freedreno/ir3/ir3_postsched.c

/*
 * Copyright (C) 2019 Google, Inc.
 *
 * 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:
 *    Rob Clark <robclark@freedesktop.org>
 */

#include "util/dag.h"
#include "util/u_math.h"

#include "ir3.h"
#include "ir3_compiler.h"
#include "ir3_context.h"

#ifdef DEBUG
#define SCHED_DEBUG (ir3_shader_debug & IR3_DBG_SCHEDMSGS)
#else
#define SCHED_DEBUG 0
#endif
#define d(fmt, ...)                                                            \
   do {                                                                        \
      if (SCHED_DEBUG) {                                                       \
         mesa_logi("PSCHED: " fmt, ##__VA_ARGS__);                             \
      }                                                                        \
   } while (0)

#define di(instr, fmt, ...)                                                    \
   do {                                                                        \
      if (SCHED_DEBUG) {                                                       \
         struct log_stream *stream = mesa_log_streami();                       \
         mesa_log_stream_printf(stream, "PSCHED: " fmt ": ", ##__VA_ARGS__);   \
         ir3_print_instr_stream(stream, instr);                                \
         mesa_log_stream_destroy(stream);                                      \
      }                                                                        \
   } while (0)

/*
 * Post RA Instruction Scheduling
 */

struct ir3_postsched_ctx {
   struct ir3 *ir;

   struct ir3_shader_variant *v;

   void *mem_ctx;
   struct ir3_block *block; /* the current block */
   struct dag *dag;

   struct list_head unscheduled_list; /* unscheduled instructions */

   int sfu_delay;
   int tex_delay;
};

struct ir3_postsched_node {
   struct dag_node dag; /* must be first for util_dynarray_foreach */
   struct ir3_instruction *instr;
   bool partially_evaluated_path;

   bool has_tex_src, has_sfu_src;

   unsigned delay;
   unsigned max_delay;
};

#define foreach_sched_node(__n, __list)                                        \
   list_for_each_entry (struct ir3_postsched_node, __n, __list, dag.link)

static bool
has_tex_src(struct ir3_instruction *instr)
{
   struct ir3_postsched_node *node = instr->data;
   return node->has_tex_src;
}

static bool
has_sfu_src(struct ir3_instruction *instr)
{
   struct ir3_postsched_node *node = instr->data;
   return node->has_sfu_src;
}

static void
schedule(struct ir3_postsched_ctx *ctx, struct ir3_instruction *instr)
{
   debug_assert(ctx->block == instr->block);

   /* remove from unscheduled_list:
    */
   list_delinit(&instr->node);

   di(instr, "schedule");

   list_addtail(&instr->node, &instr->block->instr_list);

   struct ir3_postsched_node *n = instr->data;
   dag_prune_head(ctx->dag, &n->dag);

   if (is_meta(instr) && (instr->opc != OPC_META_TEX_PREFETCH))
      return;

   if (is_sfu(instr)) {
      ctx->sfu_delay = 8;
   } else if (has_sfu_src(instr)) {
      ctx->sfu_delay = 0;
   } else if (ctx->sfu_delay > 0) {
      ctx->sfu_delay--;
   }

   if (is_tex_or_prefetch(instr)) {
      ctx->tex_delay = 10;
   } else if (has_tex_src(instr)) {
      ctx->tex_delay = 0;
   } else if (ctx->tex_delay > 0) {
      ctx->tex_delay--;
   }
}

static void
dump_state(struct ir3_postsched_ctx *ctx)
{
   if (!SCHED_DEBUG)
      return;

   foreach_sched_node (n, &ctx->dag->heads) {
      di(n->instr, "maxdel=%3d    ", n->max_delay);

      util_dynarray_foreach (&n->dag.edges, struct dag_edge, edge) {
         struct ir3_postsched_node *child =
            (struct ir3_postsched_node *)edge->child;

         di(child->instr, " -> (%d parents) ", child->dag.parent_count);
      }
   }
}

/* Determine if this is an instruction that we'd prefer not to schedule
 * yet, in order to avoid an (ss) sync.  This is limited by the sfu_delay
 * counter, ie. the more cycles it has been since the last SFU, the less
 * costly a sync would be.
 */
static bool
would_sync(struct ir3_postsched_ctx *ctx, struct ir3_instruction *instr)
{
   if (ctx->sfu_delay) {
      if (has_sfu_src(instr))
         return true;
   }

   if (ctx->tex_delay) {
      if (has_tex_src(instr))
         return true;
   }

   return false;
}

/* find instruction to schedule: */
static struct ir3_instruction *
choose_instr(struct ir3_postsched_ctx *ctx)
{
   struct ir3_postsched_node *chosen = NULL;

   dump_state(ctx);

   foreach_sched_node (n, &ctx->dag->heads) {
      if (!is_meta(n->instr))
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "prio: chose (meta)");
      return chosen->instr;
   }

