Support for MSVS default calling convention options (/Gd, /Gz, /Gv, /Gr)

[• a.makarov]

Summary

Patch for bug #27711

[rnk]

include/clang/Basic/LangOptions.def

219–220

Let's get rid of this and have it use a single DefaultCallingConv LangOpt.

include/clang/Driver/CC1Options.td

613

Let's unify the -cc1 layer with -mrtd, and just have a single -fdefault-calling-convention=stdcall/etc flag.

lib/AST/ASTContext.cpp

8627

I don't think we need to guard this on MSVCCompat, it'll be unset usually. It will also help us avoid a special path for MRTD.

8633–8636

Neither fastcall nor stdcall can be applied to variadic functions.

[majnemer]

lib/AST/ASTContext.cpp

8604–8606

Do these flags not have an effect on methods?

[rnk]

lib/AST/ASTContext.cpp

8604–8606

Nope:
https://msdn.microsoft.com/en-us/library/46t77ak2.aspx
"for all functions except C++ member functions..."

[majnemer]

lib/AST/ASTContext.cpp

8604–8606

Yeah, that's what the documentation says. But do they really have no effect? :)

[• a.makarov]

lib/AST/ASTContext.cpp

8604–8606

Yes, I've checked. Member functions are not affected =)

[• a.makarov]

lib/AST/ASTContext.cpp

8633–8636

As I've got from MSDN, vectorcall and stdcall cannot be applied to vararg functions. Are you sure about fastcall?)

[• a.makarov]

Thanks for the review! I've updated the patch, please take a look.
Modifications:

• the dependency from MS compatibility mode is removed;
• the option is renamed into '-fdefault-calling-conv' (since it's not in MS compatibility mode);
• the '-mrtd' option is now an alias for '-fdefault-calling-conv=stdcall';
• 'stdcall' is now ignored for variadic functions;
• since 'vectorcall' requires SSE2 or higher (https://msdn.microsoft.com/en-us/library/dn375768.aspx) the necessary check is added

[majnemer]

include/clang/Basic/LangOptions.def

175

I'd remove the "MS" from this langopt now that it helps implement -mrtd.

[• a.makarov]

Renamed option 'DefaultMSCallingConv' into 'DefaultCallingConv' and enum 'DefaultMSCallingConvention' into 'DefaultCallingConvention'.

[rnk]

include/clang/Driver/CC1Options.td

615

Doesn't this have to live in Options.td if you want it to be available in the driver interface? Otherwise it's a -cc1-only flag.

lib/Sema/SemaDeclAttr.cpp

3898–3903

Use leading upper case variables to achieve consistency with our insanity, please. :)

[• a.makarov]

I've updated the patch. Please take a look.

[rnk]

Thanks, lgtm!

[• a.makarov]

Thanks!

include/clang/Basic/LangOptions.h

public:
 
   enum PragmaMSPointersToMembersKind {
     PPTMK_BestCase,
     PPTMK_FullGeneralitySingleInheritance,
     PPTMK_FullGeneralityMultipleInheritance,
     PPTMK_FullGeneralityVirtualInheritance
   };
 
+  enum DefaultMSCallingConvention {
+    DCC_None,
+    DCC_CDecl,
+    DCC_FastCall,
+    DCC_StdCall,
+    DCC_VectorCall
+  };
+
   enum AddrSpaceMapMangling { ASMM_Target, ASMM_On, ASMM_Off };
 
   enum MSVCMajorVersion {
     MSVC2010 = 16,
     MSVC2012 = 17,
     MSVC2013 = 18,
     MSVC2015 = 19
   };

include/clang/Basic/LangOptions.def

 COMPATIBLE_LANGOPT(UnsafeFPMath      , 1, 0, "Unsafe Floating Point Math")
 
 BENIGN_LANGOPT(ObjCGCBitmapPrint , 1, 0, "printing of GC's bitmap layout for __weak/__strong ivars")
 
