diff --git a/clang/include/clang/Basic/DiagnosticOptions.def b/clang/include/clang/Basic/DiagnosticOptions.def
index 7be81f6b6a9541546896ab5abccea553a721e3b3..4ad691188a69e892f3dfbd19692c53d3cc184b72 100644
--- a/clang/include/clang/Basic/DiagnosticOptions.def
+++ b/clang/include/clang/Basic/DiagnosticOptions.def
@@ -95,6 +95,8 @@ VALUE_DIAGOPT(TabStop, 32, DefaultTabStop) /// The distance between tab stops.
 /// Column limit for formatting message diagnostics, or 0 if unused.
 VALUE_DIAGOPT(MessageLength, 32, 0)
 
+DIAGOPT(GccCompatible, 1, 0) /// -fgcc_compatible
+
 #undef DIAGOPT
 #undef ENUM_DIAGOPT
 #undef VALUE_DIAGOPT
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
index ad366821f3cbff1153654f2bcad21381fa14313c..ee547b38130f1c2ef82264dc0d67cecf61411fc9 100644
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -449,6 +449,8 @@ ENUM_LANGOPT(ExtendIntArgs, ExtendArgsKind, 1, ExtendArgsKind::ExtendTo32,
 
 VALUE_LANGOPT(FuchsiaAPILevel, 32, 0, "Fuchsia API level")
 
+LANGOPT(GccCompatible, 1, 0, "Enable gcc compatibility.")
+
 // This option will be removed in the future once the backend
 // supports all operations (like division or float-to-integer conversion)
 // on large _BitInts.
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 3cab37b21aaf3f4bee4daecb21bd90d3cb5cf069..cffa38d83d0e3b55740a1050cd18d49506ac634b 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -522,6 +522,12 @@ defvar std = !strconcat("LangStandard::getLangStandardForKind(", lang_std.KeyPat
 
 // Developer Driver Options
 
+def fgcc_compatible : Flag<["-"], "fgcc-compatible">, Group<f_Group>,
+  MarshallingInfoFlag<DiagnosticOpts<"GccCompatible">>, Flags<[CC1Option, NoArgumentUnused]>,
+  HelpText<"Enable gcc compatibility.">;
+def fno_gcc_compatible : Flag<["-"], "fno-gcc-compatible">, Group<f_Group>,
+  Flags<[CC1Option, NoArgumentUnused]>;
+
 def internal_Group : OptionGroup<"<clang internal options>">, Flags<[HelpHidden]>;
 def internal_driver_Group : OptionGroup<"<clang driver internal options>">,
   Group<internal_Group>, HelpText<"DRIVER OPTIONS">;
diff --git a/clang/lib/Basic/Warnings.cpp b/clang/lib/Basic/Warnings.cpp
index cc8c138233ca1d9fcc4ef04840b87fb2efb94655..8d0095b6645ecf47b08d3490ae643602a4796530 100644
--- a/clang/lib/Basic/Warnings.cpp
+++ b/clang/lib/Basic/Warnings.cpp
@@ -29,6 +29,10 @@
 #include <utility>
 using namespace clang;
 
+#include <set>
+std::set<std::string> GccCompatibleWhitelist{"stringop-overflow",
+                                             "maybe-uninitialized"};
+
 // EmitUnknownDiagWarning - Emit a warning and typo hint for unknown warning
 // opts
 static void EmitUnknownDiagWarning(DiagnosticsEngine &Diags,
@@ -129,6 +133,11 @@ void clang::ProcessWarningOptions(DiagnosticsEngine &Diags,
         continue;
       }
 
+      if (Opts.GccCompatible) {
+        if (GccCompatibleWhitelist.find(std::string(Opt)) != GccCompatibleWhitelist.end())
+          continue;
+      }
+      
       // -Werror/-Wno-error is a special case, not controlled by the option
       // table. It also has the "specifier" form of -Werror=foo. GCC supports
       // the deprecated -Werror-implicit-function-declaration which is used by
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 3704ed8586682677882acb8e1b82bfc14b1d07a5..6dbe535bea371d739cc0e765dd9b90c1843746df 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4542,6 +4542,17 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   CmdArgs.push_back("-triple");
   CmdArgs.push_back(Args.MakeArgString(TripleStr));
 
+  if (Args.hasFlag(options::OPT_fgcc_compatible,
+                   options::OPT_fno_gcc_compatible, false)) {
+    CmdArgs.push_back("-Wno-error=int-conversion");
+    CmdArgs.push_back("-Wno-unused-private-field");
+    CmdArgs.push_back("-Wno-empty-body");
+    CmdArgs.push_back("-Wno-pointer-to-enum-cast");
+    CmdArgs.push_back("-Wno-unused-but-set-variable");
+    Args.AddLastArg(CmdArgs, options::OPT_fgcc_compatible,
+                    options::OPT_fno_gcc_compatible);
+  }
+
   if (const Arg *MJ = Args.getLastArg(options::OPT_MJ)) {
     DumpCompilationDatabase(C, MJ->getValue(), TripleStr, Output, Input, Args);
     Args.ClaimAllArgs(options::OPT_MJ);
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 2dd96e68bb92fe19691f642f9fca4c3b44fbd2a8..62924edcade00d7624c35f3719b618a1da8d2e56 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -3557,6 +3557,9 @@ void CompilerInvocation::GenerateLangArgs(const LangOptions &Opts,
 
   if (!Opts.RandstructSeed.empty())
     GenerateArg(Args, OPT_frandomize_layout_seed_EQ, Opts.RandstructSeed, SA);
+
+  if(Opts.GccCompatible)
+    GenerateArg(Args, OPT_fgcc_compatible, SA);
 }
 
 bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
@@ -4107,6 +4110,10 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
   if (const Arg *A = Args.getLastArg(OPT_frandomize_layout_seed_EQ))
     Opts.RandstructSeed = A->getValue(0);
 
+  Opts.GccCompatible = Args.hasArg(options::OPT_fgcc_compatible,
+                                   options::OPT_fno_gcc_compatible,
+                                   /*Default=*/false);
+
   return Diags.getNumErrors() == NumErrorsBefore;
 }
 
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
index 5310db3c882bc688d643d16126591584ce10d425..2921a22cc73e5c1af69a3c0adeff40b2371ee324 100644
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -1448,6 +1448,9 @@ void Preprocessor::emitMacroDeprecationWarning(const Token &Identifier) const {
   assert(A.DeprecationInfo &&
          "Macro deprecation warning without recorded annotation!");
   const MacroAnnotationInfo &Info = *A.DeprecationInfo;
+  if (getLangOpts().GccCompatible)
+    if (Identifier.getIdentifierInfo()->isStr("ATOMIC_VAR_INIT"))
+      return;
   if (Info.Message.empty())
     Diag(Identifier, diag::warn_pragma_deprecated_macro_use)
         << Identifier.getIdentifierInfo() << 0;