[DAGCombiner] Refactor and improve ReduceLoadOpStoreWidth (#119564)

This patch make a couple of improvements to ReduceLoadOpStoreWidth.

When determining the minimum size of "NewBW" we now take byte boundaries
into account. If we for example touch bits 6-10 we shouldn't accept
NewBW=8, because we would fail later when detecting that we can't access
bits from two different bytes in memory using a single load. Instead we
make sure to align LSB/MSB according to byte size boundaries up front
before searching for a viable "NewBW".

In the past we only tried to find a "ShAmt" that was a multiple of
"NewBW", but now we use a sliding window technique to scan for a viable
"ShAmt" that is a multiple of the byte size. This can help out finding
more opportunities for optimization (specially if the original type
isn't byte sized, and for big-endian targets when the original
load/store is aligned on the most significant bit).

0 files changed, 0 insertions, 0 deletions