/*
 * Copyright (C) 2010 Marek Olšák <maraeo@gmail.com>
 *
 * All Rights Reserved.
 *
 * 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 COPYRIGHT OWNER(S) AND/OR ITS SUPPLIERS 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 "radeon_remove_constants.h"

void rc_remove_unused_constants(struct radeon_compiler *c, void *user)
{
	unsigned **out_remap_table = (unsigned**)user;
        unsigned char *const_used;
        unsigned *remap_table;
        unsigned *inv_remap_table;
        unsigned has_rel_addr = 0;
        unsigned is_identity = 1;
	unsigned are_externals_remapped = 0;
        struct rc_constant *constants = c->Program.Constants.Constants;

        if (!c->Program.Constants.Count) {
                *out_remap_table = NULL;
                return;
        }

        const_used = malloc(c->Program.Constants.Count);
        memset(const_used, 0, c->Program.Constants.Count);

	/* Pass 1: Mark used constants. */
        for (struct rc_instruction *inst = c->Program.Instructions.Next;
             inst != &c->Program.Instructions; inst = inst->Next) {
                const struct rc_opcode_info *opcode = rc_get_opcode_info(inst->U.I.Opcode);

                for (unsigned i = 0; i < opcode->NumSrcRegs; i++) {
                        if (inst->U.I.SrcReg[i].File == RC_FILE_CONSTANT) {
                                if (inst->U.I.SrcReg[i].RelAddr) {
                                        has_rel_addr = 1;
                                } else {
                                        const_used[inst->U.I.SrcReg[i].Index] = 1;
                                }
                        }
                }
        }

        /* Pass 2: If there is relative addressing, mark all externals as used. */
        if (has_rel_addr) {
                for (unsigned i = 0; i < c->Program.Constants.Count; i++)
                        if (constants[i].Type == RC_CONSTANT_EXTERNAL)
                                const_used[i] = 1;
        }

        /* Pass 3: Make the remapping table and remap constants.
	 * This pass removes unused constants simply by overwriting them by other constants. */
        remap_table = malloc(c->Program.Constants.Count * sizeof(unsigned));
        inv_remap_table = malloc(c->Program.Constants.Count * sizeof(unsigned));
        unsigned new_count = 0;

        for (unsigned i = 0; i < c->Program.Constants.Count; i++) {
                if (const_used[i]) {
                        remap_table[new_count] = i;
                        inv_remap_table[i] = new_count;

                        if (i != new_count) {
				if (constants[i].Type == RC_CONSTANT_EXTERNAL)
					are_externals_remapped = 1;

				constants[new_count] = constants[i];
                                is_identity = 0;
                        }
                        new_count++;
                }
        }

	/*  is_identity ==> new_count == old_count
	 * !is_identity ==> new_count <  old_count */
	assert( is_identity || new_count <  c->Program.Constants.Count);
	assert(!(has_rel_addr && are_externals_remapped));

        /* Pass 4: Redirect reads of all constants to their new locations. */
        if (!is_identity) {
                for (struct rc_instruction *inst = c->Program.Instructions.Next;
                     inst != &c->Program.Instructions; inst = inst->Next) {
                        const struct rc_opcode_info *opcode = rc_get_opcode_info(inst->U.I.Opcode);

                        for (unsigned i = 0; i < opcode->NumSrcRegs; i++) {
                                if (inst->U.I.SrcReg[i].File == RC_FILE_CONSTANT) {
                                        inst->U.I.SrcReg[i].Index = inv_remap_table[inst->U.I.SrcReg[i].Index];
                                }
                        }
                }

	}

	/* Set the new constant count. Note that new_count may be less than
	 * Count even though the remapping function is identity. In that case,
	 * the constants have been removed at the end of the array. */
	c->Program.Constants.Count = new_count;

	if (are_externals_remapped) {
                *out_remap_table = remap_table;
        } else {
                *out_remap_table = NULL;
                free(remap_table);
        }

        free(const_used);
        free(inv_remap_table);
}