Fix optimization regressions for operations on [x; n]-initialized arrays.
Fixes#35662 by using `!=` instead of `<` as the stop condition for `[x; n]` initialization loops.
Also included is cc2009f02d, a hack to run the GVN pass twice, another time after InstCombine.
This hack results in removal of redundant `memset` and `memcpy` calls (from loops over arrays).
cc @nrc Can we get performance numbers on this? Not sure if it regresses anything else.
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