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restructured ASH & limit to -32...31

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This commit is contained in:
folkert van heusden 2022-03-20 21:20:15 +01:00
parent ca213298bb
commit 2ac02d91c2
1 changed files with 6 additions and 7 deletions
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13
cpu.cpp
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@ -479,21 +479,20 @@ bool cpu::additional_double_operand_instructions(const uint16_t instr)
case 2: { // ASH
int16_t R = getRegister(reg), oldR = R;
uint16_t a = getGAMAddress(dst_mode, dst_reg, false, false);
int16_t shift = b->read(a, false);
int16_t shift = b->read(a, false) & 077; // mask of lower 6 bit
if (shift > 0) {
if (shift == 0)
setPSW_c(false);
else if (shift < 32) {
R <<= shift - 1;
setPSW_c(R & 0x8000);
R <<= 1;
}
else if (shift < 0) {
R >>= -(shift + 1);
else {
R >>= 64 - shift - 1;
setPSW_c(R & 1);
R >>= 1;
}
else {
setPSW_c(false);
}
setPSW_n(R < 0);
setPSW_z(R == 0);