1/*
2 * Copyright © 2015 Broadcom
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 "util/macros.h"
25#include "nir.h"
26#include "nir_builder.h"
27
28/** @file nir_lower_load_const_to_scalar.c
29 *
30 * Replaces vector nir_load_const instructions with a series of loads and a
31 * vec[234] to reconstruct the original vector (on the assumption that
32 * nir_lower_alu_to_scalar() will then be used to split it up).
33 *
34 * This gives NIR a chance to CSE more operations on a scalar shader, when the
35 * same value was used in different vector contant loads.
36 */
37
38static void
39lower_load_const_instr_scalar(nir_load_const_instr *lower)
40{
41   if (lower->def.num_components == 1)
42      return;
43
44   nir_builder b;
45   nir_builder_init(&b, nir_cf_node_get_function(&lower->instr.block->cf_node));
46   b.cursor = nir_before_instr(&lower->instr);
47
48   /* Emit the individual loads. */
49   nir_ssa_def *loads[4];
50   for (unsigned i = 0; i < lower->def.num_components; i++) {
51      nir_load_const_instr *load_comp =
52         nir_load_const_instr_create(b.shader, 1, lower->def.bit_size);
53      if (lower->def.bit_size == 64)
54         load_comp->value.f64[0] = lower->value.f64[i];
55      else
56         load_comp->value.u32[0] = lower->value.u32[i];
57      assert(lower->def.bit_size == 64 || lower->def.bit_size == 32);
58      nir_builder_instr_insert(&b, &load_comp->instr);
59      loads[i] = &load_comp->def;
60   }
61
62   /* Batch things back together into a vector. */
63   nir_ssa_def *vec = nir_vec(&b, loads, lower->def.num_components);
64
65   /* Replace the old load with a reference to our reconstructed vector. */
66   nir_ssa_def_rewrite_uses(&lower->def, nir_src_for_ssa(vec));
67   nir_instr_remove(&lower->instr);
68}
69
70static void
71nir_lower_load_const_to_scalar_impl(nir_function_impl *impl)
72{
73   nir_foreach_block(block, impl) {
74      nir_foreach_instr_safe(instr, block) {
75         if (instr->type == nir_instr_type_load_const)
76            lower_load_const_instr_scalar(nir_instr_as_load_const(instr));
77      }
78   }
79}
80
81void
82nir_lower_load_const_to_scalar(nir_shader *shader)
83{
84   nir_foreach_function(function, shader) {
85      if (function->impl)
86         nir_lower_load_const_to_scalar_impl(function->impl);
87   }
88}
89