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
44namespace {
45
46/**
47 * Visitor class for replacing expressions with ir_constant values.
48 */
49
50class ir_vec_index_to_cond_assign_visitor : public ir_hierarchical_visitor {
51public:
52   ir_vec_index_to_cond_assign_visitor()
53   {
54      progress = false;
55   }
56
57   ir_rvalue *convert_vec_index_to_cond_assign(void *mem_ctx,
58                                               ir_rvalue *orig_vector,
59                                               ir_rvalue *orig_index,
60                                               const glsl_type *type);
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
76ir_rvalue *
77ir_vec_index_to_cond_assign_visitor::convert_vec_index_to_cond_assign(void *mem_ctx,
78                                                                      ir_rvalue *orig_vector,
79                                                                      ir_rvalue *orig_index,
80                                                                      const glsl_type *type)
81{
82   ir_assignment *assign, *value_assign;
83   ir_variable *index, *var, *value;
84   ir_dereference *deref, *deref_value;
85   unsigned i;
86
87
88   exec_list list;
89
90   /* Store the index to a temporary to avoid reusing its tree. */
91   assert(orig_index->type == glsl_type::int_type ||
92          orig_index->type == glsl_type::uint_type);
93   index = new(base_ir) ir_variable(orig_index->type,
94				    "vec_index_tmp_i",
95				    ir_var_temporary);
96   list.push_tail(index);
97   deref = new(base_ir) ir_dereference_variable(index);
98   assign = new(base_ir) ir_assignment(deref, orig_index, NULL);
99   list.push_tail(assign);
100
101   /* Store the value inside a temp, thus avoiding matrixes duplication */
102   value = new(base_ir) ir_variable(orig_vector->type, "vec_value_tmp",
103                                    ir_var_temporary);
104   list.push_tail(value);
105   deref_value = new(base_ir) ir_dereference_variable(value);
106   value_assign = new(base_ir) ir_assignment(deref_value, orig_vector);
107   list.push_tail(value_assign);
108
109   /* Temporary where we store whichever value we swizzle out. */
110   var = new(base_ir) ir_variable(type, "vec_index_tmp_v",
111				  ir_var_temporary);
112   list.push_tail(var);
113
114   /* Generate a single comparison condition "mask" for all of the components
115    * in the vector.
116    */
117   ir_rvalue *const cond_deref =
118      compare_index_block(&list, index, 0,
119                          orig_vector->type->vector_elements,
120			  mem_ctx);
121
122   /* Generate a conditional move of each vector element to the temp. */
123   for (i = 0; i < orig_vector->type->vector_elements; i++) {
124      ir_rvalue *condition_swizzle =
125         new(base_ir) ir_swizzle(cond_deref->clone(mem_ctx, NULL),
126                                 i, 0, 0, 0, 1);
127
128      /* Just clone the rest of the deref chain when trying to get at the
129       * underlying variable.
130       */
131      ir_rvalue *swizzle =
132	 new(base_ir) ir_swizzle(deref_value->clone(mem_ctx, NULL),
133				 i, 0, 0, 0, 1);
134
135      deref = new(base_ir) ir_dereference_variable(var);
136      assign = new(base_ir) ir_assignment(deref, swizzle, condition_swizzle);
137      list.push_tail(assign);
138   }
139
140   /* Put all of the new instructions in the IR stream before the old
141    * instruction.
142    */
143   base_ir->insert_before(&list);
144
145   this->progress = true;
146   return new(base_ir) ir_dereference_variable(var);
147}
148
149ir_rvalue *
150ir_vec_index_to_cond_assign_visitor::convert_vector_extract_to_cond_assign(ir_rvalue *ir)
151{
152   ir_expression *const expr = ir->as_expression();
153
154   if (expr == NULL || expr->operation != ir_binop_vector_extract)
155      return ir;
156
157   return convert_vec_index_to_cond_assign(ralloc_parent(ir),
158                                           expr->operands[0],
159                                           expr->operands[1],
160                                           ir->type);
161}
162
163ir_visitor_status
164ir_vec_index_to_cond_assign_visitor::visit_enter(ir_expression *ir)
165{
166   unsigned int i;
167
168   for (i = 0; i < ir->get_num_operands(); i++) {
169      ir->operands[i] = convert_vector_extract_to_cond_assign(ir->operands[i]);
170   }
171
172   return visit_continue;
173}
174
175ir_visitor_status
176ir_vec_index_to_cond_assign_visitor::visit_enter(ir_swizzle *ir)
177{
178   /* Can't be hit from normal GLSL, since you can't swizzle a scalar (which
179    * the result of indexing a vector is.  But maybe at some point we'll end up
180    * using swizzling of scalars for vector construction.
181    */
182   ir->val = convert_vector_extract_to_cond_assign(ir->val);
183
184   return visit_continue;
185}
186
187ir_visitor_status
188ir_vec_index_to_cond_assign_visitor::visit_leave(ir_assignment *ir)
189{
190   ir->rhs = convert_vector_extract_to_cond_assign(ir->rhs);
191
192   if (ir->condition) {
193      ir->condition = convert_vector_extract_to_cond_assign(ir->condition);
194   }
195
196   return visit_continue;
197}
198
199ir_visitor_status
200ir_vec_index_to_cond_assign_visitor::visit_enter(ir_call *ir)
201{
202   foreach_in_list_safe(ir_rvalue, param, &ir->actual_parameters) {
203      ir_rvalue *new_param = convert_vector_extract_to_cond_assign(param);
204
205      if (new_param != param) {
206	 param->replace_with(new_param);
207      }
208   }
209
210   return visit_continue;
211}
212
213ir_visitor_status
214ir_vec_index_to_cond_assign_visitor::visit_enter(ir_return *ir)
215{
216   if (ir->value) {
217      ir->value = convert_vector_extract_to_cond_assign(ir->value);
218   }
219
220   return visit_continue;
221}
222
223ir_visitor_status
224ir_vec_index_to_cond_assign_visitor::visit_enter(ir_if *ir)
225{
226   ir->condition = convert_vector_extract_to_cond_assign(ir->condition);
227
228   return visit_continue;
229}
230
231bool
232do_vec_index_to_cond_assign(exec_list *instructions)
233{
234   ir_vec_index_to_cond_assign_visitor v;
235
236   visit_list_elements(&v, instructions);
237
238   return v.progress;
239}
240