diff --git a/byterun/src/compiler.cpp b/byterun/src/compiler.cpp
index d9cc2d5a3..122218d0f 100644
--- a/byterun/src/compiler.cpp
+++ b/byterun/src/compiler.cpp
@@ -42,14 +42,52 @@ std::vector<U> transform(std::vector<T> v, const std::function<U(T &&)> &f) {
   return result;
 }
 
+template <typename T> void insert(std::vector<T> &x, std::vector<T> &&y) {
+  x.insert(x.end(), std::move_iterator(y.begin()), std::move_iterator(y.end()));
+}
+
+template <typename T> std::vector<T> reverse(std::vector<T> &&x) {
+  std::reverse(x.begin(), x.end());
+  return std::move(x);
+}
+
 template <typename T> std::vector<T> concat(std::vector<T> &&x) {
   return std::move(x);
 }
 
-template <typename T, typename... Args>
-std::vector<T> concat(std::vector<T> &&x, std::vector<T> &&y, Args &&...args) {
-  x.insert(x.end(), std::move_iterator(y.begin()), std::move_iterator(y.end()));
-  return concat(std::move(x), std::forward<Args>(args)...);
+// --> declarations
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, T>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args);
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, std::optional<T>>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args);
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, std::vector<T>>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args);
+// <--
+
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, std::vector<T>>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args) {
+  insert(x, std::move(y));
+  return concat<T, Args...>(std::move(x), std::forward<Args>(args)...);
+}
+
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, T>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args) {
+  x.push_back(std::move(y));
+  return concat<T, Args...>(std::move(x), std::forward<Args>(args)...);
+}
+
+template <typename T, typename U, typename... Args>
+  requires std::is_same_v<U, std::optional<T>>
+std::vector<T> concat(std::vector<T> &&x, U &&y, Args &&...args) {
+  if (y) {
+    x.push_back(std::move(*y));
+  }
+  return concat<T, Args...>(std::move(x), std::forward<Args>(args)...);
 }
 
 // template <typename T, typename... Args>
@@ -167,6 +205,7 @@ const auto r12 = Register::from_number(12);
 const auto r13 = Register::from_number(13);
 const auto r14 = Register::from_number(14);
 const auto r15 = Register::from_number(15);
+
 const std::vector<Register::T> argument_registers = {rdi, rsi, rdx,
                                                      rcx, r8,  r9};
 const std::vector<Register::T> extra_caller_saved_registers = {r10, r11, r12,
@@ -276,6 +315,8 @@ using M = Opnd::M;
 using R = Opnd::R;
 using S = Opnd::S;
 
+/* Value that could be used to fill unused stack locations.
+   Garbage is not allowed as it will affect GC. */
 struct ArgumentLocation {
   struct Register {
     Opnd opnd;
@@ -466,13 +507,13 @@ struct ValT {
     std::string s;
   };
   struct Local {
-    int n;
+    size_t n;
   };
   struct Arg {
-    int n;
+    size_t n;
   };
   struct Access {
-    int n;
+    size_t n;
   };
   struct Fun {
     std::string s;
@@ -550,6 +591,10 @@ template <typename U> struct AbstractSymbolicStack {
 
     const W &operator*() const { return val; }
     const W &operator->() const { return val; }
+
+    template <typename S> bool is() const {
+      return std::holds_alternative<S>(val);
+    }
   };
   using Stack = SymbolicLocation::Stack;
   using Register = SymbolicLocation::Register;
@@ -665,8 +710,9 @@ struct SymbolicStack {
   using R = AbSS::StackState::R;
   using E = AbSS::StackState::E;
 
-  using Stack = AbSS::SymbolicLocation::Stack;
-  using Register = AbSS::SymbolicLocation::Register;
+  using SymbolicLocation = AbSS::SymbolicLocation;
+  using Stack = SymbolicLocation::Stack;
+  using Register = SymbolicLocation::Register;
 
