clang should emulate GCC's -fabi-version=<X>

[steleman]

Summary

This changeset provides an implementation of GCC's -fabi-version=<X> flag.

-fabi-version is documented at GCC here:
https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html

GCC implements it here:
${top_srcdir}/gcc/c-family/c-cppbuiltin.c

[steleman]

The diff is based on 3.6.2.

tools/clang/include/clang/Basic/LangOptions.def

               "default struct packing maximum alignment")
 VALUE_LANGOPT(MaxTypeAlign  , 32, 0,
               "default maximum alignment for types")
+VALUE_LANGOPT(GXXABIVersion , 32, 0,
+              "Use specified GNU C++ Standard Library ABI version")
 VALUE_LANGOPT(PICLevel    , 2, 0, "__PIC__ level")
 VALUE_LANGOPT(PIELevel    , 2, 0, "__PIE__ level")
 LANGOPT(GNUInline         , 1, 0, "GNU inline semantics")

tools/clang/include/clang/Driver/Options.td

 def ffp_contract : Joined<["-"], "ffp-contract=">, Group<f_Group>,
   Flags<[CC1Option]>, HelpText<"Form fused FP ops (e.g. FMAs): fast (everywhere)"
   " | on (according to FP_CONTRACT pragma, default) | off (never fuse)">;
+def fabi_version_EQ : Joined<["-"], "fabi-version=">, Group<f_Group>,
+  Flags<[CC1Option]>, HelpText<"Use specified GNU C++ ABI version">;
 
 def ffor_scope : Flag<["-"], "ffor-scope">, Group<f_Group>;
 def fno_for_scope : Flag<["-"], "fno-for-scope">, Group<f_Group>;

tools/clang/lib/Driver/Tools.cpp

     CmdArgs.push_back(A->getValue());
   }
 
+  if (Arg *A = Args.getLastArg(options::OPT_fabi_version_EQ)) {
+    StringRef v = A->getValue();
+    CmdArgs.push_back(Args.MakeArgString("-fabi-version=" + v));
+    A->claim();
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_fpcc_struct_return,
                                options::OPT_freg_struct_return)) {
     if (getToolChain().getArch() != llvm::Triple::x86) {

tools/clang/lib/Frontend/CompilerInvocation.cpp

   Opts.EmitAllDecls = Args.hasArg(OPT_femit_all_decls);
   Opts.PackStruct = getLastArgIntValue(Args, OPT_fpack_struct_EQ, 0, Diags);
   Opts.MaxTypeAlign = getLastArgIntValue(Args, OPT_fmax_type_align_EQ, 0, Diags);
+  Opts.GXXABIVersion = getLastArgIntValue(Args, OPT_fabi_version_EQ, 0, Diags);
   Opts.PICLevel = getLastArgIntValue(Args, OPT_pic_level, 0, Diags);
   Opts.PIELevel = getLastArgIntValue(Args, OPT_pie_level, 0, Diags);
   Opts.Static = Args.hasArg(OPT_static_define);

tools/clang/lib/Frontend/InitPreprocessor.cpp

     Builder.defineMacro("__GNUC_MINOR__", "2");
     Builder.defineMacro("__GNUC_PATCHLEVEL__", "1");
     Builder.defineMacro("__GNUC__", "4");
+    // GCC provides a number of C++ ABI Versions in:
+    // ${top_srcdir}/gcc/c-family/c-cppbuiltin.c
+    // Currently valid GXX ABI Versions are documented here:
+    // https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html
+    // clang only supports a subset.
+    switch (LangOpts.GXXABIVersion) {
+    default:
     Builder.defineMacro("__GXX_ABI_VERSION", "1002");
+      break;
+    case 4:
+      Builder.defineMacro("__GXX_ABI_VERSION", "1004");
+      break;
+    case 5:
+      Builder.defineMacro("__GXX_ABI_VERSION", "1005");
+      break;
+    case 6:
+      Builder.defineMacro("__GXX_ABI_VERSION", "1006");
+      break;
+    case 7:
+      Builder.defineMacro("__GXX_ABI_VERSION", "1007");
+      break;
+    case 8:
+      Builder.defineMacro("__GXX_ABI_VERSION", "1008");
+      break;
+    }
   }
 
   // Define macros for the C11 / C++11 memory orderings