tor-browser

trailers-gc-stress.js (7091B)

---

// |jit-test| skip-if: getBuildConfiguration("simulator")

// This test is intended to test what was committed in
//
//  Bug 1817385 - wasm-gc: reduce cost of allocation and GC paths
//  and
//  Bug 1820120 - Manage Wasm{Array,Struct}Object OOL-storage-blocks
//                using a thread-private cache
//
// and in particular the latter.  The patches in these bugs reduce the cost of
// wasm-gc struct/array allocation and collection, in part by better
// integrating those objects with our generational GC facility.
//
// Existing tests do not cover all of those paths.  In particular they do not
// exercise both set-subtraction algorithms in Nursery::freeTrailerBlocks.
// This test does, though.
//
// The test first creates an "primary" array of 1500 elements.  Each element
// is a reference to a secondary array of between 1 and 50 int32s.  These
// secondary arrays have size chosen randomly, and the elements are also
// random.
//
// Then, elements of the primary array are replaced.  An index in the range 0
// .. N - 1 is randomly chosen, and the element there is replaced by a
// randomly-created secondary array.  This is repeated 500,000 times with
// N = 800.
//
// Finally, all of the above is repeated, but with N = 1200.
//
// As a result just over a million arrays and their trailer blocks, of various
// sizes, are allocated and deallocated.  With N = 800, in
// js::Nursery::freeTrailerBlocks, we end up with trailersRemovedUsed_ of
// around 800, so one of the set-subtraction algorithms is exercised.
// With N = 1200, the other is exercised.  It's not entirely clear why changing
// N causes trailersRemovedUsed_ to have more or less the same value during
// nursery collection, but the correlation does seem fairly robust.
//
// The test is skipped on the simulator because it takes too long to run, and
// triggers timeouts.

let t =
`(module

  ;; A simple pseudo-random number generator.
  ;; Produces numbers in the range 0 .. 2^16-1.
  (global $rngState
    (mut i32) (i32.const 1)
  )
  (func $rand (export "rand") (result i32)
    (local $t i32)
    ;; update $rngState
    (local.set $t (global.get $rngState))
    (local.set $t (i32.mul (local.get $t) (i32.const 1103515245)))
    (local.set $t (i32.add (local.get $t) (i32.const 12345)))
    (global.set $rngState (local.get $t))
    ;; pull 16 random bits out of it
    (local.set $t (i32.shr_u (local.get $t) (i32.const 15)))
    (local.set $t (i32.and (local.get $t) (i32.const 0xFFFF)))
    (local.get $t)
  )

  ;; Array types
  (type $tArrayI32      (array (mut i32)))  ;; "secondary array" above
  (type $tArrayArrayI32 (array (mut (ref null $tArrayI32)))) ;; "primary array"

  ;; Create an array ("secondary array") containing random numbers, with a
  ;; size between 1 and 50, also randomly chosen.
  (func $createSecondaryArray (export "createSecondaryArray")
                              (result (ref $tArrayI32))
    (local $i i32)
    (local $nElems i32)
    (local $arr (ref $tArrayI32))
    (local.set $nElems (call $rand))
    (local.set $nElems (i32.rem_u (local.get $nElems) (i32.const 50)))
    (local.set $nElems (i32.add   (local.get $nElems) (i32.const 1)))
    (local.set $arr (array.new $tArrayI32 (i32.const 0) (local.get $nElems)))
    (loop $cont
      (array.set $tArrayI32 (local.get $arr) (local.get $i) (call $rand))
      (local.set $i (i32.add (local.get $i) (i32.const 1)))
      (br_if $cont (i32.lt_u (local.get $i) (local.get $nElems)))
    )
    (local.get $arr)
  )

  ;; Create an array (the "primary array") of 1500 elements of
  ;; type ref-of-tArrayI32.
  (func $createPrimaryArray (export "createPrimaryArray")
                            (result (ref $tArrayArrayI32))
    (local $i i32)
    (local $arrarr (ref $tArrayArrayI32))
    (local.set $arrarr (array.new $tArrayArrayI32 (ref.null $tArrayI32)
                                                  (i32.const 1500)))
    (loop $cont
      (array.set $tArrayArrayI32 (local.get $arrarr)
                                 (local.get $i) (call $createSecondaryArray))
      (local.set $i (i32.add (local.get $i) (i32.const 1)))
      (br_if $cont (i32.lt_u (local.get $i) (i32.const 1500)))
    )
    (local.get $arrarr)
  )

  ;; Use $createPrimaryArray to create an initial array.  Then randomly replace
  ;; elements for a while.
  (func $churn (export "churn") (param $thresh i32) (result i32)
    (local $i i32)
    (local $j i32)
    (local $finalSum i32)
    (local $arrarr (ref $tArrayArrayI32))
    (local $arr (ref null $tArrayI32))
    (local $arrLen i32)
    (local.set $arrarr (call $createPrimaryArray))
    ;; This loop iterates 500,000 times.  Each iteration, it chooses
    ;; a randomly element in $arrarr and replaces it with a new
    ;; random array of 32-bit ints.
    (loop $cont
      ;; make $j be a random number in 0 .. $thresh-1.
      ;; Then replace that index in $arrarr with a new random arrayI32.
      (local.set $j (i32.rem_u (call $rand) (local.get $thresh)))
      (array.set $tArrayArrayI32 (local.get $arrarr)
                                 (local.get $j) (call $createSecondaryArray))
      (local.set $i (i32.add (local.get $i) (i32.const 1)))
      (br_if $cont (i32.lt_u (local.get $i) (i32.const 500000)))
    )

    ;; Finally, compute a checksum by summing all the numbers
    ;; in all secondary arrays.  This simply assumes that all of the refs to
    ;; secondary arrays are non-null, which isn't per-se guaranteed by the
    ;; previous loop, but it works in this case because the RNG
    ;; produces each index value to overwrite at least once.
    (local.set $finalSum (i32.const 0))
    (local.set $i (i32.const 0)) ;; loop var for the outer loop
    (loop $outer
      ;; body of outer loop
      ;; $arr = $arrarr[i]
      (local.set $arr (array.get $tArrayArrayI32 (local.get $arrarr)
                      (local.get $i)))
      ;; iterate over $arr
      (local.set $arrLen (array.len (local.get $arr)))
      (local.set $j (i32.const 0)) ;; loop var for the inner loop
      (loop $inner
        ;; body of inner loop
        (local.set $finalSum
                   (i32.rotl (local.get $finalSum) (i32.const 1)))
        (local.set $finalSum
                   (i32.xor (local.get $finalSum)
                            (array.get $tArrayI32 (local.get $arr)
                                                  (local.get $j))))
        ;; loop control for the inner loop
        (local.set $j (i32.add (local.get $j) (i32.const 1)))
        (br_if $inner (i32.lt_u (local.get $j) (local.get $arrLen)))
      )
      ;; loop control for the outer loop
      (local.set $i (i32.add (local.get $i) (i32.const 1)))
      (br_if $outer (i32.lt_u (local.get $i) (i32.const 1500)))
    )

    ;; finally, roll in the final value of the RNG state
    (i32.xor (local.get $finalSum) (global.get $rngState))
  )
)`;

let i = wasmEvalText(t);
let fns = i.exports;

assertEq(fns.churn(800), -575895114);
assertEq(fns.churn(1200), -1164697516);