The host_read*, and host_write* functions currently rely on
casting unaligned memory to translate from byte arrays into
higher-level types (like 16and 32bit ints), however this
approach is implementation specific, can cause undefined
behavior, and forces the compiler to use less efficient
aliasing rules.
Unaligned memory casts have historically been corrected by
expanding multi-byte types into their constituents bytes,
shifting them, and re-packing. They've also been solved using
union objects to access the same underlying memory for each
member (legal under C, but not C++). However, we use memcpy
which is compact, readable, universally compatible, and
compiles down efficient inline single-instructions; therefore
imparting no penalty.
This commit adds host_add* functions (for 16 and 32bit values)
that add a host-formatted value to the implied value at a
memory address.
This commit adds handling for quad-words as well: host_readq,
host_writeq, which we use in the cache, which otherwise suffers
from the same alignment issues.
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