351 lines
8.1 KiB
C
351 lines
8.1 KiB
C
/*---------------------------------------------------------------------------+
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| reg_compare.c |
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| Compare two floating point registers |
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| Copyright (C) 1992,1993,1994,1997 |
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| W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
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| E-mail billm@suburbia.net |
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+---------------------------------------------------------------------------*/
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/*---------------------------------------------------------------------------+
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| compare() is the core FPU_REG comparison function |
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+---------------------------------------------------------------------------*/
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#include "fpu_system.h"
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#include "exception.h"
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#include "fpu_emu.h"
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#include "control_w.h"
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#include "status_w.h"
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static int compare(FPU_REG const *b, int tagb)
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{
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int diff, exp0, expb;
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u_char st0_tag;
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FPU_REG *st0_ptr;
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FPU_REG x, y;
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u_char st0_sign, signb = getsign(b);
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st0_ptr = &st(0);
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st0_tag = FPU_gettag0();
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st0_sign = getsign(st0_ptr);
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if (tagb == TAG_Special)
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tagb = FPU_Special(b);
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if (st0_tag == TAG_Special)
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st0_tag = FPU_Special(st0_ptr);
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if (((st0_tag != TAG_Valid) && (st0_tag != TW_Denormal))
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|| ((tagb != TAG_Valid) && (tagb != TW_Denormal))) {
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if (st0_tag == TAG_Zero) {
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if (tagb == TAG_Zero)
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return COMP_A_eq_B;
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if (tagb == TAG_Valid)
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return ((signb ==
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SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
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if (tagb == TW_Denormal)
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return ((signb ==
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SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
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| COMP_Denormal;
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} else if (tagb == TAG_Zero) {
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if (st0_tag == TAG_Valid)
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return ((st0_sign ==
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SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
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if (st0_tag == TW_Denormal)
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return ((st0_sign ==
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SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
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| COMP_Denormal;
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}
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if (st0_tag == TW_Infinity) {
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if ((tagb == TAG_Valid) || (tagb == TAG_Zero))
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return ((st0_sign ==
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SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
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else if (tagb == TW_Denormal)
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return ((st0_sign ==
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SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
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| COMP_Denormal;
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else if (tagb == TW_Infinity) {
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/* The 80486 book says that infinities can be equal! */
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return (st0_sign == signb) ? COMP_A_eq_B :
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((st0_sign ==
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SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B);
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}
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/* Fall through to the NaN code */
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} else if (tagb == TW_Infinity) {
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if ((st0_tag == TAG_Valid) || (st0_tag == TAG_Zero))
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return ((signb ==
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SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B);
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if (st0_tag == TW_Denormal)
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return ((signb ==
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SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
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| COMP_Denormal;
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/* Fall through to the NaN code */
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}
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/* The only possibility now should be that one of the arguments
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is a NaN */
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if ((st0_tag == TW_NaN) || (tagb == TW_NaN)) {
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int signalling = 0, unsupported = 0;
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if (st0_tag == TW_NaN) {
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signalling =
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(st0_ptr->sigh & 0xc0000000) == 0x80000000;
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unsupported = !((exponent(st0_ptr) == EXP_OVER)
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&& (st0_ptr->
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sigh & 0x80000000));
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}
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if (tagb == TW_NaN) {
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signalling |=
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(b->sigh & 0xc0000000) == 0x80000000;
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unsupported |= !((exponent(b) == EXP_OVER)
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&& (b->sigh & 0x80000000));
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}
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if (signalling || unsupported)
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return COMP_No_Comp | COMP_SNaN | COMP_NaN;
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else
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/* Neither is a signaling NaN */
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return COMP_No_Comp | COMP_NaN;
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}
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EXCEPTION(EX_Invalid);
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}
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if (st0_sign != signb) {
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return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
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| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
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COMP_Denormal : 0);
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}
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if ((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) {
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FPU_to_exp16(st0_ptr, &x);
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FPU_to_exp16(b, &y);
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st0_ptr = &x;
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b = &y;
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exp0 = exponent16(st0_ptr);
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expb = exponent16(b);
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} else {
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exp0 = exponent(st0_ptr);
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expb = exponent(b);
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}
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#ifdef PARANOID
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if (!(st0_ptr->sigh & 0x80000000))
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EXCEPTION(EX_Invalid);
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if (!(b->sigh & 0x80000000))
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EXCEPTION(EX_Invalid);
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#endif /* PARANOID */
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diff = exp0 - expb;
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if (diff == 0) {
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diff = st0_ptr->sigh - b->sigh; /* Works only if ms bits are
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identical */
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if (diff == 0) {
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diff = st0_ptr->sigl > b->sigl;
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if (diff == 0)
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diff = -(st0_ptr->sigl < b->sigl);
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}
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}
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if (diff > 0) {
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return ((st0_sign == SIGN_POS) ? COMP_A_gt_B : COMP_A_lt_B)
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| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
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COMP_Denormal : 0);
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}
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if (diff < 0) {
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return ((st0_sign == SIGN_POS) ? COMP_A_lt_B : COMP_A_gt_B)
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| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
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COMP_Denormal : 0);
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}
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return COMP_A_eq_B
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| (((st0_tag == TW_Denormal) || (tagb == TW_Denormal)) ?
