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Fix ad hoc popcount; ARM does carry 'backwards'.

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This commit is contained in:
Thomas Harte 2024-03-07 13:27:41 -05:00
parent f5225b69e5
commit 0e92885ed5
1 changed files with 8 additions and 4 deletions
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12
InstructionSets/ARM/Executor.hpp
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@ -143,11 +143,13 @@ struct Executor {
conditions = operand1 - operand2;
if constexpr (flags.operation() == DataProcessingOperation::SBC) {
conditions -= registers_.c();
conditions += registers_.c() - 1;
}
if constexpr (flags.set_condition_codes()) {
registers_.set_c(Numeric::carried_out<false, 31>(operand1, operand2, conditions));
// "For a subtraction, including the comparison instruction CMP, C is set to 0 if
// the subtraction produced a borrow (that is, an unsigned underflow), and to 1 otherwise."
registers_.set_c(!Numeric::carried_out<false, 31>(operand1, operand2, conditions));
registers_.set_v(Numeric::overflow<false>(operand1, operand2, conditions));
}
@ -365,8 +367,10 @@ struct Executor {
// the base.
// TODO: use std::popcount when adopting C++20.
uint32_t total = ((list & 0xa) >> 1) + (list & 0x5);
total = ((list & 0xc) >> 2) + (list & 0x3);
uint32_t total = ((list & 0xaaa) >> 1) + (list & 0x555);
total = ((total & 0xccc) >> 2) + (total & 0x333);
total = ((total & 0x0f0) >> 4) + (total & 0xf0f);
total = ((total & 0xff0) >> 8) + (total & 0x00f);
uint32_t final_address;
if constexpr (!flags.add_offset()) {