x86/math-emu/fpu_etc.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*---------------------------------------------------------------------------+
0003  |  fpu_etc.c                                                                |
0004  |                                                                           |
0005  | Implement a few FPU instructions.                                         |
0006  |                                                                           |
0007  | Copyright (C) 1992,1993,1994,1997                                         |
0008  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
0009  |                       Australia.  E-mail   billm@suburbia.net             |
0010  |                                                                           |
0011  |                                                                           |
0012  +---------------------------------------------------------------------------*/
0013
0014 #include "fpu_system.h"
0015 #include "exception.h"
0016 #include "fpu_emu.h"
0017 #include "status_w.h"
0018 #include "reg_constant.h"
0019
0020 static void fchs(FPU_REG *st0_ptr, u_char st0tag)
0021 {
0022     if (st0tag ^ TAG_Empty) {
0023         signbyte(st0_ptr) ^= SIGN_NEG;
0024         clear_C1();
0025     } else
0026         FPU_stack_underflow();
0027 }
0028
0029 static void fabs(FPU_REG *st0_ptr, u_char st0tag)
0030 {
0031     if (st0tag ^ TAG_Empty) {
0032         setpositive(st0_ptr);
0033         clear_C1();
0034     } else
0035         FPU_stack_underflow();
0036 }
0037
0038 static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
0039 {
0040     switch (st0tag) {
0041     case TAG_Zero:
0042         setcc(SW_C3);
0043         break;
0044     case TAG_Valid:
0045         if (getsign(st0_ptr) == SIGN_POS)
0046             setcc(0);
0047         else
0048             setcc(SW_C0);
0049         break;
0050     case TAG_Special:
0051         switch (FPU_Special(st0_ptr)) {
0052         case TW_Denormal:
0053             if (getsign(st0_ptr) == SIGN_POS)
0054                 setcc(0);
0055             else
0056                 setcc(SW_C0);
0057             if (denormal_operand() < 0) {
0058 #ifdef PECULIAR_486
0059                 /* This is weird! */
0060                 if (getsign(st0_ptr) == SIGN_POS)
0061                     setcc(SW_C3);
0062 #endif /* PECULIAR_486 */
0063                 return;
0064             }
0065             break;
0066         case TW_NaN:
0067             setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
0068             EXCEPTION(EX_Invalid);
0069             break;
0070         case TW_Infinity:
0071             if (getsign(st0_ptr) == SIGN_POS)
0072                 setcc(0);
0073             else
0074                 setcc(SW_C0);
0075             break;
0076         default:
0077             setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
0078             EXCEPTION(EX_INTERNAL | 0x14);
0079             break;
0080         }
0081         break;
0082     case TAG_Empty:
0083         setcc(SW_C0 | SW_C2 | SW_C3);
0084         EXCEPTION(EX_StackUnder);
0085         break;
0086     }
0087 }
0088
0089 static void fxam(FPU_REG *st0_ptr, u_char st0tag)
0090 {
0091     int c = 0;
0092     switch (st0tag) {
0093     case TAG_Empty:
0094         c = SW_C3 | SW_C0;
0095         break;
0096     case TAG_Zero:
0097         c = SW_C3;
0098         break;
0099     case TAG_Valid:
0100         c = SW_C2;
0101         break;
0102     case TAG_Special:
0103         switch (FPU_Special(st0_ptr)) {
0104         case TW_Denormal:
0105             c = SW_C2 | SW_C3;  /* Denormal */
0106             break;
0107         case TW_NaN:
0108             /* We also use NaN for unsupported types. */
0109             if ((st0_ptr->sigh & 0x80000000)
0110                 && (exponent(st0_ptr) == EXP_OVER))
0111                 c = SW_C0;
0112             break;
0113         case TW_Infinity:
0114             c = SW_C2 | SW_C0;
0115             break;
0116         }
0117     }
0118     if (getsign(st0_ptr) == SIGN_NEG)
0119         c |= SW_C1;
0120     setcc(c);
0121 }
0122
0123 static FUNC_ST0 const fp_etc_table[] = {
0124     fchs, fabs, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal,
0125     ftst_, fxam, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal
0126 };
0127
0128 void FPU_etc(void)
0129 {
0130     (fp_etc_table[FPU_rm]) (&st(0), FPU_gettag0());
0131 }