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sign extend during shift

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folkert van heusden 2022-03-20 21:39:22 +01:00
parent e12e97341b
commit e4432448f1
1 changed files with 12 additions and 2 deletions
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14
cpu.cpp
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@ -489,7 +489,12 @@ bool cpu::additional_double_operand_instructions(const uint16_t instr)
R <<= 1;
}
else {
R >>= 64 - shift - 1;
// extend sign-bit
if (R & 0x8000) // convert to unsigned 32b int & extend sign
R = (uint32_t(R) | 0xffff0000) >> (64 - shift - 1);
else
R >>= 64 - shift - 1;
setPSW_c(R & 1);
R >>= 1;
}
@ -522,7 +527,12 @@ bool cpu::additional_double_operand_instructions(const uint16_t instr)
R0R1 <<= 1;
}
else {
R0R1 >>= 64 - shift - 1;
// extend sign-bit
if (R0R1 & 0x80000000) // convert to unsigned 64b int & extend sign
R0R1 = (uint64_t(R0R1) | 0xffffffff0000) >> (64 - shift - 1);
else
R0R1 >>= 64 - shift - 1;
setPSW_c(R0R1 & 1);