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      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_small_immediates.c
     26  *
     27  * Turns references to small constant uniform values into small immediates
     28  * fields.
     29  */
     30 
     31 #include "vc4_qir.h"
     32 #include "vc4_qpu.h"
     33 
     34 static bool debug;
     35 
     36 bool
     37 qir_opt_small_immediates(struct vc4_compile *c)
     38 {
     39         bool progress = false;
     40 
     41         qir_for_each_inst_inorder(inst, c) {
     42                 /* The small immediate value sits in the raddr B field, so we
     43                  * can't have 2 small immediates in one instruction (unless
     44                  * they're the same value, but that should be optimized away
     45                  * elsewhere).
     46                  */
     47                 bool uses_small_imm = false;
     48                 for (int i = 0; i < qir_get_nsrc(inst); i++) {
     49                         if (inst->src[i].file == QFILE_SMALL_IMM)
     50                                 uses_small_imm = true;
     51                 }
     52                 if (uses_small_imm)
     53                         continue;
     54 
     55                 /* Don't propagate small immediates into the top-end bounds
     56                  * checking for indirect UBO loads.  The kernel doesn't parse
     57                  * small immediates and rejects the shader in this case.  UBO
     58                  * loads are much more expensive than the uniform load, and
     59                  * indirect UBO regions are usually much larger than a small
     60                  * immediate, so it's not worth updating the kernel to allow
     61                  * optimizing it.
     62                  */
     63                 if (inst->op == QOP_MIN_NOIMM)
     64                         continue;
     65 
     66                 for (int i = 0; i < qir_get_nsrc(inst); i++) {
     67                         struct qreg src = qir_follow_movs(c, inst->src[i]);
     68 
     69                         if (src.file != QFILE_UNIF ||
     70                             src.pack ||
     71                             c->uniform_contents[src.index] !=
     72                             QUNIFORM_CONSTANT) {
     73                                 continue;
     74                         }
     75 
     76                         if (qir_is_tex(inst) &&
     77                             i == qir_get_tex_uniform_src(inst)) {
     78                                 /* No turning the implicit uniform read into
     79                                  * an immediate.
     80                                  */
     81                                 continue;
     82                         }
     83 
     84                         uint32_t imm = c->uniform_data[src.index];
     85                         uint32_t small_imm = qpu_encode_small_immediate(imm);
     86                         if (small_imm == ~0)
     87                                 continue;
     88 
     89                         if (debug) {
     90                                 fprintf(stderr, "opt_small_immediate() from: ");
     91                                 qir_dump_inst(c, inst);
     92                                 fprintf(stderr, "\n");
     93                         }
     94                         inst->src[i].file = QFILE_SMALL_IMM;
     95                         inst->src[i].index = imm;
     96                         if (debug) {
     97                                 fprintf(stderr, "to: ");
     98                                 qir_dump_inst(c, inst);
     99                                 fprintf(stderr, "\n");
    100                         }
    101                         progress = true;
    102                         break;
    103                 }
    104         }
    105 
    106         return progress;
    107 }
    108