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/*

 * Copyright © 2014 Intel Corporation

 *

 * Permission is hereby granted, free of charge, to any person obtaining a

 * copy of this software and associated documentation files (the "Software"),

 * to deal in the Software without restriction, including without limitation

 * the rights to use, copy, modify, merge, publish, distribute, sublicense,

 * and/or sell copies of the Software, and to permit persons to whom the

 * Software is furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice (including the next

 * paragraph) shall be included in all copies or substantial portions of the

 * Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING

 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS

 * IN THE SOFTWARE.

 *

 * Authors:

 *    Jason Ekstrand (jason@jlekstrand.net)

 *

 */

#include "nir.h"

/*

 * This pass lowers the neg, abs, and sat operations to source modifiers on

 * ALU operations to make things nicer for the backend.  It's just much

 * easier to not have them when we're doing optimizations.

 */

static bool

nir_lower_to_source_mods_block(nir_block *block, void *state)

{

   nir_foreach_instr(block, instr) {

      if (instr->type != nir_instr_type_alu)

         continue;

      nir_alu_instr *alu = nir_instr_as_alu(instr);

      for (unsigned i = 0; i < nir_op_infos[alu->op].num_inputs; i++) {

         if (!alu->src[i].src.is_ssa)

            continue;

         if (alu->src[i].src.ssa->parent_instr->type != nir_instr_type_alu)

            continue;

         nir_alu_instr *parent = nir_instr_as_alu(alu->src[i].src.ssa->parent_instr);

         if (parent->dest.saturate)

            continue;

         switch (nir_op_infos[alu->op].input_types[i]) {

         case nir_type_float:

            if (parent->op != nir_op_fmov)

               continue;

            break;

         case nir_type_int:

            if (parent->op != nir_op_imov)

               continue;

            break;

         default:

            continue;

         }

         /* We can only do a rewrite if the source we are copying is SSA.

          * Otherwise, moving the read might invalidly reorder reads/writes

          * on a register.

          */

         if (!parent->src[0].src.is_ssa)

            continue;

         nir_instr_rewrite_src(instr, &alu->src[i].src, parent->src[0].src);

         if (alu->src[i].abs) {

            /* abs trumps both neg and abs, do nothing */

         } else {

            alu->src[i].negate = (alu->src[i].negate != parent->src[0].negate);

            alu->src[i].abs |= parent->src[0].abs;

         }

         for (int j = 0; j < 4; ++j) {

            if (!nir_alu_instr_channel_used(alu, i, j))

               continue;

            alu->src[i].swizzle[j] = parent->src[0].swizzle[alu->src[i].swizzle[j]];

         }

         if (list_empty(&parent->dest.dest.ssa.uses) &&

             list_empty(&parent->dest.dest.ssa.if_uses))

            nir_instr_remove(&parent->instr);

      }

      switch (alu->op) {

      case nir_op_fsat:

         alu->op = nir_op_fmov;

         alu->dest.saturate = true;

         break;

      case nir_op_ineg:

         alu->op = nir_op_imov;

         alu->src[0].negate = !alu->src[0].negate;

         break;

      case nir_op_fneg:

         alu->op = nir_op_fmov;

         alu->src[0].negate = !alu->src[0].negate;

         break;

      case nir_op_iabs:

         alu->op = nir_op_imov;

         alu->src[0].abs = true;

         alu->src[0].negate = false;

         break;

      case nir_op_fabs:

         alu->op = nir_op_fmov;

         alu->src[0].abs = true;

         alu->src[0].negate = false;

         break;

      default:

         break;

      }

      /* We've covered sources.  Now we're going to try and saturate the

       * destination if we can.

       */

      if (!alu->dest.dest.is_ssa)

         continue;

      /* We can only saturate float destinations */

      if (nir_op_infos[alu->op].output_type != nir_type_float)

         continue;

      if (!list_empty(&alu->dest.dest.ssa.if_uses))

         continue;

      bool all_children_are_sat = true;

      nir_foreach_use(&alu->dest.dest.ssa, child_src) {

         assert(child_src->is_ssa);

         nir_instr *child = child_src->parent_instr;

         if (child->type != nir_instr_type_alu) {

            all_children_are_sat = false;

            continue;

         }

         nir_alu_instr *child_alu = nir_instr_as_alu(child);

         if (child_alu->src[0].negate || child_alu->src[0].abs) {

            all_children_are_sat = false;

            continue;

         }

         if (child_alu->op != nir_op_fsat &&

             !(child_alu->op == nir_op_fmov && child_alu->dest.saturate)) {

            all_children_are_sat = false;

            continue;

         }

      }

      if (!all_children_are_sat)

         continue;

      alu->dest.saturate = true;

      nir_foreach_use(&alu->dest.dest.ssa, child_src) {

         assert(child_src->is_ssa);

         nir_instr *child = child_src->parent_instr;

         assert(child->type == nir_instr_type_alu);

         nir_alu_instr *child_alu = nir_instr_as_alu(child);

         child_alu->op = nir_op_fmov;

         child_alu->dest.saturate = false;

         /* We could propagate the dest of our instruction to the

          * destinations of the uses here.  However, one quick round of

          * copy propagation will clean that all up and then we don't have

          * the complexity.

          */

      }

   }

   return true;

}

static void

nir_lower_to_source_mods_impl(nir_function_impl *impl)

{

   nir_foreach_block(impl, nir_lower_to_source_mods_block, NULL);

}

void

nir_lower_to_source_mods(nir_shader *shader)

{

   nir_foreach_overload(shader, overload) {

      if (overload->impl)

         nir_lower_to_source_mods_impl(overload->impl);

   }

}