1 files changed, 13 insertions, 7 deletions
diff --git a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
index f00142de50..65c8c1a561 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -9,21 +9,21 @@
 
 #define DEBUG_TYPE "arm-disassembler"
 
+#include "llvm/MC/MCDisassembler.h"
 #include "MCTargetDesc/ARMAddressingModes.h"
-#include "MCTargetDesc/ARMMCExpr.h"
 #include "MCTargetDesc/ARMBaseInfo.h"
+#include "MCTargetDesc/ARMMCExpr.h"
 #include "llvm/MC/EDInstInfo.h"
-#include "llvm/MC/MCInst.h"
-#include "llvm/MC/MCInstrDesc.h"
-#include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCContext.h"
-#include "llvm/MC/MCDisassembler.h"
+#include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCFixedLenDisassembler.h"
+#include "llvm/MC/MCInst.h"
+#include "llvm/MC/MCInstrDesc.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/Support/Debug.h"
-#include "llvm/Support/MemoryObject.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/LEB128.h"
+#include "llvm/Support/MemoryObject.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/raw_ostream.h"
 #include <vector>
@@ -1281,7 +1281,13 @@ static DecodeStatus DecodeBitfieldMaskOperand(MCInst &Inst, unsigned Val,
   unsigned lsb = fieldFromInstruction(Val, 0, 5);
 
   DecodeStatus S = MCDisassembler::Success;
-  if (lsb > msb) Check(S, MCDisassembler::SoftFail);
+  if (lsb > msb) {
+    Check(S, MCDisassembler::SoftFail);
+    // The check above will cause the warning for the "potentially undefined
+    // instruction encoding" but we can't build a bad MCOperand value here
+    // with a lsb > msb or else printing the MCInst will cause a crash.
+    lsb = msb;
+  }
 
   uint32_t msb_mask = 0xFFFFFFFF;
   if (msb != 31) msb_mask = (1U << (msb+1)) - 1;