src/gallium/drivers/freedreno/ir3/ir3_legalize.c

   1 /* -*- mode: C; c-file-style: "k&r"; tab-width 4; indent-tabs-mode: t; -*- */
   2
   3 /*
   4  * Copyright (C) 2014 Rob Clark <robclark@freedesktop.org>
   5  *
   6  * Permission is hereby granted, free of charge, to any person obtaining a
   7  * copy of this software and associated documentation files (the "Software"),
   8  * to deal in the Software without restriction, including without limitation
   9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  10  * and/or sell copies of the Software, and to permit persons to whom the
  11  * Software is furnished to do so, subject to the following conditions:
  12  *
  13  * The above copyright notice and this permission notice (including the next
  14  * paragraph) shall be included in all copies or substantial portions of the
  15  * Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  *
  25  * Authors:
  26  *    Rob Clark <robclark@freedesktop.org>
  27  */
  28
  29 #include "util/u_math.h"
  30
  31 #include "freedreno_util.h"
  32
  33 #include "ir3.h"
  34
  35 /*
  36  * Legalize:
  37  *
  38  * We currently require that scheduling ensures that we have enough nop's
  39  * in all the right places.  The legalize step mostly handles fixing up
  40  * instruction flags ((ss)/(sy)/(ei)), and collapses sequences of nop's
  41  * into fewer nop's w/ rpt flag.
  42  */
  43
  44 struct ir3_legalize_ctx {
  45         bool has_samp;
  46         int max_bary;
  47 };
  48
  49 /* We want to evaluate each block from the position of any other
  50  * predecessor block, in order that the flags set are the union
  51  * of all possible program paths.  For stopping condition, we
  52  * want to stop when the pair of <pred-block, current-block> has
  53  * been visited already.
  54  *
  55  * XXX is that completely true?  We could have different needs_xyz
  56  * flags set depending on path leading to pred-block.. we could
  57  * do *most* of this based on chasing src instructions ptrs (and
  58  * following all phi srcs).. except the write-after-read hazzard.
  59  *
  60  * For now we just set ss/sy flag on first instruction on block,
  61  * and handle everything within the block as before.
  62  */
  63
  64 static void
  65 legalize_block(struct ir3_legalize_ctx *ctx, struct ir3_block *block)
  66 {
  67         struct ir3_instruction *last_input = NULL;
  68         struct ir3_instruction *last_rel = NULL;
  69         struct list_head instr_list;
  70         regmask_t needs_ss_war;       /* write after read */
  71         regmask_t needs_ss;
  72         regmask_t needs_sy;
  73
  74         regmask_init(&needs_ss_war);
  75         regmask_init(&needs_ss);
  76         regmask_init(&needs_sy);
  77
  78         /* remove all the instructions from the list, we'll be adding
  79          * them back in as we go
  80          */
  81         list_replace(&block->instr_list, &instr_list);
  82         list_inithead(&block->instr_list);
  83
  84         list_for_each_entry_safe (struct ir3_instruction, n, &instr_list, node) {
  85                 struct ir3_register *reg;
  86                 unsigned i;
  87
  88                 if (is_meta(n))
  89                         continue;
  90
  91                 if (is_input(n)) {
  92                         struct ir3_register *inloc = n->regs[1];
  93                         assert(inloc->flags & IR3_REG_IMMED);
  94                         ctx->max_bary = MAX2(ctx->max_bary, inloc->iim_val);
  95                 }
  96
  97                 /* NOTE: consider dst register too.. it could happen that
  98                  * texture sample instruction (for example) writes some
  99                  * components which are unused.  A subsequent instruction
 100                  * that writes the same register can race w/ the sam instr
 101                  * resulting in undefined results:
 102                  */
 103                 for (i = 0; i < n->regs_count; i++) {
 104                         reg = n->regs[i];
 105
 106                         if (reg_gpr(reg)) {
 107
 108                                 /* TODO: we probably only need (ss) for alu
 109                                  * instr consuming sfu result.. need to make
 110                                  * some tests for both this and (sy)..
