@
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 5, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 4, 1) != 0)
         align = 8;
@@ -2802,26 +2871,26 @@
   }
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeVLD3LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD3LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2833,53 +2902,53 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 5, 3);
       break;
     case 1:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 6, 2);
       if (fieldFromInstruction32(Insn, 5, 1))
         inc = 2;
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 4, 2))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 6, 1))
         inc = 2;
       break;
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVST3LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST3LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2891,22 +2960,22 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 5, 3);
       break;
     case 1:
       if (fieldFromInstruction32(Insn, 4, 1))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 6, 2);
       if (fieldFromInstruction32(Insn, 5, 1))
         inc = 2;
       break;
     case 2:
       if (fieldFromInstruction32(Insn, 4, 2))
-        return false; // UNDEFINED
+        return Fail; // UNDEFINED
       index = fieldFromInstruction32(Insn, 7, 1);
       if (fieldFromInstruction32(Insn, 6, 1))
         inc = 2;
@@ -2914,27 +2983,27 @@
   }
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
 
-static bool DecodeVLD4LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVLD4LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -2946,7 +3015,7 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
         align = 4;
@@ -2968,33 +3037,33 @@
       break;
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder));
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }
 
-static bool DecodeVST4LN(llvm::MCInst &Inst, unsigned Insn,
+static DecodeStatus DecodeVST4LN(llvm::MCInst &Inst, unsigned Insn,
                          uint64_t Address, const void *Decoder) {
+  DecodeStatus S = Success;
+
   unsigned Rn = fieldFromInstruction32(Insn, 16, 4);
   unsigned Rm = fieldFromInstruction32(Insn, 0, 4);
   unsigned Rd = fieldFromInstruction32(Insn, 12, 4);
@@ -3006,7 +3075,7 @@
   unsigned inc = 1;
   switch (size) {
     default:
-      return false;
+      return Fail;
     case 0:
       if (fieldFromInstruction32(Insn, 4, 1))
         align = 4;
@@ -3029,22 +3098,20 @@
   }
 
   if (Rm != 0xF) { // Writeback
-    if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   }
-  if (!DecodeGPRRegisterClass(Inst, Rn, Address, Decoder)) return false;
+  CHECK(S, DecodeGPRRegisterClass(Inst, Rn, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(align));
   if (Rm != 0xF && Rm != 0xD) {
-    if (!DecodeGPRRegisterClass(Inst, Rm, Address, Decoder))
-      return false;
+    CHECK(S, DecodeGPRRegisterClass(Inst, Rm, Address, Decoder));
   }
 
-  if (!DecodeDPRRegisterClass(Inst, Rd, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder)) return false;
-  if (!DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder)) return false;
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+2*inc, Address, Decoder));
+  CHECK(S, DecodeDPRRegisterClass(Inst, Rd+3*inc, Address, Decoder));
   Inst.addOperand(MCOperand::CreateImm(index));
 
-  return true;
+  return S;
 }