diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -80,7 +80,10 @@
 New Compiler Flags
 ------------------
 
-- ...
+- The -fgnuc-version= flag now controls the value of ``__GNUC__`` and related
+  macros. This flag does not enable or disable any GCC extensions implemented in
+  Clang. Setting the version to zero causes Clang to leave ``__GNUC__`` and
+  other GNU-namespaced macros, such as ``__GXX_WEAK__``, undefined.
 
 Deprecated Compiler Flags
 -------------------------
diff --git a/clang/docs/UsersManual.rst b/clang/docs/UsersManual.rst
--- a/clang/docs/UsersManual.rst
+++ b/clang/docs/UsersManual.rst
@@ -701,6 +701,13 @@
 -------------
 Clang options that don't fit neatly into other categories.
 
+.. option:: -fgnuc-version=
+
+  This flag controls the value of ``__GNUC__`` and related macros. This flag
+  does not enable or disable any GCC extensions implemented in Clang. Setting
+  the version to zero causes Clang to leave ``__GNUC__`` and other
+  GNU-namespaced macros, such as ``__GXX_WEAK__``, undefined.
+
 .. option:: -MV
 
   When emitting a dependency file, use formatting conventions appropriate
diff --git a/clang/include/clang/Basic/LangOptions.def b/clang/include/clang/Basic/LangOptions.def
--- a/clang/include/clang/Basic/LangOptions.def
+++ b/clang/include/clang/Basic/LangOptions.def
@@ -111,6 +111,7 @@
 BENIGN_LANGOPT(AsmPreprocessor, 1, 0, "preprocessor in asm mode")
 LANGOPT(GNUMode           , 1, 1, "GNU extensions")
 LANGOPT(GNUKeywords       , 1, 1, "GNU keywords")
+VALUE_LANGOPT(GNUCVersion , 32, 0, "GNU C compatibility version")
 BENIGN_LANGOPT(ImplicitInt, 1, !C99 && !CPlusPlus, "C89 implicit 'int'")
 LANGOPT(Digraphs          , 1, 0, "digraphs")
 BENIGN_LANGOPT(HexFloats  , 1, C99, "C99 hexadecimal float constants")
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -1187,6 +1187,9 @@
 
 def ffreestanding : Flag<["-"], "ffreestanding">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Assert that the compilation takes place in a freestanding environment">;
+def fgnuc_version_EQ : Joined<["-"], "fgnuc-version=">, Group<f_Group>,
+  HelpText<"Sets various macros to claim compatibility with the given GCC version (default is 4.2.1)">,
+  Flags<[CC1Option, CoreOption]>;
 def fgnu_keywords : Flag<["-"], "fgnu-keywords">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Allow GNU-extension keywords regardless of language standard">;
 def fgnu89_inline : Flag<["-"], "fgnu89-inline">, Group<f_Group>, Flags<[CC1Option]>,
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -4875,13 +4875,36 @@
     CmdArgs.push_back("-fuse-line-directives");
 
   // -fms-compatibility=0 is default.
-  if (Args.hasFlag(options::OPT_fms_compatibility,
-                   options::OPT_fno_ms_compatibility,
-                   (IsWindowsMSVC &&
-                    Args.hasFlag(options::OPT_fms_extensions,
-                                 options::OPT_fno_ms_extensions, true))))
+  bool IsMSVCCompat = Args.hasFlag(
+      options::OPT_fms_compatibility, options::OPT_fno_ms_compatibility,
+      (IsWindowsMSVC && Args.hasFlag(options::OPT_fms_extensions,
+                                     options::OPT_fno_ms_extensions, true)));
+  if (IsMSVCCompat)
     CmdArgs.push_back("-fms-compatibility");
 