 111                                  */
 112                                 if (regmask_get(&needs_ss, reg)) {
 113                                         n->flags |= IR3_INSTR_SS;
 114                                         regmask_init(&needs_ss);
 115                                 }
 116
 117                                 if (regmask_get(&needs_sy, reg)) {
 118                                         n->flags |= IR3_INSTR_SY;
 119                                         regmask_init(&needs_sy);
 120                                 }
 121                         }
 122
 123                         /* TODO: is it valid to have address reg loaded from a
 124                          * relative src (ie. mova a0, c<a0.x+4>)?  If so, the
 125                          * last_rel check below should be moved ahead of this:
 126                          */
 127                         if (reg->flags & IR3_REG_RELATIV)
 128                                 last_rel = n;
 129                 }
 130
 131                 if (n->regs_count > 0) {
 132                         reg = n->regs[0];
 133                         if (regmask_get(&needs_ss_war, reg)) {
 134                                 n->flags |= IR3_INSTR_SS;
 135                                 regmask_init(&needs_ss_war); // ??? I assume?
 136                         }
 137
 138                         if (last_rel && (reg->num == regid(REG_A0, 0))) {
 139                                 last_rel->flags |= IR3_INSTR_UL;
 140                                 last_rel = NULL;
 141                         }
 142                 }
 143
 144                 /* cat5+ does not have an (ss) bit, if needed we need to
 145                  * insert a nop to carry the sync flag.  Would be kinda
 146                  * clever if we were aware of this during scheduling, but
 147                  * this should be a pretty rare case:
 148                  */
 149                 if ((n->flags & IR3_INSTR_SS) && (n->category >= 5)) {
 150                         struct ir3_instruction *nop;
 151                         nop = ir3_NOP(block);
 152                         nop->flags |= IR3_INSTR_SS;
 153                         n->flags &= ~IR3_INSTR_SS;
 154                 }
 155
 156                 /* need to be able to set (ss) on first instruction: */
 157                 if (list_empty(&block->instr_list) && (n->category >= 5))
 158                         ir3_NOP(block);
 159
 160                 if (is_nop(n) && !list_empty(&block->instr_list)) {
 161                         struct ir3_instruction *last = list_last_entry(&block->instr_list,
 162                                         struct ir3_instruction, node);
 163                         if (is_nop(last) && (last->repeat < 5)) {
 164                                 last->repeat++;
 165                                 last->flags |= n->flags;
 166                                 continue;
 167                         }
 168                 }
 169
 170                 list_addtail(&n->node, &block->instr_list);
 171
 172                 if (is_sfu(n))
 173                         regmask_set(&needs_ss, n->regs[0]);
 174
 175                 if (is_tex(n)) {
 176                         /* this ends up being the # of samp instructions.. but that
 177                          * is ok, everything else only cares whether it is zero or
 178                          * not.  We do this here, rather than when we encounter a
 179                          * SAMP decl, because (especially in binning pass shader)
 180                          * the samp instruction(s) could get eliminated if the
 181                          * result is not used.
