Add flag to request Clang is ABI-compatible with older versions of itself

This patch adds a flag -fclang-abi-compat that can be used to request that
Clang attempts to be ABI-compatible with some older version of itself.

This is provided on a best-effort basis; right now, this can be used to undo
the ABI change in r310401, reverting Clang to its prior C++ ABI for pass/return
by value of class types affected by that change, and to undo the ABI change in
r262688, reverting Clang to using integer registers rather than SSE registers
for passing <1 x long long> vectors. The intent is that we will maintain this
backwards compatibility path as we make ABI-breaking fixes in future.

The reversion to the old behavior for r310401 is also applied to the PS4 target
since that change is not part of its platform ABI (which is essentially to do
whatever Clang 3.2 did).

llvm-svn: 311823

clang/include/clang/Driver/Options.td

@@ -711,6 +711,9 @@ def fbuiltin : Flag<["-"], "fbuiltin">, Group<f_Group>;
 def fbuiltin_module_map : Flag <["-"], "fbuiltin-module-map">, Group<f_Group>,
   Flags<[DriverOption]>, HelpText<"Load the clang builtins module map file.">;
 def fcaret_diagnostics : Flag<["-"], "fcaret-diagnostics">, Group<f_Group>;
+def fclang_abi_compat_EQ : Joined<["-"], "fclang-abi-compat=">, Group<f_clang_Group>,
+  Flags<[CC1Option]>, MetaVarName<"<version>">, Values<"<major>.<minor>,latest">,
+  HelpText<"Attempt to match the ABI of Clang <version>">;
 def fclasspath_EQ : Joined<["-"], "fclasspath=">, Group<f_Group>;
 def fcolor_diagnostics : Flag<["-"], "fcolor-diagnostics">, Group<f_Group>,
   Flags<[CoreOption, CC1Option]>, HelpText<"Use colors in diagnostics">;

clang/include/clang/Frontend/CodeGenOptions.def

@@ -120,6 +120,10 @@ CODEGENOPT(NoZeroInitializedInBSS , 1, 0) ///< -fno-zero-initialized-in-bss.
 ENUM_CODEGENOPT(ObjCDispatchMethod, ObjCDispatchMethodKind, 2, Legacy)
 CODEGENOPT(OmitLeafFramePointer , 1, 0) ///< Set when -momit-leaf-frame-pointer is
                                         ///< enabled.
+
+/// A version of Clang that we should attempt to be ABI-compatible with.
+ENUM_CODEGENOPT(ClangABICompat, ClangABI, 4, ClangABI::Latest)
+
 VALUE_CODEGENOPT(OptimizationLevel, 2, 0) ///< The -O[0-3] option specified.
 VALUE_CODEGENOPT(OptimizeSize, 2, 0) ///< If -Os (==1) or -Oz (==2) is specified.
 

clang/include/clang/Frontend/CodeGenOptions.h

@@ -69,6 +69,23 @@ public:
     LocalExecTLSModel
   };
 
+  /// Clang versions with different platform ABI conformance.
+  enum class ClangABI {
+    /// Attempt to be ABI-compatible with code generated by Clang 3.8.x
+    /// (SVN r257626). This causes <1 x long long> to be passed in an
+    /// integer register instead of an SSE register on x64_64.
+    Ver3_8,
+
+    /// Attempt to be ABI-compatible with code generated by Clang 4.0.x
+    /// (SVN r291814). This causes move operations to be ignored when
+    /// determining whether a class type can be passed or returned directly.
+    Ver4,
+
+    /// Conform to the underlying platform's C and C++ ABIs as closely
+    /// as we can.
+    Latest
+  };
+
   enum StructReturnConventionKind {
     SRCK_Default,  // No special option was passed.
     SRCK_OnStack,  // Small structs on the stack (-fpcc-struct-return).

