src/freedreno/ir3/ir3_nir_analyze_ubo_ranges.c

/*
 * Copyright © 2019 Google, Inc.
 *
 * 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 "ir3_compiler.h"
#include "compiler/nir/nir.h"
#include "compiler/nir/nir_builder.h"
#include "util/u_math.h"

static inline bool
get_ubo_load_range(nir_shader *nir, nir_intrinsic_instr *instr, uint32_t alignment, struct ir3_ubo_range *r)
{
	uint32_t offset = nir_intrinsic_range_base(instr);
	uint32_t size = nir_intrinsic_range(instr);

	/* If the offset is constant, the range is trivial (and NIR may not have
	 * figured it out).
	 */
	if (nir_src_is_const(instr->src[1])) {
		offset = nir_src_as_uint(instr->src[1]);
		size = nir_intrinsic_dest_components(instr) * 4;
	}

	/* If we haven't figured out the range accessed in the UBO, bail. */
	if (size == ~0)
		return false;

	r->start = ROUND_DOWN_TO(offset, alignment * 16);
	r->end = ALIGN(offset + size, alignment * 16);

	return true;
}

static bool
get_ubo_info(nir_intrinsic_instr *instr, struct ir3_ubo_info *ubo)
{
	if (nir_src_is_const(instr->src[0])) {
		ubo->block = nir_src_as_uint(instr->src[0]);
		ubo->bindless_base = 0;
		ubo->bindless = false;
		return true;
	} else {
		nir_intrinsic_instr *rsrc = ir3_bindless_resource(instr->src[0]);
		if (rsrc && nir_src_is_const(rsrc->src[0])) {
			ubo->block = nir_src_as_uint(rsrc->src[0]);
			ubo->bindless_base = nir_intrinsic_desc_set(rsrc);
			ubo->bindless = true;
			return true;
		}
	}
	return false;
}

/**
 * Get an existing range, but don't create a new range associated with
 * the ubo, but don't create a new one if one does not already exist.
 */
static const struct ir3_ubo_range *
get_existing_range(nir_intrinsic_instr *instr,
				   const struct ir3_ubo_analysis_state *state)
{
	struct ir3_ubo_info ubo = {};

	if (!get_ubo_info(instr, &ubo))
		return NULL;

	for (int i = 0; i < IR3_MAX_UBO_PUSH_RANGES; i++) {
		const struct ir3_ubo_range *range = &state->range[i];
		if (range->end < range->start) {
			break;
		} else if (!memcmp(&range->ubo, &ubo, sizeof(ubo))) {
			return range;
		}
	}

	return NULL;
}

/**
 * Get an existing range, or create a new one if necessary/possible.
 */
static struct ir3_ubo_range *
get_range(nir_intrinsic_instr *instr, struct ir3_ubo_analysis_state *state)
{
	struct ir3_ubo_info ubo = {};

	if (!get_ubo_info(instr, &ubo))
		return NULL;

	for (int i = 0; i < IR3_MAX_UBO_PUSH_RANGES; i++) {
		struct ir3_ubo_range *range = &state->range[i];
		if (range->end < range->start) {
			/* We don't have a matching range, but there are more available.
			 */
			range->ubo = ubo;
			return range;
		} else if (!memcmp(&range->ubo, &ubo, sizeof(ubo))) {
			return range;
		}
	}

	return NULL;
}

static void
gather_ubo_ranges(nir_shader *nir, nir_intrinsic_instr *instr,
		struct ir3_ubo_analysis_state *state, uint32_t alignment,
		uint32_t *upload_remaining)
{
	if (ir3_shader_debug & IR3_DBG_NOUBOOPT)
		return;

	struct ir3_ubo_range *old_r = get_range(instr, state);
	if (!old_r)
		return;

	struct ir3_ubo_range r;
	if (!get_ubo_load_range(nir, instr, alignment, &r))
		return;

	r.start = MIN2(r.start, old_r->start);
	r.end = MAX2(r.end, old_r->end);

	/* If adding this range would definitely put us over the limit, don't try.
	 * Prevents sparse access or large indirects from occupying all the
	 * planned UBO space
	 */
	uint32_t added = (old_r->start - r.start) + (r.end - old_r->end);
	if (added >= *upload_remaining)
		return;