 182                          */
 183                         ctx->has_samp = true;
 184                         regmask_set(&needs_sy, n->regs[0]);
 185                 } else if (is_mem(n)) {
 186                         regmask_set(&needs_sy, n->regs[0]);
 187                 }
 188
 189                 /* both tex/sfu appear to not always immediately consume
 190                  * their src register(s):
 191                  */
 192                 if (is_tex(n) || is_sfu(n) || is_mem(n)) {
 193                         foreach_src(reg, n) {
 194                                 if (reg_gpr(reg))
 195                                         regmask_set(&needs_ss_war, reg);
 196                         }
 197                 }
 198
 199                 if (is_input(n))
 200                         last_input = n;
 201         }
 202
 203         if (last_input) {
 204                 /* special hack.. if using ldlv to bypass interpolation,
 205                  * we need to insert a dummy bary.f on which we can set
 206                  * the (ei) flag:
 207                  */
 208                 if (is_mem(last_input) && (last_input->opc == OPC_LDLV)) {
 209                         struct ir3_instruction *baryf;
 210
 211                         /* (ss)bary.f (ei)r63.x, 0, r0.x */
 212                         baryf = ir3_instr_create(block, 2, OPC_BARY_F);
 213                         baryf->flags |= IR3_INSTR_SS;
 214                         ir3_reg_create(baryf, regid(63, 0), 0);
 215                         ir3_reg_create(baryf, 0, IR3_REG_IMMED)->iim_val = 0;
 216                         ir3_reg_create(baryf, regid(0, 0), 0);
 217
 218                         /* insert the dummy bary.f after last_input: */
 219                         list_delinit(&baryf->node);
 220                         list_add(&baryf->node, &last_input->node);
 221
 222                         last_input = baryf;
 223                 }
 224                 last_input->regs[0]->flags |= IR3_REG_EI;
 225         }
 226
 227         if (last_rel)
 228                 last_rel->flags |= IR3_INSTR_UL;
 229
 230         list_first_entry(&block->instr_list, struct ir3_instruction, node)
 231                 ->flags |= IR3_INSTR_SS | IR3_INSTR_SY;
 232 }
 233
 234 /* NOTE: branch instructions are always the last instruction(s)
 235  * in the block.  We take advantage of this as we resolve the
 236  * branches, since "if (foo) break;" constructs turn into
 237  * something like:
 238  *
 239  *   block3 {
 240  *      ...
 241  *      0029:021: mov.s32s32 r62.x, r1.y
 242  *      0082:022: br !p0.x, target=block5
 243  *      0083:023: br p0.x, target=block4
 244  *      // succs: if _[0029:021: mov.s32s32] block4; else block5;
 245  *   }
 246  *   block4 {
 247  *      0084:024: jump, target=block6
 248  *      // succs: block6;
 249  *   }
 250  *   block5 {
 251  *      0085:025: jump, target=block7
 252  *      // succs: block7;
 253  *   }
 254  *
 255  * ie. only instruction in block4/block5 is a jump, so when
 256  * resolving branches we can easily detect this by checking
 257  * that the first instruction in the target block is itself
 258  * a jump, and setup the br directly to the jump's target
 259  * (and strip back out the now unreached jump)
 260  *
 261  * TODO sometimes we end up with things like:
 262  *
 263  *    br !p0.x, #2
 264  *    br p0.x, #12
 265  *    add.u r0.y, r0.y, 1
 266  *
 267  * If we swapped the order of the branches, we could drop one.
 268  */
 269 static struct ir3_block *
 270 resolve_dest_block(struct ir3_block *block)
 271 {
 272         /* special case for last block: */
 273         if (!block->successors[0])
 274                 return block;
 275
 276         /* NOTE that we may or may not have inserted the jump
 277          * in the target block yet, so conditions to resolve
 278          * the dest to the dest block's successor are:
 279          *
 280          *   (1) successor[1] == NULL &&
 281          *   (2) (block-is-empty || only-instr-is-jump)
 282          */
 283         if (block->successors[1] == NULL) {
 284                 if (list_empty(&block->instr_list)) {
 285                         return block->successors[0];
 286                 } else if (list_length(&block->instr_list) == 1) {
 287                         struct ir3_instruction *instr = list_first_entry(
 288                                         &block->instr_list, struct ir3_instruction, node);
 289                         if (is_flow(instr) && (instr->opc == OPC_JUMP))
 290                                 return block->successors[0];
 291                 }
 292         }
 293         return block;
 294 }
 295
 296 static bool
 297 resolve_jump(struct ir3_instruction *instr)
 298 {
 299         struct ir3_block *tblock =
 300                 resolve_dest_block(instr->cat0.target);
 301         struct ir3_instruction *target;
 302
 303         if (tblock != instr->cat0.target) {
 304                 list_delinit(&instr->cat0.target->node);
 305                 instr->cat0.target = tblock;
 306                 return true;
 307         }
 308
 309         target = list_first_entry(&tblock->instr_list,
 310                                 struct ir3_instruction, node);
 311
 312         if ((!target) || (target->ip == (instr->ip + 1))) {
 313                 list_delinit(&instr->node);
 314                 return true;
 315         } else {
 316                 instr->cat0.immed =
 317                         (int)target->ip - (int)instr->ip;
 318         }
 319         return false;
 320 }
 321
 322 /* resolve jumps, removing jumps/branches to immediately following
 323  * instruction which we end up with from earlier stages.  Since
 324  * removing an instruction can invalidate earlier instruction's
 325  * branch offsets, we need to do this iteratively until no more
 326  * branches are removed.
