src/panfrost/util/pan_lower_xfb.c

/*
 * Copyright (C) 2022 Collabora Ltd.
 *
 * 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"

static void
lower_xfb_output(nir_builder *b, nir_intrinsic_instr *intr,
                 unsigned start_component, unsigned num_components,
                 unsigned buffer, unsigned offset_words)
{
        assert(buffer < MAX_XFB_BUFFERS);
        assert(nir_intrinsic_component(intr) == 0); // TODO

        /* Transform feedback info in units of words, convert to bytes. */
        uint16_t stride = b->shader->info.xfb_stride[buffer] * 4;
        assert(stride != 0);

        uint16_t offset = offset_words * 4;

        nir_ssa_def *index = nir_iadd(b,
                nir_imul(b, nir_load_instance_id(b),
                            nir_load_num_vertices(b)),
                nir_load_vertex_id_zero_base(b));

        BITSET_SET(b->shader->info.system_values_read, SYSTEM_VALUE_VERTEX_ID_ZERO_BASE);
        BITSET_SET(b->shader->info.system_values_read, SYSTEM_VALUE_INSTANCE_ID);

        nir_ssa_def *buf = nir_load_xfb_address(b, 64, .base = buffer);
        nir_ssa_def *addr =
                nir_iadd(b, buf, nir_u2u64(b,
                                    nir_iadd_imm(b,
                                                 nir_imul_imm(b, index, stride),
                                                 offset)));

        assert(intr->src[0].is_ssa && "must lower XFB before lowering SSA");
        nir_ssa_def *src = intr->src[0].ssa;
        nir_ssa_def *value = nir_channels(b, src, BITFIELD_MASK(num_components) << start_component);
        nir_store_global(b, addr, 4, value, BITFIELD_MASK(num_components));
}

static bool
lower_xfb(nir_builder *b, nir_instr *instr, UNUSED void *data)
{
        if (instr->type != nir_instr_type_intrinsic)
                return false;

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

        bool progress = false;

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

        for (unsigned i = 0; i < 2; ++i) {
                nir_io_xfb xfb = i ? nir_intrinsic_io_xfb2(intr) : nir_intrinsic_io_xfb(intr);
                for (unsigned j = 0; j < 2; ++j) {
                        if (!xfb.out[j].num_components) continue;

                        lower_xfb_output(b, intr, i*2 + j,
                                                     xfb.out[j].num_components,
                                                     xfb.out[j].buffer,
                                                     xfb.out[j].offset);
                        progress = true;
                }
        }

        nir_instr_remove(instr);
        return progress;
}

bool
pan_lower_xfb(nir_shader *nir)
{
        return nir_shader_instructions_pass(nir, lower_xfb,
                                            nir_metadata_block_index |
                                            nir_metadata_dominance, NULL);
}