path: root/src/gallium/drivers/freedreno/ir3/ir3_cp.c

/* -*- mode: C; c-file-style: "k&r"; tab-width 4; indent-tabs-mode: t; -*- */

/*
 * Copyright (C) 2014 Rob Clark <robclark@freedesktop.org>
 *
 * 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.
 *
 * Authors:
 *    Rob Clark <robclark@freedesktop.org>
 */

#include "freedreno_util.h"

#include "ir3.h"

/*
 * Copy Propagate:
 */

/* is it a type preserving mov, with ok flags? */
static bool is_eligible_mov(struct ir3_instruction *instr, bool allow_flags)
{
	if (is_same_type_mov(instr)) {
		struct ir3_register *dst = instr->regs[0];
		struct ir3_register *src = instr->regs[1];
		struct ir3_instruction *src_instr = ssa(src);

		/* only if mov src is SSA (not const/immed): */
		if (!src_instr)
			return false;

		/* no indirect: */
		if (dst->flags & IR3_REG_RELATIV)
			return false;
		if (src->flags & IR3_REG_RELATIV)
			return false;

		if (!allow_flags)
			if (src->flags & (IR3_REG_FABS | IR3_REG_FNEG |
					IR3_REG_SABS | IR3_REG_SNEG | IR3_REG_BNOT))
				return false;

		/* TODO: remove this hack: */
		if (is_meta(src_instr) && (src_instr->opc == OPC_META_FO))
			return false;
		/* TODO: we currently don't handle left/right neighbors
		 * very well when inserting parallel-copies into phi..
		 * to avoid problems don't eliminate a mov coming out
		 * of phi..
		 */
		if (is_meta(src_instr) && (src_instr->opc == OPC_META_PHI))
			return false;
		return true;
	}
	return false;
}

static unsigned cp_flags(unsigned flags)
{
	/* only considering these flags (at least for now): */
	flags &= (IR3_REG_CONST | IR3_REG_IMMED |
			IR3_REG_FNEG | IR3_REG_FABS |
			IR3_REG_SNEG | IR3_REG_SABS |
			IR3_REG_BNOT | IR3_REG_RELATIV);
	return flags;
}

static bool valid_flags(struct ir3_instruction *instr, unsigned n,
		unsigned flags)
{
	unsigned valid_flags;
	flags = cp_flags(flags);

	/* If destination is indirect, then source cannot be.. at least
	 * I don't think so..
	 */
	if ((instr->regs[0]->flags & IR3_REG_RELATIV) &&
			(flags & IR3_REG_RELATIV))
		return false;

	/* clear flags that are 'ok' */
	switch (instr->category) {
	case 1:
		valid_flags = IR3_REG_IMMED | IR3_REG_CONST | IR3_REG_RELATIV;
		if (flags & ~valid_flags)
			return false;
		break;
	case 5:
		/* no flags allowed */
		if (flags)
			return false;
		break;
	case 6:
		valid_flags = IR3_REG_IMMED;
		if (flags & ~valid_flags)
			return false;
		break;
	case 2:
		valid_flags = ir3_cat2_absneg(instr->opc) |
				IR3_REG_CONST | IR3_REG_RELATIV;

		if (ir3_cat2_int(instr->opc))
			valid_flags |= IR3_REG_IMMED;

		if (flags & ~valid_flags)
			return false;

		if (flags & (IR3_REG_CONST | IR3_REG_IMMED)) {
			unsigned m = (n ^ 1) + 1;
			/* cannot deal w/ const in both srcs:
			 * (note that some cat2 actually only have a single src)
			 */
			if (m < instr->regs_count) {
				struct ir3_register *reg = instr->regs[m];
				if ((flags & IR3_REG_CONST) && (reg->flags & IR3_REG_CONST))
					return false;
				if ((flags & IR3_REG_IMMED) && (reg->flags & IR3_REG_IMMED))
					return false;
			}
			/* cannot be const + ABS|NEG: */
			if (flags & (IR3_REG_FABS | IR3_REG_FNEG |
					IR3_REG_SABS | IR3_REG_SNEG | IR3_REG_BNOT))
				return false;
		}
		break;
	case 3:
		valid_flags = ir3_cat3_absneg(instr->opc) |
				IR3_REG_CONST | IR3_REG_RELATIV;

		if (flags & ~valid_flags)
			return false;

		if (flags & (IR3_REG_CONST | IR3_REG_RELATIV)) {
			/* cannot deal w/ const/relativ in 2nd src: */
			if (n == 1)
				return false;
		}

