mesa/src/broadcom/compiler/v3d_nir_lower_io.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 "compiler/v3d_compiler.h"
#include "compiler/nir/nir_builder.h"

/**
 * Walks the NIR generated by TGSI-to-NIR or GLSL-to-NIR to lower its io
 * intrinsics into something amenable to the V3D architecture.
 *
 * Most of the work is turning the VS's store_output intrinsics from working
 * on a base representing the gallium-level vec4 driver_location to an offset
 * within the VPM, and emitting the header that's read by the fixed function
 * hardware between the VS and FS.
 *
 * We also adjust the offsets on uniform loads to be in bytes, since that's
 * what we need for indirect addressing with general TMU access.
 */

struct v3d_nir_lower_io_state {
        int pos_vpm_offset;
        int vp_vpm_offset;
        int zs_vpm_offset;
        int rcp_wc_vpm_offset;
        int psiz_vpm_offset;
        int varyings_vpm_offset;

        BITSET_WORD varyings_stored[BITSET_WORDS(V3D_MAX_FS_INPUTS)];

        nir_ssa_def *pos[4];
};

static void
v3d_nir_store_output(nir_builder *b, int base, nir_ssa_def *chan)
{
        nir_intrinsic_instr *intr =
                nir_intrinsic_instr_create(b->shader, nir_intrinsic_store_output);
        nir_ssa_dest_init(&intr->instr, &intr->dest,
                          1, intr->dest.ssa.bit_size, NULL);
        intr->num_components = 1;

        intr->src[0] = nir_src_for_ssa(chan);
        intr->src[1] = nir_src_for_ssa(nir_imm_int(b, 0));

        nir_intrinsic_set_base(intr, base);
        nir_intrinsic_set_write_mask(intr, 0x1);
        nir_intrinsic_set_component(intr, 0);

        nir_builder_instr_insert(b, &intr->instr);
}

/* Convert the uniform offset to bytes.  If it happens to be a constant,
 * constant-folding will clean up the shift for us.
 */
static void
v3d_nir_lower_uniform(struct v3d_compile *c, nir_builder *b,
                      nir_intrinsic_instr *intr)
{
        b->cursor = nir_before_instr(&intr->instr);

        nir_intrinsic_set_base(intr, nir_intrinsic_base(intr) * 16);

        nir_instr_rewrite_src(&intr->instr,
                              &intr->src[0],
                              nir_src_for_ssa(nir_ishl(b, intr->src[0].ssa,
                                                       nir_imm_int(b, 4))));
}

static int
v3d_varying_slot_vpm_offset(struct v3d_compile *c, nir_variable *var, int chan)
{
        int component = var->data.location_frac + chan;

        for (int i = 0; i < c->vs_key->num_fs_inputs; i++) {
                struct v3d_varying_slot slot = c->vs_key->fs_inputs[i];

                if (v3d_slot_get_slot(slot) == var->data.location &&
                    v3d_slot_get_component(slot) == component) {
                        return i;
                }
        }

        return -1;
}

/* Lowers a store_output(gallium driver location) to a series of store_outputs
 * with a driver_location equal to the offset in the VPM.
 */
static void
v3d_nir_lower_vpm_output(struct v3d_compile *c, nir_builder *b,
                         nir_intrinsic_instr *intr,
                         struct v3d_nir_lower_io_state *state)
{
        b->cursor = nir_before_instr(&intr->instr);

        int start_comp = nir_intrinsic_component(intr);
        nir_ssa_def *src = nir_ssa_for_src(b, intr->src[0],
                                           intr->num_components);

        nir_variable *var = NULL;
        nir_foreach_variable(scan_var, &c->s->outputs) {
                if (scan_var->data.driver_location != nir_intrinsic_base(intr) ||
                    start_comp < scan_var->data.location_frac ||
                    start_comp >= scan_var->data.location_frac +
                    glsl_get_components(scan_var->type)) {
                        continue;
                }
                var = scan_var;
        }

        /* Save off the components of the position for the setup of VPM inputs
         * read by fixed function HW.
         */
        if (var->data.location == VARYING_SLOT_POS) {
                for (int i = 0; i < intr->num_components; i++) {
                        state->pos[start_comp + i] = nir_channel(b, src, i);
                }
        }

        /* Just psiz to the position in the FF header right now. */
        if (var->data.location == VARYING_SLOT_PSIZ &&
            state->psiz_vpm_offset != -1) {
                v3d_nir_store_output(b, state->psiz_vpm_offset, src);
        }

        /* Scalarize outputs if it hasn't happened already, since we want to
         * schedule each VPM write individually.  We can skip any outut
         * components not read by the FS.
         */
        for (int i = 0; i < intr->num_components; i++) {
                int vpm_offset =
                        v3d_varying_slot_vpm_offset(c, var,
                                                    i +
                                                    start_comp -
                                                    var->data.location_frac);

                if (vpm_offset == -1)
                        continue;

                BITSET_SET(state->varyings_stored, vpm_offset);

                v3d_nir_store_output(b, state->varyings_vpm_offset + vpm_offset,
                                     nir_channel(b, src, i));
        }

        nir_instr_remove(&intr->instr);
}

static void
v3d_nir_lower_io_instr(struct v3d_compile *c, nir_builder *b,
                       struct nir_instr *instr,
                       struct v3d_nir_lower_io_state *state)
{
        if (instr->type != nir_instr_type_intrinsic)
                return;
        nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);

        switch (intr->intrinsic) {
        case nir_intrinsic_load_uniform:
                v3d_nir_lower_uniform(c, b, intr);
                break;

        case nir_intrinsic_store_output:
                if (c->s->info.stage == MESA_SHADER_VERTEX)
                        v3d_nir_lower_vpm_output(c, b, intr, state);
                break;

        default:
                break;
        }
}

/* Remap the output var's .driver_location.  This is purely for
 * nir_print_shader() so that store_output can map back to a variable name.
 */
static void
v3d_nir_lower_io_update_output_var_base(struct v3d_compile *c,
                                        struct v3d_nir_lower_io_state *state)
{
        nir_foreach_variable_safe(var, &c->s->outputs) {
                if (var->data.location == VARYING_SLOT_POS &&
                    state->pos_vpm_offset != -1) {
                        var->data.driver_location = state->pos_vpm_offset;
                        continue;
                }

                if (var->data.location == VARYING_SLOT_PSIZ &&
                    state->psiz_vpm_offset != -1) {
                        var->data.driver_location = state->psiz_vpm_offset;
                        continue;
                }

                int vpm_offset = v3d_varying_slot_vpm_offset(c, var, 0);
                if (vpm_offset != -1) {
                        var->data.driver_location =
                                state->varyings_vpm_offset + vpm_offset;
                } else {
                        /* If we couldn't find a mapping for the var, delete
                         * it so that its old .driver_location doesn't confuse
                         * nir_print_shader().
                         */
                        exec_node_remove(&var->node);
                }
        }
}

static void
v3d_nir_setup_vpm_layout(struct v3d_compile *c,
                         struct v3d_nir_lower_io_state *state)
{
        uint32_t vpm_offset = 0;

        if (c->vs_key->is_coord) {
                state->pos_vpm_offset = vpm_offset;
                vpm_offset += 4;
        } else {
                state->pos_vpm_offset = -1;
        }

        state->vp_vpm_offset = vpm_offset;
        vpm_offset += 2;

        if (!c->vs_key->is_coord) {
                state->zs_vpm_offset = vpm_offset++;
                state->rcp_wc_vpm_offset = vpm_offset++;
        } else {
                state->zs_vpm_offset = -1;
                state->rcp_wc_vpm_offset = -1;
        }

        if (c->vs_key->per_vertex_point_size)
                state->psiz_vpm_offset = vpm_offset++;
        else
                state->psiz_vpm_offset = -1;

        state->varyings_vpm_offset = vpm_offset;

        c->vpm_output_size = vpm_offset + c->vs_key->num_fs_inputs;
}

static void
v3d_nir_emit_ff_vpm_outputs(struct v3d_compile *c, nir_builder *b,
                            struct v3d_nir_lower_io_state *state)
{
        for (int i = 0; i < 4; i++) {
                if (!state->pos[i])
                        state->pos[i] = nir_ssa_undef(b, 1, 32);
        }

        nir_ssa_def *rcp_wc = nir_frcp(b, state->pos[3]);

        if (state->pos_vpm_offset != -1) {
                for (int i = 0; i < 4; i++) {
                        v3d_nir_store_output(b, state->pos_vpm_offset + i,
                                             state->pos[i]);
                }
        }

        for (int i = 0; i < 2; i++) {
                nir_ssa_def *pos;
                nir_ssa_def *scale;
                pos = state->pos[i];
                if (i == 0)
                        scale = nir_load_viewport_x_scale(b);
                else
                        scale = nir_load_viewport_y_scale(b);
                pos = nir_fmul(b, pos, scale);
                pos = nir_fmul(b, pos, rcp_wc);
                pos = nir_f2i32(b, nir_fround_even(b, pos));
                v3d_nir_store_output(b, state->vp_vpm_offset + i,
                                     pos);
        }

        if (state->zs_vpm_offset != -1) {
                nir_ssa_def *z = state->pos[2];
                z = nir_fmul(b, z, nir_load_viewport_z_scale(b));
                z = nir_fmul(b, z, rcp_wc);
                z = nir_fadd(b, z, nir_load_viewport_z_offset(b));
                v3d_nir_store_output(b, state->zs_vpm_offset, z);
        }

        if (state->rcp_wc_vpm_offset != -1)
                v3d_nir_store_output(b, state->rcp_wc_vpm_offset, rcp_wc);

        /* Store 0 to varyings requested by the FS but not stored in the VS.
         * This should be undefined behavior, but glsl-routing seems to rely
         * on it.
         */
        for (int i = 0; i < c->vs_key->num_fs_inputs; i++) {
                if (!BITSET_TEST(state->varyings_stored, i)) {
                        v3d_nir_store_output(b, state->varyings_vpm_offset + i,
                                             nir_imm_int(b, 0));
                }
        }
}

void
v3d_nir_lower_io(nir_shader *s, struct v3d_compile *c)
{
        struct v3d_nir_lower_io_state state = { 0 };

        /* Set up the layout of the VPM outputs. */
        if (s->info.stage == MESA_SHADER_VERTEX)
                v3d_nir_setup_vpm_layout(c, &state);

        nir_foreach_function(function, s) {
                if (function->impl) {
                        nir_builder b;
                        nir_builder_init(&b, function->impl);

                        nir_foreach_block(block, function->impl) {
                                nir_foreach_instr_safe(instr, block)
                                        v3d_nir_lower_io_instr(c, &b, instr,
                                                               &state);
                        }

                        nir_block *last = nir_impl_last_block(function->impl);
                        b.cursor = nir_after_block(last);
                        if (s->info.stage == MESA_SHADER_VERTEX)
                                v3d_nir_emit_ff_vpm_outputs(c, &b, &state);

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

        if (s->info.stage == MESA_SHADER_VERTEX)
                v3d_nir_lower_io_update_output_var_base(c, &state);
}