[X86] Fix __code_model_*__ predefine names

[mcgrathr]

Summary

GCC defines code_model_* (two trailing underscores), not
__code_model_*_ (one trailing underscore).

[MaskRay]

LG. The full story:

// gcc/config/i386/i386-c.c
    case CM_SMALL:
    case CM_SMALL_PIC:
      def_or_undef (parse_in, "__code_model_small__");
      break;
    case CM_MEDIUM:
    case CM_MEDIUM_PIC:
      def_or_undef (parse_in, "__code_model_medium__");
      break;
    case CM_LARGE:
    case CM_LARGE_PIC:
      def_or_undef (parse_in, "__code_model_large__");
      break;
    case CM_32:
      def_or_undef (parse_in, "__code_model_32__");
      break;
    case CM_KERNEL:
      def_or_undef (parse_in, "__code_model_kernel__");
      break;

[mcgrathr]

Thanks! Can you land it for me?

clang/lib/Basic/Targets/X86.cpp

 void X86TargetInfo::getTargetDefines(const LangOptions &Opts,
                                      MacroBuilder &Builder) const {
   // Inline assembly supports X86 flag outputs.
   Builder.defineMacro("__GCC_ASM_FLAG_OUTPUTS__");
 
   std::string CodeModel = getTargetOpts().CodeModel;
   if (CodeModel == "default")
     CodeModel = "small";
-  Builder.defineMacro("__code_model_" + CodeModel + "_");
+  Builder.defineMacro("__code_model_" + CodeModel + "__");
 
   // Target identification.
   if (getTriple().getArch() == llvm::Triple::x86_64) {
     Builder.defineMacro("__amd64__");
     Builder.defineMacro("__amd64");
     Builder.defineMacro("__x86_64");
     Builder.defineMacro("__x86_64__");
     if (getTriple().getArchName() == "x86_64h") {

clang/test/Preprocessor/init.c

 // X86_64:#define __USER_LABEL_PREFIX__
 // X86_64:#define __WCHAR_MAX__ 2147483647
 // X86_64:#define __WCHAR_TYPE__ int
 // X86_64:#define __WCHAR_WIDTH__ 32
 // X86_64:#define __WINT_TYPE__ int
 // X86_64:#define __WINT_WIDTH__ 32
 // X86_64:#define __amd64 1
 // X86_64:#define __amd64__ 1
-// X86_64:#define __code_model_small_ 1
+// X86_64:#define __code_model_small__ 1
 // X86_64:#define __x86_64 1
 // X86_64:#define __x86_64__ 1
 //
 // RUN: %clang_cc1 -E -dM -ffreestanding -triple=x86_64h-none-none < /dev/null | FileCheck -match-full-lines -check-prefix X86_64H %s
 //
 // X86_64H:#define __x86_64 1
 // X86_64H:#define __x86_64__ 1
 // X86_64H:#define __x86_64h 1
 // X86_64H:#define __x86_64h__ 1
 //
 // 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
+// X86_MEDIUM:#define __code_model_medium__ 1
 //
 // 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
 // X32:#define __BIGGEST_ALIGNMENT__ 16
 // X32:#define __BYTE_ORDER__ __ORDER_LITTLE_ENDIAN__