clang/lib/CodeGen/ABIInfo.h

@@ -24,6 +24,7 @@ namespace llvm {
 
 namespace clang {
   class ASTContext;
+  class CodeGenOptions;
   class TargetInfo;
 
 namespace CodeGen {
@@ -68,6 +69,7 @@ namespace swiftcall {
     llvm::LLVMContext &getVMContext() const;
     const llvm::DataLayout &getDataLayout() const;
     const TargetInfo &getTarget() const;
+    const CodeGenOptions &getCodeGenOpts() const;
 
     /// Return the calling convention to use for system runtime
     /// functions.

clang/lib/CodeGen/CodeGenTypes.cpp

@@ -44,6 +44,10 @@ CodeGenTypes::~CodeGenTypes() {
     delete &*I++;
 }
 
+const CodeGenOptions &CodeGenTypes::getCodeGenOpts() const {
+  return CGM.getCodeGenOpts();
+}
+
 void CodeGenTypes::addRecordTypeName(const RecordDecl *RD,
                                      llvm::StructType *Ty,
                                      StringRef suffix) {

clang/lib/CodeGen/CodeGenTypes.h

@@ -178,6 +178,7 @@ public:
   const TargetInfo &getTarget() const { return Target; }
   CGCXXABI &getCXXABI() const { return TheCXXABI; }
   llvm::LLVMContext &getLLVMContext() { return TheModule.getContext(); }
+  const CodeGenOptions &getCodeGenOpts() const;
 
   /// ConvertType - Convert type T into a llvm::Type.
   llvm::Type *ConvertType(QualType T);

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -62,9 +62,20 @@ public:
 
   bool classifyReturnType(CGFunctionInfo &FI) const override;
 
+  bool passClassIndirect(const CXXRecordDecl *RD) const {
+    // Clang <= 4 used the pre-C++11 rule, which ignores move operations.
+    // The PS4 platform ABI follows the behavior of Clang 3.2.
+    if (CGM.getCodeGenOpts().getClangABICompat() <=
+            CodeGenOptions::ClangABI::Ver4 ||
+        CGM.getTriple().getOS() == llvm::Triple::PS4)
+      return RD->hasNonTrivialDestructor() ||
+             RD->hasNonTrivialCopyConstructor();
+    return !canCopyArgument(RD);
+  }
+
   RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override {
     // If C++ prohibits us from making a copy, pass by address.
-    if (!canCopyArgument(RD))
+    if (passClassIndirect(RD))
       return RAA_Indirect;
     return RAA_Default;
   }
@@ -1012,7 +1023,7 @@ bool ItaniumCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
     return false;
 
   // If C++ prohibits us from making a copy, return by address.
-  if (!canCopyArgument(RD)) {
+  if (passClassIndirect(RD)) {
     auto Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
     FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
     return true;

clang/lib/CodeGen/TargetInfo.cpp

@@ -184,7 +184,11 @@ const TargetInfo &ABIInfo::getTarget() const {
   return CGT.getTarget();
 }
 
-bool ABIInfo:: isAndroid() const { return getTarget().getTriple().isAndroid(); }
+const CodeGenOptions &ABIInfo::getCodeGenOpts() const {
+  return CGT.getCodeGenOpts();
+}
+
+bool ABIInfo::isAndroid() const { return getTarget().getTriple().isAndroid(); }
 
 bool ABIInfo::isHomogeneousAggregateBaseType(QualType Ty) const {
   return false;
@@ -2112,9 +2116,14 @@ class X86_64ABIInfo : public SwiftABIInfo {
     return !getTarget().getTriple().isOSDarwin();
   }
 
-  /// GCC classifies <1 x long long> as SSE but compatibility with older clang
+  /// GCC classifies <1 x long long> as SSE but some platform ABIs choose to
-  // compilers require us to classify it as INTEGER.
+  /// classify it as INTEGER (for compatibility with older clang compilers).
   bool classifyIntegerMMXAsSSE() const {
+    // Clang <= 3.8 did not do this.
+    if (getCodeGenOpts().getClangABICompat() <=
+        CodeGenOptions::ClangABI::Ver3_8)
+      return false;
+
     const llvm::Triple &Triple = getTarget().getTriple();
     if (Triple.isOSDarwin() || Triple.getOS() == llvm::Triple::PS4)
       return false;

clang/lib/Driver/ToolChains/Clang.cpp

@@ -2933,6 +2933,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
 
   addPGOAndCoverageFlags(C, D, Output, Args, CmdArgs);
 