   // type t
 
@@ -694,7 +740,7 @@ struct SymbolicStack {
     };
   }
 
-  static Opnd opnd_from_loc(const T &v, const AbSS::SymbolicLocation &loc) {
+  static Opnd opnd_from_loc(const T &v, const SymbolicLocation &loc) {
     return std::visit(
         utils::multifunc{
             [](const Register &x) -> Opnd { return {Opnd::R{x.r}}; },
@@ -900,7 +946,8 @@ public:
   /* is rdx register in use */
   bool rdx_in_use() const { return nargs > 2; }
 
-  std::vector<Opnd> arguments_locations(size_t n) {
+  std::pair<std::vector<SymbolicStack::SymbolicLocation>, size_t>
+  arguments_locations(size_t n) {
     // TODO
     // if n < argument_registers_size then
     //   ( Array.to_list (Array.sub argument_registers 0 n)
@@ -1421,7 +1468,7 @@ std::vector<Instr> compile_binop(Env<Prg, mode_> &env, Opr op) {
    stack. As we do not have control where does the C compiler locate them in the
    moment of GC, we have to explicitly locate them on the stack. And to the
    runtime function we are passing a reference to their location. */
-const std::vector<std::string> safepoint_functions = {
+const std::unordered_set<std::string> safepoint_functions = {
     utils::labeled("s__Infix_58"),     utils::labeled("substring"),
     utils::labeled("clone"),           utils::labeled_builtin("string"),
     utils::labeled("stringcat"),       utils::labeled("string"),
@@ -1434,16 +1481,261 @@ const std::vector<std::string> safepoint_functions = {
     /* Lsprintf, or Bsprintf is an extra dirty hack that probably works */
 };
 
-const std::vector<std::pair<std::string, size_t>> vararg_functions = {
+const std::unordered_map<std::string, size_t> vararg_functions = {
     {utils::labeled("printf"), 1},
     {utils::labeled("fprintf"), 2},
     {utils::labeled("sprintf"), 1},
     {utils::labeled("failure"), 1},
 };
 
