Archipelago » qemu

/*

 * 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"

#define CASE_OP_32_64(x)                        \

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

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

typedef enum {

    TCG_TEMP_UNDEF = 0,

    TCG_TEMP_CONST,

    TCG_TEMP_COPY,

} tcg_temp_state;

struct tcg_temp_info {

    tcg_temp_state state;

    uint16_t prev_copy;

    uint16_t next_copy;

    tcg_target_ulong val;

    tcg_target_ulong mask;

};

static struct tcg_temp_info temps[TCG_MAX_TEMPS];

/* Reset TEMP's state to TCG_TEMP_UNDEF.  If TEMP only had one copy, remove

   the copy flag from the left temp.  */

static void reset_temp(TCGArg temp)

{

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

        if (temps[temp].prev_copy == temps[temp].next_copy) {

            temps[temps[temp].next_copy].state = TCG_TEMP_UNDEF;

        } else {

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

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

        }

    }

    temps[temp].state = TCG_TEMP_UNDEF;

    temps[temp].mask = -1;

}

/* Reset all temporaries, given that there are NB_TEMPS of them.  */

static void reset_all_temps(int nb_temps)

{

    int i;

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

        temps[i].state = TCG_TEMP_UNDEF;

        temps[i].mask = -1;

    }

}

static int op_bits(TCGOpcode op)

{

    const TCGOpDef *def = &tcg_op_defs[op];

    return def->flags & TCG_OPF_64BIT ? 64 : 32;

}

static TCGOpcode op_to_movi(TCGOpcode op)

{

    switch (op_bits(op)) {

    case 32:

        return INDEX_op_movi_i32;

    case 64:

        return INDEX_op_movi_i64;

    default:

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

                "function op_bits.\n");

        tcg_abort();

    }

}

static TCGArg find_better_copy(TCGContext *s, TCGArg temp)

{

    TCGArg i;

    /* If this is already a global, we can't do better. */

    if (temp < s->nb_globals) {

        return temp;

    }

    /* Search for a global first. */

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

        if (i < s->nb_globals) {

            return i;

        }

    }

    /* If it is a temp, search for a temp local. */

    if (!s->temps[temp].temp_local) {

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

            if (s->temps[i].temp_local) {

                return i;

            }

        }

    }

    /* Failure to find a better representation, return the same temp. */

    return temp;

}

static bool temps_are_copies(TCGArg arg1, TCGArg arg2)

{

    TCGArg i;

    if (arg1 == arg2) {

        return true;

    }

    if (temps[arg1].state != TCG_TEMP_COPY

        || temps[arg2].state != TCG_TEMP_COPY) {

        return false;

    }

    for (i = temps[arg1].next_copy ; i != arg1 ; i = temps[i].next_copy) {

        if (i == arg2) {

            return true;

        }

    }

    return false;

}

static void tcg_opt_gen_mov(TCGContext *s, TCGArg *gen_args,

                            TCGArg dst, TCGArg src)

{

    reset_temp(dst);

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

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

    if (s->temps[src].type == s->temps[dst].type) {

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

            temps[src].state = TCG_TEMP_COPY;

            temps[src].next_copy = src;

            temps[src].prev_copy = src;

        }

        temps[dst].state = TCG_TEMP_COPY;

        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)

{

    reset_temp(dst);

    temps[dst].state = TCG_TEMP_CONST;

    temps[dst].val = val;

    temps[dst].mask = val;

    gen_args[0] = dst;

    gen_args[1] = val;

}

static TCGOpcode op_to_mov(TCGOpcode op)

{

    switch (op_bits(op)) {

    case 32:

        return INDEX_op_mov_i32;

    case 64:

        return INDEX_op_mov_i64;

    default:

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

                "function op_bits.\n");

        tcg_abort();

    }

}

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

{

    uint64_t l64, h64;

    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;

    CASE_OP_32_64(and):

        return x & y;

    CASE_OP_32_64(or):

        return x | y;