+  if (auto *ABICompatArg = Args.getLastArg(options::OPT_fclang_abi_compat_EQ))
+    ABICompatArg->render(Args, CmdArgs);
+
   // Add runtime flag for PS4 when PGO or Coverage are enabled.
   if (getToolChain().getTriple().isPS4CPU())
     PS4cpu::addProfileRTArgs(getToolChain(), Args, CmdArgs);

clang/lib/Frontend/CompilerInvocation.cpp

@@ -573,6 +573,33 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   if (!Opts.ProfileInstrumentUsePath.empty())
     setPGOUseInstrumentor(Opts, Opts.ProfileInstrumentUsePath);
 
+  if (Arg *A = Args.getLastArg(OPT_fclang_abi_compat_EQ)) {
+    Opts.setClangABICompat(CodeGenOptions::ClangABI::Latest);
+
+    StringRef Ver = A->getValue();
+    std::pair<StringRef, StringRef> VerParts = Ver.split('.');
+    unsigned Major, Minor = 0;
+
+    // Check the version number is valid: either 3.x (0 <= x <= 9) or
+    // y or y.0 (4 <= y <= current version).
+    if (!VerParts.first.startswith("0") &&
+        !VerParts.first.getAsInteger(10, Major) &&
+        3 <= Major && Major <= CLANG_VERSION_MAJOR &&
+        (Major == 3 ? VerParts.second.size() == 1 &&
+                      !VerParts.second.getAsInteger(10, Minor)
+                    : VerParts.first.size() == Ver.size() ||
+                      VerParts.second == "0")) {
+      // Got a valid version number.
+      if (Major == 3 && Minor <= 8)
+        Opts.setClangABICompat(CodeGenOptions::ClangABI::Ver3_8);
+      else if (Major <= 4)
+        Opts.setClangABICompat(CodeGenOptions::ClangABI::Ver4);
+    } else if (Ver != "latest") {
+      Diags.Report(diag::err_drv_invalid_value)
+          << A->getAsString(Args) << A->getValue();
+    }
+  }
+
   Opts.CoverageMapping =
       Args.hasFlag(OPT_fcoverage_mapping, OPT_fno_coverage_mapping, false);
   Opts.DumpCoverageMapping = Args.hasArg(OPT_dump_coverage_mapping);

clang/test/CodeGenCXX/clang-abi-compat.cpp

@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=3.0 %s -emit-llvm -o - | FileCheck --check-prefix=PRE39 --check-prefix=PRE5 %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=3.8 %s -emit-llvm -o - | FileCheck --check-prefix=PRE39 --check-prefix=PRE5 %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=3.9 %s -emit-llvm -o - | FileCheck --check-prefix=V39 --check-prefix=PRE5 %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=4.0 %s -emit-llvm -o - | FileCheck --check-prefix=V39 --check-prefix=PRE5 %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=5 %s -emit-llvm -o - | FileCheck --check-prefix=V39 --check-prefix=V5 %s
+// RUN: %clang_cc1 -std=c++17 -triple x86_64-linux-gnu -fclang-abi-compat=latest %s -emit-llvm -o - | FileCheck --check-prefix=V39 --check-prefix=V5 %s
+
+typedef __attribute__((vector_size(8))) long long v1xi64;
+void clang39(v1xi64) {}
+// PRE39: @_Z7clang39Dv1_x(i64
+// V39: @_Z7clang39Dv1_x(double
+
+struct A {
+  A(const A&) = default;
+  A(A&&);
+};
+void clang5(A) {}
+// PRE5: @_Z6clang51A()
+// V5: @_Z6clang51A(%{{.*}}*