 BENIGN_LANGOPT(AccessControl     , 1, 1, "C++ access control")
 LANGOPT(CharIsSigned      , 1, 1, "signed char")
 LANGOPT(ShortWChar        , 1, 0, "unsigned short wchar_t")
 ENUM_LANGOPT(MSPointerToMemberRepresentationMethod, PragmaMSPointersToMembersKind, 2, PPTMK_BestCase, "member-pointer representation method")
+ENUM_LANGOPT(DefaultMSCallingConv, DefaultMSCallingConvention, 3, DCC_None, "default calling convention")
 
 LANGOPT(ShortEnums        , 1, 0, "short enum types")
 
 LANGOPT(OpenCL            , 1, 0, "OpenCL")
 LANGOPT(OpenCLVersion     , 32, 0, "OpenCL version")
 LANGOPT(NativeHalfType    , 1, 0, "Native half type support")
 LANGOPT(NativeHalfArgsAndReturns, 1, 0, "Native half args and returns")
 LANGOPT(HalfArgsAndReturns, 1, 0, "half args and returns")

 LANGOPT(NoBitFieldTypeAlign , 1, 0, "bit-field type alignment")
 LANGOPT(HexagonQdsp6Compat , 1, 0, "hexagon-qdsp6 backward compatibility")
 LANGOPT(ObjCAutoRefCount , 1, 0, "Objective-C automated reference counting")
 LANGOPT(ObjCWeakRuntime     , 1, 0, "__weak support in the ARC runtime")
 LANGOPT(ObjCWeak            , 1, 0, "Objective-C __weak in ARC and MRC files")
 LANGOPT(ObjCSubscriptingLegacyRuntime         , 1, 0, "Subscripting support in legacy ObjectiveC runtime")
 LANGOPT(FakeAddressSpaceMap , 1, 0, "OpenCL fake address space map")
 ENUM_LANGOPT(AddressSpaceMapMangling , AddrSpaceMapMangling, 2, ASMM_Target, "OpenCL address space map mangling mode")
 
-LANGOPT(MRTD , 1, 0, "-mrtd calling convention")
 BENIGN_LANGOPT(DelayedTemplateParsing , 1, 0, "delayed template parsing")
 LANGOPT(BlocksRuntimeOptional , 1, 0, "optional blocks runtime")
 
 ENUM_LANGOPT(GC, GCMode, 2, NonGC, "Objective-C Garbage Collection mode")
 ENUM_LANGOPT(ValueVisibilityMode, Visibility, 3, DefaultVisibility,
              "value symbol visibility")
 ENUM_LANGOPT(TypeVisibilityMode, Visibility, 3, DefaultVisibility,
              "type symbol visibility")
 ENUM_LANGOPT(StackProtector, StackProtectorMode, 2, SSPOff,

include/clang/Driver/CC1Options.td

 def fno_rtti_data : Flag<["-"], "fno-rtti-data">,
   HelpText<"Control emission of RTTI data">;
 def fnative_half_type: Flag<["-"], "fnative-half-type">,
   HelpText<"Use the native half type for __fp16 instead of promoting to float">;
 def fnative_half_arguments_and_returns : Flag<["-"], "fnative-half-arguments-and-returns">,
   HelpText<"Use the native __fp16 type for arguments and returns (and skip ABI-specific lowering)">;
 def fallow_half_arguments_and_returns : Flag<["-"], "fallow-half-arguments-and-returns">,
   HelpText<"Allow function arguments and returns of type half">;
+def fdefault_calling_conv_EQ : Joined<["-"], "fdefault-calling-conv=">,
+  HelpText<"Set default MS calling convention">;
+def mrtd : Flag<["-"], "mrtd">, Group<m_Group>,
+  Alias<fdefault_calling_conv_EQ>, AliasArgs<["stdcall"]>,
+  HelpText<"Make StdCall the default calling convention">;
 
 // C++ TSes.
 def fcoroutines : Flag<["-"], "fcoroutines">,
   HelpText<"Enable support for the C++ Coroutines TS">;
 
