[Mesa-dev] [PATCH 07/16] i965/fs: Support coalescing registers of size > 1.

[Jordan Justen]

On Fri, Jan 10, 2014 at 11:12 AM, Jordan Justen <jljusten at gmail.com> wrote:
> On Thu, Dec 19, 2013 at 1:40 PM, Matt Turner <mattst88 at gmail.com> wrote:
>> total instructions in shared programs: 1550048 -> 1549880 (-0.01%)
>> instructions in affected programs:     1896 -> 1728 (-8.86%)
>> ---
>>  src/mesa/drivers/dri/i965/brw_fs.cpp | 80 ++++++++++++++++++++++++++----------
>>  1 file changed, 58 insertions(+), 22 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> index 1a16f4e..39041e3 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
>> @@ -2265,6 +2265,12 @@ fs_visitor::register_coalesce()
>>
>>     calculate_live_intervals();
>>
>> +   int src_size = 0;
>> +   int channels_remaining = 0;
>> +   int reg_from = -1, reg_to = -1;
>> +   int reg_to_offset[MAX_SAMPLER_MESSAGE_SIZE];
>> +   fs_inst *mov[MAX_SAMPLER_MESSAGE_SIZE];
>> +
>>     foreach_list_safe(node, &this->instructions) {
>>        fs_inst *inst = (fs_inst *)node;
>>
>> @@ -2276,11 +2282,14 @@ fs_visitor::register_coalesce()
>>           inst->src[0].abs ||
>>           inst->src[0].smear != -1 ||
>>           inst->dst.file != GRF ||
>> -         inst->dst.type != inst->src[0].type ||
>> -         virtual_grf_sizes[inst->src[0].reg] != 1) {
>> +         inst->dst.type != inst->src[0].type) {
>>          continue;
>>        }
>>
>> +      if (virtual_grf_sizes[inst->src[0].reg] >
>> +          virtual_grf_sizes[inst->dst.reg])
>> +         continue;
>
> Why isn't this != rather than >?
>
>>        int var_from = live_intervals->var_from_reg(&inst->src[0]);
>>        int var_to = live_intervals->var_from_reg(&inst->dst);
>>
>> @@ -2288,31 +2297,58 @@ fs_visitor::register_coalesce()
>>            !inst->dst.equals(inst->src[0]))
>>           continue;
>>
>> -      int reg_from = inst->src[0].reg;
>> -      assert(inst->src[0].reg_offset == 0);
>> -      int reg_to = inst->dst.reg;
>> -      int reg_to_offset = inst->dst.reg_offset;
>> +      if (reg_from != inst->src[0].reg) {
>> +         reg_from = inst->src[0].reg;
>> +
>> +         src_size = virtual_grf_sizes[inst->src[0].reg];
>> +         assert(src_size <= MAX_SAMPLER_MESSAGE_SIZE);
>> +
>> +         channels_remaining = src_size;
>> +         memset(mov, 0, sizeof(mov));
>> +
>> +         reg_to = inst->dst.reg;
>> +      }
>> +
>> +      if (reg_to != inst->dst.reg)
>> +         continue;
>> +
>> +      const int offset = inst->src[0].reg_offset;
>> +      reg_to_offset[offset] = inst->dst.reg_offset;
>> +      mov[offset] = inst;
>> +      channels_remaining--;
>> +
>> +      if (channels_remaining)
>> +         continue;
>> +
>> +      for (int i = 0; i < src_size; i++) {
>> +         if (mov[i])
>> +            mov[i]->remove();
>> +      }
>>
>>        foreach_list(node, &this->instructions) {
>>          fs_inst *scan_inst = (fs_inst *)node;
>>
>> -        if (scan_inst->dst.file == GRF &&
>> -            scan_inst->dst.reg == reg_from) {
>> -           scan_inst->dst.reg = reg_to;
>> -           scan_inst->dst.reg_offset = reg_to_offset;
>> -        }
>> -        for (int i = 0; i < 3; i++) {
>> -           if (scan_inst->src[i].file == GRF &&
>> -               scan_inst->src[i].reg == reg_from) {
>> -              scan_inst->src[i].reg = reg_to;
>> -              scan_inst->src[i].reg_offset = reg_to_offset;
>> -           }
>> -        }
>> -      }
>> +         for (int i = 0; i < src_size; i++) {
>> +            if (mov[i]) {
>
> Shouldn't this always be taken?

The next patch seems to invalidate this question.

>> +               if (scan_inst->dst.file == GRF &&
>> +                   scan_inst->dst.reg == reg_from &&
>> +                   scan_inst->dst.reg_offset == i) {
>> +                  scan_inst->dst.reg = reg_to;
>> +                  scan_inst->dst.reg_offset = reg_to_offset[i];
>> +               }
>> +               for (int j = 0; j < 3; j++) {
>> +                  if (scan_inst->src[j].file == GRF &&
>> +                      scan_inst->src[j].reg == reg_from &&
>> +                      scan_inst->src[j].reg_offset == i) {
>> +                     scan_inst->src[j].reg = reg_to;
>> +                     scan_inst->src[j].reg_offset = reg_to_offset[i];
>> +                  }
>> +               }
>>
>> -      inst->remove();
>> -      progress = true;
>> -      continue;
>> +               progress = true;
>> +            }
>> +         }
>> +      }
>
> Couldn't we assign progress = true here instead? Ie, outside 2 of the
> 3 nested for loops.

The next patch seems to invalidate this question too.

>>     }
>>
>>     if (progress)
>> --
>> 1.8.3.2
>>
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