clang/test/CodeGenCXX/uncopyable-args.cpp

@@ -1,4 +1,6 @@
-// RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=NEWABI
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-unknown-unknown -fclang-abi-compat=4.0 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=OLDABI
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-scei-ps4 -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=OLDABI
 // RUN: %clang_cc1 -std=c++11 -triple x86_64-windows-msvc -emit-llvm -o - %s -fms-compatibility -fms-compatibility-version=18 | FileCheck %s -check-prefix=WIN64 -check-prefix=WIN64-18
 // RUN: %clang_cc1 -std=c++11 -triple x86_64-windows-msvc -emit-llvm -o - %s -fms-compatibility -fms-compatibility-version=19 | FileCheck %s -check-prefix=WIN64 -check-prefix=WIN64-19
 
@@ -56,8 +58,10 @@ void bar() {
 // CHECK-LABEL: define void @_ZN9move_ctor3barEv()
 // CHECK: call void @_Z{{.*}}C1Ev(
 // CHECK-NOT: call
-// CHECK: call void @_ZN9move_ctor3fooENS_1AE(%"struct.move_ctor::A"* %{{.*}})
+// NEWABI: call void @_ZN9move_ctor3fooENS_1AE(%"struct.move_ctor::A"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN9move_ctor3fooENS_1AE(%"struct.move_ctor::A"*)
+// OLDABI: call void @_ZN9move_ctor3fooENS_1AE(i8* %{{.*}})
+// NEWABI-LABEL: declare void @_ZN9move_ctor3fooENS_1AE(%"struct.move_ctor::A"*)
+// OLDABI-LABEL: declare void @_ZN9move_ctor3fooENS_1AE(i8*)
 
 // WIN64-LABEL: declare void @"\01?foo@move_ctor@@YAXUA@1@@Z"(%"struct.move_ctor::A"*)
 }
@@ -76,8 +80,10 @@ void bar() {
 // CHECK-LABEL: define void @_ZN11all_deleted3barEv()
 // CHECK: call void @_Z{{.*}}C1Ev(
 // CHECK-NOT: call
-// CHECK: call void @_ZN11all_deleted3fooENS_1AE(%"struct.all_deleted::A"* %{{.*}})
+// NEWABI: call void @_ZN11all_deleted3fooENS_1AE(%"struct.all_deleted::A"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN11all_deleted3fooENS_1AE(%"struct.all_deleted::A"*)
+// OLDABI: call void @_ZN11all_deleted3fooENS_1AE(i8* %{{.*}})
+// NEWABI-LABEL: declare void @_ZN11all_deleted3fooENS_1AE(%"struct.all_deleted::A"*)
+// OLDABI-LABEL: declare void @_ZN11all_deleted3fooENS_1AE(i8*)
 
 // WIN64-LABEL: declare void @"\01?foo@all_deleted@@YAXUA@1@@Z"(%"struct.all_deleted::A"*)
 }
@@ -95,8 +101,10 @@ void bar() {
 // CHECK-LABEL: define void @_ZN18implicitly_deleted3barEv()
 // CHECK: call void @_Z{{.*}}C1Ev(
 // CHECK-NOT: call
-// CHECK: call void @_ZN18implicitly_deleted3fooENS_1AE(%"struct.implicitly_deleted::A"* %{{.*}})
+// NEWABI: call void @_ZN18implicitly_deleted3fooENS_1AE(%"struct.implicitly_deleted::A"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN18implicitly_deleted3fooENS_1AE(%"struct.implicitly_deleted::A"*)
+// OLDABI: call void @_ZN18implicitly_deleted3fooENS_1AE(i8* %{{.*}})
+// NEWABI-LABEL: declare void @_ZN18implicitly_deleted3fooENS_1AE(%"struct.implicitly_deleted::A"*)
+// OLDABI-LABEL: declare void @_ZN18implicitly_deleted3fooENS_1AE(i8*)
 
