Index: llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
===================================================================
--- llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -523,6 +523,7 @@
     Match_RequiresV6,
     Match_RequiresThumb2,
     Match_RequiresV8,
+    Match_RequiresFlagSetting,
 #define GET_OPERAND_DIAGNOSTIC_TYPES
 #include "ARMGenAsmMatcher.inc"
 
@@ -8905,7 +8906,7 @@
       ;
     // If we're parsing Thumb1, reject it completely.
     if (isThumbOne() && Inst.getOperand(OpNo).getReg() != ARM::CPSR)
-      return Match_MnemonicFail;
+      return Match_RequiresFlagSetting;
     // If we're parsing Thumb2, which form is legal depends on whether we're
     // in an IT block.
     if (isThumbTwo() && Inst.getOperand(OpNo).getReg() != ARM::CPSR &&
@@ -9171,6 +9172,8 @@
     return Error(IDLoc, "instruction variant requires Thumb2");
   case Match_RequiresV8:
     return Error(IDLoc, "instruction variant requires ARMv8 or later");
+  case Match_RequiresFlagSetting:
+    return Error(IDLoc, "no flag-preserving variant of this instruction available");
   case Match_ImmRange0_15: {
     SMLoc ErrorLoc = ((ARMOperand &)*Operands[ErrorInfo]).getStartLoc();
     if (ErrorLoc == SMLoc()) ErrorLoc = IDLoc;
Index: llvm/trunk/test/MC/ARM/thumb-diagnostics.s
===================================================================
--- llvm/trunk/test/MC/ARM/thumb-diagnostics.s
+++ llvm/trunk/test/MC/ARM/thumb-diagnostics.s
@@ -11,7 +11,7 @@
 
 @ ADD instruction w/o 'S' suffix.
         add r1, r2, r3
-@ CHECK-ERRORS: error: invalid instruction
+@ CHECK-ERRORS: error: no flag-preserving variant of this instruction available
 @ CHECK-ERRORS:         add r1, r2, r3
 @ CHECK-ERRORS:         ^