src/compiler/nir/nir_lower_point_size.c

   1 /*
   2  * Copyright © 2019 Raspberry Pi
   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 #include "nir_builder.h"
  25
  26 /** @file nir_lower_point_size.c
  27  *
  28  * The OpenGL spec requires that implementations clamp gl_PointSize to an
  29  * implementation-dependant point size range. The OpenGL ES 3.0 spec further
  30  * requires that this range must match GL_ALIASED_POINT_SIZE_RANGE.
  31  * Some hardware such as V3D don't clamp to a valid range automatically so
  32  * the driver must clamp the point size written by the shader manually to a
  33  * valid range.
  34  */
  35
  36 static void
  37 lower_point_size_instr(nir_builder *b, nir_instr *psiz_instr,
  38                        float min, float max)
  39 {
  40    b->cursor = nir_before_instr(psiz_instr);
  41
  42    nir_intrinsic_instr *instr = nir_instr_as_intrinsic(psiz_instr);
  43
  44    /* Some fixed function vertex programs generate PSIZ as a vec4
  45     * instead of a scalar, where the actual point size is stored in the
  46     * first component.
  47     */
  48    assert(instr->src[1].is_ssa);
  49    nir_ssa_def *psiz = nir_channel(b, instr->src[1].ssa, 0);
  50
  51    if (min > 0.0f)
  52       psiz = nir_fmax(b, psiz, nir_imm_float(b, min));
  53
  54    if (max > 0.0f)
  55       psiz = nir_fmin(b, psiz, nir_imm_float(b, max));
  56
  57    nir_ssa_def *src_chans[4];
  58    src_chans[0] = psiz;
  59    for (int i = 1; i < instr->src[1].ssa->num_components; i++)
  60       src_chans[i] = nir_channel(b, instr->src[1].ssa, i);
  61    nir_ssa_def *lowered_src =
  62       nir_vec(b, src_chans, instr->src[1].ssa->num_components);
  63
  64    nir_instr_rewrite_src(&instr->instr, &instr->src[1],
  65                          nir_src_for_ssa(lowered_src));
  66 }
  67
  68 static bool
  69 instr_is_point_size(const nir_instr *instr)
  70 {
  71    if (instr->type != nir_instr_type_intrinsic)
  72       return false;
  73
  74    nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
  75    if (intr->intrinsic != nir_intrinsic_store_deref)
  76       return false;
  77
  78    nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
  79    nir_variable *var = nir_deref_instr_get_variable(deref);
  80    if (var->data.location != VARYING_SLOT_PSIZ)
  81       return false;
  82
  83    return true;
  84 }
  85
  86 /**
  87  * Clamps gl_PointSize to the range [min, max]. If either min or max are not
  88  * greater than 0 then no clamping is done for that side of the range.
  89  */
  90 bool
  91 nir_lower_point_size(nir_shader *s, float min, float max)
  92 {
  93    assert(s->info.stage != MESA_SHADER_FRAGMENT &&
  94           s->info.stage != MESA_SHADER_COMPUTE);
  95
  96    assert(min > 0.0f || max > 0.0f);
  97    assert(min <= 0.0f || max <= 0.0f || min <= max);
  98
  99    bool progress = false;
 100    nir_foreach_function(function, s) {
 101       if (!function->impl)
 102          continue;
 103
 104       nir_builder b;
 105       nir_builder_init(&b, function->impl);
 106
 107       nir_foreach_block(block, function->impl) {
 108          nir_foreach_instr_safe(instr, block) {
 109             if (instr_is_point_size(instr)) {
 110                lower_point_size_instr(&b, instr, min, max);
 111                progress = true;
 112             }
 113          }
 114       }
 115
 116       if (progress) {
 117          nir_metadata_preserve(function->impl,
 118                                nir_metadata_block_index |
 119                                nir_metadata_dominance);
 120       }
 121    }
 122
 123    return progress;
 124 }