x86/math-emu/reg_constant.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 /*---------------------------------------------------------------------------+
0003  |  reg_constant.c                                                           |
0004  |                                                                           |
0005  | All of the constant FPU_REGs                                              |
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 "fpu_emu.h"
0016 #include "status_w.h"
0017 #include "reg_constant.h"
0018 #include "control_w.h"
0019
0020 #define MAKE_REG(s, e, l, h) { l, h, \
0021         (u16)((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
0022
0023 FPU_REG const CONST_1 = MAKE_REG(POS, 0, 0x00000000, 0x80000000);
0024 #if 0
0025 FPU_REG const CONST_2 = MAKE_REG(POS, 1, 0x00000000, 0x80000000);
0026 FPU_REG const CONST_HALF = MAKE_REG(POS, -1, 0x00000000, 0x80000000);
0027 #endif /*  0  */
0028 static FPU_REG const CONST_L2T = MAKE_REG(POS, 1, 0xcd1b8afe, 0xd49a784b);
0029 static FPU_REG const CONST_L2E = MAKE_REG(POS, 0, 0x5c17f0bc, 0xb8aa3b29);
0030 FPU_REG const CONST_PI = MAKE_REG(POS, 1, 0x2168c235, 0xc90fdaa2);
0031 FPU_REG const CONST_PI2 = MAKE_REG(POS, 0, 0x2168c235, 0xc90fdaa2);
0032 FPU_REG const CONST_PI4 = MAKE_REG(POS, -1, 0x2168c235, 0xc90fdaa2);
0033 static FPU_REG const CONST_LG2 = MAKE_REG(POS, -2, 0xfbcff799, 0x9a209a84);
0034 static FPU_REG const CONST_LN2 = MAKE_REG(POS, -1, 0xd1cf79ac, 0xb17217f7);
0035
0036 /* Extra bits to take pi/2 to more than 128 bits precision. */
0037 FPU_REG const CONST_PI2extra = MAKE_REG(NEG, -66,
0038                     0xfc8f8cbb, 0xece675d1);
0039
0040 /* Only the sign (and tag) is used in internal zeroes */
0041 FPU_REG const CONST_Z = MAKE_REG(POS, EXP_UNDER, 0x0, 0x0);
0042
0043 /* Only the sign and significand (and tag) are used in internal NaNs */
0044 /* The 80486 never generates one of these
0045 FPU_REG const CONST_SNAN = MAKE_REG(POS, EXP_OVER, 0x00000001, 0x80000000);
0046  */
0047 /* This is the real indefinite QNaN */
0048 FPU_REG const CONST_QNaN = MAKE_REG(NEG, EXP_OVER, 0x00000000, 0xC0000000);
0049
0050 /* Only the sign (and tag) is used in internal infinities */
0051 FPU_REG const CONST_INF = MAKE_REG(POS, EXP_OVER, 0x00000000, 0x80000000);
0052
0053 static void fld_const(FPU_REG const * c, int adj, u_char tag)
0054 {
0055     FPU_REG *st_new_ptr;
0056
0057     if (STACK_OVERFLOW) {
0058         FPU_stack_overflow();
0059         return;
0060     }
0061     push();
0062     reg_copy(c, st_new_ptr);
0063     st_new_ptr->sigl += adj;    /* For all our fldxxx constants, we don't need to
0064                        borrow or carry. */
0065     FPU_settag0(tag);
0066     clear_C1();
0067 }
0068
0069 /* A fast way to find out whether x is one of RC_DOWN or RC_CHOP
0070    (and not one of RC_RND or RC_UP).
0071    */
0072 #define DOWN_OR_CHOP(x)  (x & RC_DOWN)
0073
0074 static void fld1(int rc)
0075 {
0076     fld_const(&CONST_1, 0, TAG_Valid);
0077 }
0078
0079 static void fldl2t(int rc)
0080 {
0081     fld_const(&CONST_L2T, (rc == RC_UP) ? 1 : 0, TAG_Valid);
0082 }
0083
0084 static void fldl2e(int rc)
0085 {
0086     fld_const(&CONST_L2E, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
0087 }
0088
0089 static void fldpi(int rc)
0090 {
0091     fld_const(&CONST_PI, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
0092 }
0093
0094 static void fldlg2(int rc)
0095 {
0096     fld_const(&CONST_LG2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
0097 }
0098
0099 static void fldln2(int rc)
0100 {
0101     fld_const(&CONST_LN2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
0102 }
0103
0104 static void fldz(int rc)
0105 {
0106     fld_const(&CONST_Z, 0, TAG_Zero);
0107 }
0108
0109 typedef void (*FUNC_RC) (int);
0110
0111 static FUNC_RC constants_table[] = {
0112     fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC) FPU_illegal
0113 };
0114
0115 void fconst(void)
0116 {
0117     (constants_table[FPU_rm]) (control_word & CW_RC);
0118 }