TCO

tco.swift

func fact1(n: Int) -> Int {
    if n == 1 {
        return 1
    } else {
        return n * fact1(n - 1)
    }
}

func fact2(n: Int, _ acc: Int) -> Int {
    if n == 1 {
        return acc
    } else {
        return fact2(n - 1, acc * n)
    }
}

print(fact1(5))
print(fact2(5, 1))

/*
swiftc -O -S tco.swift

__TF3tco5fact1FSiSi:
	pushq	%rbp
	movq	%rsp, %rbp
	pushq	%rbx
	pushq	%rax
	movq	%rdi, %rbx
	movl	$1, %eax
	cmpq	$1, %rbx
	je	LBB1_3
	movq	%rbx, %rdi
	decq	%rdi
	jo	LBB1_4
	callq	__TF3tco5fact1FSiSi
	imulq	%rax, %rbx
	movq	%rbx, %rax
	jo	LBB1_4
LBB1_3:
	addq	$8, %rsp
	popq	%rbx
	popq	%rbp
	retq
LBB1_4:
	ud2

	.private_extern	__TF3tco5fact2FTSiSi_Si
	.globl	__TF3tco5fact2FTSiSi_Si
	.align	4, 0x90
__TF3tco5fact2FTSiSi_Si:
	pushq	%rbp
	movq	%rsp, %rbp
	cmpq	$1, %rdi
	je	LBB2_4
	.align	4, 0x90
LBB2_1:
	movq	%rdi, %rax
	decq	%rax
	jo	LBB2_5
	imulq	%rdi, %rsi
	jo	LBB2_5
	cmpq	$1, %rax
	movq	%rax, %rdi
	jne	LBB2_1
LBB2_4:
	movq	%rsi, %rax
	popq	%rbp
	retq
LBB2_5:
	ud2

	.private_extern	__TMLGCs23_ContiguousArrayStorageP__
	.section	__DATA,__datacoal_nt,coalesced
	.globl	__TMLGCs23_ContiguousArrayStorageP__
	.weak_definition	__TMLGCs23_ContiguousArrayStorageP__
	.align	3
*/