In the past, SPIRV-Cross threw an error in this case because it couldn't
work out which swizzle from the auxiliary buffer needs to be passed.
Now, we pass the swizzle around with the texture object, like a combined
image-sampler and its associated sampler.
If not enough components are provided in the shader,
the shader MSL compiler throws an error rather than make components
undefined. This hurts portability, so we need to add explicit padding
here.
MSL does not support value semantics for arrays (sigh), so we need to
force constant references and deal with copies if we have a different
address space than what we end up guessing.
A flat array was consuming way too much memory and was far too slow to
initialize properly with a very large ID bound (8 million IDs, showed up as #1 hotspot in perf).
Meta struct does not have to be in-order as we never iterate over it in
a meaningful way, so using a hashmap here is reasonable. Very few IDs
should need decorations or meta-data, so this should also be a quite
decent memory save.
For the pathological case, a 6x uplift was observed.
This is a fairly fundamental change on how IDs are handled.
It serves many purposes:
- Improve performance. We only need to iterate over IDs which are
relevant at any one time.
- Makes sure we iterate through IDs in SPIR-V module declaration order
rather than ID space. IDs don't have to be monotonically increasing,
which was an assumption SPIRV-Cross used to have. It has apparently
never been a problem until now.
- Support LUTs of structs. We do this by interleaving declaration of
constants and struct types in SPIR-V module order.
To support this, the ParsedIR interface needed to change slightly.
Before setting any ID with variant_set<T> we let ParsedIR know
that an ID with a specific type has been added. The surface for change
should be minimal.
ParsedIR will maintain a per-type list of IDs which the cross-compiler
will need to consider for later.
Instead of looping over ir.ids[] (which can be extremely large), we loop
over types now, using:
ir.for_each_typed_id<SPIRVariable>([&](uint32_t id, SPIRVariable &var) {
handle_variable(var);
});
Now we make sure that we're never looking at irrelevant types.
This allows shaders to declare and use pointer-type variables. Pointers
may be loaded and stored, be the result of an `OpSelect`, be passed to
and returned from functions, and even be passed as inputs to the `OpPhi`
instruction. All types of pointers may be used as variable pointers.
Variable pointers to storage buffers and workgroup memory may even be
loaded from and stored to, as though they were ordinary variables. In
addition, this enables using an interior pointer to an array as though
it were an array pointer itself using the `OpPtrAccessChain`
instruction.
This is a rather large and involved change, mostly because this is
somewhat complicated with a lot of moving parts. It's a wonder
SPIRV-Cross's output is largely unchanged. Indeed, many of these changes
are to accomplish exactly that! Perhaps the largest source of changes
was the violation of the assumption that, when emitting types, the
pointer type didn't matter.
One of the test cases added by the change doesn't optimize very well;
the output of `spirv-opt` here is invalid SPIR-V. I need to file a bug
with SPIRV-Tools about this.
I wanted to test that variable pointers to images worked too, but I
couldn't figure out how to propagate the access qualifier properly--in
MSL, it's part of the type, so getting this right is important. I've
punted on that for now.
This is required to avoid relying on complex sub-expression elimination
in compilers, and generates cleaner code.
The problem case is if a complex expression is used in an access chain,
like:
Composite comp = buffer[texture(...)];
vec4 a = comp.a + comp.b + comp.c;
Before, we did not have common subexpression tracking for
OpLoad/OpAccessChain, so we easily ended up with code like:
vec4 a = buffer[texture(...)].a + buffer[texture(...)].b + buffer[texture(...)].c;
A good compiler will optimize this, but we should not rely on it, and
forcing texture(...) to a temporary also looks better.
The solution is to add a vector "implied_expression_reads", which works
similarly to expression_dependencies. We also need an extra mechanism in
to_expression which lets us skip expression read checking and do it
later. E.g. for expr -> access chain -> load, we should only trigger
a read of expr when using the loaded expression.
Based on a patch by Stefan Dösinger.
Metal cannot do signedness conversion on vertex attributes, and for good
reason. Putting a `uint4` into an `int4`, or a `char4` into a `uint4`,
would lose those values that are outside the range of the target type.
