DavidKreitzer added a comment. LGTM ================ Comment at: lib/Target/X86/X86InstrInfo.cpp:5310 @@ +5309,3 @@ + + if (Subtarget.is64Bit()) { + assert(MIB->getOpcode() == X86::MOV64ImmSExti8 || ---------------- Much better, thanks! http://reviews.llvm.org/D15549