Bochs/bochs/cpu/fpu/ferr.cc

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/////////////////////////////////////////////////////////////////////////
// $Id$
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/////////////////////////////////////////////////////////////////////////
//
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// Copyright (c) 2003-2017 Stanislav Shwartsman
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// Written by Stanislav Shwartsman [sshwarts at sourceforge net]
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
//
/////////////////////////////////////////////////////////////////////////
#define NEED_CPU_REG_SHORTCUTS 1
#include "bochs.h"
#include "cpu/cpu.h"
#define LOG_THIS BX_CPU_THIS_PTR
#if BX_SUPPORT_FPU
#include "softfloat-specialize.h"
void BX_CPU_C::FPU_stack_overflow(bxInstruction_c *i)
{
/* The masked response */
if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
{
BX_CPU_THIS_PTR the_i387.FPU_push();
BX_WRITE_FPU_REG(floatx80_default_nan, 0);
}
FPU_exception(i, FPU_EX_Stack_Overflow);
}
void BX_CPU_C::FPU_stack_underflow(bxInstruction_c *i, int stnr, int pop_stack)
{
/* The masked response */
if (BX_CPU_THIS_PTR the_i387.is_IA_masked())
{
BX_WRITE_FPU_REG(floatx80_default_nan, stnr);
if (pop_stack)
BX_CPU_THIS_PTR the_i387.FPU_pop();
}
FPU_exception(i, FPU_EX_Stack_Underflow);
}
/* Returns unmasked exceptions if occured */
unsigned BX_CPU_C::FPU_exception(bxInstruction_c *i, unsigned exception, bx_bool is_store)
{
/* Extract only the bits which we use to set the status word */
exception &= (FPU_SW_Exceptions_Mask);
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Bit32u status = FPU_PARTIAL_STATUS;
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
if (exception & (FPU_EX_Invalid | FPU_EX_Zero_Div))
unmasked &= (FPU_EX_Invalid | FPU_EX_Zero_Div);
/* Set summary bits iff exception isn't masked */
if (unmasked) {
FPU_PARTIAL_STATUS |= (FPU_SW_Summary | FPU_SW_Backward);
// when FOPCODE deprecation is set, FOPCODE is updated only when unmasked x87 exception occurs
if (is_cpu_extension_supported(BX_ISA_FOPCODE_DEPRECATION))
BX_CPU_THIS_PTR the_i387.foo = i->foo();
// when FOPCODE deprecation is set, FCS/FDP are updated only when unmasked x87 exception occurs
if (is_cpu_extension_supported(BX_ISA_FDP_DEPRECATION)) {
if (! i->modC0()) {
BX_CPU_THIS_PTR the_i387.fds = BX_CPU_THIS_PTR sregs[i->seg()].selector.value;
BX_CPU_THIS_PTR the_i387.fdp = RMAddr(i);
}
}
}
if (exception & FPU_EX_Invalid) {
// FPU_EX_Invalid cannot come with any other exception but x87 stack fault
FPU_PARTIAL_STATUS |= exception;
if (exception & FPU_SW_Stack_Fault) {
if (! (exception & FPU_SW_C1)) {
/* This bit distinguishes over- from underflow for a stack fault,
and roundup from round-down for precision loss. */
FPU_PARTIAL_STATUS &= ~FPU_SW_C1;
}
}
return unmasked;
}
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if (exception & FPU_EX_Zero_Div) {
FPU_PARTIAL_STATUS |= FPU_EX_Zero_Div;
return unmasked;
}
if (exception & FPU_EX_Denormal) {
FPU_PARTIAL_STATUS |= FPU_EX_Denormal;
if (unmasked & FPU_EX_Denormal)
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return unmasked & FPU_EX_Denormal;
}
/* Set the corresponding exception bits */
FPU_PARTIAL_STATUS |= exception;
if (exception & FPU_EX_Precision)
{
if (! (exception & FPU_SW_C1)) {
/* This bit distinguishes over- from underflow for a stack fault,
and roundup from round-down for precision loss. */
FPU_PARTIAL_STATUS &= ~FPU_SW_C1;
}
}
// If #P unmasked exception occured the result still has to be
// written to the destination.
unmasked &= ~FPU_EX_Precision;
if (unmasked & (FPU_EX_Underflow | FPU_EX_Overflow)) {
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// If unmasked over- or underflow occurs and dest is a memory location:
// - the TOS and destination operands remain unchanged
// - the inexact-result condition is not reported and C1 flag is cleared
// - no result is stored in the memory
// If the destination is in the register stack, adjusted resulting value
// is stored in the destination operand.
if (! is_store) {
unmasked &= ~(FPU_EX_Underflow | FPU_EX_Overflow);
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}
else {
FPU_PARTIAL_STATUS &= ~FPU_SW_C1; // clear C1 flag
if (! (status & FPU_EX_Precision))
FPU_PARTIAL_STATUS &= ~FPU_EX_Precision;
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}
}
return unmasked;
}
#endif