+  // Handle -fgcc-version, if present.
+  VersionTuple GNUCVer;
+  if (Arg *A = Args.getLastArg(options::OPT_fgnuc_version_EQ)) {
+    // Check that the version has 1 to 3 components and the minor and patch
+    // versions fit in two decimal digits.
+    StringRef Val = A->getValue();
+    Val = Val.empty() ? "0" : Val; // Treat "" as 0 or disable.
+    bool Invalid = GNUCVer.tryParse(Val);
+    unsigned Minor = GNUCVer.getMinor().getValueOr(0);
+    unsigned Patch = GNUCVer.getSubminor().getValueOr(0);
+    if (Invalid || GNUCVer.getBuild() || Minor >= 100 || Patch >= 100) {
+      D.Diag(diag::err_drv_invalid_value)
+          << A->getAsString(Args) << A->getValue();
+    }
+  } else if (!IsMSVCCompat) {
+    // Imitate GCC 4.2.1 by default if -fms-compatibility is not in effect.
+    GNUCVer = VersionTuple(4, 2, 1);
+  }
+  if (!GNUCVer.empty()) {
+    CmdArgs.push_back(
+        Args.MakeArgString("-fgnuc-version=" + GNUCVer.getAsString()));
+  }
+
   VersionTuple MSVT = TC.computeMSVCVersion(&D, Args);
   if (!MSVT.empty())
     CmdArgs.push_back(
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -2250,6 +2250,7 @@
   Opts.Digraphs = Std.hasDigraphs();
   Opts.GNUMode = Std.isGNUMode();
   Opts.GNUInline = !Opts.C99 && !Opts.CPlusPlus;
+  Opts.GNUCVersion = 0;
   Opts.HexFloats = Std.hasHexFloats();
   Opts.ImplicitInt = Std.hasImplicitInt();
 
@@ -2574,6 +2575,21 @@
         (Opts.ObjCRuntime.getKind() == ObjCRuntime::FragileMacOSX);
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_fgnuc_version_EQ)) {
+    // Check that the version has 1 to 3 components and the minor and patch
+    // versions fit in two decimal digits.
+    VersionTuple GNUCVer;
+    bool Invalid = GNUCVer.tryParse(A->getValue());
+    unsigned Major = GNUCVer.getMajor();
+    unsigned Minor = GNUCVer.getMinor().getValueOr(0);
+    unsigned Patch = GNUCVer.getSubminor().getValueOr(0);
+    if (Invalid || GNUCVer.getBuild() || Minor >= 100 || Patch >= 100) {
+      Diags.Report(diag::err_drv_invalid_value)
+          << A->getAsString(Args) << A->getValue();
+    }
+    Opts.GNUCVersion = Major * 100 * 100 + Minor * 100 + Patch;
+  }
+
   if (Args.hasArg(OPT_fgnu89_inline)) {
     if (Opts.CPlusPlus)
       Diags.Report(diag::err_drv_argument_not_allowed_with)
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -574,13 +574,22 @@
   Builder.defineMacro("__clang_version__",
                       "\"" CLANG_VERSION_STRING " "
                       + getClangFullRepositoryVersion() + "\"");
-  if (!LangOpts.MSVCCompat) {
-    // Currently claim to be compatible with GCC 4.2.1-5621, but only if we're
-    // not compiling for MSVC compatibility
-    Builder.defineMacro("__GNUC_MINOR__", "2");
-    Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
-    Builder.defineMacro("__GNUC__", "4");
+
+  if (LangOpts.GNUCVersion != 0) {
+    // Major, minor, patch, are given two decimal places each, so 4.2.1 becomes
+    // 40201.
+    unsigned GNUCMajor = LangOpts.GNUCVersion / 100 / 100;
+    unsigned GNUCMinor = LangOpts.GNUCVersion / 100 % 100;
+    unsigned GNUCPatch = LangOpts.GNUCVersion % 100;
+    Builder.defineMacro("__GNUC__", Twine(GNUCMajor));
+    Builder.defineMacro("__GNUC_MINOR__", Twine(GNUCMinor));
+    Builder.defineMacro("__GNUC_PATCHLEVEL__", Twine(GNUCPatch));
     Builder.defineMacro("__GXX_ABI_VERSION", "1002");
+
+    if (LangOpts.CPlusPlus) {
+      Builder.defineMacro("__GNUG__", Twine(GNUCMajor));
+      Builder.defineMacro("__GXX_WEAK__");
+    }
   }
 
   // Define macros for the C11 / C++11 memory orderings
@@ -619,7 +628,7 @@
   if (!LangOpts.GNUMode && !LangOpts.MSVCCompat)
     Builder.defineMacro("__STRICT_ANSI__");
 
-  if (!LangOpts.MSVCCompat && LangOpts.CPlusPlus11)
+  if (LangOpts.GNUCVersion && LangOpts.CPlusPlus11)
     Builder.defineMacro("__GXX_EXPERIMENTAL_CXX0X__");
 
   if (LangOpts.ObjC) {
@@ -699,7 +708,7 @@
 
   if (!LangOpts.MSVCCompat && LangOpts.Exceptions)
     Builder.defineMacro("__EXCEPTIONS");
-  if (!LangOpts.MSVCCompat && LangOpts.RTTI)
+  if (LangOpts.GNUCVersion && LangOpts.RTTI)
     Builder.defineMacro("__GXX_RTTI");
 
   if (LangOpts.SjLjExceptions)
@@ -713,11 +722,8 @@
   if (LangOpts.Deprecated)
     Builder.defineMacro("__DEPRECATED");
 
