7d39906acc
This code uses the cr0 task switched bit to disable the FPU upon task switch, which allows the kernel to delay copying the registers until another task starts using them. Or better yet, if no other thread actually uses the registers, then it won't need to do any copying at all!
85 lines
2 KiB
C++
85 lines
2 KiB
C++
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012.
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This file is part of Sortix.
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Sortix is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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Sortix. If not, see <http://www.gnu.org/licenses/>.
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float.cpp
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Handles saving and restoration of floating point numbers.
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*******************************************************************************/
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#include <sortix/kernel/platform.h>
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#include "../interrupt.h"
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#include "../thread.h"
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#include "float.h"
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namespace Sortix {
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namespace Float {
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static Thread* fputhread;
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static inline void InitFPU()
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{
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asm volatile ("fninit");
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}
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static inline void SaveState(uint8_t* dest)
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{
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ASSERT( (((unsigned long) dest) & (16UL-1UL)) == 0 );
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asm volatile ("fxsave (%0)" : : "r"(dest));
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}
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static inline void LoadState(const uint8_t* src)
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{
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ASSERT( (((unsigned long) src) & (16UL-1UL)) == 0 );
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asm volatile ("fxrstor (%0)" : : "r"(src));
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}
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static void OnFPUAccess(CPU::InterruptRegisters* /*regs*/, void* /*user*/)
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{
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EnableFPU();
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Thread* thread = CurrentThread();
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if ( thread == fputhread )
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return;
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if ( fputhread )
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SaveState(fputhread->fpuenvaligned);
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fputhread = thread;
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if ( !thread->fpuinitialized )
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{
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InitFPU();
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thread->fpuinitialized = true;
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return;
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}
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LoadState(thread->fpuenvaligned);
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}
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void Init()
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{
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fputhread = CurrentThread();
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ASSERT(fputhread);
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Interrupt::RegisterHandler(7, OnFPUAccess, NULL);
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}
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void NofityTaskExit()
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{
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fputhread = NULL;
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DisableFPU();
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}
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} // namespace Float
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} // namespace Sortix
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