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i386: use floatx80_scale for fscale (nw)

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This commit is contained in:
cracyc 2019-07-08 14:26:33 -05:00
parent 873547cea2
commit e5b13284bc
2 changed files with 2 additions and 42 deletions
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22
src/devices/cpu/i386/x87ops.hxx
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@ -3312,27 +3312,7 @@ void i386_device::x87_fscale(uint8_t modrm)
else else
{ {
m_x87_sw &= ~X87_SW_C1; m_x87_sw &= ~X87_SW_C1;
value = ST(0); value = floatx80_scale(ST(0), ST(1));
// Set the rounding mode to truncate
uint16_t old_cw = m_x87_cw;
uint16_t new_cw = (old_cw & ~(X87_CW_RC_MASK << X87_CW_RC_SHIFT)) | (X87_CW_RC_ZERO << X87_CW_RC_SHIFT);
x87_write_cw(new_cw);
// Interpret ST(1) as an integer
uint32_t st1 = floatx80_to_int32(floatx80_round_to_int(ST(1)));
// Restore the rounding mode
x87_write_cw(old_cw);
// Get the unbiased exponent of ST(0)
int16_t exp = (ST(0).high & 0x7fff) - 0x3fff;
// Calculate the new exponent
exp = (exp + st1 + 0x3fff) & 0x7fff;
// Write it back
value.high = (value.high & ~0x7fff) + exp;
} }
if (x87_check_exceptions()) if (x87_check_exceptions())

22
src/devices/machine/i8087.cpp
View File

@ -3415,27 +3415,7 @@ void i8087_device::fscale(u8 modrm)
else else
{ {
m_sw &= ~X87_SW_C1; m_sw &= ~X87_SW_C1;
value = ST(0); value = floatx80_scale(ST(0), ST(1));
// Set the rounding mode to truncate
u16 old_cw = m_cw;
u16 new_cw = (old_cw & ~(X87_CW_RC_MASK << X87_CW_RC_SHIFT)) | (X87_CW_RC_ZERO << X87_CW_RC_SHIFT);
write_cw(new_cw);
// Interpret ST(1) as an integer
u32 st1 = floatx80_to_int32(floatx80_round_to_int(ST(1)));
// Restore the rounding mode
write_cw(old_cw);
// Get the unbiased exponent of ST(0)
int16_t exp = (ST(0).high & 0x7fff) - 0x3fff;
// Calculate the new exponent
exp = (exp + st1 + 0x3fff) & 0x7fff;
// Write it back
value.high = (value.high & ~0x7fff) + exp;
} }
if (check_exceptions()) if (check_exceptions())