Index: lib/CodeGen/TargetInfo.cpp
===================================================================
--- lib/CodeGen/TargetInfo.cpp	(revision 182601)
+++ lib/CodeGen/TargetInfo.cpp	(working copy)
@@ -1274,8 +1274,16 @@
   void getDependentLibraryOption(llvm::StringRef Lib,
                                  llvm::SmallString<24> &Opt) const {
     Opt = "/DEFAULTLIB:";
-    Opt += Lib;
+
+    // If the argument does not end in .lib, automatically add the suffix. This
+    // matches the behavior of MSVC.
+    std::string ArgStr = Lib;
+    if (Lib.size() <= 4 || 
+        Lib.substr(Lib.size() - 4).compare_lower(".lib") != 0) {
+      ArgStr += ".lib";
   }
+    Opt += ArgStr;
+  }
 };
 
 class WinX86_64TargetCodeGenInfo : public TargetCodeGenInfo {
@@ -1300,8 +1308,16 @@
   void getDependentLibraryOption(llvm::StringRef Lib,
                                  llvm::SmallString<24> &Opt) const {
     Opt = "/DEFAULTLIB:";
-    Opt += Lib;
+
+    // If the argument does not end in .lib, automatically add the suffix. This
+    // matches the behavior of MSVC.
+    std::string ArgStr = Lib;
+    if (Lib.size() <= 4 || 
+        Lib.substr(Lib.size() - 4).compare_lower(".lib") != 0) {
+      ArgStr += ".lib";
   }
+    Opt += ArgStr;
+  }
 };
 
 }
Index: lib/Sema/SemaAttr.cpp
===================================================================
--- lib/Sema/SemaAttr.cpp	(revision 182601)
+++ lib/Sema/SemaAttr.cpp	(working copy)
@@ -272,10 +272,9 @@
   case PCK_Linker:
     Consumer.HandleLinkerOptionPragma(Arg);
     return;
-  case PCK_Lib: {
+  case PCK_Lib:
     Consumer.HandleDependentLibrary(Arg);
     return;
-  }
   case PCK_Compiler:
   case PCK_ExeStr:
   case PCK_User:
Index: test/CodeGen/pragma-comment.c
===================================================================
--- test/CodeGen/pragma-comment.c	(revision 182601)
+++ test/CodeGen/pragma-comment.c	(working copy)
@@ -3,15 +3,21 @@
 // RUN: %clang_cc1 %s -triple i686-pc-linux -fms-extensions -emit-llvm -o - | FileCheck -check-prefix LINUX %s
 
 #pragma comment(lib, "msvcrt.lib")
+#pragma comment(lib, "kernel32")
+#pragma comment(lib, "USER32.LIB")
 
 #define BAR "2"
 #pragma comment(linker," /bar=" BAR)
 
 // CHECK: !llvm.module.flags = !{!0}
 // CHECK: !0 = metadata !{i32 6, metadata !"Linker Options", metadata ![[link_opts:[0-9]+]]}
-// CHECK: ![[link_opts]] = metadata !{metadata ![[msvcrt:[0-9]+]], metadata ![[bar:[0-9]+]]}
+// CHECK: ![[link_opts]] = metadata !{metadata ![[msvcrt:[0-9]+]], metadata ![[kernel32:[0-9]+]], metadata ![[USER32:[0-9]+]], metadata ![[bar:[0-9]+]]}
 // CHECK: ![[msvcrt]] = metadata !{metadata !"/DEFAULTLIB:msvcrt.lib"}
+// CHECK: ![[kernel32]] = metadata !{metadata !"/DEFAULTLIB:kernel32.lib"}
+// CHECK: ![[USER32]] = metadata !{metadata !"/DEFAULTLIB:USER32.LIB"}
 // CHECK: ![[bar]] = metadata !{metadata !" /bar=2"}
 
 // LINUX: metadata !{metadata !"-lmsvcrt.lib"}
+// LINUX: metadata !{metadata !"-lkernel32"}
+// LINUX: metadata !{metadata !"-lUSER32.LIB"}
 // LINUX: metadata !{metadata !" /bar=2"}
Index: test/Modules/autolink.m
===================================================================
--- test/Modules/autolink.m	(revision 182601)
+++ test/Modules/autolink.m	(working copy)
@@ -35,7 +35,7 @@
 // CHECK: !4 = metadata !{i32 6, metadata !"Linker Options", metadata ![[AUTOLINK_OPTIONS:[0-9]+]]}
 // CHECK: ![[AUTOLINK_OPTIONS]] = metadata !{metadata ![[AUTOLINK_FRAMEWORK:[0-9]+]], metadata ![[AUTOLINK:[0-9]+]], metadata ![[DEPENDSONMODULE:[0-9]+]], metadata ![[MODULE:[0-9]+]], metadata ![[NOUMBRELLA:[0-9]+]]}
 // CHECK: ![[AUTOLINK_FRAMEWORK]] = metadata !{metadata !"-framework", metadata !"autolink_framework"}
-// CHECK: ![[AUTOLINK]] = metadata !{metadata !"{{(-l|/DEFAULTLIB:)}}autolink"}
+// CHECK: ![[AUTOLINK]] = metadata !{metadata !"{{(-l|/DEFAULTLIB:)}}autolink.lib"}
 // CHECK: ![[DEPENDSONMODULE]] = metadata !{metadata !"-framework", metadata !"DependsOnModule"}
 // CHECK: ![[MODULE]] = metadata !{metadata !"-framework", metadata !"Module"}
 // CHECK: ![[NOUMBRELLA]] = metadata !{metadata !"-framework", metadata !"NoUmbrella"}