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/*

 * Optimizations for Tiny Code Generator for QEMU

 *

 * Copyright (c) 2010 Samsung Electronics.

 * Contributed by Kirill Batuzov <batuzovk@ispras.ru>

 *

 * 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 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 "config.h"

#include <stdlib.h>

#include <stdio.h>

#include "qemu-common.h"

#include "tcg-op.h"

#if TCG_TARGET_REG_BITS == 64

#define CASE_OP_32_64(x)                        \

        glue(glue(case INDEX_op_, x), _i32):    \

        glue(glue(case INDEX_op_, x), _i64)

#else

#define CASE_OP_32_64(x)                        \

        glue(glue(case INDEX_op_, x), _i32)

#endif

typedef enum {

    TCG_TEMP_UNDEF = 0,

    TCG_TEMP_CONST,

    TCG_TEMP_COPY,

    TCG_TEMP_HAS_COPY,

    TCG_TEMP_ANY

} tcg_temp_state;

struct tcg_temp_info {

    tcg_temp_state state;

    uint16_t prev_copy;

    uint16_t next_copy;

    tcg_target_ulong val;

};

static struct tcg_temp_info temps[TCG_MAX_TEMPS];

/* Reset TEMP's state to TCG_TEMP_ANY.  If TEMP was a representative of some

   class of equivalent temp's, a new representative should be chosen in this

   class. */

static void reset_temp(TCGArg temp, int nb_temps, int nb_globals)

{

    int i;

    TCGArg new_base = (TCGArg)-1;

    if (temps[temp].state == TCG_TEMP_HAS_COPY) {

        for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {

            if (i >= nb_globals) {

                temps[i].state = TCG_TEMP_HAS_COPY;

                new_base = i;

                break;

            }

        }

        for (i = temps[temp].next_copy; i != temp; i = temps[i].next_copy) {

            if (new_base == (TCGArg)-1) {

                temps[i].state = TCG_TEMP_ANY;

            } else {

                temps[i].val = new_base;

            }

        }

        temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;

        temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;

    } else if (temps[temp].state == TCG_TEMP_COPY) {

        temps[temps[temp].next_copy].prev_copy = temps[temp].prev_copy;

        temps[temps[temp].prev_copy].next_copy = temps[temp].next_copy;

        new_base = temps[temp].val;

    }

    temps[temp].state = TCG_TEMP_ANY;

    if (new_base != (TCGArg)-1 && temps[new_base].next_copy == new_base) {

        temps[new_base].state = TCG_TEMP_ANY;

    }

}

static int op_bits(int op)

{

    switch (op) {

    case INDEX_op_mov_i32:

    case INDEX_op_add_i32:

    case INDEX_op_sub_i32:

    case INDEX_op_mul_i32:

        return 32;

#if TCG_TARGET_REG_BITS == 64

    case INDEX_op_mov_i64:

    case INDEX_op_add_i64:

    case INDEX_op_sub_i64:

    case INDEX_op_mul_i64:

        return 64;

#endif

    default:

        fprintf(stderr, "Unrecognized operation %d in op_bits.\n", op);

        tcg_abort();

    }

}

static int op_to_movi(int op)

{

    switch (op_bits(op)) {

    case 32:

        return INDEX_op_movi_i32;

#if TCG_TARGET_REG_BITS == 64

    case 64:

        return INDEX_op_movi_i64;

#endif

    default:

        fprintf(stderr, "op_to_movi: unexpected return value of "

                "function op_bits.\n");

        tcg_abort();

    }

}

static void tcg_opt_gen_mov(TCGArg *gen_args, TCGArg dst, TCGArg src,

                            int nb_temps, int nb_globals)

{

        reset_temp(dst, nb_temps, nb_globals);

        assert(temps[src].state != TCG_TEMP_COPY);

        if (src >= nb_globals) {

            assert(temps[src].state != TCG_TEMP_CONST);

            if (temps[src].state != TCG_TEMP_HAS_COPY) {

                temps[src].state = TCG_TEMP_HAS_COPY;

                temps[src].next_copy = src;

                temps[src].prev_copy = src;

            }

            temps[dst].state = TCG_TEMP_COPY;

            temps[dst].val = src;

            temps[dst].next_copy = temps[src].next_copy;

            temps[dst].prev_copy = src;

            temps[temps[dst].next_copy].prev_copy = dst;

            temps[src].next_copy = dst;

