diff --git a/vlib/v/gen/native/amd64.v b/vlib/v/gen/native/amd64.v
index 91fac27b48..2d850b0fdd 100644
--- a/vlib/v/gen/native/amd64.v
+++ b/vlib/v/gen/native/amd64.v
@@ -662,20 +662,29 @@ fn (mut g Gen) mov_var_to_reg(reg Register, var Var, config VarConfig) {
 	}
 }
 
-fn (mut g Gen) call(addr int) {
-	if g.pref.arch == .arm64 {
-		g.bl()
-		return
-	}
+fn (mut g Gen) call_addr_at(addr int, at i64) i64 {
 	// Need to calculate the difference between current position (position after the e8 call)
 	// and the function to call.
 	// +5 is to get the posistion "e8 xx xx xx xx"
 	// Not sure about the -1.
-	rel := 0xffffffff - (g.buf.len + 5 - addr - 1)
+	return 0xffffffff - (at + 5 - addr - 1)
+}
+
+fn (mut g Gen) call(addr int) i64 {
+	if g.pref.arch == .arm64 {
+		g.bl()
+		return 0
+	}
+
+	rel := g.call_addr_at(addr, g.pos())
+	c_addr := g.pos()
 	// println('call addr=$addr.hex2() rel_addr=$rel.hex2() pos=$g.buf.len')
 	g.write8(0xe8)
-	g.write32(rel)
+
+	g.write32(int(rel))
 	g.println('call $addr')
+
+	return c_addr
 }
 
 fn (mut g Gen) syscall() {
@@ -813,8 +822,29 @@ fn (mut g Gen) mul8_var(reg Register, var_offset int) {
 }
 
 fn (mut g Gen) leave() {
-	g.write8(0xc9)
-	g.println('leave')
+	g.println('; label 0: return')
+	if g.defer_stmts.len != 0 {
+		// save return value
+		g.push(.rax)
+		for defer_stmt in g.defer_stmts.reverse() {
+			name := '_defer$defer_stmt.idx_in_fn'
+			defer_var := g.get_var_offset(name)
+			g.mov_var_to_reg(.rax, LocalVar{defer_var, ast.i64_type_idx, name})
+			g.cmp_zero(.rax)
+			label := g.labels.new_label()
+			jump_addr := g.cjmp(.je)
+			g.labels.patches << LabelPatch{
+				id: label
+				pos: jump_addr
+			}
+			g.stmts(defer_stmt.stmts)
+			g.labels.addrs[label] = g.pos()
+		}
+		g.pop(.rax)
+	}
+	g.mov_reg(.rsp, .rbp)
+	g.pop(.rbp)
+	g.ret()
 }
 
 // returns label's relative address
@@ -1341,11 +1371,7 @@ fn (mut g Gen) sar8(r Register, val u8) {
 	g.println('sar $r, $val')
 }
 
-pub fn (mut g Gen) call_fn(node ast.CallExpr) {
-	if g.pref.arch == .arm64 {
-		g.call_fn_arm64(node)
-		return
-	}
+pub fn (mut g Gen) call_fn_amd64(node ast.CallExpr) {
 	name := node.name
 	mut n := name
 	if !n.contains('.') {
@@ -1387,6 +1413,12 @@ pub fn (mut g Gen) call_fn(node ast.CallExpr) {
 	g.println('call `${name}()`')
 }
 
+fn (mut g Gen) call_builtin_amd64(name string) i64 {
+	call_addr := g.call(0)
+	g.println('call builtin `$name`')
+	return call_addr
+}
+
 fn (mut g Gen) patch_calls() {
 	for c in g.callpatches {
 		addr := g.fn_addr[c.name]
@@ -2083,31 +2115,22 @@ fn (mut g Gen) fn_decl_amd64(node ast.FnDecl) {
 		g.ret()
 		return
 	}
-	// g.leave()
 	g.labels.addrs[0] = g.pos()
-	g.println('; label 0: return')
-	if g.defer_stmts.len != 0 {
-		// save return value
-		g.push(.rax)
-		for defer_stmt in g.defer_stmts.reverse() {
-			name := '_defer$defer_stmt.idx_in_fn'
-			defer_var := g.get_var_offset(name)
-			g.mov_var_to_reg(.rax, LocalVar{defer_var, ast.i64_type_idx, name})
-			g.cmp_zero(.rax)
-			label := g.labels.new_label()
-			jump_addr := g.cjmp(.je)
-			g.labels.patches << LabelPatch{
-				id: label
-				pos: jump_addr
-			}
-			g.stmts(defer_stmt.stmts)
-			g.labels.addrs[label] = g.pos()
-		}
-		g.pop(.rax)
-	}
-	g.mov_reg(.rsp, .rbp)
-	g.pop(.rbp)
-	g.ret()
+	g.leave()
+}
+
+pub fn (mut g Gen) builtin_decl_amd64(builtin BuiltinFn) {
+	g.push(.rbp)
+	g.mov_reg(.rbp, .rsp)
+	local_alloc_pos := g.pos()
+	g.sub(.rsp, 0)
+
+	builtin.body(builtin, g)
+	g.println('; stack frame size: $g.stack_var_pos')
+	g.write32_at(local_alloc_pos + 3, g.stack_var_pos)
+
+	g.labels.addrs[0] = g.pos()
+	g.leave()
 }
 
