ir/pp/lower.c

/*
 * Copyright (c) 2017 Lima Project
 *
 * 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, sub license,
 * 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 NON-INFRINGEMENT. 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.
 *
 */

#include "util/bitscan.h"
#include "util/ralloc.h"

#include "ppir.h"

static bool ppir_lower_const(ppir_block *block, ppir_node *node)
{
   if (ppir_node_is_root(node)) {
      ppir_node_delete(node);
      return true;
   }

   assert(ppir_node_has_single_succ(node));

   ppir_node *succ = ppir_node_first_succ(node);
   ppir_dest *dest = ppir_node_get_dest(node);

   switch (succ->type) {
   case ppir_node_type_alu:
   case ppir_node_type_branch:
      /* ALU and branch can consume consts directly */
      dest->type = ppir_target_pipeline;
      /* Reg will be updated in node_to_instr later */
      dest->pipeline = ppir_pipeline_reg_const0;

      /* single succ can still have multiple references to this node */
      for (int i = 0; i < ppir_node_get_src_num(succ); i++) {
         ppir_src *src = ppir_node_get_src(succ, i);
         if (src && src->node == node) {
            src->type = ppir_target_pipeline;
            src->pipeline = ppir_pipeline_reg_const0;
         }
      }
      return true;
   default:
      /* Create a move for everyone else */
      break;
   }

   ppir_node *move = ppir_node_insert_mov(node);
   if (unlikely(!move))
      return false;

   ppir_debug("lower const create move %d for %d\n",
              move->index, node->index);

   /* Need to be careful with changing src/dst type here:
    * it has to be done *after* successors have their children
    * replaced, otherwise ppir_node_replace_child() won't find
    * matching src/dst and as result won't work
    */
   ppir_src *mov_src = ppir_node_get_src(move, 0);
   mov_src->type = dest->type = ppir_target_pipeline;
   mov_src->pipeline = dest->pipeline = ppir_pipeline_reg_const0;

   return true;
}

static bool ppir_lower_swap_args(ppir_block *block, ppir_node *node)
{
   /* swapped op must be the next op */
   node->op++;

   assert(node->type == ppir_node_type_alu);
   ppir_alu_node *alu = ppir_node_to_alu(node);
   assert(alu->num_src == 2);

   ppir_src tmp = alu->src[0];
   alu->src[0] = alu->src[1];
   alu->src[1] = tmp;
   return true;
}

static bool ppir_lower_load(ppir_block *block, ppir_node *node)
{
   ppir_dest *dest = ppir_node_get_dest(node);
   if (ppir_node_is_root(node) && !node->succ_different_block &&
       dest->type == ppir_target_ssa) {
      ppir_node_delete(node);
      return true;
   }

   /* load can have multiple successors in case if we duplicated load node
    * that has load node in source
    */
   if ((ppir_node_has_single_src_succ(node) || ppir_node_is_root(node)) &&
       !node->succ_different_block &&
       dest->type != ppir_target_register) {
      ppir_node *succ = ppir_node_first_succ(node);
      switch (succ->type) {
      case ppir_node_type_alu:
      case ppir_node_type_branch: {
         /* single succ can still have multiple references to this node */
         for (int i = 0; i < ppir_node_get_src_num(succ); i++) {
            ppir_src *src = ppir_node_get_src(succ, i);
            if (src && src->node == node) {
               /* Can consume uniforms directly */
               src->type = dest->type = ppir_target_pipeline;
               src->pipeline = dest->pipeline = ppir_pipeline_reg_uniform;
            }
         }
         return true;
      }
      default:
         /* Create mov for everyone else */
         break;
      }
   }

   ppir_node *move = ppir_node_insert_mov(node);
   if (unlikely(!move))
      return false;

   ppir_src *mov_src = ppir_node_get_src(move, 0);
   mov_src->type = dest->type = ppir_target_pipeline;
   mov_src->pipeline = dest->pipeline = ppir_pipeline_reg_uniform;

   return true;
}

static bool ppir_lower_ddxy(ppir_block *block, ppir_node *node)
{
   assert(node->type == ppir_node_type_alu);
   ppir_alu_node *alu = ppir_node_to_alu(node);

   alu->src[1] = alu->src[0];
   if (node->op == ppir_op_ddx)
      alu->src[1].negate = !alu->src[1].negate;
   else if (node->op == ppir_op_ddy)
      alu->src[0].negate = !alu->src[0].negate;
   else
      assert(0);