-  if (!LangOpts.MSVCCompat && LangOpts.CPlusPlus) {
-    Builder.defineMacro("__GNUG__", "4");
-    Builder.defineMacro("__GXX_WEAK__");
+  if (!LangOpts.MSVCCompat && LangOpts.CPlusPlus)
     Builder.defineMacro("__private_extern__", "extern");
-  }
 
   if (LangOpts.MicrosoftExt) {
     if (LangOpts.WChar) {
@@ -927,7 +933,7 @@
   else
     Builder.defineMacro("__FINITE_MATH_ONLY__", "0");
 
-  if (!LangOpts.MSVCCompat) {
+  if (LangOpts.GNUCVersion) {
     if (LangOpts.GNUInline || LangOpts.CPlusPlus)
       Builder.defineMacro("__GNUC_GNU_INLINE__");
     else
@@ -964,7 +970,7 @@
 #undef DEFINE_LOCK_FREE_MACRO
   };
   addLockFreeMacros("__CLANG_ATOMIC_");
-  if (!LangOpts.MSVCCompat)
+  if (LangOpts.GNUCVersion)
     addLockFreeMacros("__GCC_ATOMIC_");
 
   if (LangOpts.NoInlineDefine)
diff --git a/clang/test/Driver/fgnuc-version.c b/clang/test/Driver/fgnuc-version.c
new file mode 100644
--- /dev/null
+++ b/clang/test/Driver/fgnuc-version.c
@@ -0,0 +1,26 @@
+//
+// Verify -fgnuc-version parsing
+//
+
+// RUN: %clang -c %s -target i686-linux -### 2>&1 | FileCheck %s -check-prefix GNUC-DEFAULT
+// GNUC-DEFAULT: "-fgnuc-version=4.2.1"
+
+// RUN: %clang -c %s -target i686-linux -fgnuc-version=100.99.99 -### 2>&1 | FileCheck %s -check-prefix GNUC-OVERRIDE
+// GNUC-OVERRIDE: "-fgnuc-version=100.99.99"
+
+// RUN: %clang -c %s -target i686-linux -fgnuc-version=0 -### 2>&1 | FileCheck %s -check-prefix GNUC-DISABLE
+// RUN: %clang -c %s -target i686-linux -fgnuc-version= -### 2>&1 | FileCheck %s -check-prefix GNUC-DISABLE
+// GNUC-DISABLE-NOT: "-fgnuc-version=
+
+// RUN: not %clang -c %s -target i686-linux -fgnuc-version=100.100.10 2>&1 | FileCheck %s -check-prefix GNUC-INVALID
+// RUN: not %clang -c %s -target i686-linux -fgnuc-version=100.10.100 2>&1 | FileCheck %s -check-prefix GNUC-INVALID
+// RUN: not %clang -c %s -target i686-linux -fgnuc-version=-1.0.0 2>&1 | FileCheck %s -check-prefix GNUC-INVALID
+// GNUC-INVALID: error: invalid value {{.*}} in '-fgnuc-version={{.*}}'
+
+// RUN: %clang -fgnuc-version=100.99.99 %s -dM -E -o - | FileCheck %s -check-prefix GNUC-LARGE
+// GNUC-LARGE: #define __GNUC_MINOR__ 99
+// GNUC-LARGE: #define __GNUC_PATCHLEVEL__ 99
+// GNUC-LARGE: #define __GNUC__ 100
+
+// RUN: %clang -fgnuc-version=100.99.99 -x c++ %s -dM -E -o - | FileCheck %s -check-prefix GXX-LARGE
+// GXX-LARGE: #define __GNUG__ 100
diff --git a/clang/test/Driver/rewrite-legacy-objc.m b/clang/test/Driver/rewrite-legacy-objc.m
--- a/clang/test/Driver/rewrite-legacy-objc.m
+++ b/clang/test/Driver/rewrite-legacy-objc.m
@@ -3,11 +3,11 @@
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fgnuc-version=4.2.1" "-fobjc-runtime=macosx-fragile" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
 // TEST0: rewrite-legacy-objc.m"
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.9.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST1 %s
 // RUN: %clang -no-canonical-prefixes -target i386-apple-macosx10.6.0 -rewrite-legacy-objc %s -o - -### 2>&1 | \
 // RUN:   FileCheck -check-prefix=TEST2 %s
-// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
-// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST1: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fgnuc-version=4.2.1" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST2: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fgnuc-version=4.2.1" "-fobjc-runtime=macosx-fragile" "-fobjc-subscripting-legacy-runtime" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
diff --git a/clang/test/Driver/rewrite-objc.m b/clang/test/Driver/rewrite-objc.m
--- a/clang/test/Driver/rewrite-objc.m
+++ b/clang/test/Driver/rewrite-objc.m
@@ -3,4 +3,4 @@
 // TEST0: clang{{.*}}" "-cc1"
 // TEST0: "-rewrite-objc"
 // FIXME: CHECK-NOT is broken somehow, it doesn't work here. Check adjacency instead.
-// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
+// TEST0: "-fmessage-length" "0" "-stack-protector" "1" "-fblocks" "-fencode-extended-block-signature" "-fregister-global-dtors-with-atexit" "-fgnuc-version=4.2.1" "-fobjc-runtime=macosx" "-fno-objc-infer-related-result-type" "-fobjc-exceptions" "-fexceptions" "-fmax-type-align=16" "-fdiagnostics-show-option"
diff --git a/clang/test/Frontend/gnu-inline.c b/clang/test/Frontend/gnu-inline.c
--- a/clang/test/Frontend/gnu-inline.c
+++ b/clang/test/Frontend/gnu-inline.c
@@ -1,9 +1,9 @@
-// RUN: %clang_cc1 -std=c89 -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
-// RUN: %clang_cc1 -std=c99 -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=STDC-INLINE %s
-// RUN: %clang_cc1 -std=c99 -fgnu89-inline -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
-// RUN: %clang_cc1 -fsyntax-only -x c++ -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
-// RUN: not %clang_cc1 -fgnu89-inline -fsyntax-only -x c++ %s 2>&1 | FileCheck --check-prefix=CXX %s
-// RUN: not %clang_cc1 -fgnu89-inline -fsyntax-only -x objective-c++ %s 2>&1 | FileCheck --check-prefix=OBJCXX %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c89 -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c99 -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=STDC-INLINE %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c99 -fgnu89-inline -fsyntax-only -x c -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -fsyntax-only -x c++ -E -dM %s | FileCheck --check-prefix=GNU-INLINE %s
+// RUN: not %clang_cc1 -fgnu89-inline -fgnuc-version=4.2.1 -fsyntax-only -x c++ %s 2>&1 | FileCheck --check-prefix=CXX %s
+// RUN: not %clang_cc1 -fgnu89-inline -fgnuc-version=4.2.1 -fsyntax-only -x objective-c++ %s 2>&1 | FileCheck --check-prefix=OBJCXX %s
 
