Add a frontend option to enable use of the swiftcall convention.

Author: rjmccall

include/swift/AST/IRGenOptions.h

@@ -150,16 +150,19 @@ class IRGenOptions {
   /// standard library.
   unsigned EnableReflectionBuiltins : 1;
 
-  /// List of backend command-line options for -embed-bitcode.
-  std::vector<uint8_t> CmdArgs;
-
   /// Should we try to build incrementally by not emitting an object file if it
   /// has the same IR hash as the module that we are preparing to emit?
   ///
   /// This is a debugging option meant to make it easier to perform compile time
   /// measurements on a non-clean build directory.
   unsigned UseIncrementalLLVMCodeGen : 1;
 
+  /// Enable use of the swiftcall calling convention.
+  unsigned UseSwiftCall : 1;
+
+  /// List of backend command-line options for -embed-bitcode.
+  std::vector<uint8_t> CmdArgs;
+
   IRGenOptions() : OutputKind(IRGenOutputKind::LLVMAssembly), Verify(true),
                    Optimize(false), Sanitize(SanitizerKind::None),
                    DebugInfoKind(IRGenDebugInfoKind::None),
@@ -170,8 +173,9 @@ class IRGenOptions {
                    PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
                    HasValueNamesSetting(false), ValueNames(false),
                    EnableReflectionMetadata(false), EnableReflectionNames(false),
-                   EnableReflectionBuiltins(false), CmdArgs(),
-                   UseIncrementalLLVMCodeGen(true)
+                   EnableReflectionBuiltins(false),
+                   UseIncrementalLLVMCodeGen(true), UseSwiftCall(false),
+                   CmdArgs()
                    {}
 
   /// Gets the name of the specified output filename.

include/swift/Option/FrontendOptions.td

@@ -73,6 +73,9 @@ def disable_objc_interop :
   Flag<["-"], "disable-objc-interop">,
   HelpText<"Disable Objective-C interop code generation and config directives">;
 
+def enable_swiftcall : Flag<["-"], "enable-swiftcall">,
+  HelpText<"Enable the use of LLVM swiftcall support">;
+
 def enable_objc_attr_requires_foundation_module :
   Flag<["-"], "enable-objc-attr-requires-foundation-module">,
   HelpText<"Enable requiring uses of @objc to require importing the "

lib/Frontend/CompilerInvocation.cpp

@@ -1217,6 +1217,8 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
   Opts.GenerateProfile |= Args.hasArg(OPT_profile_generate);
   Opts.PrintInlineTree |= Args.hasArg(OPT_print_llvm_inline_tree);
 
+  Opts.UseSwiftCall = Args.hasArg(OPT_enable_swiftcall);
+
   // This is set to true by default.
   Opts.UseIncrementalLLVMCodeGen &=
     !Args.hasArg(OPT_disable_incremental_llvm_codegeneration);