   alu->num_src = 2;

   return true;
}

static bool ppir_lower_texture(ppir_block *block, ppir_node *node)
{
   ppir_dest *dest = ppir_node_get_dest(node);

   if (ppir_node_has_single_succ(node) && dest->type == ppir_target_ssa) {
      ppir_node *succ = ppir_node_first_succ(node);
      dest->type = ppir_target_pipeline;
      dest->pipeline = ppir_pipeline_reg_sampler;

      for (int i = 0; i < ppir_node_get_src_num(succ); i++) {
         ppir_src *src = ppir_node_get_src(succ, i);
         if (src && src->node == node) {
            src->type = ppir_target_pipeline;
            src->pipeline = ppir_pipeline_reg_sampler;
         }
      }
      return true;
   }

   /* Create move node as fallback */
   ppir_node *move = ppir_node_insert_mov(node);
   if (unlikely(!move))
      return false;

   ppir_debug("lower texture create move %d for %d\n",
              move->index, node->index);

   ppir_src *mov_src = ppir_node_get_src(move, 0);
   mov_src->type = dest->type = ppir_target_pipeline;
   mov_src->pipeline = dest->pipeline = ppir_pipeline_reg_sampler;

   return true;
}

/* Check if the select condition and ensure it can be inserted to
 * the scalar mul slot */
static bool ppir_lower_select(ppir_block *block, ppir_node *node)
{
   ppir_alu_node *alu = ppir_node_to_alu(node);
   ppir_src *src0 = &alu->src[0];
   ppir_src *src1 = &alu->src[1];
   ppir_src *src2 = &alu->src[2];

   /* If the condition is already an alu scalar whose only successor
    * is the select node, just turn it into pipeline output. */
   /* The (src2->node == cond) case is a tricky exception.
    * The reason is that we must force cond to output to ^fmul -- but
    * then it no longer writes to a register and it is impossible to
    * reference ^fmul in src2. So in that exceptional case, also fall
    * back to the mov. */
   ppir_node *cond = src0->node;
   if (cond &&
       cond->type == ppir_node_type_alu &&
       ppir_node_has_single_succ(cond) &&
       ppir_target_is_scalar(ppir_node_get_dest(cond)) &&
       ppir_node_schedulable_slot(cond, PPIR_INSTR_SLOT_ALU_SCL_MUL) &&
       src2->node != cond) {

      ppir_dest *cond_dest = ppir_node_get_dest(cond);
      cond_dest->type = ppir_target_pipeline;
      cond_dest->pipeline = ppir_pipeline_reg_fmul;

      ppir_node_target_assign(src0, cond);

      /* src1 could also be a reference from the same node as
       * the condition, so update it in that case. */
      if (src1->node && src1->node == cond)
         ppir_node_target_assign(src1, cond);

      return true;
   }

   /* If the condition can't be used for any reason, insert a mov
    * so that the condition can end up in ^fmul */
   ppir_node *move = ppir_node_create(block, ppir_op_mov, -1, 0);
   if (!move)
      return false;
   list_addtail(&move->list, &node->list);

   ppir_alu_node *move_alu = ppir_node_to_alu(move);
   ppir_src *move_src = move_alu->src;
   move_src->type = src0->type;
   move_src->ssa = src0->ssa;
   move_src->swizzle[0] = src0->swizzle[0];
   move_alu->num_src = 1;

   ppir_dest *move_dest = &move_alu->dest;
   move_dest->type = ppir_target_pipeline;
   move_dest->pipeline = ppir_pipeline_reg_fmul;
   move_dest->write_mask = 1;

   ppir_node *pred = src0->node;
   ppir_dep *dep = ppir_dep_for_pred(node, pred);
   if (dep)
      ppir_node_replace_pred(dep, move);
   else
      ppir_node_add_dep(node, move, ppir_dep_src);

   /* pred can be a register */
   if (pred)
      ppir_node_add_dep(move, pred, ppir_dep_src);

   ppir_node_target_assign(src0, move);

