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      1 /*
      2  * Copyright (C) 2019 Collabora, Ltd.
      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 FROM,
     20  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
     21  * SOFTWARE.
     22  */
     23 
     24 #include "compiler/nir/nir.h"
     25 #include "compiler/nir/nir_builder.h"
     26 
     27 bool midgard_nir_lod_errata(nir_shader *shader);
     28 
     29 /* Workarounds errata pertaining to early Midgard chips where the settings for
     30  * min_lod/max_lod/lod_bias are ignored in the sampler descriptor when
     31  * texturing with a textureLod instruction. The workaround is to load these
     32  * constants in as system values and perform the bias/clamp in the shader.
     33  */
     34 
     35 static bool
     36 nir_lod_errata_instr(nir_builder *b, nir_instr *instr, void *data)
     37 {
     38         if (instr->type != nir_instr_type_tex)
     39                 return false;
     40 
     41         nir_tex_instr *tex = nir_instr_as_tex(instr);
     42         b->cursor = nir_before_instr(instr);
     43 
     44         /* The errata only applies to textureLod ("TEXGRD") */
     45         if (tex->op != nir_texop_txl)
     46                 return false;
     47 
     48         /* Let's grab the sampler parameters */
     49         nir_intrinsic_instr *l = nir_intrinsic_instr_create(b->shader,
     50                         nir_intrinsic_load_sampler_lod_parameters_pan);
     51         l->num_components = 3;
     52         nir_ssa_dest_init(&l->instr, &l->dest, 3, 32, NULL);
     53 
     54         /* TODO: Indirect samplers, separate sampler objects XXX */
     55         nir_src idx = nir_src_for_ssa(nir_imm_int(b, tex->texture_index));
     56         nir_src_copy(&l->src[0], &idx);
     57 
     58         nir_builder_instr_insert(b, &l->instr);
     59         nir_ssa_def *params = &l->dest.ssa;
     60 
     61         /* Extract the individual components */
     62         nir_ssa_def *min_lod = nir_channel(b, params, 0);
     63         nir_ssa_def *max_lod = nir_channel(b, params, 1);
     64         nir_ssa_def *lod_bias = nir_channel(b, params, 2);
     65 
     66         /* Rewrite the LOD with bias/clamps. Order sensitive. */
     67         for (unsigned i = 0; i < tex->num_srcs; i++) {
     68                 if (tex->src[i].src_type != nir_tex_src_lod)
     69                         continue;
     70 
     71                 nir_ssa_def *lod = nir_ssa_for_src(b, tex->src[i].src, 1);
     72 
     73                 nir_ssa_def *biased = nir_fadd(b, lod, lod_bias);
     74                 nir_ssa_def *clamped = nir_fmin(b,
     75                                 nir_fmax(b, biased, min_lod), max_lod);
     76 
     77                 nir_instr_rewrite_src(&tex->instr, &tex->src[i].src,
     78                                 nir_src_for_ssa(clamped));
     79         }
     80 
     81         return true;
     82 }
     83 
     84 bool
     85 midgard_nir_lod_errata(nir_shader *shader)
     86 {
     87         return nir_shader_instructions_pass(shader,
     88                                             nir_lod_errata_instr,
     89                                             nir_metadata_block_index | nir_metadata_dominance,
     90                                             NULL);
     91 }
     92