src/compiler/glsl/lower_vector_derefs.cpp

   1 /*
   2  * Copyright © 2013 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 #include "ir.h"
  24 #include "ir_builder.h"
  25 #include "ir_rvalue_visitor.h"
  26 #include "ir_optimization.h"
  27 #include "main/mtypes.h"
  28
  29 using namespace ir_builder;
  30
  31 namespace {
  32
  33 class vector_deref_visitor : public ir_rvalue_enter_visitor {
  34 public:
  35    vector_deref_visitor(void *mem_ctx, gl_shader_stage shader_stage)
  36       : progress(false), shader_stage(shader_stage),
  37         factory(&factory_instructions, mem_ctx)
  38    {
  39    }
  40
  41    virtual ~vector_deref_visitor()
  42    {
  43    }
  44
  45    virtual void handle_rvalue(ir_rvalue **rv);
  46    virtual ir_visitor_status visit_enter(ir_assignment *ir);
  47
  48    bool progress;
  49    gl_shader_stage shader_stage;
  50    exec_list factory_instructions;
  51    ir_factory factory;
  52 };
  53
  54 } /* anonymous namespace */
  55
  56 ir_visitor_status
  57 vector_deref_visitor::visit_enter(ir_assignment *ir)
  58 {
  59    if (!ir->lhs || ir->lhs->ir_type != ir_type_dereference_array)
  60       return ir_rvalue_enter_visitor::visit_enter(ir);
  61
  62    ir_dereference_array *const deref = (ir_dereference_array *) ir->lhs;
  63    if (!deref->array->type->is_vector())
  64       return ir_rvalue_enter_visitor::visit_enter(ir);
  65
  66    /* SSBOs and shared variables are backed by memory and may be accessed by
  67     * multiple threads simultaneously.  It's not safe to lower a single
  68     * component store to a load-vec-store because it may race with writes to
  69     * other components.
  70     */
  71    ir_variable *var = deref->variable_referenced();
  72    if (var->data.mode == ir_var_shader_storage ||
  73        var->data.mode == ir_var_shader_shared)
  74       return ir_rvalue_enter_visitor::visit_enter(ir);
  75
  76    ir_rvalue *const new_lhs = deref->array;
  77
  78    void *mem_ctx = ralloc_parent(ir);
  79    ir_constant *old_index_constant =
  80       deref->array_index->constant_expression_value(mem_ctx);
  81    if (!old_index_constant) {
  82       if (shader_stage == MESA_SHADER_TESS_CTRL &&
  83           deref->variable_referenced()->data.mode == ir_var_shader_out) {
  84          /* Tessellation control shader outputs act as if they have memory
  85           * backing them and if we have writes from multiple threads
  86           * targeting the same vec4 (this can happen for patch outputs), the
  87           * load-vec-store pattern of ir_triop_vector_insert doesn't work.
  88           * Instead, we have to lower to a series of conditional write-masked
  89           * assignments.
  90           */
  91          ir_variable *const src_temp =
  92             factory.make_temp(ir->rhs->type, "scalar_tmp");
  93
  94          /* The newly created variable declaration goes before the assignment
  95           * because we're going to set it as the new LHS.
  96           */
  97          ir->insert_before(factory.instructions);
  98          ir->set_lhs(new(mem_ctx) ir_dereference_variable(src_temp));
  99
 100          ir_variable *const arr_index =
 101             factory.make_temp(deref->array_index->type, "index_tmp");
 102          factory.emit(assign(arr_index, deref->array_index));
 103
 104          for (unsigned i = 0; i < new_lhs->type->vector_elements; i++) {
 105             ir_constant *const cmp_index =
 106                ir_constant::zero(factory.mem_ctx, deref->array_index->type);
 107             cmp_index->value.u[0] = i;
 108
 109             ir_rvalue *const lhs_clone = new_lhs->clone(factory.mem_ctx, NULL);
 110             ir_dereference_variable *const src_temp_deref =
 111                new(mem_ctx) ir_dereference_variable(src_temp);
 112
 113             if (new_lhs->ir_type != ir_type_swizzle) {
 114                assert(lhs_clone->as_dereference());
 115                ir_assignment *cond_assign =
 116                   new(mem_ctx) ir_assignment(lhs_clone->as_dereference(),
 117                                              src_temp_deref,
 118                                              equal(arr_index, cmp_index),
 119                                              WRITEMASK_X << i);
 120                factory.emit(cond_assign);
 121             } else {
 122                ir_assignment *cond_assign =
 123                   new(mem_ctx) ir_assignment(swizzle(lhs_clone, i, 1),
 124                                              src_temp_deref,
 125                                              equal(arr_index, cmp_index));
 126                factory.emit(cond_assign);
 127             }
 128          }
 129          ir->insert_after(factory.instructions);
 130       } else {
 131          ir->rhs = new(mem_ctx) ir_expression(ir_triop_vector_insert,
 132                                               new_lhs->type,
 133                                               new_lhs->clone(mem_ctx, NULL),
 134                                               ir->rhs,
 135                                               deref->array_index);
 136          ir->write_mask = (1 << new_lhs->type->vector_elements) - 1;
 137          ir->set_lhs(new_lhs);
 138       }
 139    } else if (new_lhs->ir_type != ir_type_swizzle) {
 140       ir->set_lhs(new_lhs);
 141       ir->write_mask = 1 << old_index_constant->get_uint_component(0);
 142    } else {
 143       /* If the "new" LHS is a swizzle, use the set_lhs helper to instead
 144        * swizzle the RHS.
 145        */
 146       unsigned component[1] = { old_index_constant->get_uint_component(0) };
 147       ir->set_lhs(new(mem_ctx) ir_swizzle(new_lhs, component, 1));
 148    }
 149
 150    return ir_rvalue_enter_visitor::visit_enter(ir);
 151 }
 152
 153 void
 154 vector_deref_visitor::handle_rvalue(ir_rvalue **rv)
 155 {
 156    if (*rv == NULL || (*rv)->ir_type != ir_type_dereference_array)
 157       return;
 158
 159    ir_dereference_array *const deref = (ir_dereference_array *) *rv;
 160    if (!deref->array->type->is_vector())
 161       return;
 162
 163    /* Back-ends need to be able to handle derefs on vectors for SSBOs, UBOs,
 164     * and shared variables.  They have to handle it for writes anyway so we
 165     * may as well require it for reads.
 166     */
 167    ir_variable *var = deref->variable_referenced();
 168    if (var && (var->data.mode == ir_var_shader_storage ||
 169                var->data.mode == ir_var_shader_shared ||
 170                (var->data.mode == ir_var_uniform &&
 171                 var->get_interface_type())))
 172       return;
 173
 174    void *mem_ctx = ralloc_parent(deref);
 175    *rv = new(mem_ctx) ir_expression(ir_binop_vector_extract,
 176                                     deref->array,
 177                                     deref->array_index);
 178 }
 179
 180 bool
 181 lower_vector_derefs(gl_linked_shader *shader)
 182 {
 183    vector_deref_visitor v(shader->ir, shader->Stage);
 184
 185    visit_list_elements(&v, shader->ir);
 186
 187    return v.progress;
 188 }