   /* src1 could also be a reference from the same node as
    * the condition, so update it in that case. */
   if (src1->node && src1->node == pred)
      ppir_node_target_assign(src1, move);

   return true;
}

static bool ppir_lower_trunc(ppir_block *block, ppir_node *node)
{
   /* Turn it into a mov with a round to integer output modifier */
   ppir_alu_node *alu = ppir_node_to_alu(node);
   ppir_dest *move_dest = &alu->dest;
   move_dest->modifier = ppir_outmod_round;
   node->op = ppir_op_mov;

   return true;
}

static bool ppir_lower_abs(ppir_block *block, ppir_node *node)
{
   /* Turn it into a mov and set the absolute modifier */
   ppir_alu_node *alu = ppir_node_to_alu(node);

   assert(alu->num_src == 1);

   alu->src[0].absolute = true;
   alu->src[0].negate = false;
   node->op = ppir_op_mov;

   return true;
}

static bool ppir_lower_neg(ppir_block *block, ppir_node *node)
{
   /* Turn it into a mov and set the negate modifier */
   ppir_alu_node *alu = ppir_node_to_alu(node);

   assert(alu->num_src == 1);

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

   return true;
}

static bool ppir_lower_sat(ppir_block *block, ppir_node *node)
{
   /* Turn it into a mov with the saturate output modifier */
   ppir_alu_node *alu = ppir_node_to_alu(node);

   assert(alu->num_src == 1);

   ppir_dest *move_dest = &alu->dest;
   move_dest->modifier = ppir_outmod_clamp_fraction;
   node->op = ppir_op_mov;

   return true;
}

static bool ppir_lower_branch_merge_condition(ppir_block *block, ppir_node *node)
{
   /* Check if we can merge a condition with a branch instruction,
    * removing the need for a select instruction */
   assert(node->type == ppir_node_type_branch);

   if (!ppir_node_has_single_pred(node))
      return false;

   ppir_node *pred = ppir_node_first_pred(node);
   assert(pred);

   if (pred->type != ppir_node_type_alu)
      return false;

   switch (pred->op)
   {
      case ppir_op_lt:
      case ppir_op_gt:
      case ppir_op_le:
      case ppir_op_ge:
      case ppir_op_eq:
      case ppir_op_ne:
         break;
      default:
         return false;
   }

   ppir_dest *dest = ppir_node_get_dest(pred);
   if (!ppir_node_has_single_succ(pred) || dest->type != ppir_target_ssa)
      return false;

   ppir_alu_node *cond = ppir_node_to_alu(pred);
   /* branch can't reference pipeline registers */
   if (cond->src[0].type == ppir_target_pipeline ||
       cond->src[1].type == ppir_target_pipeline)
      return false;

   /* branch can't use flags */
   if (cond->src[0].negate || cond->src[0].absolute ||
       cond->src[1].negate || cond->src[1].absolute)
      return false;

   /* at this point, it can be successfully be replaced. */
   ppir_branch_node *branch = ppir_node_to_branch(node);
   switch (pred->op)
   {
      case ppir_op_le:
         branch->cond_gt = true;
         break;
      case ppir_op_lt:
         branch->cond_eq = true;
         branch->cond_gt = true;
         break;
      case ppir_op_ge:
         branch->cond_lt = true;
         break;
      case ppir_op_gt:
         branch->cond_eq = true;
         branch->cond_lt = true;
         break;
      case ppir_op_eq:
         branch->cond_lt = true;
         branch->cond_gt = true;
         break;
      case ppir_op_ne:
         branch->cond_eq = true;
         break;
      default:
         assert(0);
         break;
   }

   assert(cond->num_src == 2);

   branch->num_src = 2;
   branch->src[0] = cond->src[0];
   branch->src[1] = cond->src[1];

   /* for all nodes before the condition */
   ppir_node_foreach_pred_safe(pred, dep) {
      /* insert the branch node as successor */
      ppir_node *p = dep->pred;
      ppir_node_remove_dep(dep);
      ppir_node_add_dep(node, p, ppir_dep_src);
   }

   ppir_node_delete(pred);

   return true;
}

static bool ppir_lower_branch(ppir_block *block, ppir_node *node)
{
   ppir_branch_node *branch = ppir_node_to_branch(node);

   /* Unconditional branch */
   if (branch->num_src == 0)
      return true;

   /* Check if we can merge a condition with the branch */
   if (ppir_lower_branch_merge_condition(block, node))
      return true;

