Add default calling convention support for regcall.

[eandrews]

Summary

Added support for regcall as default calling convention. Also added code to exclude main when applying default calling conventions.

[rnk]

lib/Sema/SemaType.cpp

3269–3273 ↗

(On Diff #119957)

I highly doubt this is correct. I have a feeling there are all kinds of ways you can get this to fire on things that aren't a function declaration. It's also inefficient to check the identifier string every time we make a function type. Please find somewhere else to add this. I'd suggest adjusting the function type in CheckMain, or some time before then, whereever we make main implicitly extern "C".

[erichkeane]

lib/Sema/SemaType.cpp

3269–3273 ↗

(On Diff #119957)

I believe the logic here was pulled from FunctionDecl's "isMain" function: https://clang.llvm.org/doxygen/classclang_1_1FunctionDecl.html#aa2b31caf653741632b16cce1ae2061cc

As this is so early in the process (at Declarator), I didn't see a good place to recommend extracting this, besides pulling it into the Declarator.

CheckMain is also run at the Decl stage, isn't it? Is your suggestion be to simply let this go through with the wrong calling-convention here, then revert it it in "CheckMain"?

[rnk]

lib/Sema/SemaType.cpp

3269–3273 ↗

(On Diff #119957)

Yep. You can look at how we use FunctionTypeUnwrapper and ASTContext::adjustFunctionType in various places to fix up function types that were built with the wrong calling convention without losing type source info.

[erichkeane]

lib/Sema/SemaType.cpp

3269–3273 ↗

(On Diff #119957)

Perfect, thanks for the examples! I am sure @eandrews can use those to track down the right place to fix this up.

[eandrews]

Updated patch to set default calling convention for main() in CheckMain()

[eandrews]

lib/Sema/SemaType.cpp

3269–3273 ↗

(On Diff #119957)

Thanks for the review! I've updated the patch. Please take a look.

[eandrews]

*ping*

[rnk]

Looks good! Sorry for the delay.

[eandrews]

No problem! Thanks!

include/clang/Basic/LangOptions.h

enum PragmaMSPointersToMembersKind {
     PPTMK_FullGeneralityVirtualInheritance
   };
 
   enum DefaultCallingConvention {
     DCC_None,
     DCC_CDecl,
     DCC_FastCall,
     DCC_StdCall,
-    DCC_VectorCall
+    DCC_VectorCall,
+    DCC_RegCall
   };
 
   enum AddrSpaceMapMangling { ASMM_Target, ASMM_On, ASMM_Off };
 
   enum MSVCMajorVersion {
     MSVC2010 = 16,
     MSVC2012 = 17,
     MSVC2013 = 18,

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">, Values<"cdecl,fastcall,stdcall,vectorcall">;
+  HelpText<"Set default calling convention">, Values<"cdecl,fastcall,stdcall,vectorcall,regcall">;
 def finclude_default_header : Flag<["-"], "finclude-default-header">,
   HelpText<"Include the default header file for OpenCL">;
 def fpreserve_vec3_type : Flag<["-"], "fpreserve-vec3-type">,
   HelpText<"Preserve 3-component vector type">;
 def fwchar_type_EQ : Joined<["-"], "fwchar-type=">,
   HelpText<"Select underlying type for wchar_t">, Values<"char,short,int">;
 def fsigned_wchar : Flag<["-"], "fsigned-wchar">,
   HelpText<"Use a signed type for wchar_t">;

include/clang/Driver/CLCompatOptions.td

 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">;
+def _SLASH_Gregcall : CLFlag<"Gregcall">,
+  HelpText<"Set __regcall 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+">;

lib/AST/ASTContext.cpp

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;
+  case LangOptions::DCC_RegCall:
+    // __regcall cannot be applied to variadic functions.
+    if (!IsVariadic)
+      return CC_X86RegCall;
+    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);
 }

lib/Driver/ToolChains/Clang.cpp

else if (MultipleArg)
       CmdArgs.push_back("-fms-memptr-rep=multiple");
     else
       CmdArgs.push_back("-fms-memptr-rep=virtual");
   }
 
   // Parse the default calling convention options.
   if (Arg *CCArg =
           Args.getLastArg(options::OPT__SLASH_Gd, options::OPT__SLASH_Gr,
-                          options::OPT__SLASH_Gz, options::OPT__SLASH_Gv)) {
+                          options::OPT__SLASH_Gz, options::OPT__SLASH_Gv,
+                          options::OPT__SLASH_Gregcall)) {
     unsigned DCCOptId = CCArg->getOption().getID();
     const char *DCCFlag = nullptr;
     bool ArchSupported = true;
     llvm::Triple::ArchType Arch = getToolChain().getArch();
     switch (DCCOptId) {
     case options::OPT__SLASH_Gd:
       DCCFlag = "-fdefault-calling-conv=cdecl";
       break;
     case options::OPT__SLASH_Gr:
       ArchSupported = Arch == llvm::Triple::x86;
       DCCFlag = "-fdefault-calling-conv=fastcall";
       break;
     case options::OPT__SLASH_Gz:
       ArchSupported = Arch == llvm::Triple::x86;
       DCCFlag = "-fdefault-calling-conv=stdcall";
       break;
     case options::OPT__SLASH_Gv:
       ArchSupported = Arch == llvm::Triple::x86 || Arch == llvm::Triple::x86_64;
       DCCFlag = "-fdefault-calling-conv=vectorcall";
       break;
+    case options::OPT__SLASH_Gregcall:
+      ArchSupported = Arch == llvm::Triple::x86 || Arch == llvm::Triple::x86_64;
+      DCCFlag = "-fdefault-calling-conv=regcall";
+      break;
     }
 
