2 files changed, 29 insertions, 0 deletions
diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.h b/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.h
index 41e2a6049d8..a7ba14141c0 100644
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.h
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassemblerCore.h
@@ -139,6 +139,31 @@ static inline void setSlice(unsigned &Bits, unsigned From, unsigned To,
   Bits |= (Val & Mask) << To;
 }
 
+// Return an integer result equal to the number of bits of x that are ones.
+static inline uint32_t
+BitCount (uint64_t x)
+{
+    // c accumulates the total bits set in x
+    uint32_t c;
+    for (c = 0; x; ++c)
+    {
+        x &= x - 1; // clear the least significant bit set
+    }
+    return c;
+}
+
+static inline bool
+BitIsSet (const uint64_t value, const uint64_t bit)
+{
+    return (value & (1ull << bit)) != 0;
+}
+
+static inline bool
+BitIsClear (const uint64_t value, const uint64_t bit)
+{
+    return (value & (1ull << bit)) == 0;
+}
+
 /// Various utilities for checking the target specific flags.
 
 /// A unary data processing instruction doesn't have an Rn operand.
diff --git a/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h b/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
index 480f8bb2bd7..b1a389abfd8 100644
--- a/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
+++ b/llvm/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
@@ -901,6 +901,10 @@ static bool DisassembleThumb1LdStMul(bool Ld, MCInst &MI, unsigned Opcode,
   }
 
   unsigned RegListBits = slice(insn, 7, 0);
+  if (BitCount(RegListBits) < 1) {
+    DEBUG(errs() << "if BitCount(registers) < 1 then UNPREDICTABLE\n");
+    return false;
+  }
 
   // Fill the variadic part of reglist.
   for (unsigned i = 0; i < 8; ++i)