fibonacci.ll

@out-str = private unnamed_addr constant [4 x i8] c"%u\0A\00", align 1

declare i32 @printf(i8*, ...)
declare i32 @atoi(i8*)

define i32 @main(i32 %argc, i8** %argv) {
  %cur = alloca i128, align 8
  store i128 1, i128* %cur, align 8

  %last = alloca i128, align 8
  store i128 1, i128* %last, align 8

  %has-enough-vars = icmp ugt i32 %argc, 1
  br i1 %has-enough-vars, label %continue, label %error
continue:
  %pointer-to-n = getelementptr inbounds i8*, i8** %argv, i32 1
  %input-n = load i8*, i8** %pointer-to-n
  %n-val = call i32 (i8*) @atoi(i8* %input-n)

  %n = alloca i32, align 4
  store i32 %n-val, i32* %n, align 4

  br label %loop
loop:
  %loop-cond-cur-n = load i32, i32* %n, align 2
  %loop-cond = icmp eq i32 %loop-cond-cur-n, 0
  br i1 %loop-cond, label %end, label %loop.body
loop.body:
    %cur-cur = load i128, i128* %cur, align 8
    %cur-last = load i128, i128* %last, align 8
    %added = add i128 %cur-cur, %cur-last
    store i128 %added, i128* %cur
    store i128 %cur-cur, i128* %last

    %cur-n = load i32, i32* %n, align 2
    %next-n = sub i32 %cur-n, 1
    store i32 %next-n, i32* %n

    br label %loop
end:
  %final-val = load i128, i128* %cur, align 8
  call i32 (i8*, ...) @printf(
    i8* getelementptr inbounds ([4 x i8], [4 x i8]* @out-str, i32 0, i32 0),
    i128 %final-val
  )

  br label %success
success:
  ret i32 0
error:
  ret i32 1
}