 // In MSVC 2013, the copy ctor is not deleted by a move assignment. In MSVC 2015, it is.
 // WIN64-18-LABEL: declare void @"\01?foo@implicitly_deleted@@YAXUA@1@@Z"(i64
@@ -116,8 +124,10 @@ void bar() {
 // CHECK-LABEL: define void @_ZN11one_deleted3barEv()
 // CHECK: call void @_Z{{.*}}C1Ev(
 // CHECK-NOT: call
-// CHECK: call void @_ZN11one_deleted3fooENS_1AE(%"struct.one_deleted::A"* %{{.*}})
+// NEWABI: call void @_ZN11one_deleted3fooENS_1AE(%"struct.one_deleted::A"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN11one_deleted3fooENS_1AE(%"struct.one_deleted::A"*)
+// OLDABI: call void @_ZN11one_deleted3fooENS_1AE(i8* %{{.*}})
+// NEWABI-LABEL: declare void @_ZN11one_deleted3fooENS_1AE(%"struct.one_deleted::A"*)
+// OLDABI-LABEL: declare void @_ZN11one_deleted3fooENS_1AE(i8*)
 
 // WIN64-LABEL: declare void @"\01?foo@one_deleted@@YAXUA@1@@Z"(%"struct.one_deleted::A"*)
 }
@@ -196,8 +206,10 @@ void bar() {
 }
 // CHECK-LABEL: define void @_ZN14two_copy_ctors3barEv()
 // CHECK: call void @_Z{{.*}}C1Ev(
-// CHECK: call void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"* %{{.*}})
+// NEWABI: call void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"*)
+// OLDABI: call void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"* byval
+// NEWABI-LABEL: declare void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"*)
+// OLDABI-LABEL: declare void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"* byval
 
 // WIN64-LABEL: declare void @"\01?foo@two_copy_ctors@@YAXUB@1@@Z"(%"struct.two_copy_ctors::B"*)
 }
@@ -209,7 +221,8 @@ struct A {
   void *p;
 };
 void *foo(A a) { return a.p; }
-// CHECK-LABEL: define i8* @_ZN15definition_only3fooENS_1AE(%"struct.definition_only::A"*
+// NEWABI-LABEL: define i8* @_ZN15definition_only3fooENS_1AE(%"struct.definition_only::A"*
+// OLDABI-LABEL: define i8* @_ZN15definition_only3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@definition_only@@YAPEAXUA@1@@Z"(%"struct.definition_only::A"*
 }
 
@@ -224,7 +237,8 @@ struct A {
   B b;
 };
 void *foo(A a) { return a.b.p; }
-// CHECK-LABEL: define i8* @_ZN17deleted_by_member3fooENS_1AE(%"struct.deleted_by_member::A"*
+// NEWABI-LABEL: define i8* @_ZN17deleted_by_member3fooENS_1AE(%"struct.deleted_by_member::A"*
+// OLDABI-LABEL: define i8* @_ZN17deleted_by_member3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@deleted_by_member@@YAPEAXUA@1@@Z"(%"struct.deleted_by_member::A"*
 }
 
@@ -238,7 +252,8 @@ struct A : B {
   A();
 };
 void *foo(A a) { return a.p; }
-// CHECK-LABEL: define i8* @_ZN15deleted_by_base3fooENS_1AE(%"struct.deleted_by_base::A"*
+// NEWABI-LABEL: define i8* @_ZN15deleted_by_base3fooENS_1AE(%"struct.deleted_by_base::A"*
+// OLDABI-LABEL: define i8* @_ZN15deleted_by_base3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@deleted_by_base@@YAPEAXUA@1@@Z"(%"struct.deleted_by_base::A"*
 }
 
@@ -253,7 +268,8 @@ struct A {
   B b;
 };
 void *foo(A a) { return a.b.p; }
-// CHECK-LABEL: define i8* @_ZN22deleted_by_member_copy3fooENS_1AE(%"struct.deleted_by_member_copy::A"*
+// NEWABI-LABEL: define i8* @_ZN22deleted_by_member_copy3fooENS_1AE(%"struct.deleted_by_member_copy::A"*
+// OLDABI-LABEL: define i8* @_ZN22deleted_by_member_copy3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@deleted_by_member_copy@@YAPEAXUA@1@@Z"(%"struct.deleted_by_member_copy::A"*
 }
 
