1/*
2 * Copyright © 2020 Igalia S.L.
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 FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 */
23
24#include "nir.h"
25#include "nir_builder.h"
26#include "program/prog_instruction.h"
27
28/* Lower gl_PointCoord to account for user requested point-coord origin
29 * and for whether draw buffer is flipped.
30 */
31
32typedef struct {
33   const gl_state_index16 *pntc_state_tokens;
34   nir_shader             *shader;
35   nir_builder             b;
36   nir_variable           *pntc_transform;
37} lower_pntc_ytransform_state;
38
39static nir_ssa_def *
40get_pntc_transform(lower_pntc_ytransform_state *state)
41{
42   if (state->pntc_transform == NULL) {
43      /* NOTE: name must be prefixed w/ "gl_" to trigger slot based
44       * special handling in uniform setup:
45       */
46      nir_variable *var = nir_variable_create(state->shader,
47                                              nir_var_uniform,
48                                              glsl_vec4_type(),
49                                              "gl_PntcYTransform");
50
51      var->num_state_slots = 1;
52      var->state_slots = ralloc_array(var, nir_state_slot, 1);
53      var->state_slots[0].swizzle = SWIZZLE_XYZW;
54      memcpy(var->state_slots[0].tokens, state->pntc_state_tokens,
55             sizeof(var->state_slots[0].tokens));
56      var->data.how_declared = nir_var_hidden;
57      state->pntc_transform = var;
58   }
59   return nir_load_var(&state->b, state->pntc_transform);
60}
61
62static void
63lower_load_pointcoord(lower_pntc_ytransform_state *state,
64                      nir_intrinsic_instr *intr)
65{
66   nir_builder *b = &state->b;
67   b->cursor = nir_after_instr(&intr->instr);
68
69   nir_ssa_def *pntc = &intr->dest.ssa;
70   nir_ssa_def *transform = get_pntc_transform(state);
71   nir_ssa_def *y = nir_channel(b, pntc, 1);
72   /* The offset is 1 if we're flipping, 0 otherwise. */
73   nir_ssa_def *offset = nir_channel(b, transform, 1);
74   /* Flip the sign of y if we're flipping. */
75   nir_ssa_def *scaled = nir_fmul(b, y, nir_channel(b, transform, 0));
76
77   /* Reassemble the vector. */
78   nir_ssa_def *flipped_pntc = nir_vec2(b,
79                                        nir_channel(b, pntc, 0),
80                                        nir_fadd(b, offset, scaled));
81
82   nir_ssa_def_rewrite_uses_after(&intr->dest.ssa, flipped_pntc,
83                                  flipped_pntc->parent_instr);
84}
85
86static void
87lower_pntc_ytransform_block(lower_pntc_ytransform_state *state,
88                            nir_block *block)
89{
90   nir_foreach_instr_safe(instr, block) {
91      if (instr->type == nir_instr_type_intrinsic) {
92         nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
93         if (intr->intrinsic == nir_intrinsic_load_deref) {
94            nir_deref_instr *deref = nir_src_as_deref(intr->src[0]);
95            nir_variable *var = nir_deref_instr_get_variable(deref);
96
97            if ((var->data.mode == nir_var_shader_in &&
98                 var->data.location == VARYING_SLOT_PNTC) ||
99                (var->data.mode == nir_var_system_value &&
100                 var->data.location == SYSTEM_VALUE_POINT_COORD)) {
101                lower_load_pointcoord(state, intr);
102            }
103         }
104      }
105   }
106}
107
108bool
109nir_lower_pntc_ytransform(nir_shader *shader,
110                          const gl_state_index16 pntc_state_tokens[][STATE_LENGTH])
111{
112    if (!shader->options->lower_wpos_pntc)
113        return false;
114
115   lower_pntc_ytransform_state state = {
116      .pntc_state_tokens = *pntc_state_tokens,
117      .shader = shader,
118      .pntc_transform = NULL,
119   };
120
121   assert(shader->info.stage == MESA_SHADER_FRAGMENT);
122
123   nir_foreach_function(function, shader) {
124      if (function->impl) {
125         nir_builder_init(&state.b, function->impl);
126
127         nir_foreach_block(block, function->impl) {
128            lower_pntc_ytransform_block(&state, block);
129         }
130         nir_metadata_preserve(function->impl, nir_metadata_block_index |
131                                               nir_metadata_dominance);
132      }
133   }
134
135   return state.pntc_transform != NULL;
136}
137