   /* If the condition cannot be merged, fall back to a
    * comparison against zero */
   ppir_const_node *zero = ppir_node_create(block, ppir_op_const, -1, 0);

   if (!zero)
      return false;

   zero->constant.value[0].f = 0;
   zero->constant.num = 1;
   zero->dest.type = ppir_target_pipeline;
   zero->dest.pipeline = ppir_pipeline_reg_const0;
   zero->dest.ssa.num_components = 1;
   zero->dest.write_mask = 0x01;

   ppir_node_target_assign(&branch->src[1], &zero->node);

   if (branch->negate)
      branch->cond_eq = true;
   else {
      branch->cond_gt = true;
      branch->cond_lt = true;
   }

   branch->num_src = 2;

   ppir_node_add_dep(&branch->node, &zero->node, ppir_dep_src);
   list_addtail(&zero->node.list, &node->list);

   return true;
}

static bool ppir_lower_accum(ppir_block *block, ppir_node *node)
{
    /* If the last argument of a node placed in PPIR_INSTR_SLOT_ALU_SCL_ADD
    * (or PPIR_INSTR_SLOT_ALU_VEC_ADD) is placed in
    * PPIR_INSTR_SLOT_ALU_SCL_MUL (or PPIR_INSTR_SLOT_ALU_VEC_MUL) we cannot
    * save a register (and an instruction) by using a pipeline register.
    * Therefore it is interesting to make sure arguments of that type are
    * the first argument by swapping arguments (if possible) */
   ppir_alu_node *alu = ppir_node_to_alu(node);

   assert(alu->num_src >= 2);

   if (alu->src[0].type == ppir_target_pipeline)
      return true;

   if (alu->src[0].type == ppir_target_ssa) {
      int *src_0_slots = ppir_op_infos[alu->src[0].node->op].slots;
      if (src_0_slots) {
         for (int i = 0; src_0_slots[i] != PPIR_INSTR_SLOT_END; i++) {
            if ((src_0_slots[i] == PPIR_INSTR_SLOT_ALU_SCL_MUL) ||
               (src_0_slots[i] == PPIR_INSTR_SLOT_ALU_VEC_MUL)) {
               return true;
            }
         }
      }
   }

   int src_to_swap = -1;
   for (int j = 1; j < alu->num_src; j++) {
      if (alu->src[j].type != ppir_target_ssa)
         continue;
      int *src_slots = ppir_op_infos[alu->src[j].node->op].slots;
      if (!src_slots)
         continue;
      for (int i = 0; src_slots[i] != PPIR_INSTR_SLOT_END; i++) {
         if ((src_slots[i] == PPIR_INSTR_SLOT_ALU_SCL_MUL) ||
             (src_slots[i] == PPIR_INSTR_SLOT_ALU_VEC_MUL)) {
            src_to_swap = j;
            break;
         }
      }
      if (src_to_swap > 0)
         break;
   }

   if (src_to_swap < 0)
      return true;

   /* Swap arguments so that we can use a pipeline register later on */
   ppir_src tmp = alu->src[0];
   alu->src[0] = alu->src[src_to_swap];
   alu->src[src_to_swap] = tmp;

   return true;
}

static bool (*ppir_lower_funcs[ppir_op_num])(ppir_block *, ppir_node *) = {
   [ppir_op_abs] = ppir_lower_abs,
   [ppir_op_neg] = ppir_lower_neg,
   [ppir_op_const] = ppir_lower_const,
   [ppir_op_ddx] = ppir_lower_ddxy,
   [ppir_op_ddy] = ppir_lower_ddxy,
   [ppir_op_lt] = ppir_lower_swap_args,
   [ppir_op_le] = ppir_lower_swap_args,
   [ppir_op_load_texture] = ppir_lower_texture,
   [ppir_op_select] = ppir_lower_select,
   [ppir_op_trunc] = ppir_lower_trunc,
   [ppir_op_sat] = ppir_lower_sat,
   [ppir_op_branch] = ppir_lower_branch,
   [ppir_op_load_uniform] = ppir_lower_load,
   [ppir_op_load_temp] = ppir_lower_load,
   [ppir_op_add] = ppir_lower_accum,
   [ppir_op_max] = ppir_lower_accum,
   [ppir_op_min] = ppir_lower_accum,
   [ppir_op_eq] = ppir_lower_accum,
   [ppir_op_ne] = ppir_lower_accum,
};

bool ppir_lower_prog(ppir_compiler *comp)
{
   list_for_each_entry(ppir_block, block, &comp->block_list, list) {
      list_for_each_entry_safe(ppir_node, node, &block->node_list, list) {
         if (ppir_lower_funcs[node->op] &&
             !ppir_lower_funcs[node->op](block, node))
            return false;
      }
   }

   return true;
}