We can trivially deal with cases where the loop tests are simply
inverted. We can also deal with cases where the condition block branches
to the merge block via other noop blocks.
This makes SPIR-V codegen easier when targeting SPIRV-Cross.
This adds a new C API for SPIRV-Cross which is intended to be stable,
both API and ABI wise.
The C++ API has been refactored a bit to make the C wrapper easier and
cleaner to write. Especially the vertex attribute / resource interfaces
for MSL has been rewritten to avoid taking mutable pointers into the
interface. This would be very annoying to wrap and it didn't fit well
with the rest of the C++ API to begin with. While doing this, I went
ahead and removed all the old deprecated interfaces.
The CMake build system has also seen an overhaul.
It is now possible to build static/shared/CLI separately with -D
options.
The shared library only exposes the C API, as it is the only ABI-stable
API. pkg-configs as well as CMake modules are exported and installed for
the shared library configuration.
We were using std::locale::global() to force a C locale which is not
safe when SPIRV-Cross is used in a multi-threaded environment.
To fix this, we could tap into various per-platform specific locale
handling to get safe thread-local locales, but since locales only affect
the decimal point in floats, we simply query the locale instead and do
the necessary radix replacement ourselves, without touching the locale.
This should be much safer and cleaner than the alternative.
Return after loading the input control point array if there are more
input points than output points, and this was one of the helper
invocations spun off to load the input points. I was hesitant to do this
initially, since the MSL spec has this to say about barriers:
> The `threadgroup_barrier` (or `simdgroup_barrier`) function must be
> encountered by all threads in a threadgroup (or SIMD-group) executing
> the kernel.
That is, if any thread executes the barrier, then all threads must
execute it, or the barrier'd invocations will hang. But, the key words
here seem to be "executing the kernel;" inactive invocations, those that
have already returned, need not encounter the barrier to prevent hangs.
Indeed, I've encountered no problems from doing this, at least on my
hardware. This also fixes a few CTS tests that were failing due to
execution ordering; apparently, my assumption that the later, invalid
data written by the helpers would get overwritten was wrong.
If a stage takes the position as both an input and an output (i.e. a
tessellation shader or a geometry shader), then we could wind up fixing
up the input position by mistake. Ensure that doesn't happen, by only
setting the `qual_pos_var_name` variable from the output position.
The tessellation levels in Metal are stored as a densely-packed array of
half-precision floating point values. But, stage-in attributes in Metal
have to have offsets and strides aligned to a multiple of four, so we
can't add them individually. Luckily for us, the arrays have lengths
less than 4. So, let's use vectors for them!
Triangles get a single attribute with a `float4`, where the outer levels
are in `.xyz` and the inner levels are in `.w`. The arrays are unpacked
as though we had added the elements individually. Quads get two: a
`float4` with the outer levels and a `float2` with the inner levels.
Further, since vectors can be indexed as arrays, there's no need to
unpack them in this case.
This also saves on precious vertex attributes. Before, we were using up
to 6 of them. Now we need two at most.
These are often arrayed builtins, which MSL maps to more than one
attribute. SPIRV-Cross automatically assigns succeeding addresses to
arrayed attributes, so we really only need the first one. This of course
assumes that the inputs are sorted by location.
Builtin attributes in SPIR-V aren't linked by location, but by their
built-in-ness. This poses a problem for MSL, since builtin inputs in
the vertex pipeline are just regular attributes. We must then assign
them locations so that they can be matched up to the attributes in the
stage input descriptor--and also to avoid duplicate attribute numbers in
tessellation evaluation shaders, where there are two different
stage-in structs, so the member index therein is no longer unique!
