This adjusts the NaN replacement logic introduced in #9928 to work around the HLSL compiler optimizing away calls to isnan, which caused that functionality to not work with ubershaders on D3D11 and D3D12 (it did work with specialized shaders, despite a warning being logged for both; that warning is also now gone). Note that the `D3DCOMPILE_IEEE_STRICTNESS` flag did not solve this issue, despite the warning suggesting that it might.
Suggested by @kayru and @jamiehayes.
Fixes https://bugs.dolphin-emu.org/issues/12620
The changed code did not match the corresponding code in VertexShaderGen. Some parts of the sky have 2 color channels in each vertex, while others only have 1, despite only color channel 0 being used and XFMEM_SETNUMCHAN being set to 1 for both of them. The old code (from #4601) caused channel 0 to be set to channel 1 if the vertex contained both color channels but the number of channels was set to 1, which is wrong.
SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.
Cel-damage depends on lighting being calculated for the first channel
even though there is no color in the vertex format (defaults to the
material color). If lighting for the channel is not enabled, the vertex
will use the default color as before.
The default value of the color is determined by the number of elements in
the vertex format. This fixes the grey cubes in Super Mario Sunshine.
If the color channel count is zero, we set the color to black before the
end of the vertex shader. It's possible that this would be undefined
behavior on hardware if a vertex color index that was greater than the
channel count was used within TEV.