		if (flags & IR3_REG_CONST) {
			/* cannot be const + ABS|NEG: */
			if (flags & (IR3_REG_FABS | IR3_REG_FNEG |
					IR3_REG_SABS | IR3_REG_SNEG | IR3_REG_BNOT))
				return false;
		}
		break;
	case 4:
		/* seems like blob compiler avoids const as src.. */
		/* TODO double check if this is still the case on a4xx */
		if (flags & IR3_REG_CONST)
			return false;
		if (flags & (IR3_REG_SABS | IR3_REG_SNEG))
			return false;
		break;
	}

	return true;
}

/* propagate register flags from src to dst.. negates need special
 * handling to cancel each other out.
 */
static void combine_flags(unsigned *dstflags, unsigned srcflags)
{
	/* if what we are combining into already has (abs) flags,
	 * we can drop (neg) from src:
	 */
	if (*dstflags & IR3_REG_FABS)
		srcflags &= ~IR3_REG_FNEG;
	if (*dstflags & IR3_REG_SABS)
		srcflags &= ~IR3_REG_SNEG;

	if (srcflags & IR3_REG_FABS)
		*dstflags |= IR3_REG_FABS;
	if (srcflags & IR3_REG_SABS)
		*dstflags |= IR3_REG_SABS;
	if (srcflags & IR3_REG_FNEG)
		*dstflags ^= IR3_REG_FNEG;
	if (srcflags & IR3_REG_SNEG)
		*dstflags ^= IR3_REG_SNEG;
	if (srcflags & IR3_REG_BNOT)
		*dstflags ^= IR3_REG_BNOT;

	*dstflags &= ~IR3_REG_SSA;
	*dstflags |= srcflags & IR3_REG_SSA;
	*dstflags |= srcflags & IR3_REG_CONST;
	*dstflags |= srcflags & IR3_REG_IMMED;
	*dstflags |= srcflags & IR3_REG_RELATIV;
	*dstflags |= srcflags & IR3_REG_ARRAY;
}

/* the "plain" MAD's (ie. the ones that don't shift first src prior to
 * multiply) can swap their first two srcs if src[0] is !CONST and
 * src[1] is CONST:
 */
static bool is_valid_mad(struct ir3_instruction *instr)
{
	return (instr->category == 3) && is_mad(instr->opc);
}

/**
 * Handle cp for a given src register.  This additionally handles
 * the cases of collapsing immedate/const (which replace the src
 * register with a non-ssa src) or collapsing mov's from relative
 * src (which needs to also fixup the address src reference by the
 * instruction).
 */
static void
reg_cp(struct ir3_instruction *instr, struct ir3_register *reg, unsigned n)
{
	struct ir3_instruction *src = ssa(reg);

	if (is_eligible_mov(src, true)) {
		/* simple case, no immed/const/relativ, only mov's w/ ssa src: */
		struct ir3_register *src_reg = src->regs[1];
		unsigned new_flags = reg->flags;

		combine_flags(&new_flags, src_reg->flags);

		if (valid_flags(instr, n, new_flags)) {
			if (new_flags & IR3_REG_ARRAY) {
				debug_assert(!(reg->flags & IR3_REG_ARRAY));
				reg->array = src_reg->array;
			}
			reg->flags = new_flags;
			reg->instr = ssa(src_reg);
		}

		src = ssa(reg);      /* could be null for IR3_REG_ARRAY case */
		if (!src)
			return;
	} else if (is_same_type_mov(src) &&
			/* cannot collapse const/immed/etc into meta instrs: */
			!is_meta(instr)) {
		/* immed/const/etc cases, which require some special handling: */
		struct ir3_register *src_reg = src->regs[1];
		unsigned new_flags = reg->flags;

		combine_flags(&new_flags, src_reg->flags);

		if (!valid_flags(instr, n, new_flags)) {
			/* special case for "normal" mad instructions, we can
			 * try swapping the first two args if that fits better.
			 */
			if ((n == 1) && is_valid_mad(instr) &&
					!(instr->regs[0 + 1]->flags & (IR3_REG_CONST | IR3_REG_RELATIV)) &&
					valid_flags(instr, 0, new_flags)) {
				/* swap src[0] and src[1]: */
				struct ir3_register *tmp;
				tmp = instr->regs[0 + 1];
				instr->regs[0 + 1] = instr->regs[1 + 1];
				instr->regs[1 + 1] = tmp;
				n = 0;
			} else {
				return;
			}
		}

		/* Here we handle the special case of mov from
		 * CONST and/or RELATIV.  These need to be handled
		 * specially, because in the case of move from CONST
		 * there is no src ir3_instruction so we need to
		 * replace the ir3_register.  And in the case of
		 * RELATIV we need to handle the address register
		 * dependency.
		 */
		if (src_reg->flags & IR3_REG_CONST) {
			/* an instruction cannot reference two different
			 * address registers:
			 */
			if ((src_reg->flags & IR3_REG_RELATIV) &&
					conflicts(instr->address, reg->instr->address))
				return;

