This seems quite strange, since the HLSL register syntax expects a valid shader model instead of D3DVERTEXTEXTURESAMPLER0 there, if anything.
After lots of thinking and debugging and trial & error I have come to the conclusion, that this is actually a mistake in the shader code, because your Proxy_D3DXCompileShaderFromFile in dx_proxy.dll probably forwards to D3DXCompileShaderFromFile, which compiles for any sting in there (which is probably a bug), while fxc.exe would fail with an error like this:
For example the depthwrite_vs20.fxc and other shaders currently contain this line, which is used for shader model vs_3_0 compiles:
This seems quite strange, since the HLSL register syntax expects a valid shader model instead of D3DVERTEXTEXTURESAMPLER0 there, if anything.
After lots of thinking and debugging and trial & error I have come to the conclusion, that this is actually a mistake in the shader code, because your Proxy_D3DXCompileShaderFromFile in dx_proxy.dll probably forwards to D3DXCompileShaderFromFile, which compiles for any sting in there (which is probably a bug), while fxc.exe would fail with an error like this: