pan_lower_helper_invocation.c

/*
 * Copyright (C) 2021 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"

/* Lower gl_HelperInvocation to (gl_SampleMaskIn == 0), this depends on
 * architectural details but is required for correct operation with
 * multisampling. NIR's lowering won't work for us, since there is no in-spec
 * way to implement load_sample_id_no_per_sample. */

static bool
pan_lower_helper_invocation_instr(nir_builder *b, nir_instr *instr, 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_load_helper_invocation)
                return false;

        b->cursor = nir_before_instr(instr);

        nir_ssa_def *mask = nir_load_sample_mask_in(b);
        nir_ssa_def *eq = nir_ieq(b, mask, nir_imm_int(b, 0));
        nir_ssa_def_rewrite_uses(&intr->dest.ssa, eq);

        return true;
}

bool
pan_lower_helper_invocation(nir_shader *shader)
{
        return nir_shader_instructions_pass(shader,
                                            pan_lower_helper_invocation_instr,
                                            nir_metadata_block_index | nir_metadata_dominance,
                                            NULL);
}