+namespace utils::call_compilation::tail {
+
+// NOTE: all comands in result are in inversed order
+void push_args_rec_inv(Env<Prg, mode_> &env, std::vector<Instr> &acc,
+                       size_t n) {
+  if (n == 0) {
+    return;
+  }
+  const auto x = env.pop();
+  utils::insert(acc, utils::reverse(mov(x, env.loc(ValT::Arg{n - 1}))));
+  push_args_rec_inv(env, acc, n - 1);
+}
+std::vector<Instr> push_args(Env<Prg, mode_> &env, size_t n) {
+  std::vector<Instr> acc;
+  push_args_rec_inv(env, acc, n);
+  std::reverse(acc.begin(), acc.end());
+  return acc;
+}
+
+} // namespace utils::call_compilation::tail
+std::vector<Instr> compile_tail_call(Env<Prg, mode_> &env,
+                                     const std::optional<std::string> &fname,
+                                     size_t nargs) {
+  using namespace utils::call_compilation::tail;
+  std::vector<Instr> pushs = push_args(env, nargs);
+
+  std::optional<Instr> setup_closure;
+  if (!fname) {
+    const auto closure = env.pop();
+    setup_closure = Mov{closure, r15};
+  }
+
+  Instr add_argc_counter = Mov{L{static_cast<int>(nargs)}, r11};
+
+  Instr jump = fname ? Instr{Jmp{*fname}} : Instr{JmpI{r15}};
+
+  env.allocate();
+  return utils::concat(std::move(pushs), Instr{Mov{rbp, rsp}}, Instr{Pop{rbp}},
+                       std::move(setup_closure), std::move(add_argc_counter),
+                       std::move(jump));
+}
+
+namespace utils::call_compilation {
+
+std::vector<Opnd> pop_arguments(Env<Prg, mode_> &env, size_t n) {
+  std::vector<Opnd> result;
+  result.reserve(n);
+  for (size_t i = 0; i < n; ++i) {
+    const auto x = env.pop();
+    result.push_back(x);
+  }
+  std::reverse(result.begin(), result.end());
+  return result;
+};
+
+namespace common {
+
+std::pair<size_t, std::vector<Instr>> setup_arguments(Env<Prg, mode_> &env,
+                                                      size_t nargs) {
+  const auto move_arguments =
+      [](std::vector<Opnd> &&args,
+         std::vector<SymbolicStack::SymbolicLocation> &&arg_locs) {
+        using Register = SymbolicStack::Register;
+        using Stack = SymbolicStack::Stack;
+
+        assert(args.size() == arg_locs.size());
+
+        std::vector<Instr> result;
+        result.reserve(args.size());
+        // NOTE: direction should be (fold left)
+        for (size_t i = 0; i < args.size(); ++i) {
+          result.push_back(
+              arg_locs[i].is<Register>()
+                  ? Instr{Mov{args[i], std::get<Register>(*arg_locs[i]).r}}
+                  : /*Stack*/ Push{args[i]});
+        }
+        std::reverse(result.begin(), result.end());
+        return result;
+      };
+  auto args = pop_arguments(env, nargs);
+  auto [arg_locs, stack_slots] = env.arguments_locations(args.size());
+  auto setup_args_code = move_arguments(std::move(args), std::move(arg_locs));
+  return {stack_slots, std::move(setup_args_code)};
+}
+
+std::optional<Instr> setup_closure(Env<Prg, mode_> &env,
+                                   const std::optional<std::string> &fname) {
+  if (!fname) {
+    return {};
+  }
+  const auto closure = env.pop();
+  return Mov{closure, r15};
+}
+
+Instr call(const std::optional<std::string> &fname) {
+  return fname ? Instr{Call{*fname}} : Instr{CallI{r15}};
+}
+
+Instr add_argc_counter(const std::optional<std::string> &fname, size_t nargs) {
+  const auto it =
+      fname ? vararg_functions.find(*fname) : vararg_functions.end();
+  size_t argc = it == vararg_functions.end() ? 0 : it->second;
+  return Mov{L{static_cast<int>(nargs - argc)}, r11};
+}
+
+} // namespace common
+
+std::pair<std::vector<Instr>, std::vector<Instr>>
+protect_registers(Env<Prg, mode_> &env) {
+  std::vector<Instr> pushr;
+  std::vector<Instr> popr;
+  if (env.has_closure) {
+    pushr.push_back(Push{r15});
+    popr.push_back(Pop{r15});
+  }
+
+  pushr = utils::concat(
+      std::move(pushr),
+      utils::transform<Opnd, Instr>(env.live_registers(),
+                                    [](const auto &r) { return Push{r}; }));
+  popr = utils::concat(
+      std::move(popr),
+      utils::transform<Opnd, Instr>(
+          env.live_registers(), [](const auto &r) -> Instr { return Pop{r}; }));
+
+  return {pushr, popr};
+}
+
+std::pair<std::optional<Instr>, std::optional<Instr>>
+align_stack(size_t saved_registers, size_t stack_arguments) {
+  const bool aligned = (saved_registers + stack_arguments) % 2 == 0;
+  if (aligned && stack_arguments == 0) {
+    return {{}, {}};
+  }
+  if (aligned) {
+    return {{},
+            {Binop{Opr::ADD, L{static_cast<int>(word_size * stack_arguments)},
+                   rsp}}};
+  }
+
+  return {Push{filler},
+          {Binop{Opr::ADD,
+                 L{static_cast<int>(word_size * (1 + stack_arguments))}, rsp}}};
+}
+
+Instr move_result(Env<Prg, mode_> &env) {
+  const auto y = env.allocate();
