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.
Now it can refuse to resize when it would disturb the metadata tracking
strategy, resulting in smaller code size, a simpler implementation, and
less fragmentation.
The previous version had a fatal flaw: it did ensureCapacity(1) on the
freelist when allocating, but I neglected to consider that you could
free() twice in a row. Silly!
This strategy allocates an intrusive freelist node with every
allocation, big or small. It also does not have the problems with resize
because in this case we can push the upper areas of freed stuff into the
corresponding freelist.
* Update wasi-libc to a00bf321eeeca836ee2a0d2d25aeb8524107b8cc
It includes a port of emscripten's allocator that performs
performs much better than the old one.
Most importantly, it includes the prerequisites to later add
support for POSIX threads.
Ran into this when using a program that uses CreateFileMapping and then trying to call `std.fs.createFile` on the mapped file. More info can be found here:
https://stackoverflow.com/questions/41844842/when-error-1224-error-user-mapped-file-occurs
Before:
```
error.Unexpected NTSTATUS=0xc0000243
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:138:40: 0x7ff74e957466 in OpenFile (test.exe.obj)
else => return unexpectedStatus(rc),
^
```
After:
```
FAIL (AccessDenied)
C:\Users\Ryan\Programming\Zig\zig\lib\std\os\windows.zig:137:30: 0x7ff7f5b776ea in OpenFile (test.exe.obj)
.USER_MAPPED_FILE => return error.AccessDenied,
^
```