But putting a `uchar4` into a `short4` or an `int4`, or a `ushort4` into
an `int4`, should work. In that case, force the signedness in the shader
to match the declared type of the host.
Unfortunately, I don't really know how to automatically test this. This
remapping is done based on input parameters normally supplied by
MoltenVK. I'm not sure how we'd set this up for the command-line
`spirv-cross` tool.
Don't use `addsat()`/`subsat()`; that'll erroneously flag cases where
the sum is exactly the maximum integer value, or the difference is
exactly 0. Also, correct the condition for the `select()` function; it's
basically `mix()` with a boolean factor.
(What was I *thinking*?)
In GLSL, 8-bit types require GL_EXT_shader_8bit_storage. 16-bit types
can use either GL_AMD_gpu_shader_int16/GL_AMD_gpu_shader_half_float or
GL_EXT_shader_16bit_storage.
When trying to validate buffer sizes, we usually need to bail out when
using SpecConstantOps, but for some very specific cases where we allow
unsized arrays currently, we can safely allow "unknown" sized arrays as
well.
This is probably the best we can do, when we have even more difficult
cases than this, we throw a more sensible error message.
This is a large refactor which splits out the SPIR-V parser from
Compiler and moves it into its more appropriately named Parser module.
The Parser is responsible for building a ParsedIR structure which is
then consumed by one or more compilers.
Compiler can take a ParsedIR by value or move reference. This should
allow for optimal case for both multiple compilations and single
compilation scenarios.
Even as of Metal 2.1, MSL still doesn't support arrays of buffers
directly. Therefore, we must manually expand them. In the prologue, we
define arrays holding the argument pointers; these arrays are what the
transpiled code ends up referencing. We might be able to do similar
things for textures and samplers prior to MSL 2.0.
Speaking of which, also enable texture arrays on iOS MSL 1.2.
It'll be useful to have an "auxiliary buffer" for other builtins--e.g.
`DrawIndex` (which should be easier to implement now), or `ViewIndex`
when someone gets around to implementing multiview.
Pass this buffer to leaf functions as well.
Test that we handle this for integer textures as well.
It's intended to be used with MoltenVK to support arbitrary
`VkComponentMapping` settings. The idea is that MoltenVK will pass a
buffer (which it set to some buffer index that isn't being used)
containing packed versions of the `VkComponentMapping` struct, one for
each sampled image.
Yes, this is horribly ugly. It is unfortunately necessary. Much of the
ugliness is to support swizzling gather operations, where we need to
alter the component that the gather operates on--something complicated
by the `gather()` method requiring the passed-in component to be a
constant expression. It doesn't even support swizzling gathers on depth
textures, though I could add that if it turns out we need it.
This requires MSL 2.0+.
Also, force `ViewportIndex` and `Layer` to be defined as the correct
type, which is always `uint` in MSL.
Since Metal doesn't yet have geometry shaders, the vertex shader (or
tessellation evaluation shader == "post-tessellation vertex shader" in
Metal jargon) is the only kind of shader that can set this output. This
currently requires an extension to Vulkan, which causes validation of
the SPIR-V binaries for the test cases to fail. Therefore, the test
cases are marked "invalid", even though they're actually perfectly valid
SPIR-V--they just won't work without the
`SPV_EXT_shader_viewport_index_layer` extension.
This is somewhat tricky, because in MSL this value is obtained through a
function, `get_sample_position()`. Since the call expression is an
rvalue, it can't be passed by reference, so functions get a copy
instead.
This was the last piece preventing us from turning on sample-rate
shading support in MoltenVK.
Implement this by flattening outputs and unflattening inputs explicitly.
This allows us to pass down a single struct instead of dealing with the
insanity that would be passing down each flattened member separately.
Remove stage_uniforms_var_id.
Seems to be dead code. Naked uniforms do not exist in SPIR-V for Vulkan,
which this seems to have been intended for. It was also unused elsewhere.
