diff --git a/include/clang/Basic/LangOptions.def b/include/clang/Basic/LangOptions.def
index 03882f8cdb099f19b80a909c3eb76b3f5eabe177..5cf40ec578f7796c3e6acd8f56a5b71c3c6e6253 100644
--- a/include/clang/Basic/LangOptions.def
+++ b/include/clang/Basic/LangOptions.def
@@ -150,6 +150,8 @@ BENIGN_LANGOPT(NumLargeByValueCopy, 32, 0,
 VALUE_LANGOPT(MSCVersion, 32, 0, 
               "version of Microsoft Visual C/C++")
 
+LANGOPT(ApplePragmaPack, 1, 0, "Apple gcc-compatible #pragma pack handling")
+
 #undef LANGOPT
 #undef VALUE_LANGOPT
 #undef BENIGN_LANGOPT
diff --git a/include/clang/Driver/CC1Options.td b/include/clang/Driver/CC1Options.td
index 1a6008e7797f11ccc5cbfb130bee087edc341066..bfcdc935e800d6f8e08f9704e88f4647c88e91d1 100644
--- a/include/clang/Driver/CC1Options.td
+++ b/include/clang/Driver/CC1Options.td
@@ -608,6 +608,8 @@ def fdeprecated_macro : Flag<"-fdeprecated-macro">,
   HelpText<"Defines the __DEPRECATED macro">;
 def fno_deprecated_macro : Flag<"-fno-deprecated-macro">,
   HelpText<"Undefines the __DEPRECATED macro">;
+def fapple_pragma_pack : Flag<"-fapple-pragma-pack">,
+  HelpText<"Enable Apple gcc-compatible #pragma pack handling">;
 
 //===----------------------------------------------------------------------===//
 // Header Search Options
diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index fea6e4fd45f4c5e98c06ab17348f5ad7f03bc5af..40a814ee75b55e08fb60505253cbd1880b66e0f2 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -261,6 +261,7 @@ def fno_PIE : Flag<"-fno-PIE">, Group<f_Group>, Flags<[NoArgumentUnused]>;
 def faccess_control : Flag<"-faccess-control">, Group<f_Group>;
 def fallow_unsupported : Flag<"-fallow-unsupported">, Group<f_Group>;
 def fapple_kext : Flag<"-fapple-kext">, Group<f_Group>;
+def fapple_pragma_pack : Flag<"-fapple-pragma-pack">, Group<f_Group>;
 def fasm : Flag<"-fasm">, Group<f_Group>;
 
 def fasm_blocks : Flag<"-fasm-blocks">, Group<f_Group>;
@@ -355,6 +356,7 @@ def fmudflap : Flag<"-fmudflap">, Group<f_Group>;
 def fnested_functions : Flag<"-fnested-functions">, Group<f_Group>;
 def fnext_runtime : Flag<"-fnext-runtime">, Group<f_Group>;
 def fno_access_control : Flag<"-fno-access-control">, Group<f_Group>;
+def fno_apple_pragma_pack : Flag<"-fno-apple-pragma-pack">, Group<f_Group>;
 def fno_asm : Flag<"-fno-asm">, Group<f_Group>;
 def fno_asynchronous_unwind_tables : Flag<"-fno-asynchronous-unwind-tables">, Group<f_Group>;
 def fno_assume_sane_operator_new : Flag<"-fno-assume-sane-operator-new">, Group<f_Group>;
diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index 4db6d007fcf5681470500725caa151d8d4efbacc..1a8c2e834cf9d3b0c077596ba4ad6a546e2fb307 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -2171,6 +2171,10 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       D.Diag(diag::warn_drv_clang_unsupported) << A->getAsString(Args);
   }
 
+  if (Args.hasFlag(options::OPT_fapple_pragma_pack,
+                   options::OPT_fno_apple_pragma_pack, false))
+    CmdArgs.push_back("-fapple-pragma-pack");
+
   // Default to -fno-builtin-str{cat,cpy} on Darwin for ARM.
   //
   // FIXME: This is disabled until clang -cc1 supports -fno-builtin-foo. PR4941.
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index 79e087e9430b69b7201c52a040c0c8c8611d9828..34ad608475867a56eb23f2b0bc8745b057790f97 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -777,6 +777,8 @@ static void LangOptsToArgs(const LangOptions &Opts,
     Res.push_back("-fdelayed-template-parsing");
   if (Opts.Deprecated)
     Res.push_back("-fdeprecated-macro");
+  if (Opts.ApplePragmaPack)
+    Res.push_back("-fapple-pragma-pack");
 }
 
 static void PreprocessorOptsToArgs(const PreprocessorOptions &Opts,
@@ -1763,6 +1765,7 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   Opts.FakeAddressSpaceMap = Args.hasArg(OPT_ffake_address_space_map);
   Opts.ParseUnknownAnytype = Args.hasArg(OPT_funknown_anytype);
   Opts.DebuggerSupport = Args.hasArg(OPT_fdebugger_support);
+  Opts.ApplePragmaPack = Args.hasArg(OPT_fapple_pragma_pack);
 
   // Record whether the __DEPRECATED define was requested.
   Opts.Deprecated = Args.hasFlag(OPT_fdeprecated_macro,
diff --git a/lib/Parse/ParsePragma.cpp b/lib/Parse/ParsePragma.cpp
index 2ccb6ea88d0f9a7d092a3deb604c8ac1f2f1bfcc..2069d31dd27c23ae2ae160bd04e3d12205db01a0 100644
--- a/lib/Parse/ParsePragma.cpp
+++ b/lib/Parse/ParsePragma.cpp
@@ -110,6 +110,12 @@ void PragmaPackHandler::HandlePragma(Preprocessor &PP,
       return;
 
     PP.Lex(Tok);
+
+    // In MSVC/gcc, #pragma pack(4) sets the alignment without affecting
+    // the push/pop stack.
+    // In Apple gcc, #pragma pack(4) is equivalent to #pragma pack(push, 4)
+    if (PP.getLangOptions().ApplePragmaPack)
+      Kind = Sema::PPK_Push;
   } else if (Tok.is(tok::identifier)) {
     const IdentifierInfo *II = Tok.getIdentifierInfo();
     if (II->isStr("show")) {
@@ -159,6 +165,11 @@ void PragmaPackHandler::HandlePragma(Preprocessor &PP,
         }
       }
     }
+  } else if (PP.getLangOptions().ApplePragmaPack) {
+    // In MSVC/gcc, #pragma pack() resets the alignment without affecting
+    // the push/pop stack.
+    // In Apple gcc #pragma pack() is equivalent to #pragma pack(pop).
+    Kind = Sema::PPK_Pop;
   }
 
   if (Tok.isNot(tok::r_paren)) {
diff --git a/test/Sema/pragma-pack-apple.c b/test/Sema/pragma-pack-apple.c
new file mode 100644
index 0000000000000000000000000000000000000000..5b33c03c38e773cf90649c5601518492ac82c4e8
--- /dev/null
+++ b/test/Sema/pragma-pack-apple.c
@@ -0,0 +1,10 @@
+// RUN: %clang -fsyntax-only %s 2>&1 | FileCheck %s
+// RUN: %clang -fsyntax-only -fapple-pragma-pack %s 2>&1 | FileCheck -check-prefix=CHECK-APPLE %s
+
+#pragma pack(push,1)
+#pragma pack(2)
+#pragma pack()
+#pragma pack(show)
+
+// CHECK: pack(show) == 8
+// CHECK-APPLE: pack(show) == 1