 /*
@@ -2177,9 +2200,13 @@ pub fn (mut g Gen) allocate_var(name string, size int, initial_val int) int {
 	return g.stack_var_pos
 }
 
-fn (mut g Gen) convert_int_to_string(r Register, buffer int) {
-	if r != .rax {
-		g.mov_reg(.rax, r)
+fn (mut g Gen) convert_int_to_string(r1 Register, r2 Register) {
+	if r1 != .rax {
+		g.mov_reg(.rax, r1)
+	}
+
+	if r2 != .rdi {
+		g.mov_reg(.rdi, r2)
 	}
 
 	// check if value in rax is zero
@@ -2193,7 +2220,13 @@ fn (mut g Gen) convert_int_to_string(r Register, buffer int) {
 	g.println('; jump to label $skip_zero_label')
 
 	// handle zeros seperately
-	g.mov_int_to_var(LocalVar{buffer, ast.u8_type_idx, ''}, '0'[0])
+	// g.mov_int_to_var(LocalVar{buffer, ast.u8_type_idx, ''}, '0'[0])
+
+	g.write8(0xc6)
+	g.write8(0x07)
+	g.write8(0x30)
+	g.println("mov BYTE PTR [rdi], '0'")
+
 	end_label := g.labels.new_label()
 	end_jmp_addr := g.jmp(0)
 	g.labels.patches << LabelPatch{
@@ -2206,7 +2239,7 @@ fn (mut g Gen) convert_int_to_string(r Register, buffer int) {
 	g.println('; label $skip_zero_label')
 
 	// load a pointer to the string to rdi
-	g.lea_var_to_reg(.rdi, buffer)
+	// g.lea_var_to_reg(.rdi, buffer)
 
 	// detect if value in rax is negative
 	g.cmp_zero(.rax)
@@ -2219,13 +2252,17 @@ fn (mut g Gen) convert_int_to_string(r Register, buffer int) {
 	g.println('; jump to label $skip_minus_label')
 
 	// add a `-` sign as the first character
-	g.mov_int_to_var(LocalVar{buffer, ast.u8_type_idx, ''}, '-'[0])
+	g.write8(0xc6)
+	g.write8(0x07)
+	g.write8(0x2d)
+	g.println("mov BYTE PTR [rdi], '-'")
+
 	g.neg(.rax) // negate our integer to make it positive
 	g.inc(.rdi) // increment rdi to skip the `-` character
 	g.labels.addrs[skip_minus_label] = g.pos()
 	g.println('; label $skip_minus_label')
 
-	g.mov_reg(.r12, .rdi) // copy the buffer position to rcx
+	g.mov_reg(.r12, .rdi) // copy the buffer position to r12
 
 	loop_label := g.labels.new_label()
 	loop_start := g.pos()
@@ -2266,7 +2303,9 @@ fn (mut g Gen) convert_int_to_string(r Register, buffer int) {
 	g.labels.addrs[loop_label] = loop_start
 
 	// after all was converted, reverse the string
-	g.reverse_string(.r12)
+	reg := g.get_builtin_arg_reg('reverse_string', 0)
+	g.mov_reg(reg, .r12)
+	g.call_builtin('reverse_string')
 
