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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"

/*

 * Implements a small peephole optimization that looks for a multiply that

 * is only ever used in an add and replaces both with an fma.

 */

struct peephole_ffma_state {

   void *mem_ctx;

   nir_function_impl *impl;

   bool progress;

};

static inline bool

are_all_uses_fadd(nir_ssa_def *def)

{

   if (!list_empty(&def->if_uses))

      return false;

   nir_foreach_use(def, use_src) {

      nir_instr *use_instr = use_src->parent_instr;

      if (use_instr->type != nir_instr_type_alu)

         return false;

      nir_alu_instr *use_alu = nir_instr_as_alu(use_instr);

      switch (use_alu->op) {

      case nir_op_fadd:

         break; /* This one's ok */

      case nir_op_imov:

      case nir_op_fmov:

      case nir_op_fneg:

      case nir_op_fabs:

         assert(use_alu->dest.dest.is_ssa);

         if (!are_all_uses_fadd(&use_alu->dest.dest.ssa))

            return false;

         break;

      default:

         return false;

      }

   }

   return true;

}

static nir_alu_instr *

get_mul_for_src(nir_alu_src *src, uint8_t swizzle[4], bool *negate, bool *abs)

{

   assert(src->src.is_ssa && !src->abs && !src->negate);

   nir_instr *instr = src->src.ssa->parent_instr;

   if (instr->type != nir_instr_type_alu)

      return NULL;

   nir_alu_instr *alu = nir_instr_as_alu(instr);

   switch (alu->op) {

   case nir_op_imov:

   case nir_op_fmov:

      alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);

      break;

   case nir_op_fneg:

      alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);

      *negate = !*negate;

      break;

   case nir_op_fabs:

      alu = get_mul_for_src(&alu->src[0], swizzle, negate, abs);

      *negate = false;

      *abs = true;

      break;

   case nir_op_fmul:

      /* Only absorb a fmul into a ffma if the fmul is is only used in fadd

       * operations.  This prevents us from being too aggressive with our

       * fusing which can actually lead to more instructions.

       */

      if (!are_all_uses_fadd(&alu->dest.dest.ssa))

         return NULL;

      break;

   default:

      return NULL;

   }

   if (!alu)

      return NULL;

   for (unsigned i = 0; i < 4; i++) {

      if (!(alu->dest.write_mask & (1 << i)))

         break;

      swizzle[i] = swizzle[src->swizzle[i]];

   }

   return alu;

}

static bool

nir_opt_peephole_ffma_block(nir_block *block, void *void_state)

{

   struct peephole_ffma_state *state = void_state;

   nir_foreach_instr_safe(block, instr) {

      if (instr->type != nir_instr_type_alu)

         continue;

      nir_alu_instr *add = nir_instr_as_alu(instr);

      if (add->op != nir_op_fadd)

         continue;

      /* TODO: Maybe bail if this expression is considered "precise"? */

      assert(add->src[0].src.is_ssa && add->src[1].src.is_ssa);

      /* This, is the case a + a.  We would rather handle this with an

       * algebraic reduction than fuse it.  Also, we want to only fuse

       * things where the multiply is used only once and, in this case,

       * it would be used twice by the same instruction.

       */

      if (add->src[0].src.ssa == add->src[1].src.ssa)

         continue;

      nir_alu_instr *mul;

      uint8_t add_mul_src, swizzle[4];

      bool negate, abs;

      for (add_mul_src = 0; add_mul_src < 2; add_mul_src++) {

         for (unsigned i = 0; i < 4; i++)

            swizzle[i] = i;

         negate = false;

         abs = false;

         mul = get_mul_for_src(&add->src[add_mul_src], swizzle, &negate, &abs);

         if (mul != NULL)

            break;

      }

      if (mul == NULL)

         continue;

      nir_ssa_def *mul_src[2];

      mul_src[0] = mul->src[0].src.ssa;

      mul_src[1] = mul->src[1].src.ssa;

      if (abs) {

         for (unsigned i = 0; i < 2; i++) {

            nir_alu_instr *abs = nir_alu_instr_create(state->mem_ctx,

                                                      nir_op_fabs);

            abs->src[0].src = nir_src_for_ssa(mul_src[i]);

            nir_ssa_dest_init(&abs->instr, &abs->dest.dest,

                              mul_src[i]->num_components, NULL);

            abs->dest.write_mask = (1 << mul_src[i]->num_components) - 1;

            nir_instr_insert_before(&add->instr, &abs->instr);

            mul_src[i] = &abs->dest.dest.ssa;

         }

      }

      if (negate) {

         nir_alu_instr *neg = nir_alu_instr_create(state->mem_ctx,

                                                   nir_op_fneg);

         neg->src[0].src = nir_src_for_ssa(mul_src[0]);

         nir_ssa_dest_init(&neg->instr, &neg->dest.dest,

                           mul_src[0]->num_components, NULL);

         neg->dest.write_mask = (1 << mul_src[0]->num_components) - 1;

         nir_instr_insert_before(&add->instr, &neg->instr);

         mul_src[0] = &neg->dest.dest.ssa;

      }

      nir_alu_instr *ffma = nir_alu_instr_create(state->mem_ctx, nir_op_ffma);

      ffma->dest.saturate = add->dest.saturate;

      ffma->dest.write_mask = add->dest.write_mask;

      for (unsigned i = 0; i < 2; i++) {

         ffma->src[i].src = nir_src_for_ssa(mul_src[i]);

         for (unsigned j = 0; j < add->dest.dest.ssa.num_components; j++)

            ffma->src[i].swizzle[j] = mul->src[i].swizzle[swizzle[j]];

      }

      nir_alu_src_copy(&ffma->src[2], &add->src[1 - add_mul_src],

                       state->mem_ctx);

      assert(add->dest.dest.is_ssa);

      nir_ssa_dest_init(&ffma->instr, &ffma->dest.dest,

                        add->dest.dest.ssa.num_components,

                        add->dest.dest.ssa.name);

      nir_ssa_def_rewrite_uses(&add->dest.dest.ssa,

                               nir_src_for_ssa(&ffma->dest.dest.ssa),

                               state->mem_ctx);

      nir_instr_insert_before(&add->instr, &ffma->instr);

      assert(list_empty(&add->dest.dest.ssa.uses));

      nir_instr_remove(&add->instr);

      state->progress = true;

   }

   return true;

}

static bool

nir_opt_peephole_ffma_impl(nir_function_impl *impl)

{

   struct peephole_ffma_state state;

   state.mem_ctx = ralloc_parent(impl);

   state.impl = impl;

   state.progress = false;

   nir_foreach_block(impl, nir_opt_peephole_ffma_block, &state);

   if (state.progress)

      nir_metadata_preserve(impl, nir_metadata_block_index |

                                  nir_metadata_dominance);

   return state.progress;

}

bool

nir_opt_peephole_ffma(nir_shader *shader)

{

   bool progress = false;

   nir_foreach_overload(shader, overload) {

      if (overload->impl)

         progress |= nir_opt_peephole_ffma_impl(overload->impl);

   }

   return progress;

}