> +HRESULT WINAPI D3DXGetShaderInputSemantics(const DWORD *byte_code, D3DXSEMANTIC *semantics, UINT *count)
> +{
> +    const DWORD *ptr = byte_code;
> +    UINT i = 0;
> +
> +    TRACE("byte_code = %p, semantics = %p, count = %p\n", byte_code, semantics, count);
> +
> +    if (!byte_code)
> +        return D3DERR_INVALIDCALL;
> +
> +    TRACE("Shader version: %#x\n", *ptr);
> +
> +    /* Look for the END token, skipping the VERSION token */
> +    while (*++ptr != D3DSIO_END)

I think you should be a bit more careful in skipping non-opcode
DWORDs, otherwise you could e.g. potentially match with constants from
DEF instructions - very unlikely to happen in practice, sure, but
since it can be easily avoided, why not?
Take a look at shader_skip_opcode() from wined3d/shader_sm1.c. You can
probably get away without having to write a table with the parameters
count for each SM1 opcode by just skipping DWORDs with the most
significant bit set (see shader_skip_unrecognized() from the same
file). Of course you still have to special case DEF but that should be
it.

> +    {
> +        /* Skip comments */
> +        if ((*ptr & D3DSI_OPCODE_MASK) == D3DSIO_COMMENT)
> +        {
> +            ptr += ((*ptr & D3DSI_COMMENTSIZE_MASK) >> D3DSI_COMMENTSIZE_SHIFT);
> +        }
> +        else if ((*ptr & D3DSI_OPCODE_MASK) == D3DSIO_DCL)
> +        {
> +            DWORD param1 = *++ptr;
> +            DWORD param2 = *++ptr;
> +            DWORD usage = param1 & 0x1f;
> +            DWORD usage_index = (param1 >> 16) & 0xf;
> +            DWORD reg_type = (((param2 >> 11) & 0x3) << 3) | ((param2 >> 28) & 0x7);
> +
> +            TRACE("D3DSIO_DCL param1: %#x, param2: %#x, usage: %u, usage_index: %u, reg_type: %u\n",
> +                   param1, param2, usage, usage_index, reg_type);
> +
> +            if (reg_type == D3DSPR_INPUT)
> +            {
> +                if (semantics)
> +                {
> +                    semantics[i].Usage = usage;
> +                    semantics[i].UsageIndex = usage_index;
> +                }
> +                i++;
> +            }
> +        }
> +    }
> +
> +    if (count)
> +        *count = i;
> +
> +    return D3D_OK;
> +}

Have you tried to implement D3DXGetShaderOutputSemantics too? I
suspect most of the code will be pretty much the same, in that case
you could move the common code to a helper function and use it from
both.
You don't necessarily need to do this right now, just mentioning a
potential follow-up.