Expose separate function sections option to compiler

Author: asuhan

include/swift/AST/IRGenOptions.h

@@ -146,6 +146,9 @@ class IRGenOptions {
   /// objects.
   unsigned EmitStackPromotionChecks : 1;
 
+  /// Emit functions to separate sections.
+  unsigned FunctionSections : 1;
+
   /// The maximum number of bytes used on a stack frame for stack promotion
   /// (includes alloc_stack allocations).
   unsigned StackPromotionSizeLimit = 1024;
@@ -249,7 +252,7 @@ class IRGenOptions {
         IntegratedREPL(false), DisableLLVMOptzns(false),
         DisableSwiftSpecificLLVMOptzns(false), DisableLLVMSLPVectorizer(false),
         DisableFPElim(true), Playground(false), EmitStackPromotionChecks(false),
-        PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
+        FunctionSections(false), PrintInlineTree(false), EmbedMode(IRGenEmbedMode::None),
         HasValueNamesSetting(false), ValueNames(false),
         EnableReflectionMetadata(true), EnableReflectionNames(true),
         EnableAnonymousContextMangledNames(false), ForcePublicLinkage(false),

include/swift/Option/FrontendOptions.td

@@ -334,6 +334,10 @@ def disable_reflection_names : Flag<["-"], "disable-reflection-names">,
   HelpText<"Disable emission of names of stored properties and enum cases in"
            "reflection metadata">;
 
+def function_sections: Flag<["-"], "function-sections">,
+  Flags<[FrontendOption, NoInteractiveOption]>,
+  HelpText<"Emit functions to separate sections.">;
+
 def stack_promotion_checks : Flag<["-"], "emit-stack-promotion-checks">,
   HelpText<"Emit runtime checks for correct stack promotion of objects.">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -1136,6 +1136,8 @@ static bool ParseIRGenArgs(IRGenOptions &Opts, ArgList &Args,
     Opts.StackPromotionSizeLimit = limit;
   }
 
+  Opts.FunctionSections = Args.hasArg(OPT_function_sections);
+
   if (Args.hasArg(OPT_autolink_force_load))
     Opts.ForceLoadSymbolName = Args.getLastArgValue(OPT_module_link_name);
 

lib/IRGen/IRGen.cpp

@@ -162,6 +162,7 @@ swift::getIRTargetOptions(IRGenOptions &Opts, ASTContext &Ctx) {
   // Explicitly request debugger tuning for LLDB which is the default
   // on Darwin platforms but not on others.
   TargetOpts.DebuggerTuning = llvm::DebuggerKind::LLDB;
+  TargetOpts.FunctionSections = Opts.FunctionSections;
 
   auto *Clang = static_cast<ClangImporter *>(Ctx.getClangModuleLoader());
   clang::TargetOptions &ClangOpts = Clang->getTargetInfo().getTargetOpts();