			/* This seems to be a hw bug, or something where the timings
			 * just somehow don't work out.  This restriction may only
			 * apply if the first src is also CONST.
			 */
			if ((instr->category == 3) && (n == 2) &&
					(src_reg->flags & IR3_REG_RELATIV) &&
					(src_reg->array.offset == 0))
				return;

			src_reg = ir3_reg_clone(instr->block->shader, src_reg);
			src_reg->flags = new_flags;
			instr->regs[n+1] = src_reg;

			if (src_reg->flags & IR3_REG_RELATIV)
				ir3_instr_set_address(instr, reg->instr->address);

			return;
		}

		if ((src_reg->flags & IR3_REG_RELATIV) &&
				!conflicts(instr->address, reg->instr->address)) {
			src_reg = ir3_reg_clone(instr->block->shader, src_reg);
			src_reg->flags = new_flags;
			instr->regs[n+1] = src_reg;
			ir3_instr_set_address(instr, reg->instr->address);

			return;
		}

		/* NOTE: seems we can only do immed integers, so don't
		 * need to care about float.  But we do need to handle
		 * abs/neg *before* checking that the immediate requires
		 * few enough bits to encode:
		 *
		 * TODO: do we need to do something to avoid accidentally
		 * catching a float immed?
		 */
		if (src_reg->flags & IR3_REG_IMMED) {
			int32_t iim_val = src_reg->iim_val;

			debug_assert((instr->category == 1) ||
					(instr->category == 6) ||
					((instr->category == 2) &&
						ir3_cat2_int(instr->opc)));

			if (new_flags & IR3_REG_SABS)
				iim_val = abs(iim_val);

			if (new_flags & IR3_REG_SNEG)
				iim_val = -iim_val;

			if (new_flags & IR3_REG_BNOT)
				iim_val = ~iim_val;

			/* other than category 1 (mov) we can only encode up to 10 bits: */
			if ((instr->category == 1) || !(iim_val & ~0x3ff)) {
				new_flags &= ~(IR3_REG_SABS | IR3_REG_SNEG | IR3_REG_BNOT);
				src_reg = ir3_reg_clone(instr->block->shader, src_reg);
				src_reg->flags = new_flags;
				src_reg->iim_val = iim_val;
				instr->regs[n+1] = src_reg;
			}

			return;
		}
	}
}

/* Handle special case of eliminating output mov, and similar cases where
 * there isn't a normal "consuming" instruction.  In this case we cannot
 * collapse flags (ie. output mov from const, or w/ abs/neg flags, cannot
 * be eliminated)
 */
static struct ir3_instruction *
eliminate_output_mov(struct ir3_instruction *instr)
{
	if (is_eligible_mov(instr, false)) {
		struct ir3_register *reg = instr->regs[1];
		if (!(reg->flags & IR3_REG_ARRAY)) {
			struct ir3_instruction *src_instr = ssa(reg);
			debug_assert(src_instr);
			return src_instr;
		}
	}
	return instr;
}

/**
 * Find instruction src's which are mov's that can be collapsed, replacing
 * the mov dst with the mov src
 */
static void
instr_cp(struct ir3_instruction *instr)
{
	struct ir3_register *reg;

	if (instr->regs_count == 0)
		return;

	if (ir3_instr_check_mark(instr))
		return;

	/* walk down the graph from each src: */
	foreach_src_n(reg, n, instr) {
		struct ir3_instruction *src = ssa(reg);

		if (!src)
			continue;

		instr_cp(src);

		/* TODO non-indirect access we could figure out which register
		 * we actually want and allow cp..
		 */
		if (reg->flags & IR3_REG_ARRAY)
			continue;

		reg_cp(instr, reg, n);
	}

	if (instr->regs[0]->flags & IR3_REG_ARRAY) {
		struct ir3_instruction *src = ssa(instr->regs[0]);
		if (src)
			instr_cp(src);
	}

	if (instr->address) {
		instr_cp(instr->address);
		ir3_instr_set_address(instr, eliminate_output_mov(instr->address));
	}
}

void
ir3_cp(struct ir3 *ir)
{
	ir3_clear_mark(ir);

	for (unsigned i = 0; i < ir->noutputs; i++) {
		if (ir->outputs[i]) {
			instr_cp(ir->outputs[i]);
			ir->outputs[i] = eliminate_output_mov(ir->outputs[i]);
		}
	}

	for (unsigned i = 0; i < ir->keeps_count; i++) {
		instr_cp(ir->keeps[i]);
		ir->keeps[i] = eliminate_output_mov(ir->keeps[i]);
	}

	list_for_each_entry (struct ir3_block, block, &ir->block_list, node) {
		if (block->condition) {
			instr_cp(block->condition);
			block->condition = eliminate_output_mov(block->condition);
		}
	}
}