src/panfrost/util/pan_lower_writeout.c

/*
 * Copyright (C) 2018-2020 Collabora, Ltd.
 * Copyright (C) 2019-2020 Icecream95
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice (including the next
 * paragraph) shall be included in all copies or substantial portions of the
 * Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 */

#include "pan_ir.h"
#include "compiler/nir/nir_builder.h"

/* Midgard can write all of color, depth and stencil in a single writeout
 * operation, so we merge depth/stencil stores with color stores.
 * If there are no color stores, we add a write to the "depth RT".
 *
 * For Bifrost, we want these combined so we can properly order
 * +ZS_EMIT with respect to +ATEST and +BLEND, as well as combining
 * depth/stencil stores into a single +ZS_EMIT op.
 */

/*
 * Get the type to report for a piece of a combined store, given the store it
 * is combining from. If there is no store to render target #0, a dummy <0.0,
 * 0.0, 0.0, 0.0> write is used, so report a matching float32 type.
 */
static nir_alu_type
pan_nir_rt_store_type(nir_intrinsic_instr *store)
{
        return store ? nir_intrinsic_src_type(store) : nir_type_float32;
}

static void
pan_nir_emit_combined_store(nir_builder *b,
                            nir_intrinsic_instr *rt0_store,
                            unsigned writeout,
                            nir_intrinsic_instr **stores)
{
        nir_intrinsic_instr *intr = nir_intrinsic_instr_create(b->shader, nir_intrinsic_store_combined_output_pan);

        intr->num_components = rt0_store ? rt0_store->src[0].ssa->num_components : 4;

        if (rt0_store)
                nir_intrinsic_set_io_semantics(intr, nir_intrinsic_io_semantics(rt0_store));
        nir_intrinsic_set_src_type(intr, pan_nir_rt_store_type(rt0_store));
        nir_intrinsic_set_dest_type(intr, pan_nir_rt_store_type(stores[2]));
        nir_intrinsic_set_component(intr, writeout);

        nir_ssa_def *zero = nir_imm_int(b, 0);
        nir_ssa_def *zero4 = nir_imm_ivec4(b, 0, 0, 0, 0);

        nir_ssa_def *src[] = {
                rt0_store ? rt0_store->src[0].ssa : zero4,
                rt0_store ? rt0_store->src[1].ssa : zero,
                stores[0] ? stores[0]->src[0].ssa : zero,
                stores[1] ? stores[1]->src[0].ssa : zero,
                stores[2] ? stores[2]->src[0].ssa : zero4,
        };

        for (int i = 0; i < ARRAY_SIZE(src); ++i)
                intr->src[i] = nir_src_for_ssa(src[i]);

        nir_builder_instr_insert(b, &intr->instr);
}
bool
pan_nir_lower_zs_store(nir_shader *nir)
{
        bool progress = false;

        if (nir->info.stage != MESA_SHADER_FRAGMENT)
                return false;

        nir_foreach_function(function, nir) {
                if (!function->impl) continue;

                nir_intrinsic_instr *stores[3] = { NULL };
                unsigned writeout = 0;

                nir_foreach_block(block, function->impl) {
                        nir_foreach_instr_safe(instr, block) {
                                if (instr->type != nir_instr_type_intrinsic)
                                        continue;

                                nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
                                if (intr->intrinsic != nir_intrinsic_store_output)
                                        continue;

                                nir_io_semantics sem = nir_intrinsic_io_semantics(intr);
                                if (sem.location == FRAG_RESULT_DEPTH) {
                                        stores[0] = intr;
                                        writeout |= PAN_WRITEOUT_Z;
                                } else if (sem.location == FRAG_RESULT_STENCIL) {
                                        stores[1] = intr;
                                        writeout |= PAN_WRITEOUT_S;
                                } else if (sem.dual_source_blend_index) {
                                        stores[2] = intr;
                                        writeout |= PAN_WRITEOUT_2;
                                }
                        }
                }

                if (!writeout) continue;

                nir_block *common_block = NULL;

                /* Ensure all stores are in the same block */
                for (unsigned i = 0; i < ARRAY_SIZE(stores); ++i) {
                        if (!stores[i])
                                continue;

                        nir_block *block = stores[i]->instr.block; 

                        if (common_block)
                                assert(common_block == block);
                        else
                                common_block = block;
                }

                bool replaced = false;

                nir_foreach_block(block, function->impl) {
                        nir_foreach_instr_safe(instr, block) {
                                if (instr->type != nir_instr_type_intrinsic)
                                        continue;

                                nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
                                if (intr->intrinsic != nir_intrinsic_store_output)
                                        continue;

                                nir_io_semantics sem = nir_intrinsic_io_semantics(intr);

                                if (sem.location < FRAG_RESULT_DATA0)
                                        continue;

                                if (sem.dual_source_blend_index)
                                        continue;

                                assert(nir_src_is_const(intr->src[1]) && "no indirect outputs");

                                nir_builder b;
                                nir_builder_init(&b, function->impl);
                                b.cursor = nir_after_block_before_jump(instr->block);

                                /* Trying to write depth twice results in the
                                 * wrong blend shader being executed on
                                 * Midgard */
                                unsigned this_store = PAN_WRITEOUT_C | (replaced ? 0 : writeout);

                                pan_nir_emit_combined_store(&b, intr, this_store, stores);

                                nir_instr_remove(instr);

                                replaced = true;
                        }
                }

                /* Insert a store to the depth RT (0xff) if needed */
                if (!replaced) {
                        nir_builder b;
                        nir_builder_init(&b, function->impl);
                        b.cursor = nir_after_block_before_jump(common_block);

                        pan_nir_emit_combined_store(&b, NULL, writeout, stores);
                }

                for (unsigned i = 0; i < ARRAY_SIZE(stores); ++i) {
                        if (stores[i])
                                nir_instr_remove(&stores[i]->instr);
                }

                nir_metadata_preserve(function->impl, nir_metadata_block_index | nir_metadata_dominance);
                progress = true;
        }

        return progress;
}