 //===----------------------------------------------------------------------===//
 // Header Search Options
 //===----------------------------------------------------------------------===//

include/clang/Driver/CLCompatOptions.td

def _SLASH_Yu : CLJoined<"Yu">,
   HelpText<"Load a pch file and use it instead of all code up to "
            "and including <filename>">,
   MetaVarName<"<filename>">;
 def _SLASH_Y_ : CLFlag<"Y-">,
   HelpText<"Disable precompiled headers, overrides /Yc and /Yu">;
 def _SLASH_Fp : CLJoined<"Fp">,
   HelpText<"Set pch filename (with /Yc and /Yu)">, MetaVarName<"<filename>">;
 
+def _SLASH_Gd : CLFlag<"Gd">,
+  HelpText<"Set __cdecl as a default calling convention">;
+def _SLASH_Gr : CLFlag<"Gr">,
+  HelpText<"Set __fastcall as a default calling convention">;
+def _SLASH_Gz : CLFlag<"Gz">,
+  HelpText<"Set __stdcall as a default calling convention">;
+def _SLASH_Gv : CLFlag<"Gv">,
+  HelpText<"Set __vectorcall as a default calling convention">;
+
 // Ignored:
 
 def _SLASH_analyze_ : CLIgnoredFlag<"analyze-">;
 def _SLASH_bigobj : CLIgnoredFlag<"bigobj">;
 def _SLASH_cgthreads : CLIgnoredJoined<"cgthreads">;
 def _SLASH_d2FastFail : CLIgnoredFlag<"d2FastFail">;
 def _SLASH_d2Zi_PLUS : CLIgnoredFlag<"d2Zi+">;
 def _SLASH_errorReport : CLIgnoredJoined<"errorReport">;
 def _SLASH_Fd : CLIgnoredJoined<"Fd">;
 def _SLASH_FC : CLIgnoredFlag<"FC">;
 def _SLASH_FS : CLIgnoredFlag<"FS">, HelpText<"Force synchronous PDB writes">;
-def _SLASH_Gd : CLIgnoredFlag<"Gd">;
 def _SLASH_GF : CLIgnoredFlag<"GF">;
 def _SLASH_GS_ : CLIgnoredFlag<"GS-">;
 def _SLASH_kernel_ : CLIgnoredFlag<"kernel-">;
 def _SLASH_nologo : CLIgnoredFlag<"nologo">;
 def _SLASH_Ob1 : CLIgnoredFlag<"Ob1">;
 def _SLASH_Ob2 : CLIgnoredFlag<"Ob2">;
 def _SLASH_Og : CLIgnoredFlag<"Og">;
 def _SLASH_openmp_ : CLIgnoredFlag<"openmp-">;

 def _SLASH_G2 : CLFlag<"G2">;
 def _SLASH_Ge : CLFlag<"Ge">;
 def _SLASH_Gh : CLFlag<"Gh">;
 def _SLASH_GH : CLFlag<"GH">;
 def _SLASH_GL : CLFlag<"GL">;
 def _SLASH_GL_ : CLFlag<"GL-">;
 def _SLASH_Gm : CLFlag<"Gm">;
 def _SLASH_Gm_ : CLFlag<"Gm-">;
-def _SLASH_Gr : CLFlag<"Gr">;
 def _SLASH_GS : CLFlag<"GS">;
 def _SLASH_GT : CLFlag<"GT">;
 def _SLASH_Guard : CLJoined<"guard:">;
-def _SLASH_Gv : CLFlag<"Gv">;
-def _SLASH_Gz : CLFlag<"Gz">;
 def _SLASH_GZ : CLFlag<"GZ">;
 def _SLASH_H : CLFlag<"H">;
 def _SLASH_homeparams : CLFlag<"homeparams">;
 def _SLASH_hotpatch : CLFlag<"hotpatch">;
 def _SLASH_kernel : CLFlag<"kernel">;
 def _SLASH_LN : CLFlag<"LN">;
 def _SLASH_MP : CLJoined<"MP">;
 def _SLASH_openmp : CLFlag<"openmp">;

