fpu_aux.c

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/*---------------------------------------------------------------------------+
 |  fpu_aux.c                                                                |
 |                                                                           |
 | Code to implement some of the FPU auxiliary instructions.                 |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1997                                         |
 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
 |                  E-mail   [email protected]                              |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "status_w.h"
#include "control_w.h"

static void fnop(void)
{
}

static void fclex(void)
{
    partial_status &=
        ~(SW_Backward | SW_Summary | SW_Stack_Fault | SW_Precision |
          SW_Underflow | SW_Overflow | SW_Zero_Div | SW_Denorm_Op |
          SW_Invalid);
    no_ip_update = 1;
}

/* Needs to be externally visible */
void finit_soft_fpu(struct i387_soft_struct *soft)
{
    struct address *oaddr, *iaddr;
    memset(soft, 0, sizeof(*soft));
    soft->cwd = 0x037f;
    soft->swd = 0;
    soft->ftop = 0; /* We don't keep top in the status word internally. */
    soft->twd = 0xffff;
    /* The behaviour is different from that detailed in
       Section 15.1.6 of the Intel manual */
    oaddr = (struct address *)&soft->foo;
    oaddr->offset = 0;
    oaddr->selector = 0;
    iaddr = (struct address *)&soft->fip;
    iaddr->offset = 0;
    iaddr->selector = 0;
    iaddr->opcode = 0;
    soft->no_update = 1;
}

void finit(void)
{
    finit_soft_fpu(&current->thread.fpu.state->soft);
}

/*
 * These are nops on the i387..
 */
#define feni fnop
#define fdisi fnop
#define fsetpm fnop

static FUNC const finit_table[] = {
    feni, fdisi, fclex, finit,
    fsetpm, FPU_illegal, FPU_illegal, FPU_illegal
};

void finit_(void)
{
    (finit_table[FPU_rm]) ();
}

static void fstsw_ax(void)
{
    *(short *)&FPU_EAX = status_word();
    no_ip_update = 1;
}

static FUNC const fstsw_table[] = {
    fstsw_ax, FPU_illegal, FPU_illegal, FPU_illegal,
    FPU_illegal, FPU_illegal, FPU_illegal, FPU_illegal
};

void fstsw_(void)
{
    (fstsw_table[FPU_rm]) ();
}

static FUNC const fp_nop_table[] = {
    fnop, FPU_illegal, FPU_illegal, FPU_illegal,
    FPU_illegal, FPU_illegal, FPU_illegal, FPU_illegal
};

void fp_nop(void)
{
    (fp_nop_table[FPU_rm]) ();
}

void fld_i_(void)
{
    FPU_REG *st_new_ptr;
    int i;
    u_char tag;

    if (STACK_OVERFLOW) {
        FPU_stack_overflow();
        return;
    }

    /* fld st(i) */
    i = FPU_rm;
    if (NOT_EMPTY(i)) {
        reg_copy(&st(i), st_new_ptr);
        tag = FPU_gettagi(i);
        push();
        FPU_settag0(tag);
    } else {
        if (control_word & CW_Invalid) {
            /* The masked response */
            FPU_stack_underflow();
        } else
            EXCEPTION(EX_StackUnder);
    }

}

void fxch_i(void)
{
    /* fxch st(i) */
    FPU_REG t;
    int i = FPU_rm;
    FPU_REG *st0_ptr = &st(0), *sti_ptr = &st(i);
    long tag_word = fpu_tag_word;
    int regnr = top & 7, regnri = ((regnr + i) & 7);
    u_char st0_tag = (tag_word >> (regnr * 2)) & 3;
    u_char sti_tag = (tag_word >> (regnri * 2)) & 3;

    if (st0_tag == TAG_Empty) {
        if (sti_tag == TAG_Empty) {
            FPU_stack_underflow();
            FPU_stack_underflow_i(i);
            return;
        }
        if (control_word & CW_Invalid) {
            /* Masked response */
            FPU_copy_to_reg0(sti_ptr, sti_tag);
        }
        FPU_stack_underflow_i(i);
        return;
    }
    if (sti_tag == TAG_Empty) {
        if (control_word & CW_Invalid) {
            /* Masked response */
            FPU_copy_to_regi(st0_ptr, st0_tag, i);
        }
        FPU_stack_underflow();
        return;
    }
    clear_C1();

    reg_copy(st0_ptr, &t);
    reg_copy(sti_ptr, st0_ptr);
    reg_copy(&t, sti_ptr);

    tag_word &= ~(3 << (regnr * 2)) & ~(3 << (regnri * 2));
    tag_word |= (sti_tag << (regnr * 2)) | (st0_tag << (regnri * 2));
    fpu_tag_word = tag_word;
}

void ffree_(void)
{
    /* ffree st(i) */
    FPU_settagi(FPU_rm, TAG_Empty);
}

void ffreep(void)
{
    /* ffree st(i) + pop - unofficial code */
    FPU_settagi(FPU_rm, TAG_Empty);
    FPU_pop();
}

void fst_i_(void)
{
    /* fst st(i) */
    FPU_copy_to_regi(&st(0), FPU_gettag0(), FPU_rm);
}

void fstp_i(void)
{
    /* fstp st(i) */
    FPU_copy_to_regi(&st(0), FPU_gettag0(), FPU_rm);
    FPU_pop();
}