Add default calling convention support for regcall.

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

Patch-By: eandrews

Differential Revision: https://reviews.llvm.org/D39210


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@317268 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Basic/LangOptions.h

@@ -77,7 +77,8 @@ public:
     DCC_CDecl,
     DCC_FastCall,
     DCC_StdCall,
-    DCC_VectorCall
+    DCC_VectorCall,
+    DCC_RegCall
   };
 
   enum AddrSpaceMapMangling { ASMM_Target, ASMM_On, ASMM_Off };

include/clang/Driver/CC1Options.td

@@ -704,7 +704,7 @@ def fnative_half_arguments_and_returns : Flag<["-"], "fnative-half-arguments-and
 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">,

include/clang/Driver/CLCompatOptions.td

@@ -302,6 +302,8 @@ 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:
 

lib/AST/ASTContext.cpp

@@ -9281,6 +9281,11 @@ CallingConv ASTContext::getDefaultCallingConvention(bool IsVariadic,
     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);
 }

lib/Driver/ToolChains/Clang.cpp

@@ -4972,7 +4972,8 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
   // 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;
@@ -4993,6 +4994,10 @@ void Clang::AddClangCLArgs(const ArgList &Args, types::ID InputType,
       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.

lib/Frontend/CompilerInvocation.cpp

@@ -2310,12 +2310,12 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   // 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)
@@ -2326,7 +2326,8 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
     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)

lib/Sema/SemaDecl.cpp

@@ -9673,6 +9673,13 @@ void Sema::CheckMain(FunctionDecl* FD, const DeclSpec& DS) {
   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

test/CodeGenCXX/default_calling_conv.cpp

@@ -3,18 +3,21 @@
 // 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
@@ -29,6 +32,9 @@ 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:
@@ -39,3 +45,8 @@ void test() {
   A a;
   a.test_member();
 }
+
+// ALL: define i32 @main
+int main() {
+  return 1;
+}

test/Driver/cl-cc-flags.c

@@ -13,6 +13,9 @@
 // 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