    CASE_OP_32_64(xor):

        return x ^ y;

    case INDEX_op_shl_i32:

        return (uint32_t)x << (uint32_t)y;

    case INDEX_op_shl_i64:

        return (uint64_t)x << (uint64_t)y;

    case INDEX_op_shr_i32:

        return (uint32_t)x >> (uint32_t)y;

    case INDEX_op_shr_i64:

        return (uint64_t)x >> (uint64_t)y;

    case INDEX_op_sar_i32:

        return (int32_t)x >> (int32_t)y;

    case INDEX_op_sar_i64:

        return (int64_t)x >> (int64_t)y;

    case INDEX_op_rotr_i32:

        x = ((uint32_t)x << (32 - y)) | ((uint32_t)x >> y);

        return x;

    case INDEX_op_rotr_i64:

        x = ((uint64_t)x << (64 - y)) | ((uint64_t)x >> y);

        return x;

    case INDEX_op_rotl_i32:

        x = ((uint32_t)x << y) | ((uint32_t)x >> (32 - y));

        return x;

    case INDEX_op_rotl_i64:

        x = ((uint64_t)x << y) | ((uint64_t)x >> (64 - y));

        return x;

    CASE_OP_32_64(not):

        return ~x;

    CASE_OP_32_64(neg):

        return -x;

    CASE_OP_32_64(andc):

        return x & ~y;

    CASE_OP_32_64(orc):

        return x | ~y;

    CASE_OP_32_64(eqv):

        return ~(x ^ y);

    CASE_OP_32_64(nand):

        return ~(x & y);

    CASE_OP_32_64(nor):

        return ~(x | y);

    CASE_OP_32_64(ext8s):

        return (int8_t)x;

    CASE_OP_32_64(ext16s):

        return (int16_t)x;

    CASE_OP_32_64(ext8u):

        return (uint8_t)x;

    CASE_OP_32_64(ext16u):

        return (uint16_t)x;

    case INDEX_op_ext32s_i64:

        return (int32_t)x;

    case INDEX_op_ext32u_i64:

        return (uint32_t)x;

    case INDEX_op_muluh_i32:

        return ((uint64_t)(uint32_t)x * (uint32_t)y) >> 32;

    case INDEX_op_mulsh_i32:

        return ((int64_t)(int32_t)x * (int32_t)y) >> 32;

    case INDEX_op_muluh_i64:

        mulu64(&l64, &h64, x, y);

        return h64;

    case INDEX_op_mulsh_i64:

        muls64(&l64, &h64, x, y);

        return h64;

    case INDEX_op_div_i32:

        /* Avoid crashing on divide by zero, otherwise undefined.  */

        return (int32_t)x / ((int32_t)y ? : 1);

    case INDEX_op_divu_i32:

        return (uint32_t)x / ((uint32_t)y ? : 1);

    case INDEX_op_div_i64:

        return (int64_t)x / ((int64_t)y ? : 1);

    case INDEX_op_divu_i64:

        return (uint64_t)x / ((uint64_t)y ? : 1);

    case INDEX_op_rem_i32:

        return (int32_t)x % ((int32_t)y ? : 1);

    case INDEX_op_remu_i32:

        return (uint32_t)x % ((uint32_t)y ? : 1);

    case INDEX_op_rem_i64:

        return (int64_t)x % ((int64_t)y ? : 1);

    case INDEX_op_remu_i64:

        return (uint64_t)x % ((uint64_t)y ? : 1);

    default:

        fprintf(stderr,

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

        tcg_abort();

    }

}

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

{

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

    if (op_bits(op) == 32) {

        res &= 0xffffffff;

    }

    return res;

}

static bool do_constant_folding_cond_32(uint32_t x, uint32_t y, TCGCond c)

