src/mesa/drivers/dri/i965/brw_lower_texture_gradients.cpp

   1 /*
   2  * Copyright © 2012 Intel Corporation
   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
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * \file brw_lower_texture_gradients.cpp
  26  */
  27
  28 #include "glsl/ir.h"
  29 #include "glsl/ir_builder.h"
  30 #include "program/prog_instruction.h"
  31 #include "brw_context.h"
  32
  33 using namespace ir_builder;
  34
  35 class lower_texture_grad_visitor : public ir_hierarchical_visitor {
  36 public:
  37    lower_texture_grad_visitor(bool has_sample_d_c)
  38       : has_sample_d_c(has_sample_d_c)
  39    {
  40       progress = false;
  41    }
  42
  43    ir_visitor_status visit_leave(ir_texture *ir);
  44
  45
  46    bool progress;
  47    bool has_sample_d_c;
  48
  49 private:
  50    void emit(ir_variable *, ir_rvalue *);
  51 };
  52
  53 /**
  54  * Emit a variable declaration and an assignment to initialize it.
  55  */
  56 void
  57 lower_texture_grad_visitor::emit(ir_variable *var, ir_rvalue *value)
  58 {
  59    base_ir->insert_before(var);
  60    base_ir->insert_before(assign(var, value));
  61 }
  62
  63 static const glsl_type *
  64 txs_type(const glsl_type *type)
  65 {
  66    unsigned dims;
  67    switch (type->sampler_dimensionality) {
  68    case GLSL_SAMPLER_DIM_1D:
  69       dims = 1;
  70       break;
  71    case GLSL_SAMPLER_DIM_2D:
  72    case GLSL_SAMPLER_DIM_RECT:
  73    case GLSL_SAMPLER_DIM_CUBE:
  74       dims = 2;
  75       break;
  76    case GLSL_SAMPLER_DIM_3D:
  77       dims = 3;
  78       break;
  79    default:
  80       unreachable("Should not get here: invalid sampler dimensionality");
  81    }
  82
  83    if (type->sampler_array)
  84       dims++;
  85
  86    return glsl_type::get_instance(GLSL_TYPE_INT, dims, 1);
  87 }
  88
  89 ir_visitor_status
  90 lower_texture_grad_visitor::visit_leave(ir_texture *ir)
  91 {
  92    /* Only lower textureGrad with cube maps or shadow samplers */
  93    if (ir->op != ir_txd ||
  94       (ir->sampler->type->sampler_dimensionality != GLSL_SAMPLER_DIM_CUBE &&
  95        !ir->shadow_comparitor))
  96       return visit_continue;
  97
  98    /* Lower textureGrad() with samplerCube* even if we have the sample_d_c
  99     * message.  GLSL provides gradients for the 'r' coordinate.  Unfortunately:
 100     *
 101     * From the Ivybridge PRM, Volume 4, Part 1, sample_d message description:
 102     * "The r coordinate contains the faceid, and the r gradients are ignored
 103     *  by hardware."
 104     */
 105    bool need_lowering = !has_sample_d_c ||
 106       ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE;
 107
 108    if (!need_lowering)
 109       return visit_continue;
 110
 111    void *mem_ctx = ralloc_parent(ir);
 112
 113    const glsl_type *grad_type = ir->lod_info.grad.dPdx->type;
 114
 115    /* Use textureSize() to get the width and height of LOD 0; swizzle away
 116     * the depth/number of array slices.
 117     */
 118    ir_texture *txs = new(mem_ctx) ir_texture(ir_txs);
 119    txs->set_sampler(ir->sampler->clone(mem_ctx, NULL),
 120                     txs_type(ir->sampler->type));
 121    txs->lod_info.lod = new(mem_ctx) ir_constant(0);
 122    ir_variable *size =
 123       new(mem_ctx) ir_variable(grad_type, "size", ir_var_temporary);
 124    if (ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE) {
 125       base_ir->insert_before(size);
 126       base_ir->insert_before(assign(size,
 127                                     swizzle_for_size(expr(ir_unop_i2f, txs), 2),
 128                                     WRITEMASK_XY));
 129       base_ir->insert_before(assign(size, new(mem_ctx) ir_constant(1.0f), WRITEMASK_Z));
 130    } else {
 131       emit(size, expr(ir_unop_i2f,
 132                       swizzle_for_size(txs, grad_type->vector_elements)));
 133    }
 134
 135    /* Scale the gradients by width and height.  Effectively, the incoming
 136     * gradients are s'(x,y), t'(x,y), and r'(x,y) from equation 3.19 in the
 137     * GL 3.0 spec; we want u'(x,y), which is w_t * s'(x,y).
 138     */
 139    ir_variable *dPdx =
 140       new(mem_ctx) ir_variable(grad_type, "dPdx", ir_var_temporary);
 141    emit(dPdx, mul(size, ir->lod_info.grad.dPdx));
 142
 143    ir_variable *dPdy =
 144       new(mem_ctx) ir_variable(grad_type, "dPdy", ir_var_temporary);
 145    emit(dPdy, mul(size, ir->lod_info.grad.dPdy));
 146
 147    /* Calculate rho from equation 3.20 of the GL 3.0 specification. */
 148    ir_rvalue *rho;
 149    if (dPdx->type->is_scalar()) {
 150       rho = expr(ir_binop_max, expr(ir_unop_abs, dPdx),
 151                                expr(ir_unop_abs, dPdy));
 152    } else {
 153       rho = expr(ir_binop_max, expr(ir_unop_sqrt, dot(dPdx, dPdx)),
 154                                expr(ir_unop_sqrt, dot(dPdy, dPdy)));
 155    }
 156
 157    /* lambda_base = log2(rho).  We're ignoring GL state biases for now.
 158     *
 159     * For cube maps the result of these formulas is giving us a value of rho
 160     * that is twice the value we should use, so divide it by 2 or,
 161     * alternatively, remove one unit from the result of the log2 computation.
 162     */
 163    ir->op = ir_txl;
 164    if (ir->sampler->type->sampler_dimensionality == GLSL_SAMPLER_DIM_CUBE) {
 165       ir->lod_info.lod = expr(ir_binop_add,
 166                               expr(ir_unop_log2, rho),
 167                               new(mem_ctx) ir_constant(-1.0f));
 168    } else {
 169       ir->lod_info.lod = expr(ir_unop_log2, rho);
 170    }
 171
 172    progress = true;
 173    return visit_continue;
 174 }
 175
 176 extern "C" {
 177
 178 bool
 179 brw_lower_texture_gradients(struct brw_context *brw,
 180                             struct exec_list *instructions)
 181 {
 182    bool has_sample_d_c = brw->gen >= 8 || brw->is_haswell;
 183    lower_texture_grad_visitor v(has_sample_d_c);
 184
 185    visit_list_elements(&v, instructions);
 186
 187    return v.progress;
 188 }
 189
 190 }