 // CXX: '-fgnu89-inline' not allowed with 'C++'
 // OBJCXX: '-fgnu89-inline' not allowed with 'Objective-C++'
diff --git a/clang/test/Headers/stdbool.cpp b/clang/test/Headers/stdbool.cpp
--- a/clang/test/Headers/stdbool.cpp
+++ b/clang/test/Headers/stdbool.cpp
@@ -1,7 +1,7 @@
-// RUN: %clang_cc1 -std=gnu++98 -E -dM %s | FileCheck --check-prefix=CHECK-GNU-COMPAT-98 %s
-// RUN: %clang_cc1 -std=gnu++11 -E -dM %s | FileCheck --check-prefix=CHECK-GNU-COMPAT-11 %s
-// RUN: %clang_cc1 -std=c++98 -E -dM %s | FileCheck --check-prefix=CHECK-CONFORMING %s
-// RUN: %clang_cc1 -fsyntax-only -std=gnu++98 -verify -Weverything %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=gnu++98 -E -dM %s | FileCheck --check-prefix=CHECK-GNU-COMPAT-98 %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=gnu++11 -E -dM %s | FileCheck --check-prefix=CHECK-GNU-COMPAT-11 %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -std=c++98 -E -dM %s | FileCheck --check-prefix=CHECK-CONFORMING %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -fsyntax-only -std=gnu++98 -verify -Weverything %s
 #include <stdbool.h>
 #define zzz
 
diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
--- a/clang/test/Preprocessor/init.c
+++ b/clang/test/Preprocessor/init.c
@@ -9,18 +9,18 @@
 // BLOCKS:#define __block __attribute__((__blocks__(byref)))
 //
 //
-// RUN: %clang_cc1 -x c++ -std=c++2a -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2A %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++2a -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX2A %s
 //
-// CXX2A:#define __GNUG__ {{.*}}
+// CXX2A:#define __GNUG__ 4
 // CXX2A:#define __GXX_EXPERIMENTAL_CXX0X__ 1
 // CXX2A:#define __GXX_RTTI 1
 // CXX2A:#define __GXX_WEAK__ 1
 // CXX2A:#define __cplusplus 201707L
 // CXX2A:#define __private_extern__ extern
 //
-// RUN: %clang_cc1 -x c++ -std=c++1z -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX1Z %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++1z -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX1Z %s
 //
-// CXX1Z:#define __GNUG__ {{.*}}
+// CXX1Z:#define __GNUG__ 4
 // CXX1Z:#define __GXX_EXPERIMENTAL_CXX0X__ 1
 // CXX1Z:#define __GXX_RTTI 1
 // CXX1Z:#define __GXX_WEAK__ 1
@@ -28,9 +28,9 @@
 // CXX1Z:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=c++1y -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX1Y %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++1y -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX1Y %s
 //
-// CXX1Y:#define __GNUG__ {{.*}}
+// CXX1Y:#define __GNUG__ 4
 // CXX1Y:#define __GXX_EXPERIMENTAL_CXX0X__ 1
 // CXX1Y:#define __GXX_RTTI 1
 // CXX1Y:#define __GXX_WEAK__ 1
@@ -38,9 +38,9 @@
 // CXX1Y:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=c++11 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX11 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++11 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX11 %s
 //
-// CXX11:#define __GNUG__ {{.*}}
+// CXX11:#define __GNUG__ 4
 // CXX11:#define __GXX_EXPERIMENTAL_CXX0X__ 1
 // CXX11:#define __GXX_RTTI 1
 // CXX11:#define __GXX_WEAK__ 1
@@ -48,9 +48,9 @@
 // CXX11:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=c++98 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX98 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++98 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix CXX98 %s
 //
-// CXX98:#define __GNUG__ {{.*}}
+// CXX98:#define __GNUG__ 4
 // CXX98:#define __GXX_RTTI 1
 // CXX98:#define __GXX_WEAK__ 1
 // CXX98:#define __cplusplus 199711L
@@ -87,7 +87,7 @@
 // C11-NOT: __cplusplus
 //
 //
-// RUN: %clang_cc1 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix COMMON %s
+// RUN: %clang_cc1 -fgnuc-version=4.2.1 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix COMMON %s
 //
 // COMMON:#define __CONSTANT_CFSTRINGS__ 1
 // COMMON:#define __FINITE_MATH_ONLY__ 0
@@ -119,41 +119,41 @@
 // RUN: %clang_cc1 -ffreestanding -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix FREESTANDING %s
 // FREESTANDING:#define __STDC_HOSTED__ 0
 //
-// RUN: %clang_cc1 -x c++ -std=gnu++2a -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2A %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++2a -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX2A %s
 //
-// GXX2A:#define __GNUG__ {{.*}}
+// GXX2A:#define __GNUG__ 4
 // GXX2A:#define __GXX_WEAK__ 1
 // GXX2A:#define __cplusplus 201707L
 // GXX2A:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=gnu++1z -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX1Z %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++1z -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX1Z %s
 //
-// GXX1Z:#define __GNUG__ {{.*}}
+// GXX1Z:#define __GNUG__ 4
 // GXX1Z:#define __GXX_WEAK__ 1
 // GXX1Z:#define __cplusplus 201703L
 // GXX1Z:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=gnu++1y -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX1Y %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++1y -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX1Y %s
 //
-// GXX1Y:#define __GNUG__ {{.*}}
+// GXX1Y:#define __GNUG__ 4
 // GXX1Y:#define __GXX_WEAK__ 1
 // GXX1Y:#define __cplusplus 201402L
 // GXX1Y:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=gnu++11 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX11 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++11 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX11 %s
 //
-// GXX11:#define __GNUG__ {{.*}}
+// GXX11:#define __GNUG__ 4
 // GXX11:#define __GXX_WEAK__ 1
 // GXX11:#define __cplusplus 201103L
 // GXX11:#define __private_extern__ extern
 //
 //
-// RUN: %clang_cc1 -x c++ -std=gnu++98 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX98 %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=gnu++98 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GXX98 %s
 //
-// GXX98:#define __GNUG__ {{.*}}
+// GXX98:#define __GNUG__ 4
 // GXX98:#define __GXX_WEAK__ 1
 // GXX98:#define __cplusplus 199711L
 // GXX98:#define __private_extern__ extern
@@ -2845,9 +2845,9 @@
 // I386:#define __i386__ 1
 // I386:#define i386 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN32 %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-CXX -check-prefix I386-LINUX-ALIGN32 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-pc-linux-gnu -target-cpu pentium4 -malign-double < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN64 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN32 %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-CXX -check-prefix I386-LINUX-ALIGN32 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-pc-linux-gnu -target-cpu pentium4 -malign-double < /dev/null | FileCheck -match-full-lines -check-prefix I386-LINUX -check-prefix I386-LINUX-ALIGN64 %s
 //
 // I386-LINUX-NOT:#define _LP64
 // I386-LINUX:#define __BIGGEST_ALIGNMENT__ 16
@@ -3047,9 +3047,9 @@
 // I386-LINUX:#define __i386__ 1
 // I386-LINUX:#define i386 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-netbsd -target-cpu i486 < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=i386-netbsd -target-cpu i486 < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD -check-prefix I386-NETBSD-CXX %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=i386-netbsd -target-cpu i486 -malign-double < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-netbsd -target-cpu i486 < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-netbsd -target-cpu i486 < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD -check-prefix I386-NETBSD-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=i386-netbsd -target-cpu i486 -malign-double < /dev/null | FileCheck -match-full-lines -check-prefix I386-NETBSD %s
 //
 //
 // I386-NETBSD-NOT:#define _LP64
@@ -3263,8 +3263,8 @@
 // I386-DECLSPEC: #define __declspec{{.*}}
 
