diff --git a/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp b/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
index 2bfdcca98d1..e02e2c3506d 100644
--- a/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
+++ b/lib/Target/ARM/AsmPrinter/ARMAsmPrinter.cpp
@@ -637,7 +637,7 @@ void
 ARMAsmPrinter::printBitfieldInvMaskImmOperand(const MachineInstr *MI, int Op) {
   const MachineOperand &MO = MI->getOperand(Op);
   uint32_t v = ~MO.getImm();
-  int32_t lsb = ffs (v) - 1;
+  int32_t lsb = CountTrailingZeros_32(v);
   int32_t width = (32 - CountLeadingZeros_32 (v)) - lsb;
   assert(MO.isImm() && "Not a valid bf_inv_mask_imm value!");
   O << "#" << lsb << ", #" << width;