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68k: fix carry flag clear in divs instruction (#3670)

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* 68k: fix carry flag clear in divs instruction

I was debugging why the HP9000/300 selftests where hanging on hp9k_3xx.
Debugger showed the following code:

move.l (a2)+, d0
move.l (a2)+, d1
move d6, ccr
divs.w d0,d1
loop: bcs.s loop

Clearly this tests whether the carry flag is cleared - the Motorola Reference
Manual says it's always cleared. However, in our implementation, it's not
cleared on overflow.

* 68k: fix carry flag clear in divu instruction

It is always cleared, even on overflow.

Signed-off-by: Sven Schnelle <svens@stackframe.org>
This commit is contained in:
Sven Schnelle 2018-06-17 23:45:31 +02:00 committed by R. Belmont
parent 87f9a820bb
commit 710589dde0
1 changed files with 4 additions and 6 deletions
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10
src/devices/cpu/m68000/m68k_in.cpp
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@ -4540,12 +4540,12 @@ M68KMAKE_OP(divs, 16, ., d)
if(src != 0)
{
m_c_flag = CFLAG_CLEAR;
if((uint32_t)*r_dst == 0x80000000 && src == -1)
{
m_not_z_flag = 0;
m_n_flag = NFLAG_CLEAR;
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = 0;
return;
}
@ -4558,7 +4558,6 @@ M68KMAKE_OP(divs, 16, ., d)
m_not_z_flag = quotient;
m_n_flag = NFLAG_16(quotient);
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = MASK_OUT_ABOVE_32(MASK_OUT_ABOVE_16(quotient) | (remainder << 16));
return;
}
@ -4578,12 +4577,12 @@ M68KMAKE_OP(divs, 16, ., .)
if(src != 0)
{
m_c_flag = CFLAG_CLEAR;
if((uint32_t)*r_dst == 0x80000000 && src == -1)
{
m_not_z_flag = 0;
m_n_flag = NFLAG_CLEAR;
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = 0;
return;
}
@ -4596,7 +4595,6 @@ M68KMAKE_OP(divs, 16, ., .)
m_not_z_flag = quotient;
m_n_flag = NFLAG_16(quotient);
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = MASK_OUT_ABOVE_32(MASK_OUT_ABOVE_16(quotient) | (remainder << 16));
return;
}
@ -4614,6 +4612,7 @@ M68KMAKE_OP(divu, 16, ., d)
if(src != 0)
{
m_c_flag = CFLAG_CLEAR;
uint32_t quotient = *r_dst / src;
uint32_t remainder = *r_dst % src;
@ -4622,7 +4621,6 @@ M68KMAKE_OP(divu, 16, ., d)
m_not_z_flag = quotient;
m_n_flag = NFLAG_16(quotient);
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = MASK_OUT_ABOVE_32(MASK_OUT_ABOVE_16(quotient) | (remainder << 16));
return;
}
@ -4640,6 +4638,7 @@ M68KMAKE_OP(divu, 16, ., .)
if(src != 0)
{
m_c_flag = CFLAG_CLEAR;
uint32_t quotient = *r_dst / src;
uint32_t remainder = *r_dst % src;
@ -4648,7 +4647,6 @@ M68KMAKE_OP(divu, 16, ., .)
m_not_z_flag = quotient;
m_n_flag = NFLAG_16(quotient);
m_v_flag = VFLAG_CLEAR;
m_c_flag = CFLAG_CLEAR;
*r_dst = MASK_OUT_ABOVE_32(MASK_OUT_ABOVE_16(quotient) | (remainder << 16));
return;
}