[PATCH vkd3d 5/7] vkd3d-shader/hlsl: Write SM4 casts to float.

[Zebediah Figura (she/her)]

On 9/9/21 6:16 PM, Matteo Bruni wrote:
> On Thu, Sep 9, 2021 at 6:02 AM Zebediah Figura <zfigura at codeweavers.com> wrote:
>>
>> Signed-off-by: Zebediah Figura <zfigura at codeweavers.com>
>> ---
>>   libs/vkd3d-shader/hlsl_sm4.c | 34 ++++++++++++++++++++++++++++++++++
>>   1 file changed, 34 insertions(+)
>>
>> diff --git a/libs/vkd3d-shader/hlsl_sm4.c b/libs/vkd3d-shader/hlsl_sm4.c
>> index 160da47fd..cac71ef7e 100644
>> --- a/libs/vkd3d-shader/hlsl_sm4.c
>> +++ b/libs/vkd3d-shader/hlsl_sm4.c
>> @@ -981,6 +981,40 @@ static void write_sm4_expr(struct hlsl_ctx *ctx,
>>           {
>>               switch (expr->op)
>>               {
>> +                case HLSL_OP1_CAST:
>> +                {
>> +                    const struct hlsl_type *src_type = arg1->data_type;
>> +
>> +                    /* Narrowing casts need to be lowered. */
>> +                    if (src_type->dimx != expr->node.data_type->dimx)
>> +                        hlsl_fixme(ctx, expr->node.loc, "Narrowing cast.\n");
>> +
>> +                    switch (src_type->base_type)
>> +                    {
>> +                        case HLSL_TYPE_HALF:
>> +                        case HLSL_TYPE_FLOAT:
>> +                            write_sm4_unary_op(buffer, VKD3D_SM4_OP_MOV, &expr->node, arg1, 0);
>> +                            break;
>> +
>> +                        case HLSL_TYPE_BOOL:
>> +                        case HLSL_TYPE_INT:
>> +                            write_sm4_unary_op(buffer, VKD3D_SM4_OP_ITOF, &expr->node, arg1, 0);
>> +                            break;
> 
> As far as I'm aware, booleans in SM4+ are represented in quite a
> peculiar way: false is represented as 0, true is canonically
> 0xffffffff. I think the idea is to be able to use the result of a
> conditional expression directly as a mask and such, but don't quote me
> on that. For sure it's different from SM1-3, which use the traditional
> 0 and 1 values for false and true.
> 
> That's probably the reason why native uses MOVC to convert from bool
> (to float or anything else) and, most importantly, NE for the opposite
> direction (with 0 as the other comparand).
> 

"(int)(bool)true" evaluates to 1 in anything I've been able to test. 
Under what circumstances do you have it evaluating to ~0?