The structurizer is implemented along the lines of what is usually called
the "structured program theorem": the control flow is completely
virtualized by mean of an additional TEMP register which stores the
block index which is currently running. The whole program is then
converted to a huge switch construction enclosed in a loop, executing
at each iteration the appropriate block and updating the register
depending on block jump instruction.
The algorithm's generality is also its major weakness: it accepts any
input program, even if its CFG is not reducible, but the output
program lacks any useful convergence information. It satisfies the
letter of the SPIR-V requirements, but it is expected that it will
be very inefficient to run on a GPU (unless a downstream compiler is
able to devirtualize the control flow and do a proper convergence
analysis pass). The algorithm is however very simple, and good enough
to at least pass tests, enabling further development. A better
alternative is expected to be upstreamed incrementally.
Side note: the structured program theorem is often called the
Böhm-Jacopini theorem; Böhm and Jacopini did indeed prove a variation
of it, but their algorithm is different from what is commontly attributed
to them and implemented here, so I opted for not using their name.
These can be disassembled by D3DDisassemble() just fine, and perhaps
more importantly, shader model 1 vertex shaders do not require dcl_
instructions in Direct3D 8.
The implementation of upload_buffer_data_with_states(), unlike the
implementation of upload_texture_data_with_states(), does not expect a
pointer to a D3D12_SUBRESOURCE_DATA, but rather, a direct pointer to the
data.
The generated Vulkan calls look right and do not trigger any
validation error, but the returned timestamp is 0. A valid
timestamp is returned if the CopyResource() call is commented,
or the second EndQuery() call is moved before CopyResource(),
or the first EndQuery() call is commented. I am not seeing any
sensible pattern here, so I guess there is just a bug in
MoltenVK.
Specifically, MoltenVK seems to be able to load from stencil, but
the specific replicating swizzle (repeating the stencil value on
all the channels) is not honored. The stencil value is read only
on the red channel.
At the current moment this is a little odd because for SM1 [test]
directives are skipped, and the [shader] directives are not executed by
the shader_runner_vulkan.c:compile_shader() but by the general
shader_runner.c:compile_shader(). So in principle it is a little weird
that we go through the vulkan runner.
But fret not, because in the future we plan to make the parser agnostic
to the language of the tests, so we will get rid of the general
shader_runner.c:compile_shader() function and instead call a
runner->compile_shader() function, defined for each runner. Granted,
most of these may call a generic implementation that uses native
compiler in Windows, and vkd3d-shader on Linux, but it would be more
conceptually correct.
If the runners require multiple calls to run_shader_tests() for
different shader model ranges, these are moved inside the sole runner
call.
For the same reason, the trace() messages are also moved inside the
runner calls.
We can now pass (sm<4) and (sm>=4) to "fail" and "todo" qualifiers, and
we can use multiple of these qualifier arguments using "&" for AND and
"|" for OR.
examples:
todo(sm>=4 & sm<6)
todo(sm<4 | sm>6)
parenthesis are not supported.
Adding additional model ranges for the tests, if we need them, should be
easier now, since they only have to be added to the "valid_args" array.
