Home | History | Annotate | Download | only in vc4 
      1 /*
      2  * Copyright  2014 Broadcom
      3  *
      4  * Permission is hereby granted, free of charge, to any person obtaining a
      5  * copy of this software and associated documentation files (the "Software"),
      6  * to deal in the Software without restriction, including without limitation
      7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
      8  * and/or sell copies of the Software, and to permit persons to whom the
      9  * Software is furnished to do so, subject to the following conditions:
     10  *
     11  * The above copyright notice and this permission notice (including the next
     12  * paragraph) shall be included in all copies or substantial portions of the
     13  * Software.
     14  *
     15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
     21  * IN THE SOFTWARE.
     22  */
     23 
     24 /**
     25  * @file vc4_opt_vpm.c
     26  *
     27  * This modifies instructions that exclusively consume a value read from the
     28  * VPM to directly read the VPM if other operands allow it.
     29  */
     30 
     31 #include "vc4_qir.h"
     32 
     33 bool
     34 qir_opt_vpm(struct vc4_compile *c)
     35 {
     36         if (c->stage == QSTAGE_FRAG)
     37                 return false;
     38 
     39         /* For now, only do this pass when we don't have control flow. */
     40         struct qblock *block = qir_entry_block(c);
     41         if (block != qir_exit_block(c))
     42                 return false;
     43 
     44         bool progress = false;
     45         uint32_t use_count[c->num_temps];
     46         memset(&use_count, 0, sizeof(use_count));
     47 
     48         qir_for_each_inst_inorder(inst, c) {
     49                 for (int i = 0; i < qir_get_nsrc(inst); i++) {
     50                         if (inst->src[i].file == QFILE_TEMP) {
     51                                 uint32_t temp = inst->src[i].index;
     52                                 use_count[temp]++;
     53                         }
     54                 }
     55         }
     56 
     57         /* For instructions reading from a temporary that contains a VPM read
     58          * result, try to move the instruction up in place of the VPM read.
     59          */
     60         qir_for_each_inst_inorder(inst, c) {
     61                 if (!inst)
     62                         continue;
     63 
     64                 if (qir_depends_on_flags(inst) || inst->sf)
     65                         continue;
     66 
     67                 if (qir_has_side_effects(c, inst) ||
     68                     qir_has_side_effect_reads(c, inst) ||
     69                     qir_is_tex(inst))
     70                         continue;
     71 
     72                 for (int j = 0; j < qir_get_nsrc(inst); j++) {
     73                         if (inst->src[j].file != QFILE_TEMP ||
     74                             inst->src[j].pack)
     75                                 continue;
     76 
     77                         uint32_t temp = inst->src[j].index;
     78 
     79                         /* Since VPM reads pull from a FIFO, we only get to
     80                          * read each VPM entry once (unless we reset the read
     81                          * pointer).  That means we can't copy-propagate a VPM
     82                          * read to multiple locations.
     83                          */
     84                         if (use_count[temp] != 1)
     85                                 continue;
     86 
     87                         struct qinst *mov = c->defs[temp];
     88                         if (!mov ||
     89                             (mov->op != QOP_MOV &&
     90                              mov->op != QOP_FMOV &&
     91                              mov->op != QOP_MMOV) ||
     92                             mov->src[0].file != QFILE_VPM) {
     93                                 continue;
     94                         }
     95 
     96                         uint32_t temps = 0;
     97                         for (int k = 0; k < qir_get_nsrc(inst); k++) {
     98                                 if (inst->src[k].file == QFILE_TEMP)
     99                                         temps++;
    100                         }
    101 
    102                         /* The instruction is safe to reorder if its other
    103                          * sources are independent of previous instructions
    104                          */
    105                         if (temps == 1) {
    106                                 inst->src[j] = mov->src[0];
    107 
    108                                 list_del(&inst->link);
    109                                 list_addtail(&inst->link, &mov->link);
    110                                 qir_remove_instruction(c, mov);
    111 
    112                                 progress = true;
    113                                 break;
    114                         }
    115                 }
    116         }
    117 
    118         return progress;
    119 }
    120