	*upload_remaining -= added;
	old_r->start = r.start;
	old_r->end = r.end;
}

/* For indirect offset, it is common to see a pattern of multiple
 * loads with the same base, but different constant offset, ie:
 *
 *    vec1 32 ssa_33 = iadd ssa_base, const_offset
 *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_33) (base=N, 0, 0)
 *
 * Detect this, and peel out the const_offset part, to end up with:
 *
 *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_base) (base=N+const_offset, 0, 0)
 *
 * Or similarly:
 *
 *    vec1 32 ssa_33 = imad24_ir3 a, b, const_offset
 *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_33) (base=N, 0, 0)
 *
 * Can be converted to:
 *
 *    vec1 32 ssa_base = imul24 a, b
 *    vec4 32 ssa_34 = intrinsic load_uniform (ssa_base) (base=N+const_offset, 0, 0)
 *
 * This gives the other opt passes something much easier to work
 * with (ie. not requiring value range tracking)
 */
static void
handle_partial_const(nir_builder *b, nir_ssa_def **srcp, int *offp)
{
	if ((*srcp)->parent_instr->type != nir_instr_type_alu)
		return;

	nir_alu_instr *alu = nir_instr_as_alu((*srcp)->parent_instr);

	if (alu->op == nir_op_imad24_ir3) {
		/* This case is slightly more complicated as we need to
		 * replace the imad24_ir3 with an imul24:
		 */
		if (!nir_src_is_const(alu->src[2].src))
			return;

		*offp += nir_src_as_uint(alu->src[2].src);
		*srcp = nir_imul24(b, nir_ssa_for_alu_src(b, alu, 0),
				nir_ssa_for_alu_src(b, alu, 1));

		return;
	}

	if (alu->op != nir_op_iadd)
		return;

	if (!(alu->src[0].src.is_ssa && alu->src[1].src.is_ssa))
		return;

	if (nir_src_is_const(alu->src[0].src)) {
		*offp += nir_src_as_uint(alu->src[0].src);
		*srcp = alu->src[1].src.ssa;
	} else if (nir_src_is_const(alu->src[1].src)) {
		*srcp = alu->src[0].src.ssa;
		*offp += nir_src_as_uint(alu->src[1].src);
	}
}

/* Tracks the maximum bindful UBO accessed so that we reduce the UBO
 * descriptors emitted in the fast path for GL.
 */
static void
track_ubo_use(nir_intrinsic_instr *instr, nir_builder *b, int *num_ubos)
{
	if (ir3_bindless_resource(instr->src[0])) {
		assert(!b->shader->info.first_ubo_is_default_ubo); /* only set for GL */
		return;
	}

	if (nir_src_is_const(instr->src[0])) {
		int block = nir_src_as_uint(instr->src[0]);
		*num_ubos = MAX2(*num_ubos, block + 1);
	} else {
		*num_ubos = b->shader->info.num_ubos;
	}
}

static bool
lower_ubo_load_to_uniform(nir_intrinsic_instr *instr, nir_builder *b,
		const struct ir3_ubo_analysis_state *state,
		int *num_ubos, uint32_t alignment)
{
	b->cursor = nir_before_instr(&instr->instr);

	/* We don't lower dynamic block index UBO loads to load_uniform, but we
	 * could probably with some effort determine a block stride in number of
	 * registers.
	 */
	const struct ir3_ubo_range *range = get_existing_range(instr, state);
	if (!range) {
		track_ubo_use(instr, b, num_ubos);
		return false;
	}

	struct ir3_ubo_range r;
	if (!get_ubo_load_range(b->shader, instr, alignment, &r)) {
		track_ubo_use(instr, b, num_ubos);
		return false;
	}

	/* After gathering the UBO access ranges, we limit the total
	 * upload. Don't lower if this load is outside the range.
	 */
	if (!(range->start <= r.start && r.end <= range->end)) {
		track_ubo_use(instr, b, num_ubos);
		return false;
	}

	nir_ssa_def *ubo_offset = nir_ssa_for_src(b, instr->src[1], 1);
	int const_offset = 0;

	handle_partial_const(b, &ubo_offset, &const_offset);

	/* UBO offset is in bytes, but uniform offset is in units of
	 * dwords, so we need to divide by 4 (right-shift by 2). For ldc the
	 * offset is in units of 16 bytes, so we need to multiply by 4. And
	 * also the same for the constant part of the offset:
	 */
	const int shift = -2;
	nir_ssa_def *new_offset = ir3_nir_try_propagate_bit_shift(b, ubo_offset, -2);
	nir_ssa_def *uniform_offset = NULL;
	if (new_offset) {
		uniform_offset = new_offset;
	} else {
		uniform_offset = shift > 0 ?
			nir_ishl(b, ubo_offset, nir_imm_int(b,  shift)) :
			nir_ushr(b, ubo_offset, nir_imm_int(b, -shift));
	}

	debug_assert(!(const_offset & 0x3));
	const_offset >>= 2;

	const int range_offset = ((int)range->offset - (int)range->start) / 4;
	const_offset += range_offset;

