kvisc/vm/in/string.c

// The OS/K Team licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

#include <in/instrs.h>

//----------------------------------------------------------------------------//

#define STR_MOVE(reg, len)                                                  \
    if (!(R(RFX) & DF)) R(reg) += len;                                      \
    else R(reg) -= len;

//----------------------------------------------------------------------------//

static void stos_impl(ctx_t *ctx, acc_t *p1, acc_t *p2, uint len)
{
    if (p1->type != A_REG)
        _except(ctx, E_ILL, "STOSX given a non-REG operand");

    writemem(ctx, p2->val, R(p1->reg), len);
    STR_MOVE(p1->reg, len);
}

IMPL_START(stosb) { stos_impl(ctx, p1, p2, 1); return 0; }
IMPL_START(stosw) { stos_impl(ctx, p1, p2, 2); return 0; }
IMPL_START(stosd) { stos_impl(ctx, p1, p2, 4); return 0; }
IMPL_START(stosq) { stos_impl(ctx, p1, p2, 8); return 0; }

//----------------------------------------------------------------------------//

static void scas_impl(ctx_t *ctx, acc_t *p1, acc_t *p2, uint len)
{
    if (p1->type != A_REG)
        _except(ctx, E_ILL, "SCASX given a non-REG operand");

    ulong x = readmemsx(ctx, R(p1->reg), len);
    COMPARE_SUB(x, p2->val);

    if (x == 0) {
        R(RFX) |= ZF;
    }

    else if (!(R(RFX)&ZF)) {
        STR_MOVE(p1->reg, len);
    }
}

IMPL_START(scasb) { scas_impl(ctx, p1, p2, 1); return 0; }
IMPL_START(scasw) { scas_impl(ctx, p1, p2, 2); return 0; }
IMPL_START(scasd) { scas_impl(ctx, p1, p2, 4); return 0; }
IMPL_START(scasq) { scas_impl(ctx, p1, p2, 8); return 0; }

//----------------------------------------------------------------------------//