fib.ll

; ModuleID = 'main'
source_filename = "main"
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
target triple = "x86_64-apple-darwin18.5.0"

declare i32 @atoi(i8*)

define i32 @main(i32 %argc, i8** %argv) {
entry:
  %0 = alloca i32
  %1 = getelementptr i8*, i8** %argv, i64 1
  %2 = load i8*, i8** %1
  %3 = call i32 @atoi(i8* %2)
  %4 = call i32 @_F3fibii(i32 %3)
  store i32 %4, i32* %0
  br label %return

return:                                           ; preds = %entry
  %5 = load i32, i32* %0
  ret i32 %5
}

define i32 @_F3fibii(i32 %n) {
entry:
  %0 = alloca i32
  %1 = sext i32 %n to i64
  %2 = icmp eq i64 %1, 0
  %3 = sext i32 %n to i64
  %4 = icmp eq i64 %3, 1
  %5 = or i1 %2, %4
  br i1 %5, label %7, label %6

; <label>:6:                                      ; preds = %entry
  br label %8

; <label>:7:                                      ; preds = %entry
  br label %match_merge

; <label>:8:                                      ; preds = %6
  %9 = sub i32 %n, 1
  %10 = call i32 @_F3fibii(i32 %9)
  %11 = sub i32 %n, 2
  %12 = call i32 @_F3fibii(i32 %11)
  %13 = add i32 %10, %12
  br label %match_merge

match_merge:                                      ; preds = %8, %7
  %14 = phi i32 [ %n, %7 ], [ %13, %8 ]
  store i32 %14, i32* %0
  br label %return

return:                                           ; preds = %match_merge
  %15 = load i32, i32* %0
  ret i32 %15

; uselistorder directives
  uselistorder i32 (i32)* @_F3fibii, { 1, 2, 0 }
  uselistorder i64 1, { 1, 0 }
}

fib.S

fib:
(__TEXT,__text) section
_main:
0000000100000f30	pushq	%rax
0000000100000f31	movq	0x8(%rsi), %rdi
0000000100000f35	callq	0x100000f88 ## symbol stub for: _atoi
0000000100000f3a	movl	%eax, %edi
0000000100000f3c	callq	__F3fibii
0000000100000f41	movl	%eax, 0x4(%rsp)
0000000100000f45	movl	0x4(%rsp), %eax
0000000100000f49	popq	%rcx
0000000100000f4a	retq
0000000100000f4b	nop
0000000100000f4c	nop
0000000100000f4d	nop
0000000100000f4e	nop
0000000100000f4f	nop
__F3fibii:
0000000100000f50	pushq	%rbp
0000000100000f51	pushq	%rbx
0000000100000f52	pushq	%rax
0000000100000f53	movl	%edi, %ebx
0000000100000f55	movslq	%edi, %rax
0000000100000f58	testq	%rax, %rax
0000000100000f5b	je	0x100000f7b
0000000100000f5d	cmpq	$0x1, %rax
0000000100000f61	je	0x100000f7b
0000000100000f63	leal	-0x1(%rbx), %edi
0000000100000f66	callq	__F3fibii
0000000100000f6b	movl	%eax, %ebp
0000000100000f6d	addl	$-0x2, %ebx
0000000100000f70	movl	%ebx, %edi
0000000100000f72	callq	__F3fibii
0000000100000f77	movl	%eax, %ebx
0000000100000f79	addl	%ebp, %ebx
0000000100000f7b	movl	%ebx, 0x4(%rsp)
0000000100000f7f	movl	%ebx, %eax
0000000100000f81	addq	$0x8, %rsp
0000000100000f85	popq	%rbx
0000000100000f86	popq	%rbp
0000000100000f87	retq