This patch allows urem by a constant to be expanded more efficiently to
avoid the need for expensive udiv instructions. This is part of the
resolution to issue #118090

Idx is already of unsigned.

In the pre-legalizer combiner, there exists a bug with UseVectorTruncate
match-apply optimization. When the destinations' types do not match the
vector element type of the G_UNMERGE_VALUES instruction, the resulting
collapsed truncate does not preserve original functional behavior. This
commit introduces a simple type check to ensure that the destination
types match the vector element type.

LegalizerHelper::lowerMemCpyFamily only execpts G_MEMCPY, G_MEMMOVE, and
G_MMSET.

Instead of reporting ___memmove as an implementation of memcpy,
make it unavailable and let the lowering logic consider memmove as
a fallback path.

This avoids a special case 1:N mapping for libcall implementations.

Directly call getIntrinsicID(), there is no need to check for
isIntrinsic() first.

This avoids using report_fatal_error and standardizes the error
message in a subset of the error conditions.

If the pointer is aligned to more than the size of the vector, we can
widen the load up to next power of 2 size, as SDAG performs.

Some of the v3 tests are currently worse - those should be addressed in
other issues.