Index: lib/Target/Mips/AsmParser/MipsAsmParser.cpp
===================================================================
--- lib/Target/Mips/AsmParser/MipsAsmParser.cpp
+++ lib/Target/Mips/AsmParser/MipsAsmParser.cpp
@@ -423,8 +423,8 @@
   // TODO: see how can we get this info.
   bool abiUsesSoftFloat() const { return false; }
 
-  /// Warn if RegNo is the current assembler temporary.
-  void warnIfAssemblerTemporary(int RegNo, SMLoc Loc);
+  /// Warn if RegNo is the same as the current AT.
+  void warnIfRegIsAT(unsigned RegNo, SMLoc Loc);
 };
 }
 
@@ -533,7 +533,7 @@
   /// target.
   unsigned getGPR32Reg() const {
     assert(isRegIdx() && (RegIdx.Kind & RegKind_GPR) && "Invalid access!");
-    AsmParser.warnIfAssemblerTemporary(RegIdx.Index, StartLoc);
+    AsmParser.warnIfRegIsAT(RegIdx.Index, StartLoc);
     unsigned ClassID = Mips::GPR32RegClassID;
     return RegIdx.RegInfo->getRegClass(ClassID).getRegister(RegIdx.Index);
   }
@@ -2194,15 +2194,10 @@
   llvm_unreachable("Implement any new match types added!");
 }
 
-void MipsAsmParser::warnIfAssemblerTemporary(int RegIndex, SMLoc Loc) {
-  if ((RegIndex != 0) && 
-      ((int)AssemblerOptions.back()->getATRegNum() == RegIndex)) {
-    if (RegIndex == 1)
-      Warning(Loc, "used $at without \".set noat\"");
-    else
-      Warning(Loc, Twine("used $") + Twine(RegIndex) + " with \".set at=$" +
-                       Twine(RegIndex) + "\"");
-  }
+void MipsAsmParser::warnIfRegIsAT(unsigned RegNo, SMLoc Loc) {
+  if (RegNo != 0 && AssemblerOptions.back()->getATRegNum() == RegNo)
+    Warning(Loc,
+            "used $at (aka $" + Twine(RegNo) + ") without \".set noat\"");
 }
 
 void
Index: test/MC/Mips/set-at-directive-explicit-at.s
===================================================================
--- test/MC/Mips/set-at-directive-explicit-at.s
+++ test/MC/Mips/set-at-directive-explicit-at.s
@@ -1,31 +1,33 @@
 # RUN: llvm-mc %s -triple=mipsel-unknown-linux -show-encoding -mcpu=mips32r2 \
 # RUN:     2>%t1 | FileCheck %s
 # RUN: FileCheck -check-prefix=WARNINGS %s < %t1
-# Check that the assembler can handle the documented syntax
-# for ".set at" and set the correct value. The correct value for $at is always
-# $1 when written by the user.
+
+# Check that the assembler can handle the documented syntax for ".set at" and
+# will set the correct value for $at.
+# Note that writing $at is always the same as writing $1.
+
     .text
 foo:
 # CHECK:   jr    $1                      # encoding: [0x08,0x00,0x20,0x00]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $at without ".set noat"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $1) without ".set noat"
     .set    at=$1
     jr    $at
 
 # CHECK:   jr    $1                      # encoding: [0x08,0x00,0x20,0x00]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $at without ".set noat"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $1) without ".set noat"
     .set    at=$1
     jr    $1
 
 # CHECK:   jr    $1                      # encoding: [0x08,0x00,0x20,0x00]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $at without ".set noat"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $1) without ".set noat"
     .set    at=$at
     jr    $at
 
 # CHECK:   jr    $1                      # encoding: [0x08,0x00,0x20,0x00]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $at without ".set noat"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $1) without ".set noat"
     .set    at=$at
     jr    $1
-# WARNINGS-NOT: warning: used $at without ".set noat"
+# WARNINGS-NOT: warning: used $at (aka $1) without ".set noat"
 
 # CHECK:   jr    $1                      # encoding: [0x08,0x00,0x20,0x00]
     .set    at=$2
@@ -41,12 +43,12 @@
     jr    $at
 
 # CHECK:   jr    $16                     # encoding: [0x08,0x00,0x00,0x02]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $16 with ".set at=$16"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $16) without ".set noat"
     .set    at=$16
     jr    $s0
 
 # CHECK:   jr    $16                     # encoding: [0x08,0x00,0x00,0x02]
-# WARNINGS: :[[@LINE+2]]:11: warning: used $16 with ".set at=$16"
+# WARNINGS: :[[@LINE+2]]:11: warning: used $at (aka $16) without ".set noat"
     .set    at=$16
     jr    $16
 # WARNINGS-NOT: warning