{

    switch (c) {

    case TCG_COND_EQ:

        return x == y;

    case TCG_COND_NE:

        return x != y;

    case TCG_COND_LT:

        return (int32_t)x < (int32_t)y;

    case TCG_COND_GE:

        return (int32_t)x >= (int32_t)y;

    case TCG_COND_LE:

        return (int32_t)x <= (int32_t)y;

    case TCG_COND_GT:

        return (int32_t)x > (int32_t)y;

    case TCG_COND_LTU:

        return x < y;

    case TCG_COND_GEU:

        return x >= y;

    case TCG_COND_LEU:

        return x <= y;

    case TCG_COND_GTU:

        return x > y;

    default:

        tcg_abort();

    }

}

static bool do_constant_folding_cond_64(uint64_t x, uint64_t y, TCGCond c)

{

    switch (c) {

    case TCG_COND_EQ:

        return x == y;

    case TCG_COND_NE:

        return x != y;

    case TCG_COND_LT:

        return (int64_t)x < (int64_t)y;

    case TCG_COND_GE:

        return (int64_t)x >= (int64_t)y;

    case TCG_COND_LE:

        return (int64_t)x <= (int64_t)y;

    case TCG_COND_GT:

        return (int64_t)x > (int64_t)y;

    case TCG_COND_LTU:

        return x < y;

    case TCG_COND_GEU:

        return x >= y;

    case TCG_COND_LEU:

        return x <= y;

    case TCG_COND_GTU:

        return x > y;

    default:

        tcg_abort();

    }

}

static bool do_constant_folding_cond_eq(TCGCond c)

{

    switch (c) {

    case TCG_COND_GT:

    case TCG_COND_LTU:

    case TCG_COND_LT:

    case TCG_COND_GTU:

    case TCG_COND_NE:

        return 0;

    case TCG_COND_GE:

    case TCG_COND_GEU:

    case TCG_COND_LE:

    case TCG_COND_LEU:

    case TCG_COND_EQ:

        return 1;

    default:

        tcg_abort();

    }

}

/* Return 2 if the condition can't be simplified, and the result

   of the condition (0 or 1) if it can */

static TCGArg do_constant_folding_cond(TCGOpcode op, TCGArg x,

                                       TCGArg y, TCGCond c)

{

    if (temps[x].state == TCG_TEMP_CONST && temps[y].state == TCG_TEMP_CONST) {

        switch (op_bits(op)) {

        case 32:

            return do_constant_folding_cond_32(temps[x].val, temps[y].val, c);

        case 64:

            return do_constant_folding_cond_64(temps[x].val, temps[y].val, c);

        default:

            tcg_abort();

        }

    } else if (temps_are_copies(x, y)) {

        return do_constant_folding_cond_eq(c);

    } else if (temps[y].state == TCG_TEMP_CONST && temps[y].val == 0) {

        switch (c) {

        case TCG_COND_LTU:

            return 0;

        case TCG_COND_GEU:

            return 1;

        default:

            return 2;

        }

    } else {

        return 2;

    }

}

/* Return 2 if the condition can't be simplified, and the result

   of the condition (0 or 1) if it can */

static TCGArg do_constant_folding_cond2(TCGArg *p1, TCGArg *p2, TCGCond c)

{

    TCGArg al = p1[0], ah = p1[1];

    TCGArg bl = p2[0], bh = p2[1];

    if (temps[bl].state == TCG_TEMP_CONST

        && temps[bh].state == TCG_TEMP_CONST) {

        uint64_t b = ((uint64_t)temps[bh].val << 32) | (uint32_t)temps[bl].val;

        if (temps[al].state == TCG_TEMP_CONST

            && temps[ah].state == TCG_TEMP_CONST) {

            uint64_t a;

            a = ((uint64_t)temps[ah].val << 32) | (uint32_t)temps[al].val;

            return do_constant_folding_cond_64(a, b, c);

        }

        if (b == 0) {

            switch (c) {

            case TCG_COND_LTU:

                return 0;

            case TCG_COND_GEU:

                return 1;

            default:

                break;

            }

        }

    }

    if (temps_are_copies(al, bl) && temps_are_copies(ah, bh)) {

        return do_constant_folding_cond_eq(c);

    }

    return 2;

}

static bool swap_commutative(TCGArg dest, TCGArg *p1, TCGArg *p2)

