majit: preserve typed object headers through allocation fusion - #1410

… has

`mapdict_frozen_unboxing_fold` carried `guard_failures=11` and
`surrogate_class_kwargs` carried `loops_aborted=12` and
`fbw_blackhole_adopted_single_frame=12`. All three `pyre/check.py` legs read
13 and 14/14 instead, on dynasm, cranelift and wasm alike, and a local dynasm
run reads the same. No leg flagged either row `UNSTABLE`.

Neither move comes from this branch. `pull_request` CI runs the merge ref, so
main reaches the suite without the branch being touched, and two commits
landed between the run where both fixtures passed (32552199619, created
04:37Z) and the one where both failed (32559523138, 07:24Z):

  b7986c8 (#1410, 05:50Z) raised this fixture's `N` from 406399 to
    2000000 and left the baseline alone.
  4bce927 (#1400, 06:21Z) re-recorded 15 jitstats files of its own.

`guard_failures` here is one per doubling of `N` -- measured at
406399/812798/2000000/4000000/8000000 as 11/12/13/14/15 -- so 11 was the
count at the old size and 13 is the count at the new one. It is the list the
comprehension builds reallocating once per doubling: main records 2 for this
fixture and is green at the larger `N`, because the loop only reaches the JIT
under this branch's `LIST_APPEND` admission, which is what took it 2 -> 11.

`surrogate_class_kwargs` keeps `REPEAT=3200`; its counters follow it, at
800/1600/3200/6400 reading `loops_aborted` 2/5/14/33 with
`fbw_blackhole_adopted_single_frame` equal at every point.

Assisted-by: Claude

… has

`mapdict_frozen_unboxing_fold` carried `guard_failures=11` and
`surrogate_class_kwargs` carried `loops_aborted=12` and
`fbw_blackhole_adopted_single_frame=12`. All three `pyre/check.py` legs read
13 and 14/14 instead, on dynasm, cranelift and wasm alike, and a local dynasm
run reads the same. No leg flagged either row `UNSTABLE`.

Neither move comes from this branch. `pull_request` CI runs the merge ref, so
main reaches the suite without the branch being touched, and two commits
landed between the run where both fixtures passed (32552199619, created
04:37Z) and the one where both failed (32559523138, 07:24Z):

  b7986c8 (#1410, 05:50Z) raised this fixture's `N` from 406399 to
    2000000 and left the baseline alone.
  4bce927 (#1400, 06:21Z) re-recorded 15 jitstats files of its own.

`guard_failures` here is one per doubling of `N` -- measured at
406399/812798/2000000/4000000/8000000 as 11/12/13/14/15 -- so 11 was the
count at the old size and 13 is the count at the new one. It is the list the
comprehension builds reallocating once per doubling: main records 2 for this
fixture and is green at the larger `N`, because the loop only reaches the JIT
under this branch's `LIST_APPEND` admission, which is what took it 2 -> 11.

`surrogate_class_kwargs` keeps `REPEAT=3200`; its counters follow it, at
800/1600/3200/6400 reading `loops_aborted` 2/5/14/33 with
`fbw_blackhole_adopted_single_frame` equal at every point.

Assisted-by: Claude

… has

`mapdict_frozen_unboxing_fold` carried `guard_failures=11` and
`surrogate_class_kwargs` carried `loops_aborted=12` and
`fbw_blackhole_adopted_single_frame=12`. All three `pyre/check.py` legs read
13 and 14/14 instead, on dynasm, cranelift and wasm alike, and a local dynasm
run reads the same. No leg flagged either row `UNSTABLE`.

Neither move comes from this branch. `pull_request` CI runs the merge ref, so
main reaches the suite without the branch being touched, and two commits
landed between the run where both fixtures passed (32552199619, created
04:37Z) and the one where both failed (32559523138, 07:24Z):

  b7986c8 (#1410, 05:50Z) raised this fixture's `N` from 406399 to
    2000000 and left the baseline alone.
  4bce927 (#1400, 06:21Z) re-recorded 15 jitstats files of its own.

`guard_failures` here is one per doubling of `N` -- measured at
406399/812798/2000000/4000000/8000000 as 11/12/13/14/15 -- so 11 was the
count at the old size and 13 is the count at the new one. It is the list the
comprehension builds reallocating once per doubling: main records 2 for this
fixture and is green at the larger `N`, because the loop only reaches the JIT
under this branch's `LIST_APPEND` admission, which is what took it 2 -> 11.

`surrogate_class_kwargs` keeps `REPEAT=3200`; its counters follow it, at
800/1600/3200/6400 reading `loops_aborted` 2/5/14/33 with
`fbw_blackhole_adopted_single_frame` equal at every point.

Assisted-by: Claude

… has

`mapdict_frozen_unboxing_fold` carried `guard_failures=11` and
`surrogate_class_kwargs` carried `loops_aborted=12` and
`fbw_blackhole_adopted_single_frame=12`. All three `pyre/check.py` legs read
13 and 14/14 instead, on dynasm, cranelift and wasm alike, and a local dynasm
run reads the same. No leg flagged either row `UNSTABLE`.

Neither move comes from this branch. `pull_request` CI runs the merge ref, so
main reaches the suite without the branch being touched, and two commits
landed between the run where both fixtures passed (32552199619, created
04:37Z) and the one where both failed (32559523138, 07:24Z):

  b7986c8 (#1410, 05:50Z) raised this fixture's `N` from 406399 to
    2000000 and left the baseline alone.
  4bce927 (#1400, 06:21Z) re-recorded 15 jitstats files of its own.

`guard_failures` here is one per doubling of `N` -- measured at
406399/812798/2000000/4000000/8000000 as 11/12/13/14/15 -- so 11 was the
count at the old size and 13 is the count at the new one. It is the list the
comprehension builds reallocating once per doubling: main records 2 for this
fixture and is green at the larger `N`, because the loop only reaches the JIT
under this branch's `LIST_APPEND` admission, which is what took it 2 -> 11.

`surrogate_class_kwargs` keeps `REPEAT=3200`; its counters follow it, at
800/1600/3200/6400 reading `loops_aborted` 2/5/14/33 with
`fbw_blackhole_adopted_single_frame` equal at every point.

Assisted-by: Claude

A local dynasm run reads loops_compiled=2, bridges_compiled=1, loops_aborted=0
and guard_failures=201, which is the value each of these three files carried
before `64ae20d6801` moved them. The wasm file kept bridges_compiled=1 and
guard_failures=201 through that commit, so only its two moved rows come back.

`surrogate_class_kwargs` also covers this path and is not touched here: main
raised its `N` from 406399 to 2000000 in #1410 after the values it carried
before the force were recorded, so there is no earlier reading to return it to.

Assisted-by: Claude