/*
 * Copyright © 2017 Ilia Mirkin
 *
 * 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 "ir3_nir.h"
#include "compiler/nir/nir_builder.h"

/* A4XX has a broken GATHER4 operation. It performs the texture swizzle on the
 * gather results, rather than before. As a result, it must be emulated with
 * direct texture calls.
 */

static nir_ssa_def *
ir3_nir_lower_tg4_to_tex_instr(nir_builder *b, nir_instr *instr, void *data)
{
	nir_tex_instr *tg4 = nir_instr_as_tex(instr);
	static const int offsets[3][2] = { {0, 1}, {1, 1}, {1, 0} };

	nir_ssa_def *results[4];
	int offset_index = nir_tex_instr_src_index(tg4, nir_tex_src_offset);
	for (int i = 0; i < 4; i++) {
		int num_srcs = tg4->num_srcs + 1 /* lod */;
		if (offset_index < 0 && i < 3)
			num_srcs++;

		nir_tex_instr *tex = nir_tex_instr_create(b->shader, num_srcs);
		tex->op = nir_texop_txl;
		tex->sampler_dim = tg4->sampler_dim;
		tex->coord_components = tg4->coord_components;
		tex->is_array = tg4->is_array;
		tex->is_shadow = tg4->is_shadow;
		tex->is_new_style_shadow = tg4->is_new_style_shadow;
		tex->texture_index = tg4->texture_index;
		tex->sampler_index = tg4->sampler_index;
		tex->dest_type = tg4->dest_type;

		for (int j = 0; j < tg4->num_srcs; j++) {
			nir_src_copy(&tex->src[j].src, &tg4->src[j].src, tex);
			tex->src[j].src_type = tg4->src[j].src_type;
		}
		if (i != 3) {
			nir_ssa_def *offset =
				nir_vec2(b, nir_imm_int(b, offsets[i][0]),
						nir_imm_int(b, offsets[i][1]));
			if (offset_index < 0) {
				tex->src[tg4->num_srcs].src = nir_src_for_ssa(offset);
				tex->src[tg4->num_srcs].src_type = nir_tex_src_offset;
			} else {
				assert(nir_tex_instr_src_size(tex, offset_index) == 2);
				nir_ssa_def *orig = nir_ssa_for_src(
					b, tex->src[offset_index].src, 2);
				tex->src[offset_index].src =
					nir_src_for_ssa(nir_iadd(b, orig, offset));
			}
		}
		tex->src[num_srcs - 1].src = nir_src_for_ssa(nir_imm_float(b, 0));
		tex->src[num_srcs - 1].src_type = nir_tex_src_lod;

		nir_ssa_dest_init(&tex->instr, &tex->dest,
				nir_tex_instr_dest_size(tex), 32, NULL);
		nir_builder_instr_insert(b, &tex->instr);

		results[i] = nir_channel(b, &tex->dest.ssa, tg4->component);
	}

	return nir_vec(b, results, 4);
}

static bool
ir3_nir_lower_tg4_to_tex_filter(const nir_instr *instr, const void *data)
{
	return (instr->type == nir_instr_type_tex &&
			nir_instr_as_tex(instr)->op == nir_texop_tg4);
}

bool
ir3_nir_lower_tg4_to_tex(nir_shader *shader)
{
	return nir_shader_lower_instructions(shader,
			ir3_nir_lower_tg4_to_tex_filter,
			ir3_nir_lower_tg4_to_tex_instr, NULL);
}