{

    TCGArg a1 = *p1, a2 = *p2;

    int sum = 0;

    sum += temps[a1].state == TCG_TEMP_CONST;

    sum -= temps[a2].state == TCG_TEMP_CONST;

    /* Prefer the constant in second argument, and then the form

       op a, a, b, which is better handled on non-RISC hosts. */

    if (sum > 0 || (sum == 0 && dest == a2)) {

        *p1 = a2;

        *p2 = a1;

        return true;

    }

    return false;

}

static bool swap_commutative2(TCGArg *p1, TCGArg *p2)

{

    int sum = 0;

    sum += temps[p1[0]].state == TCG_TEMP_CONST;

    sum += temps[p1[1]].state == TCG_TEMP_CONST;

    sum -= temps[p2[0]].state == TCG_TEMP_CONST;

    sum -= temps[p2[1]].state == TCG_TEMP_CONST;

    if (sum > 0) {

        TCGArg t;

        t = p1[0], p1[0] = p2[0], p2[0] = t;

        t = p1[1], p1[1] = p2[1], p2[1] = t;

        return true;

    }

    return false;

}

/* 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, nb_temps, nb_globals, nb_call_args;

    tcg_target_ulong mask, affected;

    TCGOpcode op;

    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 the other copies are

       available through the doubly linked circular list. */

    nb_temps = s->nb_temps;

    nb_globals = s->nb_globals;

    reset_all_temps(nb_temps);

    nb_ops = tcg_opc_ptr - s->gen_opc_buf;

    gen_args = args;

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

        op = s->gen_opc_buf[op_index];

        def = &tcg_op_defs[op];

        /* Do copy propagation */

        if (op == INDEX_op_call) {

            int nb_oargs = args[0] >> 16;

            int nb_iargs = args[0] & 0xffff;

            for (i = nb_oargs + 1; i < nb_oargs + nb_iargs + 1; i++) {

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

                    args[i] = find_better_copy(s, args[i]);

                }

            }

        } else {

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

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

                    args[i] = find_better_copy(s, args[i]);

                }

            }

        }

        /* For commutative operations make constant second argument */

        switch (op) {

        CASE_OP_32_64(add):

        CASE_OP_32_64(mul):

        CASE_OP_32_64(and):

        CASE_OP_32_64(or):

        CASE_OP_32_64(xor):

        CASE_OP_32_64(eqv):

        CASE_OP_32_64(nand):

        CASE_OP_32_64(nor):

        CASE_OP_32_64(muluh):

        CASE_OP_32_64(mulsh):

            swap_commutative(args[0], &args[1], &args[2]);

            break;

        CASE_OP_32_64(brcond):

            if (swap_commutative(-1, &args[0], &args[1])) {

                args[2] = tcg_swap_cond(args[2]);

            }

            break;

        CASE_OP_32_64(setcond):

            if (swap_commutative(args[0], &args[1], &args[2])) {

                args[3] = tcg_swap_cond(args[3]);

            }

            break;

        CASE_OP_32_64(movcond):

            if (swap_commutative(-1, &args[1], &args[2])) {

                args[5] = tcg_swap_cond(args[5]);

            }

            /* For movcond, we canonicalize the "false" input reg to match

               the destination reg so that the tcg backend can implement

               a "move if true" operation.  */

            if (swap_commutative(args[0], &args[4], &args[3])) {

                args[5] = tcg_invert_cond(args[5]);

            }

            break;

        CASE_OP_32_64(add2):

            swap_commutative(args[0], &args[2], &args[4]);

            swap_commutative(args[1], &args[3], &args[5]);

            break;

        CASE_OP_32_64(mulu2):

        CASE_OP_32_64(muls2):

            swap_commutative(args[0], &args[2], &args[3]);

            break;

        case INDEX_op_brcond2_i32:

            if (swap_commutative2(&args[0], &args[2])) {

                args[4] = tcg_swap_cond(args[4]);

