Smaller version of zkEngine's kth_factor example

_Nebula Kth Factor.md

An improvement upon https://github.com/ICME-Lab/zkEngine_dev/blob/main/wasm/nebula/kth_factor.wat

	Upstream	This version
Wasm memory size	1.06 MiB	64 KiB
Wasm bytes	16001	459
WAT lines	7226	81

compile.sh

rustc -C opt-level=3 -C link-arg=-zstack-size=2048 -C panic=abort --target wasm32-unknown-unknown kth_factor.rs

kth_factor.rs

#![no_std]
#![no_main]

#[panic_handler]
fn panic_handler(_: &core::panic::PanicInfo) -> ! {
    loop {}
}

#[no_mangle]
pub extern "C" fn kth_factor(n: u32, k: usize) -> u32 {
    let mut count = 0;
    
    for i in 1..=n {
        if n % i == 0 {
            count += 1;
            if count == k {
                return i;
            }
        }
    }

    0xffffffff
}

kth_factor.wat

(module $my_kth_factor.wasm
 (type $0 (func (param i32 i32) (result i32)))
 (global $__stack_pointer (mut i32) (i32.const 2048))
 (global $global$1 i32 (i32.const 2048))
 (global $global$2 i32 (i32.const 2048))
 (memory $0 1)
 (export "memory" (memory $0))
 (export "kth_factor" (func $kth_factor))
 (export "__data_end" (global $global$1))
 (export "__heap_base" (global $global$2))
 (func $kth_factor (param $0 i32) (param $1 i32) (result i32)
  (local $2 i32)
  (local $3 i32)
  (local $4 i32)
  (local.set $2
   (i32.const -1)
  )
  (block $block
   (br_if $block
    (i32.eqz
     (local.get $0)
    )
   )
   (local.set $3
    (i32.const 0)
   )
   (local.set $4
    (i32.const 1)
   )
   (loop $label
    (block $block1
     (br_if $block1
      (i32.rem_u
       (local.get $0)
       (local.get $4)
      )
     )
     (br_if $block1
      (i32.ne
       (local.tee $3
        (i32.add
         (local.get $3)
         (i32.const 1)
        )
       )
       (local.get $1)
      )
     )
     (local.set $2
      (local.get $4)
     )
     (br $block)
    )
    (br_if $block
     (i32.ge_u
      (local.get $4)
      (local.get $0)
     )
    )
    (br_if $label
     (i32.le_u
      (local.tee $4
       (i32.add
        (local.get $4)
        (i32.lt_u
         (local.get $4)
         (local.get $0)
        )
       )
      )
      (local.get $0)
     )
    )
   )
  )
  (local.get $2)
 )
 ;; custom section "producers", size 51
 ;; features section: mutable-globals, nontrapping-float-to-int, bulk-memory, sign-ext, reference-types, multivalue, bulk-memory-opt
)