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).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@311823 91177308-0d34-0410-b5e6-96231b3b80d8

14 files changed, 160 insertions, 23 deletions

diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index 2c58e27363..88b7680e4f 100644
--- a/include/clang/Driver/Options.td
+++ b/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">;
diff --git a/include/clang/Frontend/CodeGenOptions.def b/include/clang/Frontend/CodeGenOptions.def
index c9040e7e40..a806c48765 100644
--- a/include/clang/Frontend/CodeGenOptions.def
+++ b/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.
 
diff --git a/include/clang/Frontend/CodeGenOptions.h b/include/clang/Frontend/CodeGenOptions.h
index 22d5d3d16e..71730a21db 100644
--- a/include/clang/Frontend/CodeGenOptions.h
+++ b/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).
diff --git a/lib/CodeGen/ABIInfo.h b/lib/CodeGen/ABIInfo.h
index e4dce2f2a0..575506da84 100644
--- a/lib/CodeGen/ABIInfo.h
+++ b/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.
diff --git a/lib/CodeGen/CodeGenTypes.cpp b/lib/CodeGen/CodeGenTypes.cpp
index 4ba0ba863c..adc3b9b4c8 100644
--- a/lib/CodeGen/CodeGenTypes.cpp
+++ b/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) {
diff --git a/lib/CodeGen/CodeGenTypes.h b/lib/CodeGen/CodeGenTypes.h
index f0b97ebde1..9d0e3ded23 100644
--- a/lib/CodeGen/CodeGenTypes.h
+++ b/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);
diff --git a/lib/CodeGen/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index 5c33f8c1af..d78c032cec 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/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;
diff --git a/lib/CodeGen/TargetInfo.cpp b/lib/CodeGen/TargetInfo.cpp
index 64ee31f83d..77b9b4caab 100644
--- a/lib/CodeGen/TargetInfo.cpp
+++ b/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
-  // compilers require us to classify it as INTEGER.
+  /// GCC classifies <1 x long long> as SSE but some platform ABIs choose to
+  /// 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;
diff --git a/lib/Driver/ToolChains/Clang.cpp b/lib/Driver/ToolChains/Clang.cpp
index fa768b70c5..47b9256f6c 100644
--- a/lib/Driver/ToolChains/Clang.cpp
+++ b/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);
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index aea3af9828..abf6b0b302 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/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);
diff --git a/test/CodeGenCXX/clang-abi-compat.cpp b/test/CodeGenCXX/clang-abi-compat.cpp
new file mode 100644
index 0000000000..409c72108f
--- /dev/null
+++ b/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(%{{.*}}*
diff --git a/test/CodeGenCXX/uncopyable-args.cpp b/test/CodeGenCXX/uncopyable-args.cpp
index ef7168cdaa..66d67e4a34 100644
--- a/test/CodeGenCXX/uncopyable-args.cpp
+++ b/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"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN9move_ctor3fooENS_1AE(%"struct.move_ctor::A"*)
+// NEWABI: call 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"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN11all_deleted3fooENS_1AE(%"struct.all_deleted::A"*)
+// NEWABI: call 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"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN18implicitly_deleted3fooENS_1AE(%"struct.implicitly_deleted::A"*)
+// NEWABI: call 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"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN11one_deleted3fooENS_1AE(%"struct.one_deleted::A"*)
+// NEWABI: call 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"* %{{.*}})
-// CHECK-LABEL: declare void @_ZN14two_copy_ctors3fooENS_1BE(%"struct.two_copy_ctors::B"*)
+// NEWABI: call 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; }
 
diff --git a/test/Driver/flags.c b/test/Driver/flags.c
index ff60caf2e0..656ac41a94 100644
--- a/test/Driver/flags.c
+++ b/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"
diff --git a/test/Frontend/clang-abi-compat.cpp b/test/Frontend/clang-abi-compat.cpp
new file mode 100644
index 0000000000..7ee94646b6
--- /dev/null
+++ b/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