We were passing a constant '1' to `emit_atomic_func_op()`--which caused
us to refer to SPIR-V value `%1`, which is almost certainly not what we
want! What we really want is to add/subtract the literal constant '1'
to/from the memory location.
This only affects the builtin when it is used, and not when it's passed
to a function. It's a lot cleaner than the way I was doing it before.
Remove the `to_expression()` hack.
In SPIR-V, builtin integral vectors can be either signed or unsigned,
but in MSL they're always unsigned. Unfortunately, the MSL spec forbids
implicit conversions between vector types--even if the corresponding
scalar types would implicitly convert. If you try, the result is a
cryptic error message such as:
```
program_source:37:60: error: cannot convert between vector values of different size ('int4' (aka 'vector_int4') and 'vector_uint4' (vector of 4 'unsigned int' values))
float4 r3 = as_type<float4>((as_type<int4>(r0) * gl_LocalInvocationID.xyyy) + as_type<int4>(r2));
~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~
```
Therefore, uses of these builtins must be explicitly cast, since the
rest of the binary likely assumes that the builtin is of its declared
type.
Two varyings (vertex outputs/fragment inputs) might have the same
location but be in different components--e.g. the compiler may have
packed what were two different varyings into a single varying vector.
Giving both varyings the same `[[user]]` attribute won't work--it may
yield unexpected results, or flat out fail to link. We could eventually
pack such varyings into a single vector, but that would require us to
handle the case where the varyings are different types--e.g. a `float`
and a `uint` packed into the same vector. For now, it seems most
prudent to give them unique `[[user]]` locations and let Apple's
compiler work out the best way to pack them.
This roughly matches their semantics in SPIR-V and MSL. For `FMin`,
`FMax`, and `FClamp`, and the Metal functions `fast::min()`,
`fast::max()`, and `fast::clamp()`, the result is undefined if any
operand is NaN. For the 'N' operations and their corresponding MSL
`precise::` functions, the result is consistent with IEEE 754 (first
non-NaN wins; result is NaN if all operands are NaN).
We can only do this with 32-bit floats, though, because Metal only
provides these variants for `float`. `half` only has one variant of
these functions that is presumably consistent with IEEE 754. I guess
that's OK; the SPIR-V spec only says that `F{Min,Max,Clamp}` are
undefined for NaNs. Performance might suffer, though.
The SPIR-V spec says that these check if the operands either are
unordered or satisfy the given condition. So that's just what we'll do,
using Metal's `isunordered()` stdlib function. Apple's optimizers ought
to be able to collapse that to a single unordered compare.
When the name of an alias global variable collides with a global
declaration, MSL would emit inconsistent names, sometimes with the
naming fix, sometimes without, because names were being tracked in two
separate meta blocks. Fix this by always redirecting parameter naming to
the original base variable as necessary.
MSL would force thread const& which would not work if the input argument
came from a different storage class.
Emit proper non-reference arguments for such values.
Add CompilerMSL::Options::disable_rasterization input/output API flag.
Disable rasterization via API flag or when writing to textures.
Disable rasterization when shader declares no output.
Add test shaders for vertex no output and write texture forcing void output.
Some projects build SPIRV-Cross as a single translation unit
and this causes a lot of warnings because the same macro is redeclared
multiple times in the different backends. This make sure that each
backend has its own namespace for internal macros.
Add CompilerMSL::Options::texture_width_max.
Emit and use spvTexelBufferCoord() function to convert 1D
texel buffer coordinates to 2D Metal texture coordinates.
Support flattening StorageOutput & StorageInput matrices and arrays.
No longer move matrix & array inputs to separate buffer.
Add separate SPIRFunction::fixup_statements_in & SPIRFunction::fixup_statements_out
instead of just SPIRFunction::fixup_statements.
Emit SPIRFunction::fixup_statements at beginning of functions.
CompilerMSL track vars_needing_early_declaration.
Pass global output variables as variables to functions that access them.
Sort input structs by location, same as output structs.
Emit struct declarations in order output, input, uniforms.
Regenerate reference shaders to new formats defined by above.
