This implements `@splat` for vectors where the element type is
divisible by 8 and a power of two. This is fairly simple as we can
store the values directly within the virtual stack. But for
all other sizes, we must first shift and bitwise-or the values
before we can store them to fit them like a packed-struct, rather
than an array.
This implements `airSplat` for the native WebAssembly backend when
the features 'simd128' or 'relaxed-simd' are enabled. The commit
supports splat where the value lives in the linear memory segment,
as well as on the stack. This saves a lot of instruction cost.
When it detects the element type is not 8, 16, 32 or 64 bits,
the backend will instead use the same strategy as if the features
where disabled.
This implements loading and storing immediate values representing
a vector with exactly 128 bits. When the vector does not equal to
128 bits, or when the simd128 or relaxed-simd features are disabled
the value will be treated as an array instead.
I did not do a full audit, but I did notice a few issues which are
resolved in this commit. Probably it would be worth adding debug
infrastructure to assert that the number of reaps equals the number of
calls to resolveInst() per air lowering function.
This implements support for loading and storing where the lhs is
of pointer type with host_size != 0. e.g. when loading a specific
field from a packed struct with a non-byte alignment such as (0:1:3).
This allows the Wasm backend to construct an instance of a packed
struct during runtime. We first allocate a local, and then
shift+or each field's value into the result local. We then finally
return this result local as value.
The commit also fixes a type-issue in `airElemVal` where we used
the element type instead of a pointer type to store the value's
address into.
This also adds support loading a runtime pointer from a packed struct.
Also, this commit improves many utility functions such as `trunc` and
`intcast` to also support non-integer types such as booleans.
Simplifies the airStructFieldPtr(index) functions to only obtain the
correct struct type and field index, which is then passed into the
structFieldPtr function. This function now calculates the byte-offset
of the field's address and returns a new `WValue` with this offset.
This means we only have to do this calculation in a single function,
and no longer have to duplicate any logic. This also handles both
regular (tagged) unions and packed unions.
This implements loading a field from a packed struct, regardless of
its field's type. This means it supports pointers, floats and
integers. The commit also extracts the logic from airTrunc into its
own `trunc` function so it can be re-used.
When lowering constants of packed structs, which are smaller than 65
bits, we lower the value to an integer rather than store it in the
constant data section. This allows us to use an immediate value,
for quick loads and stores.
