[ARM] Diagnose ARM MOVT without :lower16: or :upper16: expression

[olista01]

Summary

This instruction was missing from the list of opcodes that we check, so we were hitting an llvm_unreachable in ARMMCCodeEmitter.cpp for the ARM MOVT instruction, rather than the diagnostic that is emitted for the other MOVW/MOVT instructions.

[rengolin]

Good catch! LGTM. Thanks!

lib/Target/ARM/AsmParser/ARMAsmParser.cpp

bool ARMAsmParser::validateInstruction(MCInst &Inst,
   }
   case ARM::tCBZ:
   case ARM::tCBNZ: {
     if (!static_cast<ARMOperand &>(*Operands[2]).isUnsignedOffset<6, 1>())
       return Error(Operands[2]->getStartLoc(), "branch target out of range");
     break;
   }
   case ARM::MOVi16:
+  case ARM::MOVTi16:
   case ARM::t2MOVi16:
   case ARM::t2MOVTi16:
     {
     // We want to avoid misleadingly allowing something like "mov r0, <symbol>"
     // especially when we turn it into a movw and the expression <symbol> does
     // not have a :lower16: or :upper16 as part of the expression.  We don't
     // want the behavior of silently truncating, which can be unexpected and
     // lead to bugs that are difficult to find since this is an easy mistake

test/MC/ARM/diagnostics.s

@ CHECK-ERRORS-V7: error: instruction requires: FPARMv8
         stm sp!, {r0, pc}^
         ldm sp!, {r0}^
 @ CHECK-ERRORS: error: system STM cannot have writeback register
 @ CHECK-ERRORS: error: writeback register only allowed on system LDM if PC in register-list
 
 foo2:
         mov r0, foo2
         movw r0, foo2
+        movt r0, foo2
+@ CHECK-ERRORS: error: immediate expression for mov requires :lower16: or :upper16
+@ CHECK-ERRORS:                 ^
 @ CHECK-ERRORS: error: immediate expression for mov requires :lower16: or :upper16
-@ CHECK-ERRORS:                 ^
+@ CHECK-ERRORS:                  ^
 @ CHECK-ERRORS: error: immediate expression for mov requires :lower16: or :upper16
 @ CHECK-ERRORS:                  ^
 
         str r0, [r0, #4]!
         str r0, [r0, r1]!
         str r0, [r0], #4
         str r0, [r0], r1
         strh r0, [r0, #2]!