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COMP_Denormal : 0);
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}
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/* This function requires that st(0) is not empty */
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int FPU_compare_st_data(FPU_REG const *loaded_data, u_char loaded_tag)
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{
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int f = 0, c;
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c = compare(loaded_data, loaded_tag);
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if (c & COMP_NaN) {
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EXCEPTION(EX_Invalid);
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f = SW_C3 | SW_C2 | SW_C0;
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} else
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switch (c & 7) {
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case COMP_A_lt_B:
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f = SW_C0;
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break;
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case COMP_A_eq_B:
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f = SW_C3;
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break;
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case COMP_A_gt_B:
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f = 0;
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break;
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case COMP_No_Comp:
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#ifdef PARANOID
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default:
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EXCEPTION(EX_INTERNAL | 0x121);
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#endif /* PARANOID */
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}
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setcc(f);
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if (c & COMP_Denormal) {
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return denormal_operand() < 0;
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}
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return 0;
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}
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static int compare_st_st(int nr)
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{
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int f = 0, c;
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FPU_REG *st_ptr;
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if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
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setcc(SW_C3 | SW_C2 | SW_C0);
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/* Stack fault */
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EXCEPTION(EX_StackUnder);
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return !(control_word & CW_Invalid);
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}
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st_ptr = &st(nr);
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c = compare(st_ptr, FPU_gettagi(nr));
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if (c & COMP_NaN) {
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setcc(SW_C3 | SW_C2 | SW_C0);
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EXCEPTION(EX_Invalid);
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return !(control_word & CW_Invalid);
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} else
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switch (c & 7) {
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case COMP_A_lt_B:
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f = SW_C0;
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break;
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case COMP_A_eq_B:
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f = SW_C3;
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break;
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case COMP_A_gt_B:
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f = 0;
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break;
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case COMP_No_Comp:
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#ifdef PARANOID
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default:
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EXCEPTION(EX_INTERNAL | 0x122);
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#endif /* PARANOID */
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}
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setcc(f);
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if (c & COMP_Denormal) {
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return denormal_operand() < 0;
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}
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return 0;
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}
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static int compare_u_st_st(int nr)
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{
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int f = 0, c;
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FPU_REG *st_ptr;
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if (!NOT_EMPTY(0) || !NOT_EMPTY(nr)) {
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setcc(SW_C3 | SW_C2 | SW_C0);
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/* Stack fault */
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EXCEPTION(EX_StackUnder);
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return !(control_word & CW_Invalid);
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}
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st_ptr = &st(nr);
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c = compare(st_ptr, FPU_gettagi(nr));
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if (c & COMP_NaN) {
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setcc(SW_C3 | SW_C2 | SW_C0);
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if (c & COMP_SNaN) { /* This is the only difference between
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un-ordered and ordinary comparisons */
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EXCEPTION(EX_Invalid);
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return !(control_word & CW_Invalid);
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}
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return 0;
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} else
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switch (c & 7) {
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case COMP_A_lt_B:
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f = SW_C0;
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break;
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case COMP_A_eq_B:
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f = SW_C3;
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break;
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case COMP_A_gt_B:
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f = 0;
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break;
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case COMP_No_Comp:
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#ifdef PARANOID
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default:
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EXCEPTION(EX_INTERNAL | 0x123);
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f = SW_C3 | SW_C2 | SW_C0;
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break;
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#endif /* PARANOID */
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}
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setcc(f);
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if (c & COMP_Denormal) {
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return denormal_operand() < 0;
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}
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return 0;
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}
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/*---------------------------------------------------------------------------*/
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void fcom_st(void)
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{
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/* fcom st(i) */
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compare_st_st(FPU_rm);
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}
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void fcompst(void)
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{
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/* fcomp st(i) */
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if (!compare_st_st(FPU_rm))
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FPU_pop();
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}
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void fcompp(void)
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{
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/* fcompp */
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if (FPU_rm != 1) {
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FPU_illegal();
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return;
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}
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if (!compare_st_st(1))
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poppop();
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}
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void fucom_(void)
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{
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/* fucom st(i) */
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compare_u_st_st(FPU_rm);
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}
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void fucomp(void)
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{
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/* fucomp st(i) */
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if (!compare_u_st_st(FPU_rm))
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FPU_pop();
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}
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void fucompp(void)
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{
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/* fucompp */
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if (FPU_rm == 1) {
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if (!compare_u_st_st(1))
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poppop();
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} else
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FPU_illegal();
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}
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