[Mesa-dev] [PATCH 06/16] i965: Add a brw_invert_cmod() function.

[Matt Turner]

On Tue, Jan 20, 2015 at 12:11 AM, Kenneth Graunke <kenneth at whitecape.org> wrote:
> On Monday, January 19, 2015 03:31:05 PM Matt Turner wrote:
>> ---
>>  src/mesa/drivers/dri/i965/brw_eu.c | 22 ++++++++++++++++++++++
>>  src/mesa/drivers/dri/i965/brw_eu.h |  1 +
>>  2 files changed, 23 insertions(+)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_eu.c b/src/mesa/drivers/dri/i965/brw_eu.c
>> index 9905972..9977eed 100644
>> --- a/src/mesa/drivers/dri/i965/brw_eu.c
>> +++ b/src/mesa/drivers/dri/i965/brw_eu.c
>> @@ -88,6 +88,28 @@ brw_swap_cmod(uint32_t cmod)
>>     }
>>  }
>>
>> +/* Returns the corresponding inverted conditional mod. */
>> +enum brw_conditional_mod
>> +brw_invert_cmod(enum brw_conditional_mod cmod)
>> +{
>> +   switch (cmod) {
>> +   case BRW_CONDITIONAL_Z:
>> +      return BRW_CONDITIONAL_NZ;
>> +   case BRW_CONDITIONAL_NZ:
>> +      return BRW_CONDITIONAL_Z;
>> +   case BRW_CONDITIONAL_G:
>> +      return BRW_CONDITIONAL_LE;
>> +   case BRW_CONDITIONAL_GE:
>> +      return BRW_CONDITIONAL_L;
>> +   case BRW_CONDITIONAL_L:
>> +      return BRW_CONDITIONAL_GE;
>> +   case BRW_CONDITIONAL_LE:
>> +      return BRW_CONDITIONAL_G;
>> +   default:
>> +      return BRW_CONDITIONAL_NONE;
>> +   }
>> +}
>
> Heh, I thought this looked familiar...apparently I wrote one too :)
> http://lists.freedesktop.org/archives/mesa-dev/2014-August/066127.html
>
> I wasn't sure whether "invert" meant "flip direction" or "negate condition"
> until I read the code.  How about calling it brw_negate_cmod instead?
>
> /* Returns a conditional modifier that negates the condition. */
> enum brw_conditional_mod
> brw_negate_cmod(uint32_t cmod)
> {
>    ...
> }
>
> Either way is fine.
> Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>

Okay, I changed the name, and in the process of thinking about that
and a comment Jason made I realized that part of this function was
wrong. When you negate, you don't want to swap Z <-> NZ. I've changed
the function accordingly:

+   switch (cmod) {
+   case BRW_CONDITIONAL_Z:
+   case BRW_CONDITIONAL_NZ:
+      return cmod;
[snip]