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restructured ASHC & limit to -32...31

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folkert van heusden 2022-03-20 21:28:12 +01:00
parent 2ac02d91c2
commit e12e97341b
1 changed files with 13 additions and 9 deletions
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22
cpu.cpp
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@ -509,20 +509,24 @@ bool cpu::additional_double_operand_instructions(const uint16_t instr)
case 3: { // ASHC
uint32_t R0R1 = (getRegister(reg) << 16) | getRegister(reg + 1);
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) {
setPSW_c(false);
}
else if (shift < 32) {
R0R1 <<= shift - 1;
if (shift > 0) {
R0R1 <<= (shift & 0b111111) - 1;
setPSW_c(R0R1 >> 31);
R0R1 <<= 1;
}
else if (shift < 0) {
R0R1 >>= -((shift & 0b111111) - 1);
setPSW_c(R0R1 & 1);
R0R1 >>= 1;
}
else {
setPSW_c(false);
R0R1 >>= 64 - shift - 1;
setPSW_c(R0R1 & 1);
R0R1 >>= 1;
}
setRegister(reg, R0R1 & 65535);