   /* Try to schedule inputs with a higher priority, if possible, as
    * the last bary.f unlocks varying storage to unblock more VS
    * warps.
    */
   foreach_sched_node (n, &ctx->dag->heads) {
      if (!is_input(n->instr))
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "prio: chose (input)");
      return chosen->instr;
   }

   /* Next prioritize discards: */
   foreach_sched_node (n, &ctx->dag->heads) {
      unsigned d =
         ir3_delay_calc_postra(ctx->block, n->instr, false, ctx->v->mergedregs);

      if (d > 0)
         continue;

      if (!is_kill_or_demote(n->instr))
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "csp: chose (kill, hard ready)");
      return chosen->instr;
   }

   /* Next prioritize expensive instructions: */
   foreach_sched_node (n, &ctx->dag->heads) {
      unsigned d =
         ir3_delay_calc_postra(ctx->block, n->instr, false, ctx->v->mergedregs);

      if (d > 0)
         continue;

      if (!(is_sfu(n->instr) || is_tex(n->instr)))
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "csp: chose (sfu/tex, hard ready)");
      return chosen->instr;
   }

   /*
    * Sometimes be better to take a nop, rather than scheduling an
    * instruction that would require an (ss) shortly after another
    * SFU..  ie. if last SFU was just one or two instr ago, and we
    * could choose between taking a nop and then scheduling
    * something else, vs scheduling the immed avail instruction that
    * would require (ss), we are better with the nop.
    */
   for (unsigned delay = 0; delay < 4; delay++) {
      foreach_sched_node (n, &ctx->dag->heads) {
         if (would_sync(ctx, n->instr))
            continue;

         unsigned d = ir3_delay_calc_postra(ctx->block, n->instr, true,
                                            ctx->v->mergedregs);

         if (d > delay)
            continue;

         if (!chosen || (chosen->max_delay < n->max_delay))
            chosen = n;
      }

      if (chosen) {
         di(chosen->instr, "csp: chose (soft ready, delay=%u)", delay);
         return chosen->instr;
      }
   }

   /* Next try to find a ready leader w/ soft delay (ie. including extra
    * delay for things like tex fetch which can be synchronized w/ sync
    * bit (but we probably do want to schedule some other instructions
    * while we wait)
    */
   foreach_sched_node (n, &ctx->dag->heads) {
      unsigned d =
         ir3_delay_calc_postra(ctx->block, n->instr, true, ctx->v->mergedregs);

      if (d > 0)
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "csp: chose (soft ready)");
      return chosen->instr;
   }

   /* Next try to find a ready leader that can be scheduled without nop's,
    * which in the case of things that need (sy)/(ss) could result in
    * stalls.. but we've already decided there is not a better option.
    */
   foreach_sched_node (n, &ctx->dag->heads) {
      unsigned d =
         ir3_delay_calc_postra(ctx->block, n->instr, false, ctx->v->mergedregs);

      if (d > 0)
         continue;

      if (!chosen || (chosen->max_delay < n->max_delay))
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "csp: chose (hard ready)");
      return chosen->instr;
   }

   /* Otherwise choose leader with maximum cost:
    *
    * TODO should we try to balance cost and delays?  I guess it is
    * a balance between now-nop's and future-nop's?
    */
   foreach_sched_node (n, &ctx->dag->heads) {
      if (!chosen || chosen->max_delay < n->max_delay)
         chosen = n;
   }

   if (chosen) {
      di(chosen->instr, "csp: chose (leader)");
      return chosen->instr;
   }

   return NULL;
}

struct ir3_postsched_deps_state {
   struct ir3_postsched_ctx *ctx;

   enum { F, R } direction;

   bool merged;

