src/gallium/drivers/vc4/vc4_nir_lower_txf_ms.c

/*
 * Copyright © 2015 Broadcom
 *
 * 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 "vc4_qir.h"
#include "kernel/vc4_packet.h"
#include "compiler/nir/nir_builder.h"

/** @file vc4_nir_lower_txf_ms.c
 * Walks the NIR generated by TGSI-to-NIR to lower its nir_texop_txf_ms
 * coordinates to do the math necessary and use a plain nir_texop_txf instead.
 *
 * MSAA textures are laid out as 32x32-aligned blocks of RGBA8888 or Z24S8.
 * We can't load them through the normal sampler path because of the lack of
 * linear support in the hardware.  So, we treat MSAA textures as a giant UBO
 * and do the math in the shader.
 */

static void
vc4_nir_lower_txf_ms_instr(struct vc4_compile *c, nir_builder *b,
                           nir_tex_instr *txf_ms)
{
        if (txf_ms->op != nir_texop_txf_ms)
                return;

        b->cursor = nir_before_instr(&txf_ms->instr);

        nir_tex_instr *txf = nir_tex_instr_create(c->s, 1);
        txf->op = nir_texop_txf;
        txf->texture = txf_ms->texture;
        txf->texture_index = txf_ms->texture_index;
        txf->coord_components = txf_ms->coord_components;
        txf->is_shadow = txf_ms->is_shadow;
        txf->is_new_style_shadow = txf_ms->is_new_style_shadow;

        nir_ssa_def *coord = NULL, *sample_index = NULL;
        for (int i = 0; i < txf_ms->num_srcs; i++) {
                assert(txf_ms->src[i].src.is_ssa);

                switch (txf_ms->src[i].src_type) {
                case nir_tex_src_coord:
                        coord = txf_ms->src[i].src.ssa;
                        break;
                case nir_tex_src_ms_index:
                        sample_index = txf_ms->src[i].src.ssa;
                        break;
                default:
                        unreachable("Unknown txf_ms src\n");
                }
        }
        assert(coord);
        assert(sample_index);

        nir_ssa_def *x = nir_channel(b, coord, 0);
        nir_ssa_def *y = nir_channel(b, coord, 1);

        uint32_t tile_w = 32;
        uint32_t tile_h = 32;
        uint32_t tile_w_shift = 5;
        uint32_t tile_h_shift = 5;
        uint32_t tile_size = (tile_h * tile_w *
                              VC4_MAX_SAMPLES * sizeof(uint32_t));
        unsigned unit = txf_ms->texture_index;
        uint32_t w = align(c->key->tex[unit].msaa_width, tile_w);
        uint32_t w_tiles = w / tile_w;

        nir_ssa_def *x_tile = nir_ushr(b, x, nir_imm_int(b, tile_w_shift));
        nir_ssa_def *y_tile = nir_ushr(b, y, nir_imm_int(b, tile_h_shift));
        nir_ssa_def *tile_addr = nir_iadd(b,
                                          nir_imul(b, x_tile,
                                                   nir_imm_int(b, tile_size)),
                                          nir_imul(b, y_tile,
                                                   nir_imm_int(b, (w_tiles *
                                                                   tile_size))));
        nir_ssa_def *x_subspan = nir_iand(b, x,
                                          nir_imm_int(b, (tile_w - 1) & ~1));
        nir_ssa_def *y_subspan = nir_iand(b, y,
                                          nir_imm_int(b, (tile_h - 1) & ~1));
        nir_ssa_def *subspan_addr = nir_iadd(b,
                                             nir_imul(b, x_subspan,
                                                      nir_imm_int(b, 2 * VC4_MAX_SAMPLES * sizeof(uint32_t))),
                                             nir_imul(b, y_subspan,
                                                      nir_imm_int(b,
                                                                  tile_w *
                                                                  VC4_MAX_SAMPLES *
                                                                  sizeof(uint32_t))));

        nir_ssa_def *pixel_addr = nir_ior(b,
                                          nir_iand(b,
                                                   nir_ishl(b, x,
                                                            nir_imm_int(b, 2)),
                                                   nir_imm_int(b, (1 << 2))),
                                          nir_iand(b,
                                                   nir_ishl(b, y,
                                                            nir_imm_int(b, 3)),
                                                   nir_imm_int(b, (1 << 3))));

        nir_ssa_def *sample_addr = nir_ishl(b, sample_index, nir_imm_int(b, 4));

        nir_ssa_def *addr = nir_iadd(b,
                                     nir_ior(b, sample_addr, pixel_addr),
                                     nir_iadd(b, subspan_addr, tile_addr));

        txf->src[0].src_type = nir_tex_src_coord;
        txf->src[0].src = nir_src_for_ssa(nir_vec2(b, addr, nir_imm_int(b, 0)));
        nir_ssa_dest_init(&txf->instr, &txf->dest, 4, 32, NULL);
        nir_builder_instr_insert(b, &txf->instr);
        nir_ssa_def_rewrite_uses(&txf_ms->dest.ssa,
                                 nir_src_for_ssa(&txf->dest.ssa));
        nir_instr_remove(&txf_ms->instr);
}

static bool
vc4_nir_lower_txf_ms_impl(struct vc4_compile *c, nir_function_impl *impl)
{
        nir_builder b;
        nir_builder_init(&b, impl);

        nir_foreach_block(block, impl) {
                nir_foreach_instr_safe(instr, block) {
                        if (instr->type == nir_instr_type_tex) {
                                vc4_nir_lower_txf_ms_instr(c, &b,
                                                nir_instr_as_tex(instr));
                        }
                }
        }

        nir_metadata_preserve(impl,
                              nir_metadata_block_index |
                              nir_metadata_dominance);

        return true;
}

void
vc4_nir_lower_txf_ms(nir_shader *s, struct vc4_compile *c)
{
        nir_foreach_function(function, s) {
                if (function->impl)
                        vc4_nir_lower_txf_ms_impl(c, function->impl);
        }
}