+  return Mov{rax, y};
+}
+
+} // namespace utils::call_compilation
+std::vector<Instr> compile_common_call(Env<Prg, mode_> &env,
+                                       const std::optional<std::string> &fname,
+                                       size_t nargs) {
+  using namespace utils::call_compilation::common;
+  using namespace utils::call_compilation;
+
+  auto add_argc_counter_code = add_argc_counter(fname, nargs);
+
+  auto [stack_slots, setup_args_code] = setup_arguments(env, nargs);
+  auto [push_registers, pop_registers] = protect_registers(env);
+  auto [align_prologue, align_epilogue] =
+      align_stack(push_registers.size(), stack_slots);
+  auto setup_closure_code = setup_closure(env, fname);
+  auto call_code = call(fname);
+  auto move_result_code = move_result(env);
+
+  return utils::concat(
+      std::move(push_registers), std::move(align_prologue),
+      std::move(setup_args_code), std::move(setup_closure_code),
+      std::move(add_argc_counter_code), std::move(call_code),
+      std::move(align_epilogue), utils::reverse(std::move(pop_registers)),
+      std::move(move_result_code));
+}
+
+namespace utils::call_compilation::safepoint {
+
+std::pair<size_t, std::vector<Instr>>
+setup_arguments(Env<Prg, mode_> &env, const std::optional<std::string> &fname,
+                size_t nargs) {
+  auto args = pop_arguments(env, nargs);
+  auto [arg_locs, stack_slots] = env.arguments_locations(args.size());
+  auto setup_args_code =
+      utils::transform<Opnd, Instr>(utils::reverse(std::move(args)),
+                                    [](const auto &arg) { return Push{arg}; });
+  setup_args_code.push_back(Mov{rsp, rdi});
+  if (*fname == utils::labeled_builtin("closure")) {
+    setup_args_code.push_back(Mov{L{box(nargs - 1)}, rsi});
+  } else if (*fname == utils::labeled_builtin("sexp") ||
+             *fname == utils::labeled_builtin("array")) {
+    setup_args_code.push_back(Mov{L{box(nargs)}, rsi});
+  }
+  return {nargs, std::move(setup_args_code)};
+}
+
+Instr call(const std::optional<std::string> &fname) { return Call{*fname}; }
+
+} // namespace utils::call_compilation::safepoint
+std::vector<Instr>
+compile_safepoint_call(Env<Prg, mode_> &env,
+                       const std::optional<std::string> &fname, size_t nargs) {
+  using namespace utils::call_compilation::safepoint;
+  using namespace utils::call_compilation;
+
+  auto [stack_slots, setup_args_code] = setup_arguments(env, fname, nargs);
+  auto [push_registers, pop_registers] = protect_registers(env);
+  auto [align_prologue, align_epilogue] =
+      align_stack(push_registers.size(), stack_slots);
+  auto call_code = call(fname);
+  auto move_result_code = move_result(env);
+
+  return utils::concat(std::move(push_registers), std::move(align_prologue),
+                       std::move(setup_args_code), std::move(call_code),
+                       std::move(align_epilogue),
+                       utils::reverse(std::move(pop_registers)),
+                       std::move(move_result_code));
+}
+
 std::vector<Instr> compile_call(Env<Prg, mode_> &env,
-                                std::optional<std::string_view> fname,
-                                size_t nargs, bool tail) {}
+                                std::optional<std::string_view> fname_in,
+                                size_t nargs, bool tail) {
+  std::optional<std::string> fname;
+  if (fname_in) {
+    fname = (*fname_in)[0] == '.' ? utils::labeled_builtin(fname->substr(1))
+                                  : std::string{*fname_in};
+  }
+
+  bool safepoint_call = false;
+  bool allowed_function = true;
+  if (fname) {
+    safepoint_call = (safepoint_functions.count(*fname) != 0);
+    const bool is_vararg = (vararg_functions.count(*fname) != 0);
+    const bool is_internal = ((*fname)[0] == 'B');
+    allowed_function = not is_internal && not is_vararg;
+  }
+
+  const bool same_arguments_count = env.nargs == nargs;
+  const bool tail_call_optimization_applicable =
+      tail && allowed_function && same_arguments_count;
+
+  if (safepoint_call) {
+    return compile_safepoint_call(env, fname, nargs);
+  }
+  if (tail_call_optimization_applicable) {
+    return compile_tail_call(env, fname, nargs);
+  }
+  return compile_common_call(env, fname, nargs);
+}
 
 enum class Patt {
   BOXED,
@@ -1860,4 +2152,10 @@ std::vector<Instr> compile(cmd, Env<Prg, mode_> &env,
 
 std::vector<Instr> compile(cmd, Env<Prg, mode_> &env,
                            const std::vector<std::string> &imports,
-                           const std::vector<SMInstr> &code) {}
+                           const std::vector<SMInstr> &code) {
+  std::vector<Instr> result;
+  for (const auto &instr : code) {
+    result =
+        utils::concat(std::move(result), compile(cmd, env, imports, instr));
+  }
+}