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List:       wine-devel
Subject:    Re: [vkd3d] Handling object components within the HLSL compiler.
From:       Zebediah Figura <zfigura () codeweavers ! com>
Date:       2022-09-20 17:50:18
Message-ID: 6fa9997e-d615-7f35-763b-26c1c7866074 () codeweavers ! com
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On 9/20/22 09:43, Francisco Casas wrote:
>>> In the future we would probably want to remove the "offset" field from
>>> the derefs, and make each hlsl_sm*.c compute the register offsets from
>>> the derefs in their index path form.
>>
>> We definitely want to get rid of "offset" from the derefs.
>>
> 
> Regarding this, after some thought I am actually not sure. Consider a 
> complex non-constant offset dereference such as 'foo[n][m]' in:
> 
> ---
> unsigned int n, m;
> 
> float4 main() : sv_target
> {
>      float4 foo[3][4] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
> 
>      return foo[n][m];
> }
> ---
> 
> So far I haven't seen these being represented with a complex expression 
> within the index of an instruction's register (I doubt that register 
> indexes can be more complex than a reference to another register plus a 
> constant offset).
> 
> Instead, a single temporal register is created and then referenced (r0 
> in this case):
> 
> ---
> ishl r0.x, cb0[0].x, l(2)
> iadd r0.x, r0.x, cb0[0].y
> mov r0.x, x0[r0.x + 0].x
> mov o0.xyzw, r0.xxxx
> ---
> 
> So it is reasonable for me to keep the deref offset instruction to serve 
> this purpose.
> 
> I suggest we review this again after once I send this patch series as a 
> merge request.

Well, when generating sm1 or sm4 IR we are going to need to be able to 
construct arbitrarily complex offsets, possibly involving new registers. 
In a sense we're going to have to generate the multiplication and 
addition instructions at translation time, instead of earlier as now. In 
essence I expect write_sm4_load() to generate almost exactly those 
instructions (modulo ishl vs imul or copy-prop optimizations...)



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