Index: llvm/include/llvm/MC/MCContext.h
===================================================================
--- llvm/include/llvm/MC/MCContext.h
+++ llvm/include/llvm/MC/MCContext.h
@@ -645,6 +645,8 @@
 
     void deallocate(void *Ptr) {}
 
+    void reportWarning(SMLoc L, const Twine &Msg);
+
     bool hadError() { return HadError; }
     void reportError(SMLoc L, const Twine &Msg);
     // Unrecoverable error has occurred. Display the best diagnostic we can
Index: llvm/lib/MC/MCContext.cpp
===================================================================
--- llvm/lib/MC/MCContext.cpp
+++ llvm/lib/MC/MCContext.cpp
@@ -606,6 +606,19 @@
 }
 
 //===----------------------------------------------------------------------===//
+// Warning Reporting
+//===----------------------------------------------------------------------===//
+
+void MCContext::reportWarning(SMLoc Loc, const Twine &Msg) {
+  // If we have a source manager use it. Otherwise, try using the inline source
+  // manager.
+  if (SrcMgr)
+    SrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
+  else if (InlineSrcMgr)
+    InlineSrcMgr->PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
+}
+
+//===----------------------------------------------------------------------===//
 // Error Reporting
 //===----------------------------------------------------------------------===//
 
Index: llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
===================================================================
--- llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
+++ llvm/lib/Target/Mips/MCTargetDesc/MipsMCCodeEmitter.cpp
@@ -585,6 +585,8 @@
   return 0;
 }
 
+static bool isBinary = false;
+
 unsigned MipsMCCodeEmitter::
 getExprOpValue(const MCExpr *Expr, SmallVectorImpl<MCFixup> &Fixups,
                const MCSubtargetInfo &STI) const {
@@ -599,6 +601,7 @@
   }
 
   if (Kind == MCExpr::Binary) {
+    isBinary = true;
     unsigned Res = getExprOpValue(cast<MCBinaryExpr>(Expr)->getLHS(), Fixups, STI);
     Res += getExprOpValue(cast<MCBinaryExpr>(Expr)->getRHS(), Fixups, STI);
     return Res;
@@ -722,6 +725,7 @@
   }
 
   if (Kind == MCExpr::SymbolRef) {
+    Ctx.reportWarning(Expr->getLoc(), "should use explicit constraints!");
     Mips::Fixups FixupKind = Mips::Fixups(0);
 
     switch(cast<MCSymbolRefExpr>(Expr)->getKind()) {
@@ -732,7 +736,12 @@
       break;
     } // switch
 
-    Fixups.push_back(MCFixup::create(0, Expr, MCFixupKind(FixupKind)));
+    if (!STI.getFeatureBits()[Mips::FeatureMips64])
+      Fixups.push_back(MCFixup::create(0, Expr, MCFixupKind(FixupKind)));
+    else {
+      if (isBinary)
+        Fixups.push_back(MCFixup::create(0, Expr, MCFixupKind(Mips::fixup_MIPS_PCLO16)));
+    }
     return 0;
   }
   return 0;
@@ -756,6 +765,7 @@
   }
   // MO must be an Expr.
   assert(MO.isExpr());
+  isBinary = false;
   return getExprOpValue(MO.getExpr(),Fixups, STI);
 }
 
Index: llvm/test/MC/Mips/reloc-directive-bad-n64.s
===================================================================
--- /dev/null
+++ llvm/test/MC/Mips/reloc-directive-bad-n64.s
@@ -0,0 +1,10 @@
+# RUN: llvm-mc -triple mips64el-unknown-linux < %s -show-encoding \
+# RUN:     -target-abi=n64 2>&1 | FileCheck %s
+	.text
+       .global main
+main:
+       nop
+       daddiu $t9, $ra, main - .    # CHECK: :[[@LINE]]:25: warning: should use explicit constraints!
+       daddiu $t9, $ra, main        # CHECK: :[[@LINE]]:25: warning: should use explicit constraints!
+       nop
+       .word main