[PATCH vkd3d] vkd3d-shader/hlsl: Support casts between all numeric types on constant folding.

[Giovanni Mascellani]

Hi.

On 30/12/21 22:55, Francisco Casas wrote:
> CONSTANT_OP2_FUNCTION(constant_value_sum,+)
> CONSTANT_OP2_FUNCTION(constant_value_sub,-)
> CONSTANT_OP2_FUNCTION(constant_value_mult,+)
> CONSTANT_OP2_FUNCTION(constant_value_neg,* (-1) + 0 *) /* horrid? */
> CONSTANT_OP2_FUNCTION(constant_value_div,/) /* horrid? */

If you ask me, the neg thing is pretty horrid indeed, I'd avoid it. 
Also, I'm pretty sure that multiplying a float by zero is not guaranteed 
to give you zero (infinity * zero = NaN, I think, and I don't know about 
NaN * zero), so depending on how you use it it might give wrong results. 
If you want to go down that route, maybe it's better to add a 
corresponding CONSTANT_OP1_FUNCTION.

Also for the OP2 variants, notice that C doesn't define the results for 
all the possible arguments given to these operations. For example 
division by zero is undefined (and often results in a crash, in 
particular I think it does on the architectures we target) and signed 
overflow is undefined too (things like INT_MAX + INT_MAX, INT_MIN * -1, 
etc). It seems that we don't use -fwrapv in vkd3d (differently from 
Wine), which means that the compiler won't scramble to fix things up for us.

Giovanni.