/*
 * Copyright (C) 2019 Alyssa Rosenzweig <alyssa@rosenzweig.io>
 *
 * 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 "compiler.h"

void mir_rewrite_index_src_single(midgard_instruction *ins, unsigned old, unsigned new)
{
        if (ins->ssa_args.src0 == old)
                ins->ssa_args.src0 = new;

        if (ins->ssa_args.src1 == old &&
            !ins->ssa_args.inline_constant)
                ins->ssa_args.src1 = new;
}


void
mir_rewrite_index_src(compiler_context *ctx, unsigned old, unsigned new)
{
        mir_foreach_instr_global(ctx, ins) {
                mir_rewrite_index_src_single(ins, old, new);
        }
}

void
mir_rewrite_index_dst(compiler_context *ctx, unsigned old, unsigned new)
{
        mir_foreach_instr_global(ctx, ins) {
                if (ins->ssa_args.dest == old)
                        ins->ssa_args.dest = new;
        }
}

void
mir_rewrite_index(compiler_context *ctx, unsigned old, unsigned new)
{
        mir_rewrite_index_src(ctx, old, new);
        mir_rewrite_index_dst(ctx, old, new);
}

/* Checks if a value is used only once (or totally dead), which is an important
 * heuristic to figure out if certain optimizations are Worth It (TM) */

bool
mir_single_use(compiler_context *ctx, unsigned value)
{
        unsigned used_count = 0;

        mir_foreach_instr_global(ctx, ins) {
                if (mir_has_arg(ins, value))
                        ++used_count;

                /* Short circuit for speed */
                if (used_count > 1)
                        return false;
        }

        return used_count <= 1;

}