Index: ELF/Target.cpp
===================================================================
--- ELF/Target.cpp
+++ ELF/Target.cpp
@@ -566,7 +566,7 @@
     relocateOne(Loc, BufEnd, R_386_TLS_LE, P, SA);
     return 0;
   }
-  llvm_unreachable("Unknown TLS optimization");
+  fatal("Unknown TLS optimization for relocation: " + Twine(Type));
 }
 
 // "Ulrich Drepper, ELF Handling For Thread-Local Storage" (5.1
@@ -911,7 +911,7 @@
     // The next relocation should be against __tls_get_addr, so skip it
     return 1;
   }
-  llvm_unreachable("Unknown TLS optimization");
+  fatal("Unknown TLS optimization for relocation: " + Twine(Type));
 }
 
 void X86_64TargetInfo::relocateOne(uint8_t *Loc, uint8_t *BufEnd, uint32_t Type,
@@ -1467,7 +1467,7 @@
   case R_AARCH64_TLSDESC_ADD_LO12_NC:
   case R_AARCH64_TLSDESC_CALL: {
     if (canBePreempted(S))
-      fatal("Unsupported TLS optimization");
+      fatal("Unsupported TLS optimization for relocation: " + Twine(Type));
     uint64_t X = S ? S->getVA<ELF64LE>() : SA;
     relocateTlsGdToLe(Type, Loc, BufEnd, P, X);
     return 0;
@@ -1477,7 +1477,7 @@
     relocateTlsIeToLe(Type, Loc, BufEnd, P, S->getVA<ELF64LE>());
     return 0;
   }
-  llvm_unreachable("Unknown TLS optimization");
+  fatal("Unknown TLS optimization for relocation: " + Twine(Type));
 }
 
 // Global-Dynamic relocations can be relaxed to Local-Exec if both binary is