include/clang/Driver/Options.td

 def mregparm_EQ : Joined<["-"], "mregparm=">, Group<m_Group>;
 def mrelax_all : Flag<["-"], "mrelax-all">, Group<m_Group>, Flags<[CC1Option,CC1AsOption]>,
   HelpText<"(integrated-as) Relax all machine instructions">;
 def mincremental_linker_compatible : Flag<["-"], "mincremental-linker-compatible">, Group<m_Group>,
   Flags<[CC1Option,CC1AsOption]>,
   HelpText<"(integrated-as) Emit an object file which can be used with an incremental linker">;
 def mno_incremental_linker_compatible : Flag<["-"], "mno-incremental-linker-compatible">, Group<m_Group>,
   HelpText<"(integrated-as) Emit an object file which cannot be used with an incremental linker">;
-def mrtd : Flag<["-"], "mrtd">, Group<m_Group>, Flags<[CC1Option]>,
-  HelpText<"Make StdCall calling convention the default">;
 def msmall_data_threshold_EQ : Joined <["-"], "msmall-data-threshold=">, Group<m_Group>;
 def msoft_float : Flag<["-"], "msoft-float">, Group<m_Group>, Flags<[CC1Option]>,
   HelpText<"Use software floating point">;
 def mno_implicit_float : Flag<["-"], "mno-implicit-float">, Group<m_Group>,
   HelpText<"Don't generate implicit floating point instructions">;
 def mimplicit_float : Flag<["-"], "mimplicit-float">, Group<m_Group>;
 def mrecip : Flag<["-"], "mrecip">, Group<m_Group>;
 def mrecip_EQ : CommaJoined<["-"], "mrecip=">, Group<m_Group>, Flags<[CC1Option]>;

lib/AST/ASTContext.cpp

if (VD->getInit() && VD->getInit()->HasSideEffects(*this) &&
       !VD->evaluateValue())
     return true;
 
   return false;
 }
 
 CallingConv ASTContext::getDefaultCallingConvention(bool IsVariadic,
                                                     bool IsCXXMethod) const {
   // Pass through to the C++ ABI object
   if (IsCXXMethod)
     return ABI->getDefaultMethodCallConv(IsVariadic);
 
-  if (LangOpts.MRTD && !IsVariadic) return CC_X86StdCall;
-
+  switch (LangOpts.getDefaultMSCallingConv()) {
+  case LangOptions::DCC_None:
+    break;
+  case LangOptions::DCC_CDecl:
+    return CC_C;
+  case LangOptions::DCC_FastCall:
+    if (getTargetInfo().hasFeature("sse2"))
+      return CC_X86FastCall;
+    break;
+  case LangOptions::DCC_StdCall:
+    if (!IsVariadic)
+      return CC_X86StdCall;
+    break;
+  case LangOptions::DCC_VectorCall:
+    // __vectorcall cannot be applied to variadic functions.
+    if (!IsVariadic)
+      return CC_X86VectorCall;
+    break;
+  }
   return Target->getDefaultCallingConv(TargetInfo::CCMT_Unknown);
 }
 
 bool ASTContext::isNearlyEmpty(const CXXRecordDecl *RD) const {
   // Pass through to the C++ ABI object
   return ABI->isNearlyEmpty(RD);
 }
 
 VTableContextBase *ASTContext::getVTableContext() {
   if (!VTContext.get()) {
     if (Target->getCXXABI().isMicrosoft())
       VTContext.reset(new MicrosoftVTableContext(*this));
     else
       VTContext.reset(new ItaniumVTableContext(*this));
   }
   return VTContext.get();
 }
 

lib/Driver/Tools.cpp

if (MostGeneralArg) {
     if (SingleArg)
       CmdArgs.push_back("-fms-memptr-rep=single");
     else if (MultipleArg)
       CmdArgs.push_back("-fms-memptr-rep=multiple");
     else
       CmdArgs.push_back("-fms-memptr-rep=virtual");
   }
 
