1/*
2 * Copyright © 2019 Red Hat
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 "ir3_nir.h"
25#include "compiler/nir/nir_builder.h"
26
27/**
28 * This pass moves varying fetches (and the instructions they depend on
29 * into the start block.
30 *
31 * We need to set the (ei) "end input" flag on the last varying fetch.
32 * And we want to ensure that all threads execute the instruction that
33 * sets (ei).  The easiest way to ensure this is to move all varying
34 * fetches into the start block.  Which is something we used to get for
35 * free by using lower_all_io_to_temps=true.
36 *
37 * This may come at the cost of additional register usage.  OTOH setting
38 * the (ei) flag earlier probably frees up more VS to run.
39 */
40
41
42typedef struct {
43	nir_shader *shader;
44	nir_block *start_block;
45	struct nir_instr *cursor;
46} state;
47
48static void move_instruction_to_start_block(state *state, nir_instr *instr);
49
50static bool
51move_src(nir_src *src, void *state)
52{
53	/* At this point we shouldn't have any non-ssa src: */
54	debug_assert(src->is_ssa);
55	move_instruction_to_start_block(state, src->ssa->parent_instr);
56	return true;
57}
58
59static void
60move_instruction_to_start_block(state *state, nir_instr *instr)
61{
62	/* first move (recursively) all src's to ensure they appear before
63	 * load*_input that we are trying to move:
64	 */
65	nir_foreach_src(instr, move_src, state);
66
67	/* and then move the instruction itself:
68	 */
69	exec_node_remove(&instr->node);
70
71	if (state->cursor) {
72		exec_node_insert_after(&state->cursor->node, &instr->node);
73	} else {
74		exec_list_push_head(&state->start_block->instr_list, &instr->node);
75	}
76
77	state->cursor = instr;
78	instr->block = state->start_block;
79}
80
81static bool
82move_varying_inputs_block(state *state, nir_block *block)
83{
84	bool progress = false;
85
86	nir_foreach_instr_safe(instr, block) {
87		if (instr->type != nir_instr_type_intrinsic)
88			continue;
89
90		nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
91
92		switch (intr->intrinsic) {
93		case nir_intrinsic_load_interpolated_input:
94		case nir_intrinsic_load_input:
95			/* TODO any others to handle? */
96			break;
97		default:
98			continue;
99		}
100
101		debug_assert(intr->dest.is_ssa);
102
103		state->cursor = NULL;
104		move_instruction_to_start_block(state, instr);
105
106		progress = true;
107	}
108
109	return progress;
110}
111
112bool
113ir3_nir_move_varying_inputs(nir_shader *shader)
114{
115	bool progress = false;
116
117	debug_assert(shader->info.stage == MESA_SHADER_FRAGMENT);
118
119	nir_foreach_function (function, shader) {
120		state state;
121
122		if (!function->impl)
123			continue;
124
125		state.shader = shader;
126		state.start_block = nir_start_block(function->impl);
127
128		bool progress = false;
129		nir_foreach_block (block, function->impl) {
130			/* don't need to move anything that is already in the first block */
131			if (block == state.start_block)
132				continue;
133			progress |= move_varying_inputs_block(&state, block);
134		}
135
136		if (progress) {
137			nir_metadata_preserve(function->impl,
138				nir_metadata_block_index | nir_metadata_dominance);
139		}
140	}
141
142	return progress;
143}
144