 	g.labels.addrs[end_label] = g.pos()
 	g.println('; label $end_label')
diff --git a/vlib/v/gen/native/builtins.v b/vlib/v/gen/native/builtins.v
new file mode 100644
index 0000000000..de0c2e4f90
--- /dev/null
+++ b/vlib/v/gen/native/builtins.v
@@ -0,0 +1,81 @@
+// Copyright (c) 2019-2022 Alexander Medvednikov. All rights reserved.
+// Use of this source code is governed by an MIT license
+// that can be found in the LICENSE file.
+module native
+
+import term
+
+struct BuiltinFn {
+	body     fn (builtin BuiltinFn, mut g Gen)
+	arg_regs []Register
+mut:
+	calls []i64 // call addresses
+}
+
+pub const inline_builtins = ['assert', 'print', 'eprint', 'println', 'eprintln', 'exit', 'C.syscall'] // classic V builtin functios accessible to the user get inlined
+
+pub fn (mut g Gen) init_builtins() {
+	g.builtins = {
+		// longer algorithms and internal functions inaccessible to the user
+		// used to keep executable size small and the bytecode distraction-free
+		'int_to_string':  BuiltinFn{
+			body: fn (builtin BuiltinFn, mut g Gen) {
+				g.convert_int_to_string(builtin.arg_regs[0], builtin.arg_regs[1])
+			}
+			arg_regs: [.rcx, .rdi]
+		}
+		'reverse_string': BuiltinFn{
+			body: fn (builtin BuiltinFn, mut g Gen) {
+				g.reverse_string(builtin.arg_regs[0])
+			}
+			arg_regs: [.rdi]
+		}
+	}
+}
+
+pub fn (mut g Gen) generate_builtins() {
+	for name, builtin in g.builtins {
+		if builtin.calls.len == 0 { // if a builtin does not get called, do not emit it
+			continue
+		}
+
+		if g.pref.is_verbose {
+			println(term.green('\n(builtin) $name:'))
+		}
+
+		g.stack_var_pos = 0
+		call_addr := g.pos()
+		g.defer_stmts.clear()
+		g.labels = &LabelTable{}
+
+		if g.pref.arch == .arm64 {
+			g.n_error('builtins are not implemented for arm64')
+		} else {
+			g.builtin_decl_amd64(builtin)
+		}
+
+		g.patch_labels()
+
+		// patch all call addresses where this builtin gets called
+		for call in builtin.calls {
+			rel := g.call_addr_at(int(call_addr), call)
+			g.write32_at(call + 1, int(rel))
+		}
+	}
+}
+
+pub fn (mut g Gen) get_builtin_arg_reg(name string, index int) Register {
+	builtin := g.builtins[name] or { panic('undefined builtin function $name') }
+	if index >= builtin.arg_regs.len {
+		g.n_error('builtin $name does only have $builtin.arg_regs.len arguments, wanted $index')
+	}
+	return builtin.arg_regs[index]
+}
+
+pub fn (mut g Gen) call_builtin(name string) {
+	if g.pref.arch == .arm64 {
+		g.n_error('builtin calls are not implemented for amd64')
+	} else {
+		g.builtins[name].calls << g.call_builtin_amd64(name)
+	}
+}
diff --git a/vlib/v/gen/native/gen.v b/vlib/v/gen/native/gen.v
index 6037ffc55c..277b1ce93b 100644
--- a/vlib/v/gen/native/gen.v
+++ b/vlib/v/gen/native/gen.v
@@ -13,8 +13,6 @@ import v.errors
 import v.pref
 import term
 
-pub const builtins = ['assert', 'print', 'eprint', 'println', 'eprintln', 'exit', 'C.syscall']
-
 interface CodeGen {
 mut:
 	g &Gen
@@ -49,6 +47,7 @@ mut:
 	strs                 []String
 	labels               &LabelTable
 	defer_stmts          []ast.DeferStmt
+	builtins             map[string]BuiltinFn
 	// macho specific
 	macho_ncmds   int
 	macho_cmdsize int
@@ -194,6 +193,7 @@ pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref &pref.Pref
 	}
 	g.code_gen.g = g
 	g.generate_header()
+	g.init_builtins()
 	for file in files {
 		/*
 		if file.warnings.len > 0 {
@@ -205,6 +205,7 @@ pub fn gen(files []&ast.File, table &ast.Table, out_name string, pref &pref.Pref
 		}
 		g.stmts(file.stmts)
 	}
+	g.generate_builtins()
 	g.generate_footer()
 	return g.nlines, g.buf.len
 }
@@ -428,11 +429,26 @@ fn (mut g Gen) gen_typeof_expr(it ast.TypeOf, newline bool) {
 	g.learel(.rax, g.allocate_string('$r$nl', 3, .rel32))
 }
 
+fn (mut g Gen) call_fn(node ast.CallExpr) {
+	if g.pref.arch == .arm64 {
+		g.call_fn_arm64(node)
+	} else {
+		g.call_fn_amd64(node)
+	}
+}
+
 fn (mut g Gen) gen_var_to_string(reg Register, var Var, config VarConfig) {
-	buffer := g.allocate_array('itoa-buffer', 1, 32) // 32 characters should be enough
-	g.mov_var_to_reg(reg, var, config)
-	g.convert_int_to_string(reg, buffer)
-	g.lea_var_to_reg(reg, buffer)
+	if config.typ.is_int() || config.typ == 0 { // TODO: fix config.typ == 0
+		buffer := g.allocate_array('itoa-buffer', 1, 32) // 32 characters should be enough
+
+		g.mov_var_to_reg(g.get_builtin_arg_reg('int_to_string', 0), var, config)
+		g.lea_var_to_reg(g.get_builtin_arg_reg('int_to_string', 1), buffer)
+		g.call_builtin('int_to_string')
+
+		g.lea_var_to_reg(reg, buffer)
+	} else {
+		g.n_error('int-to-string conversion only implemented for integer types, got $config.typ')
+	}
 }
 
 pub fn (mut g Gen) gen_print_from_expr(expr ast.Expr, name string) {