   /* Track the mapping between sched node (instruction) that last
    * wrote a given register (in whichever direction we are iterating
    * the block)
    *
    * Note, this table is twice as big as the # of regs, to deal with
    * half-precision regs.  The approach differs depending on whether
    * the half and full precision register files are "merged" (conflict,
    * ie. a6xx+) in which case we consider each full precision dep
    * as two half-precision dependencies, vs older separate (non-
    * conflicting) in which case the first half of the table is used
    * for full precision and 2nd half for half-precision.
    */
   struct ir3_postsched_node *regs[2 * 256];
};

/* bounds checking read/write accessors, since OoB access to stuff on
 * the stack is gonna cause a bad day.
 */
#define dep_reg(state, idx)                                                    \
   *({                                                                         \
      assert((idx) < ARRAY_SIZE((state)->regs));                               \
      &(state)->regs[(idx)];                                                   \
   })

static void
add_dep(struct ir3_postsched_deps_state *state,
        struct ir3_postsched_node *before, struct ir3_postsched_node *after)
{
   if (!before || !after)
      return;

   assert(before != after);

   if (state->direction == F) {
      dag_add_edge(&before->dag, &after->dag, NULL);
   } else {
      dag_add_edge(&after->dag, &before->dag, NULL);
   }
}

static void
add_single_reg_dep(struct ir3_postsched_deps_state *state,
                   struct ir3_postsched_node *node, unsigned num, int src_n)
{
   struct ir3_postsched_node *dep = dep_reg(state, num);

   if (src_n >= 0 && dep && state->direction == F) {
      unsigned d = ir3_delayslots(dep->instr, node->instr, src_n, true);
      node->delay = MAX2(node->delay, d);
      if (is_tex_or_prefetch(dep->instr))
         node->has_tex_src = true;
      if (is_tex_or_prefetch(dep->instr))
         node->has_sfu_src = true;
   }

   add_dep(state, dep, node);
   if (src_n < 0) {
      dep_reg(state, num) = node;
   }
}

/* This is where we handled full vs half-precision, and potential conflicts
 * between half and full precision that result in additional dependencies.
 * The 'reg' arg is really just to know half vs full precision.
 *
 * If non-negative, then this adds a dependency on a source register, and
 * src_n is the index passed into ir3_delayslots() for calculating the delay:
 * If positive, corresponds to node->instr->regs[src_n]. If negative, then
 * this is for a destination register.
 */
static void
add_reg_dep(struct ir3_postsched_deps_state *state,
            struct ir3_postsched_node *node, const struct ir3_register *reg,
            unsigned num, int src_n)
{
   if (state->merged) {
      /* Make sure that special registers like a0.x that are written as
       * half-registers don't alias random full registers by pretending that
       * they're full registers:
       */
      if ((reg->flags & IR3_REG_HALF) && !is_reg_special(reg)) {
         /* single conflict in half-reg space: */
         add_single_reg_dep(state, node, num, src_n);
      } else {
         /* two conflicts in half-reg space: */
         add_single_reg_dep(state, node, 2 * num + 0, src_n);
         add_single_reg_dep(state, node, 2 * num + 1, src_n);
      }
   } else {
      if (reg->flags & IR3_REG_HALF)
         num += ARRAY_SIZE(state->regs) / 2;
      add_single_reg_dep(state, node, num, src_n);
   }
}

static void
calculate_deps(struct ir3_postsched_deps_state *state,
               struct ir3_postsched_node *node)
{
   /* Add dependencies on instructions that previously (or next,
    * in the reverse direction) wrote any of our src registers:
    */
   foreach_src_n (reg, i, node->instr) {
      if (reg->flags & (IR3_REG_CONST | IR3_REG_IMMED))
         continue;

      if (reg->flags & IR3_REG_RELATIV) {
         /* mark entire array as read: */
         for (unsigned j = 0; j < reg->size; j++) {
            add_reg_dep(state, node, reg, reg->array.base + j, i);
         }
      } else {
         assert(reg->wrmask >= 1);
         u_foreach_bit (b, reg->wrmask) {
            add_reg_dep(state, node, reg, reg->num + b, i);
         }
      }
   }

