[Mesa-dev] [PATCH 8/8] i965/vec4: Do copy before constant propagation after opt_vector_float().

[Matt Turner]

On 12/22/14, Ian Romanick <idr at freedesktop.org> wrote:
> On 12/21/2014 03:24 PM, Matt Turner wrote:
>> total instructions in shared programs: 5877012 -> 5876617 (-0.01%)
>> instructions in affected programs:     33140 -> 32745 (-1.19%)
>>
>> From before the commit that allows VF constant propagation (which hurt
>> some programs) to here, the results are:
>>
>> total instructions in shared programs: 5877951 -> 5876617 (-0.02%)
>> instructions in affected programs:     123444 -> 122110 (-1.08%)
>>
>> with no programs hurt.
>> ---
>>  src/mesa/drivers/dri/i965/brw_vec4.cpp | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> b/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> index d36a735..c9ba338 100644
>> --- a/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_vec4.cpp
>> @@ -1800,6 +1800,7 @@ vec4_visitor::run()
>>
>>     if (opt_vector_float()) {
>>        opt_cse();
>> +      opt_copy_propagation(false);
>
> The commit messages suggest the above line should go before the
> opt_cse() call.

Right, saying "after opt_cse()" seems too general though. How about:

> i965/vec4: Do separate copy followed by constant propagation after opt_vector_float().

>>        opt_copy_propagation();
>
> Seeing these two lines together makes the default parameter to
> opt_copy_propagation feel a little icky... but I guess the
> OPT(opt_copy_propagation()) in vec4_visitor::run won't really work
> otherwise.
>
> Maybe pass an explicit true here anyway?

The OPT macro is actually variadic and passes extra arguments to the
optimization pass, but I think I like the default argument there, and
explicitly passing true/false in the opt_vector_float() block to show
explicitly what's going on.