        }

        gen_args[0] = dst;

        gen_args[1] = src;

}

static void tcg_opt_gen_movi(TCGArg *gen_args, TCGArg dst, TCGArg val,

                             int nb_temps, int nb_globals)

{

        reset_temp(dst, nb_temps, nb_globals);

        temps[dst].state = TCG_TEMP_CONST;

        temps[dst].val = val;

        gen_args[0] = dst;

        gen_args[1] = val;

}

static int op_to_mov(int op)

{

    switch (op_bits(op)) {

    case 32:

        return INDEX_op_mov_i32;

#if TCG_TARGET_REG_BITS == 64

    case 64:

        return INDEX_op_mov_i64;

#endif

    default:

        fprintf(stderr, "op_to_mov: unexpected return value of "

                "function op_bits.\n");

        tcg_abort();

    }

}

static TCGArg do_constant_folding_2(int op, TCGArg x, TCGArg y)

{

    switch (op) {

    CASE_OP_32_64(add):

        return x + y;

    CASE_OP_32_64(sub):

        return x - y;

    CASE_OP_32_64(mul):

        return x * y;

    default:

        fprintf(stderr,

                "Unrecognized operation %d in do_constant_folding.\n", op);

        tcg_abort();

    }

}

static TCGArg do_constant_folding(int op, TCGArg x, TCGArg y)

{

    TCGArg res = do_constant_folding_2(op, x, y);

#if TCG_TARGET_REG_BITS == 64

    if (op_bits(op) == 32) {

        res &= 0xffffffff;

    }

#endif

    return res;

}

/* Propagate constants and copies, fold constant expressions. */

static TCGArg *tcg_constant_folding(TCGContext *s, uint16_t *tcg_opc_ptr,

                                    TCGArg *args, TCGOpDef *tcg_op_defs)

{

    int i, nb_ops, op_index, op, nb_temps, nb_globals, nb_call_args;

    const TCGOpDef *def;

    TCGArg *gen_args;

    TCGArg tmp;

    /* Array VALS has an element for each temp.

       If this temp holds a constant then its value is kept in VALS' element.

       If this temp is a copy of other ones then this equivalence class'

       representative is kept in VALS' element.

       If this temp is neither copy nor constant then corresponding VALS'

       element is unused. */

    nb_temps = s->nb_temps;

    nb_globals = s->nb_globals;

    memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));

    nb_ops = tcg_opc_ptr - gen_opc_buf;

    gen_args = args;

    for (op_index = 0; op_index < nb_ops; op_index++) {

        op = gen_opc_buf[op_index];

        def = &tcg_op_defs[op];

        /* Do copy propagation */

        if (!(def->flags & (TCG_OPF_CALL_CLOBBER | TCG_OPF_SIDE_EFFECTS))) {

            assert(op != INDEX_op_call);

            for (i = def->nb_oargs; i < def->nb_oargs + def->nb_iargs; i++) {

                if (temps[args[i]].state == TCG_TEMP_COPY) {

                    args[i] = temps[args[i]].val;

                }

            }

        }

        /* For commutative operations make constant second argument */

        switch (op) {

        CASE_OP_32_64(add):

        CASE_OP_32_64(mul):

            if (temps[args[1]].state == TCG_TEMP_CONST) {

                tmp = args[1];

                args[1] = args[2];

                args[2] = tmp;

            }

            break;

        default:

            break;

        }

        /* Simplify expression if possible. */

        switch (op) {

        CASE_OP_32_64(add):

        CASE_OP_32_64(sub):

            if (temps[args[1]].state == TCG_TEMP_CONST) {

                /* Proceed with possible constant folding. */

                break;

            }

            if (temps[args[2]].state == TCG_TEMP_CONST

                && temps[args[2]].val == 0) {

                if ((temps[args[0]].state == TCG_TEMP_COPY

                    && temps[args[0]].val == args[1])

                    || args[0] == args[1]) {

                    args += 3;

                    gen_opc_buf[op_index] = INDEX_op_nop;

