1 /*
2 * Copyright © 2010 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 lower_vec_index_to_cond_assign.cpp
26 *
27 * Turns indexing into vector types to a series of conditional moves
28 * of each channel's swizzle into a temporary.
29 *
30 * Most GPUs don't have a native way to do this operation, and this
31 * works around that. For drivers using both this pass and
32 * ir_vec_index_to_swizzle, there's a risk that this pass will happen
33 * before sufficient constant folding to find that the array index is
34 * constant. However, we hope that other optimization passes,
35 * particularly constant folding of assignment conditions and copy
36 * propagation, will result in the same code in the end.
37 */
38
39 #include "ir.h"
40 #include "ir_visitor.h"
41 #include "ir_optimization.h"
42 #include "compiler/glsl_types.h"
43 #include "ir_builder.h"
44 #include "program/prog_instruction.h"
45
46 using namespace ir_builder;
47
48 namespace {
49
50 /**
51 * Visitor class for replacing expressions with ir_constant values.
52 */
53
54 class ir_vec_index_to_cond_assign_visitor : public ir_hierarchical_visitor {
55 public:
ir_vec_index_to_cond_assign_visitor()56 ir_vec_index_to_cond_assign_visitor()
57 : progress(false)
58 {
59 /* empty */
60 }
61
62 ir_rvalue *convert_vector_extract_to_cond_assign(ir_rvalue *ir);
63
64 virtual ir_visitor_status visit_enter(ir_expression *);
65 virtual ir_visitor_status visit_enter(ir_swizzle *);
66 virtual ir_visitor_status visit_leave(ir_assignment *);
67 virtual ir_visitor_status visit_enter(ir_return *);
68 virtual ir_visitor_status visit_enter(ir_call *);
69 virtual ir_visitor_status visit_enter(ir_if *);
70
71 bool progress;
72 };
73
74 } /* anonymous namespace */
75
76 ir_rvalue *
convert_vector_extract_to_cond_assign(ir_rvalue * ir)77 ir_vec_index_to_cond_assign_visitor::convert_vector_extract_to_cond_assign(ir_rvalue *ir)
78 {
79 ir_expression *const expr = ir->as_expression();
80
81 if (expr == NULL)
82 return ir;
83
84 if (expr->operation == ir_unop_interpolate_at_centroid ||
85 expr->operation == ir_binop_interpolate_at_offset ||
86 expr->operation == ir_binop_interpolate_at_sample) {
87 /* Lower interpolateAtXxx(some_vec[idx], ...) to
88 * interpolateAtXxx(some_vec, ...)[idx] before lowering to conditional
89 * assignments, to maintain the rule that the interpolant is an l-value
90 * referring to a (part of a) shader input.
91 *
92 * This is required when idx is dynamic (otherwise it gets lowered to
93 * a swizzle).
94 */
95 ir_expression *const interpolant = expr->operands[0]->as_expression();
96 if (!interpolant || interpolant->operation != ir_binop_vector_extract)
97 return ir;
98
99 ir_rvalue *vec_input = interpolant->operands[0];
100 ir_expression *const vec_interpolate =
101 new(base_ir) ir_expression(expr->operation, vec_input->type,
102 vec_input, expr->operands[1]);
103
104 this->progress = true;
105 return new(base_ir) ir_expression(ir_binop_vector_extract, ir->type,
106 vec_interpolate,
107 interpolant->operands[1]);
108 }
109
110 return ir;
111 }
112
113 ir_visitor_status
visit_enter(ir_expression * ir)114 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_expression *ir)
115 {
116 for (unsigned i = 0; i < ir->num_operands; i++)
117 ir->operands[i] = convert_vector_extract_to_cond_assign(ir->operands[i]);
118
119 return visit_continue;
120 }
121
122 ir_visitor_status
visit_enter(ir_swizzle * ir)123 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_swizzle *ir)
124 {
125 /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
126 * the result of indexing a vector is. But maybe at some point we'll end up
127 * using swizzling of scalars for vector construction.
128 */
129 ir->val = convert_vector_extract_to_cond_assign(ir->val);
130
131 return visit_continue;
132 }
133
134 ir_visitor_status
visit_leave(ir_assignment * ir)135 ir_vec_index_to_cond_assign_visitor::visit_leave(ir_assignment *ir)
136 {
137 ir->rhs = convert_vector_extract_to_cond_assign(ir->rhs);
138
139 return visit_continue;
140 }
141
142 ir_visitor_status
visit_enter(ir_call * ir)143 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_call *ir)
144 {
145 foreach_in_list_safe(ir_rvalue, param, &ir->actual_parameters) {
146 ir_rvalue *new_param = convert_vector_extract_to_cond_assign(param);
147
148 if (new_param != param) {
149 param->replace_with(new_param);
150 }
151 }
152
153 return visit_continue;
154 }
155
156 ir_visitor_status
visit_enter(ir_return * ir)157 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_return *ir)
158 {
159 if (ir->value)
160 ir->value = convert_vector_extract_to_cond_assign(ir->value);
161
162 return visit_continue;
163 }
164
165 ir_visitor_status
visit_enter(ir_if * ir)166 ir_vec_index_to_cond_assign_visitor::visit_enter(ir_if *ir)
167 {
168 ir->condition = convert_vector_extract_to_cond_assign(ir->condition);
169
170 return visit_continue;
171 }
172
173 bool
do_vec_index_to_cond_assign(exec_list * instructions)174 do_vec_index_to_cond_assign(exec_list *instructions)
175 {
176 ir_vec_index_to_cond_assign_visitor v;
177
178 visit_list_elements(&v, instructions);
179
180 return v.progress;
181 }
182