arch/x86/math-emu/reg_constant.c

   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
  20 #define MAKE_REG(s,e,l,h) { l, h, \
  21                             ((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
  54 static void fld_const(FPU_REG const *c, int adj, u_char tag)
  55 {
  56   FPU_REG *st_new_ptr;
  57
  58   if ( STACK_OVERFLOW )
  59     {
  60       FPU_stack_overflow();
  61       return;
  62     }
  63   push();
  64   reg_copy(c, st_new_ptr);
  65   st_new_ptr->sigl += adj;  /* For all our fldxxx constants, we don't need to
  66                                borrow or carry. */
  67   FPU_settag0(tag);
  68   clear_C1();
  69 }
  70
  71 /* A fast way to find out whether x is one of RC_DOWN or RC_CHOP
  72    (and not one of RC_RND or RC_UP).
  73    */
  74 #define DOWN_OR_CHOP(x)  (x & RC_DOWN)
  75
  76 static void fld1(int rc)
  77 {
  78   fld_const(&CONST_1, 0, TAG_Valid);
  79 }
  80
  81 static void fldl2t(int rc)
  82 {
  83   fld_const(&CONST_L2T, (rc == RC_UP) ? 1 : 0, TAG_Valid);
  84 }
  85
  86 static void fldl2e(int rc)
  87 {
  88   fld_const(&CONST_L2E, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  89 }
  90
  91 static void fldpi(int rc)
  92 {
  93   fld_const(&CONST_PI, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  94 }
  95
  96 static void fldlg2(int rc)
  97 {
  98   fld_const(&CONST_LG2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
  99 }
 100
 101 static void fldln2(int rc)
 102 {
 103   fld_const(&CONST_LN2, DOWN_OR_CHOP(rc) ? -1 : 0, TAG_Valid);
 104 }
 105
 106 static void fldz(int rc)
 107 {
 108   fld_const(&CONST_Z, 0, TAG_Zero);
 109 }
 110
 111 typedef void (*FUNC_RC)(int);
 112
 113 static FUNC_RC constants_table[] = {
 114   fld1, fldl2t, fldl2e, fldpi, fldlg2, fldln2, fldz, (FUNC_RC)FPU_illegal
 115 };
 116
 117 void fconst(void)
 118 {
 119   (constants_table[FPU_rm])(control_word & CW_RC);
 120 }