fibonacci.ll

declare i32 @printf(i8* noalias nocapture, ...)

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

define i32 @main() {
  entry:
    br label %header

  header:
    %x = phi i32 [ 10, %entry ], [ %next_x, %header ]
    %fib_res = call i32 @fib(i32 %x)

    call i32 (i8*, ...) @printf(i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i32 0, i32 0), i32 %fib_res)

    %next_x = sub nsw i32 %x, 1
    %should_break = icmp eq i32 %fib_res, 0
    br i1 %should_break, label %tail, label %header

  tail:
    ret i32 0
}

define i32 @fib(i32 %n) inlinehint nofree willreturn nosync nounwind readnone speculatable {
    switch i32 %n, label %fib [ i32 0, label %identity
                                i32 1, label %identity ]

  identity:
    ret i32 %n

  fib:
    %minus_one = sub nsw i32 %n, 1
    %minus_two = sub nsw i32 %n, 2

    %first = tail call i32 @fib(i32 %minus_one)
    %second = tail call i32 @fib(i32 %minus_two)

    %sum = add nsw i32 %first, %second
    ret i32 %sum
}