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Initial creation of sourceware repository
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Stan Shebs
212
sim/erc32/float.c
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212
sim/erc32/float.c
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/*
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* This file is part of SIS.
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*
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* SIS, SPARC instruction simulator. Copyright (C) 1995 Jiri Gaisler, European
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* Space Agency
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*
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* This program is free software; you can redistribute it and/or modify it under
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* the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 675
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* Mass Ave, Cambridge, MA 02139, USA.
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*
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*
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* This file implements the interface between the host and the simulated
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* FPU. IEEE trap handling is done as follows:
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* 1. In the host, all IEEE traps are masked
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* 2. After each simulated FPU instruction, check if any exception occured
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* by reading the exception bits from the host FPU status register
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* (get_accex()).
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* 3. Propagate any exceptions to the simulated FSR.
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* 4. Clear host exception bits
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*
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*
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* This can also be done using ieee_flags() library routine on sun.
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*/
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#include "sis.h"
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/* Forward declarations */
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extern uint32 _get_sw PARAMS ((void));
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extern uint32 _get_cw PARAMS ((void));
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static void __setfpucw PARAMS ((unsigned short fpu_control));
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/* This host dependent routine should return the accrued exceptions */
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int
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get_accex()
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{
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#ifdef sparc
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return ((_get_fsr_raw() >> 5) & 0x1F);
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#elif i386
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uint32 accx;
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accx = _get_sw() & 0x3f;
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accx = ((accx & 1) << 4) | ((accx & 2) >> 1) | ((accx & 4) >> 1) |
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(accx & 8) | ((accx & 16) >> 2) | ((accx & 32) >> 5);
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return(accx);
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#else
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return(0);
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#warning no fpu trap support for this target
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#endif
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}
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/* How to clear the accrued exceptions */
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void
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clear_accex()
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{
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#ifdef sparc
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set_fsr((_get_fsr_raw() & ~0x3e0));
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#elif i386
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asm("
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.text
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fnclex
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");
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#else
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#warning no fpu trap support for this target
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#endif
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}
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/* How to map SPARC FSR onto the host */
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void
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set_fsr(fsr)
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uint32 fsr;
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{
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#ifdef sparc
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_set_fsr_raw(fsr & ~0x0f800000);
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#elif i386
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void __setfpucw(unsigned short fpu_control);
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uint32 rawfsr;
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fsr >>= 30;
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switch (fsr) {
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case 0:
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case 2: break;
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case 1: fsr = 3;
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case 3: fsr = 1;
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}
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rawfsr = _get_cw();
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rawfsr |= (fsr << 10) | 0x3ff;
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__setfpucw(rawfsr);
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#else
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#warning no fpu trap support for this target
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#endif
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}
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/* Host dependent support functions */
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#ifdef sparc
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asm("
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.text
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.align 4
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.global __set_fsr_raw,_set_fsr_raw
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__set_fsr_raw:
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_set_fsr_raw:
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save %sp,-104,%sp
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st %i0,[%fp+68]
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ld [%fp+68], %fsr
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mov 0,%i0
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ret
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restore
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.align 4
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.global __get_fsr_raw
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.global _get_fsr_raw
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__get_fsr_raw:
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_get_fsr_raw:
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save %sp,-104,%sp
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st %fsr,[%fp+68]
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ld [%fp+68], %i0
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ret
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restore
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");
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#elif i386
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asm("
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.text
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.align 8
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.globl _get_sw,__get_sw
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__get_sw:
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_get_sw:
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pushl %ebp
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movl %esp,%ebp
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movl $0,%eax
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fnstsw %ax
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movl %ebp,%esp
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popl %ebp
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ret
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.align 8
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.globl _get_cw,__get_cw
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__get_cw:
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_get_cw:
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pushl %ebp
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movl %esp,%ebp
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subw $2,%esp
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fnstcw -2(%ebp)
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movw -2(%ebp),%eax
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movl %ebp,%esp
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popl %ebp
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ret
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");
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#else
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#warning no fpu trap support for this target
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#endif
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#if i386
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/* #if defined _WIN32 || defined __GO32__ */
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/* This is so floating exception handling works on NT
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These definitions are from the linux fpu_control.h, which
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doesn't exist on NT.
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default to:
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- extended precision
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- rounding to nearest
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- exceptions on overflow, zero divide and NaN
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*/
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#define _FPU_DEFAULT 0x1372
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#define _FPU_RESERVED 0xF0C0 /* Reserved bits in cw */
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static void
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__setfpucw(unsigned short fpu_control)
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{
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volatile unsigned short cw;
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/* If user supplied _fpu_control, use it ! */
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if (!fpu_control)
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{
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/* use defaults */
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fpu_control = _FPU_DEFAULT;
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}
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/* Get Control Word */
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__asm__ volatile ("fnstcw %0" : "=m" (cw) : );
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/* mask in */
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cw &= _FPU_RESERVED;
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cw = cw | (fpu_control & ~_FPU_RESERVED);
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/* set cw */
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__asm__ volatile ("fldcw %0" :: "m" (cw));
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}
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/* #endif */
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#endif
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