perfScoreUnhandledInstruction will now assert in a DEBUG or CHECKED b…

…uild when it encounters an unhanded instruction

src/coreclr/src/jit/emit.cpp

@@ -1146,18 +1146,17 @@ float emitter::insEvaluateExecutionCost(instrDesc* id)
 //              if we return these are updated with default values
 //
 // Notes:
-//     When validating that the PerfScore handles every instruction.
-//     the #if 0 block is changed into a #ifdef DEBUG
-//     We will print the instruction and instruction group
+//     We print the instruction and instruction group
 //     and instead of returning we will assert
 //
-//     Otherwise we will return default latencies of 1 cycle.
+//     This method asserts with a debug/checked build
+//     and returns default latencies of 1 cycle otherwise.
 //
 void emitter::perfScoreUnhandledInstruction(instrDesc* id, insExecutionCharacteristics* pResult)
 {
-// Change this to #ifdef DEBUG to assert on any unhandled instructions
-#if 0
-    printf("PerfScore: unhandled instruction: %s, format %s", codeGen->genInsName(id->idIns()), emitIfName(id->idInsFmt()));
+#ifdef DEBUG
+    printf("PerfScore: unhandled instruction: %s, format %s", codeGen->genInsName(id->idIns()),
+           emitIfName(id->idInsFmt()));
     assert(!"PerfScore: unhandled instruction");
 #endif
     pResult->insThroughput = PERFSCORE_THROUGHPUT_1C;