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=mips-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS32BE -check-prefix MIPS32BE-C %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=mips-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS32BE -check-prefix MIPS32BE-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=mips-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS32BE -check-prefix MIPS32BE-C %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=mips-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS32BE -check-prefix MIPS32BE-CXX %s
 //
 // MIPS32BE:#define MIPSEB 1
 // MIPS32BE:#define _ABIO32 1
@@ -3682,10 +3682,10 @@
 // MIPS32EL:#define _mips 1
 // MIPS32EL:#define mips 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 \
 // RUN:            -triple=mips64-none-none -target-abi n32 < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix MIPSN32BE -check-prefix MIPSN32BE-C %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding \
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 \
 // RUN:            -triple=mips64-none-none -target-abi n32 < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix MIPSN32BE -check-prefix MIPSN32BE-CXX %s
 //
@@ -3993,7 +3993,7 @@
 // MIPSN32BE: #define _mips 1
 // MIPSN32BE: #define mips 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 \
 // RUN:            -triple=mips64el-none-none -target-abi n32 < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix MIPSN32EL %s
 //
@@ -4300,8 +4300,8 @@
 // MIPSN32EL: #define _mips 1
 // MIPSN32EL: #define mips 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=mips64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS64BE %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=mips64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS64BE -check-prefix MIPS64BE-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=mips64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS64BE %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=mips64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix MIPS64BE -check-prefix MIPS64BE-CXX %s
 //
 // MIPS64BE:#define MIPSEB 1
 // MIPS64BE:#define _ABI64 3
@@ -6838,13 +6838,13 @@
 // PPC64-LINUX:#define __ppc64__ 1
 // PPC64-LINUX:#define __ppc__ 1
 
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu -target-abi elfv1-qpx < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64le-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64le-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=powerpc64le-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu -target-abi elfv1-qpx < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu -target-abi elfv1 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv1 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=powerpc64le-unknown-linux-gnu -target-abi elfv2 < /dev/null | FileCheck -match-full-lines -check-prefix PPC64-ELFv2 %s
 // PPC64-ELFv1:#define _CALL_ELF 1
 // PPC64-ELFv2:#define _CALL_ELF 2
 //
@@ -7980,12 +7980,12 @@
 // S390X:#define __s390__ 1
 // S390X:#define __s390x__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc-none-none < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc-rtems-elf < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc-none-netbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=sparc-none-openbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=sparc-none-none < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT -check-prefix SPARC-DEFAULT-CXX %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=sparc-none-openbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD -check-prefix SPARC-NETOPENBSD-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-none-none < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-rtems-elf < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-none-netbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-none-openbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-none-none < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-DEFAULT -check-prefix SPARC-DEFAULT-CXX %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=sparc-none-openbsd < /dev/null | FileCheck -match-full-lines -check-prefix SPARC -check-prefix SPARC-NETOPENBSD -check-prefix SPARC-NETOPENBSD-CXX %s
 //
 // SPARC-NOT:#define _LP64
 // SPARC:#define __BIGGEST_ALIGNMENT__ 8
@@ -8185,8 +8185,8 @@
 // SPARC:#define __sparcv8 1
 // SPARC:#define sparc 1
 
