Factorial in LLVM bytecode

fact.ll

; the string used in printf
@.str = private unnamed_addr constant [4 x i8] c"%d\0A\00", align 1

define i64 @fact(i64 %n) nounwind readnone ssp uwtable {
entry:
    ; go to retn if n is 1, else branch to retfactn
    %0 = icmp eq i64 %n, 1
    br i1 %0, label %retn, label %retfactn

retn:
    ret i64 %n

retfactn:
    ; subtract 1 from n and call fact with this value,
    ; then multiply the result by n
    %n1 = add i64 %n, -1
    %1 = tail call i64 @fact(i64 %n1) nounwind ssp
    %2 = mul i64 %1, %n
    ret i64 %2
}

define i32 @main(i32 %argc, i8** nocapture %argv) nounwind ssp {
entry:
    ; get the factorial value of 15
    %0 = tail call i64 @fact(i64 15)
    ; weird shit needed to call printf...
    %1 = tail call i32 (i8*, ...)* @printf(i8* getelementptr inbounds ([4 x i8]* @.str, i64 0, i64 0), i64 %0) nounwind
    ret i32 0
}

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