1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26 
  27 /*
  28  *      Copyright (c) 1990, 1991 UNIX System Laboratories, Inc.
  29  *      Copyright (c) 1988 AT&T
  30  *        All Rights Reserved
  31  */
  32 
  33 /*
  34  * Establish the default settings for the floating-point state for a C language
  35  * program:
  36  *      rounding mode           -- round to nearest default by OS,
  37  *      exceptions enabled      -- all masked
  38  *      sticky bits             -- all clear by default by OS.
  39  *      precision control       -- double extended
  40  * Set _fp_hw according to what floating-point hardware is available.
  41  * Set _sse_hw according to what SSE hardware is available.
  42  * Set __flt_rounds according to the rounding mode.
  43  */
  44 
  45 #pragma weak _fpstart = __fpstart
  46 
  47 #include        "lint.h"
  48 #include        <sys/types.h>
  49 #include        <sys/sysi86.h>    /* for SI86FPHW/SI86FPSTART definitions */
  50 #include        <sys/fp.h>        /* for FPU_CW_INIT and SSE_MXCSR_INIT */
  51 
  52 extern int      __fltrounds();
  53 
  54 int     _fp_hw;                 /* default: bss: 0 == no hardware */
  55 int     _sse_hw;                /* default: bss: 0 == no sse */
  56 int     __flt_rounds;           /* ANSI rounding mode */
  57 
  58 void
  59 __fpstart()
  60 {
  61         /*
  62          * query OS for HW status and ensure the x87 and (optional)
  63          * SSE control words are (will be) set correctly.
  64          */
  65         if ((_sse_hw = sysi86(SI86FPSTART,
  66             &_fp_hw, FPU_CW_INIT, SSE_MXCSR_INIT)) == -1) {
  67                 extern void _putcw();
  68 
  69                 /*
  70                  * (fallback to old syscall on old kernels)
  71                  */
  72                 _sse_hw = 0;
  73                 (void) sysi86(SI86FPHW, &_fp_hw);
  74                 _putcw(0x133f);
  75         }
  76 
  77         /*
  78          * At this point the x87 fp environment that has been (or more
  79          * hopefully, will be) established by the kernel is:
  80          *
  81          * affine infinity      0x1000
  82          * round to nearest     0x0000
  83          * 64-bit doubles       0x0300
  84          * precision, underflow, overflow, zero-divide, denorm, invalid masked
  85          *                      0x003f
  86          *
  87          * which conforms to the 4th edition i386 ABI definition.
  88          *
  89          * Additionally, if we have SSE hardware, we've also masked all
  90          * the same traps, and have round to nearest.
  91          */
  92 
  93         __flt_rounds = 1;       /* ANSI way of saying round-to-nearest */
  94 }