sysdeps/powerpc/fpu/fenv_libc.h

   1 /* Internal libc stuff for floating point environment routines.
   2    Copyright (C) 1997, 2006 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #ifndef _FENV_LIBC_H
  21 #define _FENV_LIBC_H    1
  22
  23 #include <fenv.h>
  24
  25 /* The sticky bits in the FPSCR indicating exceptions have occurred.  */
  26 #define FPSCR_STICKY_BITS ((FE_ALL_EXCEPT | FE_ALL_INVALID) & ~FE_INVALID)
  27
  28 /* Equivalent to fegetenv, but returns a fenv_t instead of taking a
  29    pointer.  */
  30 #define fegetenv_register() \
  31         ({ fenv_t env; asm volatile ("mffs %0" : "=f" (env)); env; })
  32
  33 /* Equivalent to fesetenv, but takes a fenv_t instead of a pointer.  */
  34 #define fesetenv_register(env) \
  35         ({ double d = (env); asm volatile ("mtfsf 0xff,%0" : : "f" (d)); })
  36
  37 /* This very handy macro:
  38    - Sets the rounding mode to 'round to nearest';
  39    - Sets the processor into IEEE mode; and
  40    - Prevents exceptions from being raised for inexact results.
  41    These things happen to be exactly what you need for typical elementary
  42    functions.  */
  43 #define relax_fenv_state() asm ("mtfsfi 7,0")
  44
  45 /* Set/clear a particular FPSCR bit (for instance,
  46    reset_fpscr_bit(FPSCR_VE);
  47    prevents INVALID exceptions from being raised).  */
  48 #define set_fpscr_bit(x) asm volatile ("mtfsb1 %0" : : "i"(x))
  49 #define reset_fpscr_bit(x) asm volatile ("mtfsb0 %0" : : "i"(x))
  50
  51 typedef union
  52 {
  53   fenv_t fenv;
  54   unsigned int l[2];
  55 } fenv_union_t;
  56
  57
  58 static inline int
  59 __fegetround (void)
  60 {
  61   int result;
  62   asm volatile ("mcrfs 7,7\n\t"
  63                 "mfcr  %0" : "=r"(result) : : "cr7");
  64   return result & 3;
  65 }
  66 #define fegetround() __fegetround()
  67
  68 static inline int
  69 __fesetround (int round)
  70 {
  71   if ((unsigned int) round < 2)
  72     {
  73        asm volatile ("mtfsb0 30");
  74        if ((unsigned int) round == 0)
  75          asm volatile ("mtfsb0 31");
  76        else
  77          asm volatile ("mtfsb1 31");
  78     }
  79   else
  80     {
  81        asm volatile ("mtfsb1 30");
  82        if ((unsigned int) round == 2)
  83          asm volatile ("mtfsb0 31");
  84        else
  85          asm volatile ("mtfsb1 31");
  86     }
  87
  88   return 0;
  89 }
  90 #define fesetround(mode) __fesetround(mode)
  91
  92 /* Definitions of all the FPSCR bit numbers */
  93 enum {
  94   FPSCR_FX = 0,    /* exception summary */
  95   FPSCR_FEX,       /* enabled exception summary */
  96   FPSCR_VX,        /* invalid operation summary */
  97   FPSCR_OX,        /* overflow */
  98   FPSCR_UX,        /* underflow */
  99   FPSCR_ZX,        /* zero divide */
 100   FPSCR_XX,        /* inexact */
 101   FPSCR_VXSNAN,    /* invalid operation for SNaN */
 102   FPSCR_VXISI,     /* invalid operation for Inf-Inf */
 103   FPSCR_VXIDI,     /* invalid operation for Inf/Inf */
 104   FPSCR_VXZDZ,     /* invalid operation for 0/0 */
 105   FPSCR_VXIMZ,     /* invalid operation for Inf*0 */
 106   FPSCR_VXVC,      /* invalid operation for invalid compare */
 107   FPSCR_FR,        /* fraction rounded [fraction was incremented by round] */
 108   FPSCR_FI,        /* fraction inexact */
 109   FPSCR_FPRF_C,    /* result class descriptor */
 110   FPSCR_FPRF_FL,   /* result less than (usually, less than 0) */
 111   FPSCR_FPRF_FG,   /* result greater than */
 112   FPSCR_FPRF_FE,   /* result equal to */
 113   FPSCR_FPRF_FU,   /* result unordered */
 114   FPSCR_20,        /* reserved */
 115   FPSCR_VXSOFT,    /* invalid operation set by software */
 116   FPSCR_VXSQRT,    /* invalid operation for square root */
 117   FPSCR_VXCVI,     /* invalid operation for invalid integer convert */
 118   FPSCR_VE,        /* invalid operation exception enable */
 119   FPSCR_OE,        /* overflow exception enable */
 120   FPSCR_UE,        /* underflow exception enable */
 121   FPSCR_ZE,        /* zero divide exception enable */
 122   FPSCR_XE,        /* inexact exception enable */
 123   FPSCR_NI         /* non-IEEE mode (typically, no denormalised numbers) */
 124   /* the remaining two least-significant bits keep the rounding mode */
 125 };
 126
 127 /* This operation (i) sets the appropriate FPSCR bits for its
 128    parameter, (ii) converts SNaN to the corresponding NaN, and (iii)
 129    otherwise passes its parameter through unchanged (in particular, -0
 130    and +0 stay as they were).  The `obvious' way to do this is optimised
 131    out by gcc.  */
 132 #define f_wash(x) \
 133    ({ double d; asm volatile ("fmul %0,%1,%2" \
 134                               : "=f"(d) \
 135                               : "f" (x), "f"((float)1.0)); d; })
 136 #define f_washf(x) \
 137    ({ float f; asm volatile ("fmuls %0,%1,%2" \
 138                              : "=f"(f) \
 139                              : "f" (x), "f"((float)1.0)); f; })
 140
 141 #endif /* fenv_libc.h */