arch/x86/math-emu/reg_constant.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*---------------------------------------------------------------------------+
   3  |  reg_constant.c                                                           |
   4  |                                                                           |
   5  | All of the constant FPU_REGs                                              |
   6  |                                                                           |
   7  | Copyright (C) 1992,1993,1994,1997                                         |
   8  |                     W. Metzenthen, 22 Parker St, Ormond, Vic 3163,        |
   9  |                     Australia.  E-mail   billm@suburbia.net               |
  10  |                                                                           |
  11  |                                                                           |
  12  +---------------------------------------------------------------------------*/
  13
  14 #include "fpu_system.h"
  15 #include "fpu_emu.h"
  16 #include "status_w.h"
  17 #include "reg_constant.h"
  18 #include "control_w.h"
  19
  20 #define MAKE_REG(s, e, l, h) { l, h, \
  21                 (u16)((EXTENDED_Ebias+(e)) | ((SIGN_##s != 0)*0x8000)) }
  22
  23 FPU_REG const CONST_1 = MAKE_REG(POS, 0, 0x00000000, 0x80000000);
  24 #if 0
  25 FPU_REG const CONST_2 = MAKE_REG(POS, 1, 0x00000000, 0x80000000);
  26 FPU_REG const CONST_HALF = MAKE_REG(POS, -1, 0x00000000, 0x80000000);
  27 #endif /*  0  */
  28 static FPU_REG const CONST_L2T = MAKE_REG(POS, 1, 0xcd1b8afe, 0xd49a784b);
  29 static FPU_REG const CONST_L2E = MAKE_REG(POS, 0, 0x5c17f0bc, 0xb8aa3b29);
  30 FPU_REG const CONST_PI = MAKE_REG(POS, 1, 0x2168c235, 0xc90fdaa2);
  31 FPU_REG const CONST_PI2 = MAKE_REG(POS, 0, 0x2168c235, 0xc90fdaa2);
  32 FPU_REG const CONST_PI4 = MAKE_REG(POS, -1, 0x2168c235, 0xc90fdaa2);
  33 static FPU_REG const CONST_LG2 = MAKE_REG(POS, -2, 0xfbcff799, 0x9a209a84);
  34 static FPU_REG const CONST_LN2 = MAKE_REG(POS, -1, 0xd1cf79ac, 0xb17217f7);
  35
  36 /* Extra bits to take pi/2 to more than 128 bits precision. */
  37 FPU_REG const CONST_PI2extra = MAKE_REG(NEG, -66,
  38                                         0xfc8f8cbb, 0xece675d1);
  39
  40 /* Only the sign (and tag) is used in internal zeroes */
  41 FPU_REG const CONST_Z = MAKE_REG(POS, EXP_UNDER, 0x0, 0x0);
  42
  43 /* Only the sign and significand (and tag) are used in internal NaNs */
  44 /* The 80486 never generates one of these
  45 FPU_REG const CONST_SNAN = MAKE_REG(POS, EXP_OVER, 0x00000001, 0x80000000);
  46  */
  47 /* This is the real indefinite QNaN */
  48 FPU_REG const CONST_QNaN = MAKE_REG(NEG, EXP_OVER, 0x00000000, 0xC0000000);
  49
  50 /* Only the sign (and tag) is used in internal infinities */
  51 FPU_REG const CONST_INF = MAKE_REG(POS, EXP_OVER, 0x00000000, 0x80000000);
  52
  53 static void fld_const(FPU_REG const * c, int adj, u_char tag)
  54 {
  55         FPU_REG *st_new_ptr;
  56
  57         if (STACK_OVERFLOW) {
  58                 FPU_stack_overflow();
  59                 return;
  60         }
  61         push();
  62         reg_copy(c, st_new_ptr);
  63         st_new_ptr->sigl += adj;        /* For all our fldxxx constants, we don't need to
  64                                            borrow or carry. */
  65         FPU_settag0(tag);
  66         clear_C1();
  67 }
  68
  69 /* A fast way to find out whether x is one of RC_DOWN or RC_CHOP
  70    (and not one of RC_RND or RC_UP).
  71    */
  72 #define DOWN_OR_CHOP(x)  (x & RC_DOWN)
  73
  74 static void fld1(int rc)
  75 {
  76         fld_const(&CONST_1, 0, TAG_Valid);
  77 }
  78
  79 static void fldl2t(int rc)
  80 {
  81         fld_const(&CONST_L2T, (rc == RC_UP) ? 1 : 0, TAG_Valid);
  82 }
  83
  84 static void fldl2e(int rc)
  85 {
  86         fld_const(&CONST_L2E, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  87 }
  88
  89 static void fldpi(int rc)
  90 {
  91         fld_const(&CONST_PI, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  92 }
  93
  94 static void fldlg2(int rc)
  95 {
  96         fld_const(&CONST_LG2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  97 }
  98
  99 static void fldln2(int rc)
 100 {
 101         fld_const(&CONST_LN2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
 102 }
 103
 104 static void fldz(int rc)
 105 {
 106         fld_const(&CONST_Z, 0, TAG_Zero);
 107 }
 108
 109 typedef void (*FUNC_RC) (int);
 110
 111 static FUNC_RC constants_table[] = {
 112         fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC) FPU_illegal
 113 };
 114
 115 void fconst(void)
 116 {
 117         (constants_table[FPU_rm]) (control_word & CW_RC);
 118 }