            }

            break;

        case INDEX_op_setcond2_i32:

            if (swap_commutative2(&args[1], &args[3])) {

                args[5] = tcg_swap_cond(args[5]);

            }

            break;

        default:

            break;

        }

        /* Simplify expressions for "shift/rot r, 0, a => movi r, 0",

           and "sub r, 0, a => neg r, a" case.  */

        switch (op) {

        CASE_OP_32_64(shl):

        CASE_OP_32_64(shr):

        CASE_OP_32_64(sar):

        CASE_OP_32_64(rotl):

        CASE_OP_32_64(rotr):

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

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

                s->gen_opc_buf[op_index] = op_to_movi(op);

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

                args += 3;

                gen_args += 2;

                continue;

            }

            break;

        CASE_OP_32_64(sub):

            {

                TCGOpcode neg_op;

                bool have_neg;

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

                    /* Proceed with possible constant folding. */

                    break;

                }

                if (op == INDEX_op_sub_i32) {

                    neg_op = INDEX_op_neg_i32;

                    have_neg = TCG_TARGET_HAS_neg_i32;

                } else {

                    neg_op = INDEX_op_neg_i64;

                    have_neg = TCG_TARGET_HAS_neg_i64;

                }

                if (!have_neg) {

                    break;

                }

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

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

                    s->gen_opc_buf[op_index] = neg_op;

                    reset_temp(args[0]);

                    gen_args[0] = args[0];

                    gen_args[1] = args[2];

                    args += 3;

                    gen_args += 2;

                    continue;

                }

            }

            break;

        default:

            break;

        }

        /* Simplify expression for "op r, a, 0 => mov r, a" cases */

        switch (op) {

        CASE_OP_32_64(add):

        CASE_OP_32_64(sub):

        CASE_OP_32_64(shl):

        CASE_OP_32_64(shr):

        CASE_OP_32_64(sar):

        CASE_OP_32_64(rotl):

        CASE_OP_32_64(rotr):

        CASE_OP_32_64(or):

        CASE_OP_32_64(xor):

            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_are_copies(args[0], args[1])) {

                    s->gen_opc_buf[op_index] = INDEX_op_nop;

                } else {

                    s->gen_opc_buf[op_index] = op_to_mov(op);

                    tcg_opt_gen_mov(s, gen_args, args[0], args[1]);

                    gen_args += 2;

                }

                args += 3;

                continue;

            }

            break;

        default:

            break;

        }

        /* Simplify using known-zero bits */

        mask = -1;

        affected = -1;

        switch (op) {

        CASE_OP_32_64(ext8s):

            if ((temps[args[1]].mask & 0x80) != 0) {

                break;

            }

        CASE_OP_32_64(ext8u):

            mask = 0xff;

            goto and_const;

        CASE_OP_32_64(ext16s):

            if ((temps[args[1]].mask & 0x8000) != 0) {

                break;

            }

        CASE_OP_32_64(ext16u):

            mask = 0xffff;

            goto and_const;

        case INDEX_op_ext32s_i64:

            if ((temps[args[1]].mask & 0x80000000) != 0) {

                break;

            }

        case INDEX_op_ext32u_i64:

            mask = 0xffffffffU;

            goto and_const;

        CASE_OP_32_64(and):

            mask = temps[args[2]].mask;

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

        and_const:

                affected = temps[args[1]].mask & ~mask;

            }

            mask = temps[args[1]].mask & mask;

            break;

        CASE_OP_32_64(sar):

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

                mask = ((tcg_target_long)temps[args[1]].mask

                        >> temps[args[2]].val);

            }

            break;

        CASE_OP_32_64(shr):

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

                mask = temps[args[1]].mask >> temps[args[2]].val;

            }

            break;

        CASE_OP_32_64(shl):

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

                mask = temps[args[1]].mask << temps[args[2]].val;

            }

            break;

        CASE_OP_32_64(neg):

            /* Set to 1 all bits to the left of the rightmost.  */

            mask = -(temps[args[1]].mask & -temps[args[1]].mask);

            break;

