Turn few asserts into errors / unreachable's

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76313 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/SystemZ/AsmPrinter/SystemZAsmPrinter.cpp b/lib/Target/SystemZ/AsmPrinter/SystemZAsmPrinter.cpp
index 24f4114..07c8ed0 100644
--- a/lib/Target/SystemZ/AsmPrinter/SystemZAsmPrinter.cpp
+++ b/lib/Target/SystemZ/AsmPrinter/SystemZAsmPrinter.cpp
@@ -183,7 +183,7 @@
   if (printInstruction(MI))
     return;
 
-  assert(0 && "Should not happen");
+  llvm_unreachable("Unreachable!");
 }
 
 void SystemZAsmPrinter::printPCRelImmOperand(const MachineInstr *MI, int OpNum) {
@@ -282,7 +282,7 @@
 
   switch (MO.getTargetFlags()) {
   default:
-    assert(0 && "Unknown target flag on GV operand");
+    llvm_unreachable("Unknown target flag on GV operand");
   case SystemZII::MO_NO_FLAG:
     break;
   case SystemZII::MO_GOTENT:    O << "@GOTENT";    break;