                } else {

                    gen_opc_buf[op_index] = op_to_mov(op);

                    tcg_opt_gen_mov(gen_args, args[0], args[1],

                                    nb_temps, nb_globals);

                    gen_args += 2;

                    args += 3;

                }

                continue;

            }

            break;

        CASE_OP_32_64(mul):

            if ((temps[args[2]].state == TCG_TEMP_CONST

                && temps[args[2]].val == 0)) {

                gen_opc_buf[op_index] = op_to_movi(op);

                tcg_opt_gen_movi(gen_args, args[0], 0, nb_temps, nb_globals);

                args += 3;

                gen_args += 2;

                continue;

            }

            break;

        }

        /* Propagate constants through copy operations and do constant

           folding.  Constants will be substituted to arguments by register

           allocator where needed and possible.  Also detect copies. */

        switch (op) {

        CASE_OP_32_64(mov):

            if ((temps[args[1]].state == TCG_TEMP_COPY

                && temps[args[1]].val == args[0])

                || args[0] == args[1]) {

                args += 2;

                gen_opc_buf[op_index] = INDEX_op_nop;

                break;

            }

            if (temps[args[1]].state != TCG_TEMP_CONST) {

                tcg_opt_gen_mov(gen_args, args[0], args[1],

                                nb_temps, nb_globals);

                gen_args += 2;

                args += 2;

                break;

            }

            /* Source argument is constant.  Rewrite the operation and

               let movi case handle it. */

            op = op_to_movi(op);

            gen_opc_buf[op_index] = op;

            args[1] = temps[args[1]].val;

            /* fallthrough */

        CASE_OP_32_64(movi):

            tcg_opt_gen_movi(gen_args, args[0], args[1], nb_temps, nb_globals);

            gen_args += 2;

            args += 2;

            break;

        CASE_OP_32_64(add):

        CASE_OP_32_64(sub):

        CASE_OP_32_64(mul):

            if (temps[args[1]].state == TCG_TEMP_CONST

                && temps[args[2]].state == TCG_TEMP_CONST) {

                gen_opc_buf[op_index] = op_to_movi(op);

                tmp = do_constant_folding(op, temps[args[1]].val,

                                          temps[args[2]].val);

                tcg_opt_gen_movi(gen_args, args[0], tmp, nb_temps, nb_globals);

                gen_args += 2;

                args += 3;

                break;

            } else {

                reset_temp(args[0], nb_temps, nb_globals);

                gen_args[0] = args[0];

                gen_args[1] = args[1];

                gen_args[2] = args[2];

                gen_args += 3;

                args += 3;

                break;

            }

        case INDEX_op_call:

            nb_call_args = (args[0] >> 16) + (args[0] & 0xffff);

            if (!(args[nb_call_args + 1] & (TCG_CALL_CONST | TCG_CALL_PURE))) {

                for (i = 0; i < nb_globals; i++) {

                    reset_temp(i, nb_temps, nb_globals);

                }

            }

            for (i = 0; i < (args[0] >> 16); i++) {

                reset_temp(args[i + 1], nb_temps, nb_globals);

            }

            i = nb_call_args + 3;

            while (i) {

                *gen_args = *args;

                args++;

                gen_args++;

                i--;

            }

            break;

        case INDEX_op_set_label:

        case INDEX_op_jmp:

        case INDEX_op_br:

        CASE_OP_32_64(brcond):

            memset(temps, 0, nb_temps * sizeof(struct tcg_temp_info));

            for (i = 0; i < def->nb_args; i++) {

                *gen_args = *args;

                args++;

                gen_args++;

            }

            break;

        default:

            /* Default case: we do know nothing about operation so no

               propagation is done.  We only trash output args.  */

            for (i = 0; i < def->nb_oargs; i++) {

                reset_temp(args[i], nb_temps, nb_globals);

            }

            for (i = 0; i < def->nb_args; i++) {

                gen_args[i] = args[i];

            }

            args += def->nb_args;

            gen_args += def->nb_args;

            break;

        }

    }

    return gen_args;

}

TCGArg *tcg_optimize(TCGContext *s, uint16_t *tcg_opc_ptr,

        TCGArg *args, TCGOpDef *tcg_op_defs)

{

    TCGArg *res;

    res = tcg_constant_folding(s, tcg_opc_ptr, args, tcg_op_defs);

    return res;

}