[ARC] Prevent InstPrinter from crashing on unknown condition codes.

[tatyana-krasnukha]

Summary

Instruction printer shouldn't crash with assertions due to incorrect input data. llvm_unreachable is not intended for runtime error handling.

[petecoup]

Thanks, can you add a test to make sure the disassembler doesn't crash in this case?

[tatyana-krasnukha]

Added a test for bcc instruction with unknown condition code.

[petecoup]

Great, thanks for doing this!

lib/Target/ARC/InstPrinter/ARCInstPrinter.cpp

 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;

 
 #include "ARCGenAsmWriter.inc"
 
+template <class T>
+static const char *BadConditionCode(T cc) {
+  DEBUG(dbgs() << "Unknown condition code passed: " << cc << "\n");
+  return "{unknown-cc}";
+}
+
 static const char *ARCBRCondCodeToString(ARCCC::BRCondCode BRCC) {
   switch (BRCC) {
   case ARCCC::BREQ:

   case ARCCC::BRHS:
     return "hs";
   }
-  llvm_unreachable("Unhandled ARCCC::BRCondCode");
+  return BadConditionCode(BRCC);
 }
 
 static const char *ARCCondCodeToString(ARCCC::CondCode CC) {

   case ARCCC::Z:
     return "z";
   }
-  llvm_unreachable("Unhandled ARCCC::CondCode");
+  return BadConditionCode(CC);
 }
 
 void ARCInstPrinter::printRegName(raw_ostream &OS, unsigned RegNo) const {