        CASE_OP_32_64(deposit):

            tmp = ((1ull << args[4]) - 1);

            mask = ((temps[args[1]].mask & ~(tmp << args[3]))

                    | ((temps[args[2]].mask & tmp) << args[3]));

            break;

        CASE_OP_32_64(or):

        CASE_OP_32_64(xor):

            mask = temps[args[1]].mask | temps[args[2]].mask;

            break;

        CASE_OP_32_64(setcond):

            mask = 1;

            break;

        CASE_OP_32_64(movcond):

            mask = temps[args[3]].mask | temps[args[4]].mask;

            break;

        default:

            break;

        }

        if (mask == 0) {

            assert(def->nb_oargs == 1);

            s->gen_opc_buf[op_index] = op_to_movi(op);

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

            args += def->nb_oargs + def->nb_iargs + def->nb_cargs;

            gen_args += 2;

            continue;

        }

        if (affected == 0) {

            assert(def->nb_oargs == 1);

            if (temps_are_copies(args[0], args[1])) {

                s->gen_opc_buf[op_index] = INDEX_op_nop;

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

                s->gen_opc_buf[op_index] = op_to_mov(op);

                tcg_opt_gen_mov(s, gen_args, args[0], args[1]);

                gen_args += 2;

            } else {

                s->gen_opc_buf[op_index] = op_to_movi(op);

                tcg_opt_gen_movi(gen_args, args[0], temps[args[1]].val);

                gen_args += 2;

            }

            args += def->nb_iargs + 1;

            continue;

        }

        /* Simplify expression for "op r, a, 0 => movi r, 0" cases */

        switch (op) {

        CASE_OP_32_64(and):

        CASE_OP_32_64(mul):

        CASE_OP_32_64(muluh):

        CASE_OP_32_64(mulsh):

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

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

                s->gen_opc_buf[op_index] = op_to_movi(op);

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

                args += 3;

                gen_args += 2;

                continue;

            }

            break;

        default:

            break;

        }

        /* Simplify expression for "op r, a, a => mov r, a" cases */

        switch (op) {

        CASE_OP_32_64(or):

        CASE_OP_32_64(and):

            if (temps_are_copies(args[1], args[2])) {

                if (temps_are_copies(args[0], args[1])) {

                    s->gen_opc_buf[op_index] = INDEX_op_nop;

                } else {

                    s->gen_opc_buf[op_index] = op_to_mov(op);

                    tcg_opt_gen_mov(s, gen_args, args[0], args[1]);

                    gen_args += 2;

                }

                args += 3;

                continue;

            }

            break;

        default:

            break;

        }

        /* Simplify expression for "op r, a, a => movi r, 0" cases */

        switch (op) {

        CASE_OP_32_64(sub):

        CASE_OP_32_64(xor):

            if (temps_are_copies(args[1], args[2])) {

                s->gen_opc_buf[op_index] = op_to_movi(op);

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

                gen_args += 2;

                args += 3;

                continue;

            }

            break;

        default:

            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_are_copies(args[0], args[1])) {

                args += 2;

                s->gen_opc_buf[op_index] = INDEX_op_nop;

                break;

            }

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

                tcg_opt_gen_mov(s, gen_args, args[0], args[1]);

                gen_args += 2;

                args += 2;

                break;

            }

            /* Source argument is constant.  Rewrite the operation and

               let movi case handle it. */

            op = op_to_movi(op);

            s->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]);

            gen_args += 2;

            args += 2;

            break;

        CASE_OP_32_64(not):

        CASE_OP_32_64(neg):

        CASE_OP_32_64(ext8s):

        CASE_OP_32_64(ext8u):

        CASE_OP_32_64(ext16s):

        CASE_OP_32_64(ext16u):

        case INDEX_op_ext32s_i64:

        case INDEX_op_ext32u_i64:

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

                s->gen_opc_buf[op_index] = op_to_movi(op);

                tmp = do_constant_folding(op, temps[args[1]].val, 0);

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

                gen_args += 2;

                args += 2;

                break;