@@ -267,7 +283,8 @@ struct A : B {
   A();
 };
 void *foo(A a) { return a.p; }
-// CHECK-LABEL: define i8* @_ZN20deleted_by_base_copy3fooENS_1AE(%"struct.deleted_by_base_copy::A"*
+// NEWABI-LABEL: define i8* @_ZN20deleted_by_base_copy3fooENS_1AE(%"struct.deleted_by_base_copy::A"*
+// OLDABI-LABEL: define i8* @_ZN20deleted_by_base_copy3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@deleted_by_base_copy@@YAPEAXUA@1@@Z"(%"struct.deleted_by_base_copy::A"*
 }
 
@@ -277,7 +294,8 @@ struct A {
   A(const A &o) = delete;
   void *p;
 };
-// CHECK-LABEL: define i8* @_ZN15explicit_delete3fooENS_1AE(%"struct.explicit_delete::A"*
+// NEWABI-LABEL: define i8* @_ZN15explicit_delete3fooENS_1AE(%"struct.explicit_delete::A"*
+// OLDABI-LABEL: define i8* @_ZN15explicit_delete3fooENS_1AE(i8*
 // WIN64-LABEL: define i8* @"\01?foo@explicit_delete@@YAPEAXUA@1@@Z"(%"struct.explicit_delete::A"*
 void *foo(A a) { return a.p; }
 }
@@ -289,7 +307,8 @@ struct A {
   // Deleted copy ctor due to rvalue ref member.
   int &&ref;
 };
-// CHECK-LABEL: define {{.*}} @_ZN28implicitly_deleted_copy_ctor3fooENS_1AE(%"struct.implicitly_deleted_copy_ctor::A"*
+// NEWABI-LABEL: define {{.*}} @_ZN28implicitly_deleted_copy_ctor3fooENS_1AE(%"struct.implicitly_deleted_copy_ctor::A"*
+// OLDABI-LABEL: define {{.*}} @_ZN28implicitly_deleted_copy_ctor3fooENS_1AE(i32*
 // WIN64-LABEL: define {{.*}} @"\01?foo@implicitly_deleted_copy_ctor@@YAAEAHUA@1@@Z"(%"struct.implicitly_deleted_copy_ctor::A"*
 int &foo(A a) { return a.ref; }
 

clang/test/Driver/flags.c

@@ -24,3 +24,6 @@
 
 // RUN: %clang -target armv7-apple-darwin10 -### -S -mno-implicit-float -mimplicit-float %s 2>&1 | FileCheck -check-prefix=TEST8 %s
 // TEST8-NOT: "-no-implicit-float"
+
+// RUN: %clang -target x86_64-linux-gnu -### -c -fclang-abi-compat=3.2 %s 2>&1 | FileCheck -check-prefix=TEST9 %s
+// TEST9: "-fclang-abi-compat=3.2"

clang/test/Frontend/clang-abi-compat.cpp

@@ -0,0 +1,15 @@
+// RUN: not %clang_cc1 -fclang-abi-compat=banana %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=2.9 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=8 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=3.10 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=4.1 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=04 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=4. %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// RUN: not %clang_cc1 -fclang-abi-compat=4.00 %s -fsyntax-only 2>&1 | FileCheck --check-prefix=INVALID %s
+// INVALID: error: invalid value '{{.*}}' in '-fclang-abi-compat={{.*}}'
+//
+// RUN: %clang_cc1 -fclang-abi-compat=3.0 %s -fsyntax-only
+// RUN: %clang_cc1 -fclang-abi-compat=3.9 %s -fsyntax-only
+// RUN: %clang_cc1 -fclang-abi-compat=4 %s -fsyntax-only
+// RUN: %clang_cc1 -fclang-abi-compat=4.0 %s -fsyntax-only
+// RUN: %clang_cc1 -fclang-abi-compat=latest %s -fsyntax-only