	/* The range_offset could be negative, if if only part of the UBO
	 * block is accessed, range->start can be greater than range->offset.
	 * But we can't underflow const_offset.  If necessary we need to
	 * insert nir instructions to compensate (which can hopefully be
	 * optimized away)
	 */
	if (const_offset < 0) {
		uniform_offset = nir_iadd_imm(b, uniform_offset, const_offset);
		const_offset = 0;
	}

	nir_intrinsic_instr *uniform =
		nir_intrinsic_instr_create(b->shader, nir_intrinsic_load_uniform);
	uniform->num_components = instr->num_components;
	uniform->src[0] = nir_src_for_ssa(uniform_offset);
	nir_intrinsic_set_base(uniform, const_offset);
	nir_ssa_dest_init(&uniform->instr, &uniform->dest,
					  uniform->num_components, instr->dest.ssa.bit_size,
					  instr->dest.ssa.name);
	nir_builder_instr_insert(b, &uniform->instr);
	nir_ssa_def_rewrite_uses(&instr->dest.ssa,
							 nir_src_for_ssa(&uniform->dest.ssa));

	nir_instr_remove(&instr->instr);

	return true;
}

static bool
instr_is_load_ubo(nir_instr *instr)
{
	if (instr->type != nir_instr_type_intrinsic)
		return false;

	nir_intrinsic_op op = nir_instr_as_intrinsic(instr)->intrinsic;

	/* nir_lower_ubo_vec4 happens after this pass. */
	assert(op != nir_intrinsic_load_ubo_vec4);

	return op == nir_intrinsic_load_ubo;
}

void
ir3_nir_analyze_ubo_ranges(nir_shader *nir, struct ir3_shader_variant *v)
{
	struct ir3_const_state *const_state = ir3_const_state(v);
	struct ir3_ubo_analysis_state *state = &const_state->ubo_state;
	struct ir3_compiler *compiler = v->shader->compiler;

	/* Limit our uploads to the amount of constant buffer space available in
	 * the hardware, minus what the shader compiler may need for various
	 * driver params.  We do this UBO-to-push-constant before the real
	 * allocation of the driver params' const space, because UBO pointers can
	 * be driver params but this pass usually eliminatings them.
	 */
	struct ir3_const_state worst_case_const_state = { };
	ir3_setup_const_state(nir, v, &worst_case_const_state);
	const uint32_t max_upload = (ir3_max_const(v) -
			worst_case_const_state.offsets.immediate) * 16;

	memset(state, 0, sizeof(*state));
	for (int i = 0; i < IR3_MAX_UBO_PUSH_RANGES; i++) {
		state->range[i].start = UINT32_MAX;
	}

	uint32_t upload_remaining = max_upload;
	nir_foreach_function (function, nir) {
		if (function->impl) {
			nir_foreach_block (block, function->impl) {
				nir_foreach_instr (instr, block) {
					if (instr_is_load_ubo(instr))
						gather_ubo_ranges(nir, nir_instr_as_intrinsic(instr),
								state, compiler->const_upload_unit,
								&upload_remaining);
				}
			}
		}
	}

	/* For now, everything we upload is accessed statically and thus will be
	 * used by the shader. Once we can upload dynamically indexed data, we may
	 * upload sparsely accessed arrays, at which point we probably want to
	 * give priority to smaller UBOs, on the assumption that big UBOs will be
	 * accessed dynamically.  Alternatively, we can track statically and
	 * dynamically accessed ranges separately and upload static rangtes
	 * first.
	 */

	uint32_t offset = v->shader->num_reserved_user_consts * 16;
	state->num_enabled = ARRAY_SIZE(state->range);
	for (uint32_t i = 0; i < ARRAY_SIZE(state->range); i++) {
		if (state->range[i].start >= state->range[i].end) {
			state->num_enabled = i;
			break;
		}

		uint32_t range_size = state->range[i].end - state->range[i].start;

		debug_assert(offset <= max_upload);
		state->range[i].offset = offset;
		assert(offset <= max_upload);
		offset += range_size;

	}
	state->size = offset;
}

bool
ir3_nir_lower_ubo_loads(nir_shader *nir, struct ir3_shader_variant *v)
{
	struct ir3_compiler *compiler = v->shader->compiler;
	/* For the binning pass variant, we re-use the corresponding draw-pass
	 * variants const_state and ubo state.  To make these clear, in this
	 * pass it is const (read-only)
	 */
	const struct ir3_const_state *const_state = ir3_const_state(v);
	const struct ir3_ubo_analysis_state *state = &const_state->ubo_state;

	int num_ubos = 0;
	bool progress = false;
	nir_foreach_function (function, nir) {
		if (function->impl) {
			nir_builder builder;
			nir_builder_init(&builder, function->impl);
			nir_foreach_block (block, function->impl) {
				nir_foreach_instr_safe (instr, block) {
					if (!instr_is_load_ubo(instr))
						continue;
					progress |=
						lower_ubo_load_to_uniform(nir_instr_as_intrinsic(instr),
								&builder, state, &num_ubos,
								compiler->const_upload_unit);
				}
			}

			nir_metadata_preserve(function->impl, nir_metadata_block_index |
								  nir_metadata_dominance);
		}
	}
	/* Update the num_ubos field for GL (first_ubo_is_default_ubo).  With
	 * Vulkan's bindless, we don't use the num_ubos field, so we can leave it
	 * incremented.
	 */
	if (nir->info.first_ubo_is_default_ubo)
	    nir->info.num_ubos = num_ubos;

	return progress;
}