codegen: accelerate startup

Function->addFnAttr("thunk") is very expensive, take it out of the fast-path
although we should be able to get rid of the rest of this soon too

src/codegen.cpp

@@ -6264,15 +6264,6 @@ static GlobalVariable *julia_const_gv(jl_value_t *val)
  return nullptr;
 }
 
-static Function *jlcall_func_to_llvm(const std::string &cname, jl_fptr_t addr, Module *m)
-{
- Function *f = Function::Create(jl_func_sig, Function::ExternalLinkage, cname, m);
- add_return_attr(f, Attribute::NonNull);
- f->addFnAttr("thunk");
- add_named_global(f, addr);
- return f;
-}
-
 extern "C" void jl_fptr_to_llvm(jl_fptr_t fptr, jl_method_instance_t *lam, int specsig)
 {
  if (imaging_mode) {
@@ -6291,7 +6282,8 @@ extern "C" void jl_fptr_to_llvm(jl_fptr_t fptr, jl_method_instance_t *lam, int s
  funcName << "jsys1_"; // it's a jlcall without a specsig
  const char* unadorned_name = jl_symbol_name(lam->def.method->name);
  funcName << unadorned_name << "_" << globalUnique++;
- Function *f = jlcall_func_to_llvm(funcName.str(), fptr, NULL);
+ Function *f = Function::Create(jl_func_sig, Function::ExternalLinkage, funcName.str());
+ add_named_global(f, fptr);
  if (specsig) {
  if (lam->functionObjectsDecls.specFunctionObject == NULL) {
  lam->functionObjectsDecls.specFunctionObject = strdup(f->getName().str().c_str());
@@ -6335,6 +6327,15 @@ static void init_julia_llvm_meta(void)
  tbaa_unionselbyte = tbaa_make_child("jtbaa_unionselbyte", tbaa_data_scalar).first;
 }
 
+static Function *jlcall_func_to_llvm(const std::string &cname, jl_fptr_t addr, Module *m)
+{
+ Function *f = Function::Create(jl_func_sig, Function::ExternalLinkage, cname, m);
+ add_return_attr(f, Attribute::NonNull);
+ f->addFnAttr("thunk");
+ add_named_global(f, addr);
+ return f;
+}
+
 static void init_julia_llvm_env(Module *m)
 {
  // every variable or function mapped in this function must be