     // MSVC doesn't warn if /Gr or /Gz is used on x64, so we don't either.
     if (ArchSupported && DCCFlag)
       CmdArgs.push_back(DCCFlag);
   }
 
   if (Arg *A = Args.getLastArg(options::OPT_vtordisp_mode_EQ))

lib/Frontend/CompilerInvocation.cpp

if (InheritanceModel == LangOptions::PPTMK_BestCase)
           << "-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::DefaultCallingConvention DefaultCC =
-        llvm::StringSwitch<LangOptions::DefaultCallingConvention>(
-            A->getValue())
+        llvm::StringSwitch<LangOptions::DefaultCallingConvention>(A->getValue())
             .Case("cdecl", LangOptions::DCC_CDecl)
             .Case("fastcall", LangOptions::DCC_FastCall)
             .Case("stdcall", LangOptions::DCC_StdCall)
             .Case("vectorcall", LangOptions::DCC_VectorCall)
+            .Case("regcall", LangOptions::DCC_RegCall)
             .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 &&
+    emitError |= (DefaultCC == LangOptions::DCC_VectorCall ||
+                  DefaultCC == LangOptions::DCC_RegCall) &&
                  !(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.setDefaultCallingConv(DefaultCC);
   }
 

lib/Sema/SemaDecl.cpp

if (getLangOpts().OpenCL) {
     FD->setInvalidDecl();
     return;
   }
 
   QualType T = FD->getType();
   assert(T->isFunctionType() && "function decl is not of function type");
   const FunctionType* FT = T->castAs<FunctionType>();
 
+  // Set default calling convention for main()
+  if (FT->getCallConv() != CC_C) {
+    FT = Context.adjustFunctionType(FT, FT->getExtInfo().withCallingConv(CC_C));
+    FD->setType(QualType(FT, 0));
+    T = Context.getCanonicalType(FD->getType());
+  }
+
   if (getLangOpts().GNUMode && !getLangOpts().CPlusPlus) {
     // In C with GNU extensions we allow main() to have non-integer return
     // type, but we should warn about the extension, and we disable the
     // implicit-return-zero rule.
 
     // GCC in C mode accepts qualified 'int'.
     if (Context.hasSameUnqualifiedType(FT->getReturnType(), Context.IntTy))
       FD->setHasImplicitReturnZero(true);

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
+// RUN: %clang_cc1 -triple i986-unknown-linux-gnu -fdefault-calling-conv=regcall -emit-llvm -o - %s | FileCheck %s --check-prefix=REGCALL --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
+// REGCALL: define x86_regcallcc void @_Z17__regcall3__test1v
 void test1() {}
 
-// fastcall, stdcall, and vectorcall all do not support variadic functions.
+// fastcall, stdcall, vectorcall and regcall do not support variadic functions.
 // CDECL: define void @_Z12testVariadicz
 // FASTCALL: define void @_Z12testVariadicz
 // STDCALL: define void @_Z12testVariadicz
 // VECTORCALL: define void @_Z12testVariadicz
+// REGCALL: define void @_Z12testVariadicz
 void testVariadic(...){}
 
 // 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 x86_regcallcc void @_Z17__regcall3__test6v
+void __attribute__((regcall)) test6() {}
+
 // ALL: define linkonce_odr void @_ZN1A11test_memberEv
 class A {
 public:
   void test_member() {}
 };
 
 void test() {
   A a;
   a.test_member();
 }
+
+// ALL: define i32 @main
+int main() {
+  return 1;
+}

test/Driver/cl-cc-flags.c

 // Note: %s must be preceded by --, otherwise it may be interpreted as a
 // command-line option, e.g. on Mac where %s is commonly under /Users.
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gd -### -- %s 2>&1 | FileCheck --check-prefix=CDECL %s
 // CDECL: -fdefault-calling-conv=cdecl
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gr -### -- %s 2>&1 | FileCheck --check-prefix=FASTCALL %s
 // FASTCALL: -fdefault-calling-conv=fastcall
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gz -### -- %s 2>&1 | FileCheck --check-prefix=STDCALL %s
 // STDCALL: -fdefault-calling-conv=stdcall
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gv -### -- %s 2>&1 | FileCheck --check-prefix=VECTORCALL %s
 // VECTORCALL: -fdefault-calling-conv=vectorcall
 
+// RUN: %clang_cl --target=i686-windows-msvc /Gregcall -### -- %s 2>&1 | FileCheck --check-prefix=REGCALL %s
+// REGCALL: -fdefault-calling-conv=regcall
+
 // Last one should win:
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gd /Gv -### -- %s 2>&1 | FileCheck --check-prefix=LASTWINS_VECTOR %s
 // LASTWINS_VECTOR: -fdefault-calling-conv=vectorcall
 
 // RUN: %clang_cl --target=i686-windows-msvc /Gv /Gd -### -- %s 2>&1 | FileCheck --check-prefix=LASTWINS_CDECL %s
 // LASTWINS_CDECL: -fdefault-calling-conv=cdecl