+  if (Args.getLastArg(options::OPT__SLASH_Gd))
+     CmdArgs.push_back("-fdefault-calling-conv=cdecl");
+  else if (Args.getLastArg(options::OPT__SLASH_Gr))
+     CmdArgs.push_back("-fdefault-calling-conv=fastcall");
+  else if (Args.getLastArg(options::OPT__SLASH_Gz))
+     CmdArgs.push_back("-fdefault-calling-conv=stdcall");
+  else if (Args.getLastArg(options::OPT__SLASH_Gv))
+     CmdArgs.push_back("-fdefault-calling-conv=vectorcall");
+
   if (Arg *A = Args.getLastArg(options::OPT_vtordisp_mode_EQ))
     A->render(Args, CmdArgs);
 
   if (!Args.hasArg(options::OPT_fdiagnostics_format_EQ)) {
     CmdArgs.push_back("-fdiagnostics-format");
     if (Args.hasArg(options::OPT__SLASH_fallback))
       CmdArgs.push_back("msvc-fallback");
     else

lib/Frontend/CompilerInvocation.cpp

#include "clang/Frontend/LangStandards.def"
   Opts.DumpRecordLayoutsSimple = Args.hasArg(OPT_fdump_record_layouts_simple);
   Opts.DumpRecordLayouts = Opts.DumpRecordLayoutsSimple
                         || Args.hasArg(OPT_fdump_record_layouts);
   Opts.DumpVTableLayouts = Args.hasArg(OPT_fdump_vtable_layouts);
   Opts.SpellChecking = !Args.hasArg(OPT_fno_spell_checking);
   Opts.NoBitFieldTypeAlign = Args.hasArg(OPT_fno_bitfield_type_align);
   Opts.SinglePrecisionConstants = Args.hasArg(OPT_cl_single_precision_constant);
   Opts.FastRelaxedMath = Args.hasArg(OPT_cl_fast_relaxed_math);
-  Opts.MRTD = Args.hasArg(OPT_mrtd);
   Opts.HexagonQdsp6Compat = Args.hasArg(OPT_mqdsp6_compat);
   Opts.FakeAddressSpaceMap = Args.hasArg(OPT_ffake_address_space_map);
   Opts.ParseUnknownAnytype = Args.hasArg(OPT_funknown_anytype);
   Opts.DebuggerSupport = Args.hasArg(OPT_fdebugger_support);
   Opts.DebuggerCastResultToId = Args.hasArg(OPT_fdebugger_cast_result_to_id);
   Opts.DebuggerObjCLiteral = Args.hasArg(OPT_fdebugger_objc_literal);
   Opts.ApplePragmaPack = Args.hasArg(OPT_fapple_pragma_pack);
   Opts.CurrentModule = Args.getLastArgValue(OPT_fmodule_name_EQ);
LangOptions::PragmaMSPointersToMembersKind InheritanceModel =
             .Default(LangOptions::PPTMK_BestCase);
     if (InheritanceModel == LangOptions::PPTMK_BestCase)
       Diags.Report(diag::err_drv_invalid_value)
           << "-fms-memptr-rep=" << A->getValue();
 
     Opts.setMSPointerToMemberRepresentationMethod(InheritanceModel);
   }
 
+  // Check for MS default calling conventions being specified.
+  if (Arg *A = Args.getLastArg(OPT_fdefault_calling_conv_EQ)) {
+    LangOptions::DefaultMSCallingConvention DefaultCC =
+        llvm::StringSwitch<LangOptions::DefaultMSCallingConvention>(
+            A->getValue())
+            .Case("cdecl", LangOptions::DCC_CDecl)
+            .Case("fastcall", LangOptions::DCC_FastCall)
+            .Case("stdcall", LangOptions::DCC_StdCall)
+            .Case("vectorcall", LangOptions::DCC_VectorCall)
+            .Default(LangOptions::DCC_None);
+    if (DefaultCC == LangOptions::DCC_None)
+      Diags.Report(diag::err_drv_invalid_value)
+          << "-fdefault-calling-conv=" << A->getValue();
+
+    llvm::Triple T(TargetOpts.Triple);
+    llvm::Triple::ArchType Arch = T.getArch();
+    bool emitError = (DefaultCC == LangOptions::DCC_FastCall ||
+                  DefaultCC == LangOptions::DCC_StdCall) &&
+                 Arch != llvm::Triple::x86;
+    emitError |= DefaultCC == LangOptions::DCC_VectorCall &&
+                 !(Arch == llvm::Triple::x86 || Arch == llvm::Triple::x86_64);
+    if (emitError)
+      Diags.Report(diag::err_drv_argument_not_allowed_with)
+          << A->getSpelling() << T.getTriple();
+    else
+      Opts.setDefaultMSCallingConv(DefaultCC);
+  }
+
   // Check if -fopenmp is specified.
   Opts.OpenMP = Args.hasArg(options::OPT_fopenmp);
   Opts.OpenMPUseTLS =
       Opts.OpenMP && !Args.hasArg(options::OPT_fnoopenmp_use_tls);
   Opts.OpenMPIsDevice =
       Opts.OpenMP && Args.hasArg(options::OPT_fopenmp_is_device);
 
