[GlobalISel][X86] fix compilation error ( -Werror=unused-function )

llvm-svn: 305786
diff --git a/llvm/lib/Target/X86/X86InstructionSelector.cpp b/llvm/lib/Target/X86/X86InstructionSelector.cpp
index cfc26cc..3dd2f86 100644
--- a/llvm/lib/Target/X86/X86InstructionSelector.cpp
+++ b/llvm/lib/Target/X86/X86InstructionSelector.cpp
@@ -567,8 +567,8 @@
     else
       return false;
 
-    const RegisterBank &RegBank = *RBI.getRegBank(DstReg, MRI, TRI);
-    unsigned DefReg = MRI.createVirtualRegister(getRegClass(DstTy, RegBank));
+    unsigned DefReg =
+        MRI.createVirtualRegister(getRegClass(DstTy, DstReg, MRI));
 
     BuildMI(*I.getParent(), I, I.getDebugLoc(),
             TII.get(TargetOpcode::SUBREG_TO_REG), DefReg)