 327  */
 328 static bool
 329 resolve_jumps(struct ir3 *ir)
 330 {
 331         list_for_each_entry (struct ir3_block, block, &ir->block_list, node)
 332                 list_for_each_entry (struct ir3_instruction, instr, &block->instr_list, node)
 333                         if (is_flow(instr) && instr->cat0.target)
 334                                 if (resolve_jump(instr))
 335                                         return true;
 336
 337         return false;
 338 }
 339
 340 /* we want to mark points where divergent flow control re-converges
 341  * with (jp) flags.  For now, since we don't do any optimization for
 342  * things that start out as a 'do {} while()', re-convergence points
 343  * will always be a branch or jump target.  Note that this is overly
 344  * conservative, since unconditional jump targets are not convergence
 345  * points, we are just assuming that the other path to reach the jump
 346  * target was divergent.  If we were clever enough to optimize the
 347  * jump at end of a loop back to a conditional branch into a single
 348  * conditional branch, ie. like:
 349  *
 350  *    add.f r1.w, r0.x, (neg)(r)c2.x   <= loop start
 351  *    mul.f r1.z, r1.z, r0.x
 352  *    mul.f r1.y, r1.y, r0.x
 353  *    mul.f r0.z, r1.x, r0.x
 354  *    mul.f r0.w, r0.y, r0.x
 355  *    cmps.f.ge r0.x, (r)c2.y, (r)r1.w
 356  *    add.s r0.x, (r)r0.x, (r)-1
 357  *    sel.f32 r0.x, (r)c3.y, (r)r0.x, c3.x
 358  *    cmps.f.eq p0.x, r0.x, c3.y
 359  *    mov.f32f32 r0.x, r1.w
 360  *    mov.f32f32 r0.y, r0.w
 361  *    mov.f32f32 r1.x, r0.z
 362  *    (rpt2)nop
 363  *    br !p0.x, #-13
 364  *    (jp)mul.f r0.x, c263.y, r1.y
 365  *
 366  * Then we'd have to be more clever, as the convergence point is no
 367  * longer a branch or jump target.
 368  */
 369 static void
 370 mark_convergence_points(struct ir3 *ir)
 371 {
 372         list_for_each_entry (struct ir3_block, block, &ir->block_list, node) {
 373                 list_for_each_entry (struct ir3_instruction, instr, &block->instr_list, node) {
 374                         if (is_flow(instr) && instr->cat0.target) {
 375                                 struct ir3_instruction *target =
 376                                         list_first_entry(&instr->cat0.target->instr_list,
 377                                                         struct ir3_instruction, node);
 378                                 target->flags |= IR3_INSTR_JP;
 379                         }
 380                 }
 381         }
 382 }
 383
 384 void
 385 ir3_legalize(struct ir3 *ir, bool *has_samp, int *max_bary)
 386 {
 387         struct ir3_legalize_ctx ctx = {
 388                         .max_bary = -1,
 389         };
 390
 391         list_for_each_entry (struct ir3_block, block, &ir->block_list, node) {
 392                 legalize_block(&ctx, block);
 393         }
 394
 395         *has_samp = ctx.has_samp;
 396         *max_bary = ctx.max_bary;
 397
 398         do {
 399                 ir3_count_instructions(ir);
 400         } while(resolve_jumps(ir));
 401
 402         mark_convergence_points(ir);
 403 }