   // Provide diagnostic when a given target is not expected to be an OpenMP

lib/Sema/SemaDeclAttr.cpp

bool Sema::CheckCallingConvAttr(const AttributeList &attr, CallingConv &CC,
   const TargetInfo &TI = Context.getTargetInfo();
   TargetInfo::CallingConvCheckResult A = TI.checkCallingConvention(CC);
   if (A != TargetInfo::CCCR_OK) {
     if (A == TargetInfo::CCCR_Warning)
       Diag(attr.getLoc(), diag::warn_cconv_ignored) << attr.getName();
 
     // This convention is not valid for the target. Use the default function or
     // method calling convention.
-    TargetInfo::CallingConvMethodType MT = TargetInfo::CCMT_Unknown;
-    if (FD)
-      MT = FD->isCXXInstanceMember() ? TargetInfo::CCMT_Member : 
-                                    TargetInfo::CCMT_NonMember;
-    CC = TI.getDefaultCallingConv(MT);
+    bool isCXXMethod = false, isVariadic = false;
+    if (FD) {
+      isCXXMethod = FD->isCXXInstanceMember();
+      isVariadic = FD->isVariadic();
+    }
+    CC = Context.getDefaultCallingConvention(isVariadic, isCXXMethod);
   }
 
   attr.setProcessingCache((unsigned) CC);
   return false;
 }
 
 /// Pointer-like types in the default address space.
 static bool isValidSwiftContextType(QualType type) {

test/CodeGenCXX/default_calling_conv.cpp

+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -fdefault-calling-conv=cdecl -emit-llvm -o - %s | FileCheck %s --check-prefix=CDECL --check-prefix=ALL
+// RUN: %clang_cc1 -triple i786-unknown-linux-gnu -target-feature +sse4.2 -fdefault-calling-conv=fastcall -emit-llvm -o - %s | FileCheck %s --check-prefix=FASTCALL --check-prefix=ALL
+// RUN: %clang_cc1 -triple i486-unknown-linux-gnu -fdefault-calling-conv=stdcall -emit-llvm -o - %s | FileCheck %s --check-prefix=STDCALL --check-prefix=ALL
+// RUN: %clang_cc1 -triple i486-unknown-linux-gnu -mrtd -emit-llvm -o - %s | FileCheck %s --check-prefix=STDCALL --check-prefix=ALL
+// RUN: %clang_cc1 -triple i986-unknown-linux-gnu -fdefault-calling-conv=vectorcall -emit-llvm -o - %s | FileCheck %s --check-prefix=VECTORCALL --check-prefix=ALL
+
+// CDECL: define void @_Z5test1v
+// FASTCALL: define x86_fastcallcc void @_Z5test1v
+// STDCALL: define x86_stdcallcc void @_Z5test1v
+// VECTORCALL: define x86_vectorcallcc void @_Z5test1v
+void test1() {}
+
+// ALL: define void @_Z5test2v
+void __attribute__((cdecl)) test2() {}
+
+// ALL: define x86_fastcallcc void @_Z5test3v
+void __attribute__((fastcall)) test3() {}
+
+// ALL: define x86_stdcallcc void @_Z5test4v
+void __attribute__((stdcall)) test4() {}
+
+// ALL: define  x86_vectorcallcc void @_Z5test5v
+void __attribute__((vectorcall)) test5() {}
+
+// ALL: define linkonce_odr void @_ZN1A11test_memberEv
+class A {
+public:
+  void test_member() {}
+};
+
+void test() {
+  A a;
+  a.test_member();
+}