LXR linux/arch/x86/math-emu/reg

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