This is intended to be used to support `VK_KHR_maintenance2`'s
tessellation domain origin feature. If `tess_domain_origin_lower_left`
is `true`, the `v` coordinate will be inverted with respect to the
domain. Additionally, in `Triangles` mode, the `v` and `w` coordinates
will be swapped. This is because the winding order is interpreted
differently in lower-left mode.
These are mapped to Metal's post-tessellation vertex functions. The
semantic difference is much less here, so this change should be simpler
than the previous one. There are still some hairy parts, though.
In MSL, the array of control point data is represented by a special
type, `patch_control_point<T>`, where `T` is a valid stage-input type.
This object must be embedded inside the patch-level stage input. For
this reason, I've added a new type to the type system to represent this.
On Mac, the number of input control points to the function must be
specified in the `patch()` attribute. This is optional on iOS.
SPIRV-Cross takes this from the `OutputVertices` execution mode; the
intent is that if it's not set in the shader itself, MoltenVK will set
it from the tessellation control shader. If you're translating these
offline, you'll have to update the control point count manually, since
this number must match the number that is passed to the
`drawPatches:...` family of methods.
Fixes#120.
This should fix a whole host of issues related to structs in the `Input`
class in a tessellation control shader.
Also, use pointer arithmetic instead of dereferencing the `ops` array.
This is critical in case we wind up stepping beyond the bounds of the
array.
There's no need to do so, since these are not stage-out structs being
returned, but regular structures being written to a buffer. This also
neatly avoids issues writing to composite (e.g. arrayed) per-patch
outputs from a tessellation control shader.
These are transpiled to kernel functions that write the output of the
shader to three buffers: one for per-vertex varyings, one for per-patch
varyings, and one for the tessellation levels. This structure is
mandated by the way Metal works, where the tessellation factors are
supplied to the draw method in their own buffer, while the per-patch and
per-vertex varyings are supplied as though they were vertex attributes;
since they have different step rates, they must be in separate buffers.
The kernel is expected to be run in a workgroup whose size is the
greater of the number of input or output control points. It uses Metal's
support for vertex-style stage input to a compute shader to get the
input values; therefore, at least one instance must run per input point.
Meanwhile, Vulkan mandates that it run at least once per output point.
Overrunning the output array is a concern, but any values written should
either be discarded or overwritten by subsequent patches. I'm probably
going to put some slop space in the buffer when I integrate this into
MoltenVK to be on the safe side.
Add bool members is_read and is_written to SPIRType::Image.
Output correct texture read/write access by marking whether textures
are read from and written to by the shader.
Override bitcast_glsl_op() to use Metal as_type<type> functions.
Add implementations of SPIR-V functions inverse(), degrees() & radians().
Map inverseSqrt() to rsqrt().
Map roundEven() to rint().
GLSL functions imageSize() and textureSize() map to equivalent
expression using MSL get_width() & get_height() functions.
Map several SPIR-V integer bitfield functions to MSL equivalents.
Map SPIR-V atomic functions to MSL equivalents.
Map texture packing and unpacking functions to MSL equivalents.
Refactor existing, and add new, image query functions.
Reorganize header lines into includes and pragmas.
Simplify type_to_glsl() logic.
Add MSL test case vert/functions.vert for added function implementations.
Add MSL test case comp/atomic.comp for added function implementations.
test_shaders.py use macOS compilation for MSL shader compilation validations.
