Almost NFC, instrumentation is as correct as it was before.
We need InstrumentationList grouped by origin instruction,
so we used stable_sort. However these objects already grouped
because we never interleave sequences of `insertShadowCheck`
of different instrunction.
Pointer sort has artifact that it was deppendent on allocator behavior,
so we could inserted checks in a different order.
There is no test, as I failed to reproduce this with `opt`. My guess
is that for reproducer we need to increase fragmentation in the
allocator.
4f4ebee10e