134 lines
4.3 KiB
C++
134 lines
4.3 KiB
C++
/////////////////////////////////////////////////////////////////////////
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// $Id$
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/////////////////////////////////////////////////////////////////////////
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//
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// Copyright (c) 2003-2009 Stanislav Shwartsman
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// Written by Stanislav Shwartsman [sshwarts at sourceforge net]
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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//
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/////////////////////////////////////////////////////////////////////////
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#define NEED_CPU_REG_SHORTCUTS 1
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#include "bochs.h"
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#include "cpu/cpu.h"
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#define LOG_THIS BX_CPU_THIS_PTR
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#if BX_SUPPORT_FPU
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#include "softfloat-specialize.h"
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void BX_CPU_C::FPU_stack_overflow(void)
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{
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/* The masked response */
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if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
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{
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BX_CPU_THIS_PTR the_i387.FPU_push();
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BX_WRITE_FPU_REG(floatx80_default_nan, 0);
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}
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FPU_exception(FPU_EX_Stack_Overflow);
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}
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void BX_CPU_C::FPU_stack_underflow(int stnr, int pop_stack)
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{
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/* The masked response */
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if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
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{
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BX_WRITE_FPU_REG(floatx80_default_nan, stnr);
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if (pop_stack)
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BX_CPU_THIS_PTR the_i387.FPU_pop();
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}
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FPU_exception(FPU_EX_Stack_Underflow);
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}
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/* Returns unmasked exceptions if occured */
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unsigned BX_CPU_C::FPU_exception(unsigned exception, bx_bool is_store)
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{
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/* Extract only the bits which we use to set the status word */
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exception &= (FPU_SW_Exceptions_Mask);
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Bit32u status = FPU_PARTIAL_STATUS;
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unsigned unmasked = exception & ~FPU_CONTROL_WORD & FPU_CW_Exceptions_Mask;
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// if IE or DZ exception happen nothing else will be reported
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if (exception & (FPU_EX_Invalid | FPU_EX_Zero_Div))
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unmasked &= (FPU_EX_Invalid | FPU_EX_Zero_Div);
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/* Set summary bits iff exception isn't masked */
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if (unmasked)
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FPU_PARTIAL_STATUS |= (FPU_SW_Summary | FPU_SW_Backward);
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if (exception & FPU_EX_Invalid) {
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// FPU_EX_Invalid cannot come with any other exception but x87 stack fault
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FPU_PARTIAL_STATUS |= exception;
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if (exception & FPU_SW_Stack_Fault) {
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if (! (exception & FPU_SW_C1)) {
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/* This bit distinguishes over- from underflow for a stack fault,
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and roundup from round-down for precision loss. */
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FPU_PARTIAL_STATUS &= ~FPU_SW_C1;
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}
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}
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return unmasked;
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}
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if (exception & FPU_EX_Zero_Div) {
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FPU_PARTIAL_STATUS |= FPU_EX_Zero_Div;
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return unmasked;
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}
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if (exception & FPU_EX_Denormal) {
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FPU_PARTIAL_STATUS |= FPU_EX_Denormal;
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if (unmasked & FPU_EX_Denormal)
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return unmasked & FPU_EX_Denormal;
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}
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/* Set the corresponding exception bits */
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FPU_PARTIAL_STATUS |= exception;
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if (exception & FPU_EX_Precision)
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{
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if (! (exception & FPU_SW_C1)) {
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/* This bit distinguishes over- from underflow for a stack fault,
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and roundup from round-down for precision loss. */
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FPU_PARTIAL_STATUS &= ~FPU_SW_C1;
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}
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}
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// If #P unmasked exception occured the result still has to be
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// written to the destination.
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unmasked &= ~FPU_EX_Precision;
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if (unmasked & (FPU_EX_Underflow | FPU_EX_Overflow)) {
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// If unmasked over- or underflow occurs and dest is a memory location:
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// - the TOS and destination operands remain unchanged
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// - the inexact-result condition is not reported and C1 flag is cleared
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// - no result is stored in the memory
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// If the destination is in the register stack, adjusted resulting value
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// is stored in the destination operand.
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if (! is_store) {
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unmasked &= ~(FPU_EX_Underflow | FPU_EX_Overflow);
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}
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else {
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FPU_PARTIAL_STATUS &= ~FPU_SW_C1; // clear C1 flag
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if (! (status & FPU_EX_Precision))
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FPU_PARTIAL_STATUS &= ~FPU_EX_Precision;
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}
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}
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return unmasked;
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}
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#endif
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