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=tce-none-none < /dev/null | FileCheck -match-full-lines -check-prefix TCE %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=tce-none-none < /dev/null | FileCheck -match-full-lines -check-prefix TCE -check-prefix TCE-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=tce-none-none < /dev/null | FileCheck -match-full-lines -check-prefix TCE %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=tce-none-none < /dev/null | FileCheck -match-full-lines -check-prefix TCE -check-prefix TCE-CXX %s
 //
 // TCE-NOT:#define _LP64
 // TCE:#define __BIGGEST_ALIGNMENT__ 4
@@ -8354,8 +8354,8 @@
 // TCE:#define __tce__ 1
 // TCE:#define tce 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 -check-prefix X86_64-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64 -check-prefix X86_64-CXX %s
 //
 // X86_64:#define _LP64 1
 // X86_64-NOT:#define _LP32 1
@@ -8562,8 +8562,8 @@
 // RUN: %clang -xc - -E -dM -mcmodel=medium --target=i386-unknown-linux < /dev/null | FileCheck -match-full-lines -check-prefix X86_MEDIUM %s
 // X86_MEDIUM:#define __code_model_medium_ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-none-none-gnux32 < /dev/null | FileCheck -match-full-lines -check-prefix X32 %s
-// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -triple=x86_64-none-none-gnux32 < /dev/null | FileCheck -match-full-lines -check-prefix X32 -check-prefix X32-CXX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none-gnux32 < /dev/null | FileCheck -match-full-lines -check-prefix X32 %s
+// RUN: %clang_cc1 -x c++ -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-none-none-gnux32 < /dev/null | FileCheck -match-full-lines -check-prefix X32 -check-prefix X32-CXX %s
 //
 // X32:#define _ILP32 1
 // X32-NOT:#define _LP64 1
@@ -8759,7 +8759,7 @@
 // X32:#define __x86_64 1
 // X32:#define __x86_64__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-unknown-cloudabi < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-CLOUDABI %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-unknown-cloudabi < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-CLOUDABI %s
 //
 // X86_64-CLOUDABI:#define _LP64 1
 // X86_64-CLOUDABI:#define __ATOMIC_ACQUIRE 2
@@ -9064,7 +9064,7 @@
 // X86_64-CLOUDABI:#define __x86_64 1
 // X86_64-CLOUDABI:#define __x86_64__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-pc-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-LINUX %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-pc-linux-gnu < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-LINUX %s
 //
 // X86_64-LINUX:#define _LP64 1
 // X86_64-LINUX:#define __BIGGEST_ALIGNMENT__ 16
@@ -9277,7 +9277,7 @@
 // X86_64-FREEBSD:#define __LDBL_DECIMAL_DIG__ 21
 // X86_64-FREEBSD:#define __STDC_MB_MIGHT_NEQ_WC__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-netbsd < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-NETBSD %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-netbsd < /dev/null | FileCheck -match-full-lines -check-prefix X86_64-NETBSD %s
 //
 // X86_64-NETBSD:#define _LP64 1
 // X86_64-NETBSD:#define __BIGGEST_ALIGNMENT__ 16
@@ -9481,7 +9481,7 @@
 // X86_64-NETBSD:#define __x86_64 1
 // X86_64-NETBSD:#define __x86_64__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64-scei-ps4 < /dev/null | FileCheck -match-full-lines -check-prefix PS4 %s
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=x86_64-scei-ps4 < /dev/null | FileCheck -match-full-lines -check-prefix PS4 %s
 //
 // PS4:#define _LP64 1
 // PS4:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__
@@ -9641,7 +9641,7 @@
 // RUN: %clang_cc1 -x objective-c -triple i386-unknown-freebsd -fobjc-runtime=gnustep-2.5 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix GNUSTEP2 %s
 // GNUSTEP2:#define __OBJC_GNUSTEP_RUNTIME_ABI__ 20
 //
-// RUN: %clang_cc1 -x c++ -std=c++98 -fno-rtti -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix NORTTI %s
+// RUN: %clang_cc1 -x c++ -fgnuc-version=4.2.1 -std=c++98 -fno-rtti -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix NORTTI %s
 // NORTTI: #define __GXX_ABI_VERSION {{.*}}
 // NORTTI-NOT:#define __GXX_RTTI
 // NORTTI:#define __STDC__ 1
@@ -9700,16 +9700,16 @@
 // XCORE:#define __LITTLE_ENDIAN__ 1
 // XCORE:#define __XS1B__ 1
 //
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm32-unknown-unknown \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=wasm32-unknown-unknown \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=WEBASSEMBLY,WEBASSEMBLY32 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm64-unknown-unknown \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=wasm64-unknown-unknown \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=WEBASSEMBLY,WEBASSEMBLY64 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm32-wasi \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=wasm32-wasi \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=WEBASSEMBLY,WEBASSEMBLY32,WEBASSEMBLY-WASI %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=wasm64-wasi \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=wasm64-wasi \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=WEBASSEMBLY,WEBASSEMBLY64,WEBASSEMBLY-WASI %s
 //
@@ -10087,7 +10087,7 @@
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple x86_64-windows-cygnus < /dev/null | FileCheck -match-full-lines -check-prefix CYGWIN-X64 %s
 // CYGWIN-X64: #define __USER_LABEL_PREFIX__
 