   /* And then after we update the state for what this instruction
    * wrote:
    */
   foreach_dst (reg, node->instr) {
      if (reg->wrmask == 0)
         continue;
      if (reg->flags & IR3_REG_RELATIV) {
         /* mark the entire array as written: */
         for (unsigned i = 0; i < reg->size; i++) {
            add_reg_dep(state, node, reg, reg->array.base + i, -1);
         }
      } else {
         assert(reg->wrmask >= 1);
         u_foreach_bit (b, reg->wrmask) {
            add_reg_dep(state, node, reg, reg->num + b, -1);
         }
      }
   }
}

static void
calculate_forward_deps(struct ir3_postsched_ctx *ctx)
{
   struct ir3_postsched_deps_state state = {
      .ctx = ctx,
      .direction = F,
      .merged = ctx->v->mergedregs,
   };

   foreach_instr (instr, &ctx->unscheduled_list) {
      calculate_deps(&state, instr->data);
   }
}

static void
calculate_reverse_deps(struct ir3_postsched_ctx *ctx)
{
   struct ir3_postsched_deps_state state = {
      .ctx = ctx,
      .direction = R,
      .merged = ctx->v->mergedregs,
   };

   foreach_instr_rev (instr, &ctx->unscheduled_list) {
      calculate_deps(&state, instr->data);
   }
}

static void
sched_node_init(struct ir3_postsched_ctx *ctx, struct ir3_instruction *instr)
{
   struct ir3_postsched_node *n =
      rzalloc(ctx->mem_ctx, struct ir3_postsched_node);

   dag_init_node(ctx->dag, &n->dag);

   n->instr = instr;
   instr->data = n;
}

static void
sched_dag_max_delay_cb(struct dag_node *node, void *state)
{
   struct ir3_postsched_node *n = (struct ir3_postsched_node *)node;
   uint32_t max_delay = 0;

   util_dynarray_foreach (&n->dag.edges, struct dag_edge, edge) {
      struct ir3_postsched_node *child =
         (struct ir3_postsched_node *)edge->child;
      max_delay = MAX2(child->max_delay, max_delay);
   }

   n->max_delay = MAX2(n->max_delay, max_delay + n->delay);
}

static void
sched_dag_init(struct ir3_postsched_ctx *ctx)
{
   ctx->mem_ctx = ralloc_context(NULL);

   ctx->dag = dag_create(ctx->mem_ctx);

   foreach_instr (instr, &ctx->unscheduled_list)
      sched_node_init(ctx, instr);

   calculate_forward_deps(ctx);
   calculate_reverse_deps(ctx);

   /*
    * To avoid expensive texture fetches, etc, from being moved ahead
    * of kills, track the kills we've seen so far, so we can add an
    * extra dependency on them for tex/mem instructions
    */
   struct util_dynarray kills;
   util_dynarray_init(&kills, ctx->mem_ctx);

   /* The last bary.f with the (ei) flag must be scheduled before any kills,
    * or the hw gets angry. Keep track of inputs here so we can add the
    * false dep on the kill instruction.
    */
   struct util_dynarray inputs;
   util_dynarray_init(&inputs, ctx->mem_ctx);

   /*
    * Normal srcs won't be in SSA at this point, those are dealt with in
    * calculate_forward_deps() and calculate_reverse_deps().  But we still
    * have the false-dep information in SSA form, so go ahead and add
    * dependencies for that here:
    */
   foreach_instr (instr, &ctx->unscheduled_list) {
      struct ir3_postsched_node *n = instr->data;

      foreach_ssa_src_n (src, i, instr) {
         if (src->block != instr->block)
            continue;

         /* we can end up with unused false-deps.. just skip them: */
         if (src->flags & IR3_INSTR_UNUSED)
            continue;

         struct ir3_postsched_node *sn = src->data;

         /* don't consider dependencies in other blocks: */
         if (src->block != instr->block)
            continue;

         dag_add_edge(&sn->dag, &n->dag, NULL);
      }

      if (is_input(instr)) {
         util_dynarray_append(&inputs, struct ir3_instruction *, instr);
      } else if (is_kill_or_demote(instr)) {
         util_dynarray_foreach (&inputs, struct ir3_instruction *, instrp) {
            struct ir3_instruction *input = *instrp;
            struct ir3_postsched_node *in = input->data;
            dag_add_edge(&in->dag, &n->dag, NULL);
         }
         util_dynarray_append(&kills, struct ir3_instruction *, instr);
      } else if (is_tex(instr) || is_mem(instr)) {
         util_dynarray_foreach (&kills, struct ir3_instruction *, instrp) {
            struct ir3_instruction *kill = *instrp;
            struct ir3_postsched_node *kn = kill->data;
            dag_add_edge(&kn->dag, &n->dag, NULL);
         }
      }
   }