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=avr \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=avr \
 // RUN:   < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix=AVR %s
 //
@@ -10295,10 +10295,10 @@
 // MSVC-X64:#define __STDCPP_DEFAULT_NEW_ALIGNMENT__ 16ULL
 
 // RUN: %clang_cc1 -E -dM -ffreestanding                \
-// RUN:   -triple=aarch64-apple-ios9 < /dev/null        \
+// RUN:  -fgnuc-version=4.2.1  -triple=aarch64-apple-ios9 < /dev/null        \
 // RUN: | FileCheck -check-prefix=DARWIN %s
 // RUN: %clang_cc1 -E -dM -ffreestanding                \
-// RUN:   -triple=aarch64-apple-macosx10.12 < /dev/null \
+// RUN:   -fgnuc-version=4.2.1 -triple=aarch64-apple-macosx10.12 < /dev/null \
 // RUN: | FileCheck -check-prefix=DARWIN %s
 
 // DARWIN:#define __STDC_NO_THREADS__ 1
@@ -10364,11 +10364,11 @@
 // ARM-DARWIN-BAREMETAL-64: #define __PTRDIFF_TYPE__ long int
 // ARM-DARWIN-BAREMETAL-64: #define __SIZE_TYPE__ long unsigned int
 
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=riscv32 < /dev/null \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=riscv32 < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix=RISCV32 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=riscv32-unknown-linux < /dev/null \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=riscv32-unknown-linux < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=RISCV32,RISCV32-LINUX %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=riscv32 \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=riscv32 \
 // RUN: -fforce-enable-int128 < /dev/null | FileCheck -match-full-lines \
 // RUN: -check-prefixes=RISCV32,RISCV32-INT128 %s
 // RISCV32: #define _ILP32 1
@@ -10575,9 +10575,9 @@
 // RISCV32-LINUX: #define linux 1
 // RISCV32-LINUX: #define unix 1
 
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=riscv64 < /dev/null \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=riscv64 < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefix=RISCV64 %s
-// RUN: %clang_cc1 -E -dM -ffreestanding -triple=riscv64-unknown-linux < /dev/null \
+// RUN: %clang_cc1 -E -dM -ffreestanding -fgnuc-version=4.2.1 -triple=riscv64-unknown-linux < /dev/null \
 // RUN:   | FileCheck -match-full-lines -check-prefixes=RISCV64,RISCV64-LINUX %s
 // RISCV64: #define _LP64 1
 // RISCV64: #define __ATOMIC_ACQUIRE 2
diff --git a/clang/test/Sema/atomic-ops.c b/clang/test/Sema/atomic-ops.c
--- a/clang/test/Sema/atomic-ops.c
+++ b/clang/test/Sema/atomic-ops.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 %s -verify -ffreestanding -fsyntax-only -triple=i686-linux-gnu -std=c11
+// RUN: %clang_cc1 %s -verify -fgnuc-version=4.2.1 -ffreestanding -fsyntax-only -triple=i686-linux-gnu -std=c11
 
 // Basic parsing/Sema tests for __c11_atomic_*