   // TODO do we want to do this after reverse-dependencies?
   dag_traverse_bottom_up(ctx->dag, sched_dag_max_delay_cb, NULL);
}

static void
sched_dag_destroy(struct ir3_postsched_ctx *ctx)
{
   ralloc_free(ctx->mem_ctx);
   ctx->mem_ctx = NULL;
   ctx->dag = NULL;
}

static void
sched_block(struct ir3_postsched_ctx *ctx, struct ir3_block *block)
{
   ctx->block = block;
   ctx->tex_delay = 0;
   ctx->sfu_delay = 0;

   /* move all instructions to the unscheduled list, and
    * empty the block's instruction list (to which we will
    * be inserting).
    */
   list_replace(&block->instr_list, &ctx->unscheduled_list);
   list_inithead(&block->instr_list);

   // TODO once we are using post-sched for everything we can
   // just not stick in NOP's prior to post-sched, and drop this.
   // for now keep this, since it makes post-sched optional:
   foreach_instr_safe (instr, &ctx->unscheduled_list) {
      switch (instr->opc) {
      case OPC_NOP:
      case OPC_B:
      case OPC_JUMP:
         list_delinit(&instr->node);
         break;
      default:
         break;
      }
   }

   sched_dag_init(ctx);

   /* First schedule all meta:input instructions, followed by
    * tex-prefetch.  We want all of the instructions that load
    * values into registers before the shader starts to go
    * before any other instructions.  But in particular we
    * want inputs to come before prefetches.  This is because
    * a FS's bary_ij input may not actually be live in the
    * shader, but it should not be scheduled on top of any
    * other input (but can be overwritten by a tex prefetch)
    */
   foreach_instr_safe (instr, &ctx->unscheduled_list)
      if (instr->opc == OPC_META_INPUT)
         schedule(ctx, instr);

   foreach_instr_safe (instr, &ctx->unscheduled_list)
      if (instr->opc == OPC_META_TEX_PREFETCH)
         schedule(ctx, instr);

   while (!list_is_empty(&ctx->unscheduled_list)) {
      struct ir3_instruction *instr = choose_instr(ctx);

      unsigned delay =
         ir3_delay_calc_postra(ctx->block, instr, false, ctx->v->mergedregs);
      d("delay=%u", delay);

      /* and if we run out of instructions that can be scheduled,
       * then it is time for nop's:
       */
      debug_assert(delay <= 6);
      while (delay > 0) {
         ir3_NOP(block);
         delay--;
      }

      schedule(ctx, instr);
   }

   sched_dag_destroy(ctx);
}

static bool
is_self_mov(struct ir3_instruction *instr)
{
   if (!is_same_type_mov(instr))
      return false;

   if (instr->dsts[0]->num != instr->srcs[0]->num)
      return false;

   if (instr->dsts[0]->flags & IR3_REG_RELATIV)
      return false;

   if (instr->cat1.round != ROUND_ZERO)
      return false;

   if (instr->srcs[0]->flags &
       (IR3_REG_CONST | IR3_REG_IMMED | IR3_REG_RELATIV | IR3_REG_FNEG |
        IR3_REG_FABS | IR3_REG_SNEG | IR3_REG_SABS | IR3_REG_BNOT))
      return false;

   return true;
}

/* sometimes we end up w/ in-place mov's, ie. mov.u32u32 r1.y, r1.y
 * as a result of places were before RA we are not sure that it is
 * safe to eliminate.  We could eliminate these earlier, but sometimes
 * they are tangled up in false-dep's, etc, so it is easier just to
 * let them exist until after RA
 */
static void
cleanup_self_movs(struct ir3 *ir)
{
   foreach_block (block, &ir->block_list) {
      foreach_instr_safe (instr, &block->instr_list) {
         for (unsigned i = 0; i < instr->deps_count; i++) {
            if (instr->deps[i] && is_self_mov(instr->deps[i])) {
               instr->deps[i] = NULL;
            }
         }

         if (is_self_mov(instr))
            list_delinit(&instr->node);
      }
   }
}

bool
ir3_postsched(struct ir3 *ir, struct ir3_shader_variant *v)
{
   struct ir3_postsched_ctx ctx = {
      .ir = ir,
      .v = v,
   };

   ir3_remove_nops(ir);
   cleanup_self_movs(ir);

   foreach_block (block, &ir->block_list) {
      sched_block(&ctx, block);
   }

   return true;
}