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Improve DAA.

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This commit is contained in:
Thomas Harte 2023-10-09 14:42:32 -04:00
parent 1b9e6e8c8e
commit 0bf2099a70
1 changed files with 14 additions and 4 deletions
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18
InstructionSets/x86/Implementation/PerformImplementation.hpp
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@ -294,15 +294,21 @@ inline void aas(CPU::RegisterPair16 &ax, Status &status) {
inline void daa(uint8_t &al, Status &status) { inline void daa(uint8_t &al, Status &status) {
/* /*
(as modified by https://www.felixcloutier.com/x86/daa ...)
old_AL ← AL;
old_CF ← CF;
CF ← 0;
IF (((AL AND 0FH) > 9) or AF = 1) IF (((AL AND 0FH) > 9) or AF = 1)
THEN THEN
AL ← AL + 6; AL ← AL + 6;
CF ← CF OR CarryFromLastAddition; (* CF OR carry from AL ← AL + 6 *) CF ← old_CF OR CarryFromLastAddition; (* CF OR carry from AL ← AL + 6 *)
AF ← 1; AF ← 1;
ELSE ELSE
AF ← 0; AF ← 0;
FI; FI;
IF ((AL AND F0H) > 90H) or CF = 1) IF ((old_AL > 99H) or old_CF = 1)
THEN THEN
AL ← AL + 60H; AL ← AL + 60H;
CF ← 1; CF ← 1;
@ -315,15 +321,19 @@ inline void daa(uint8_t &al, Status &status) {
decimal carry in either digit of the result (see the “Operation” section above). decimal carry in either digit of the result (see the “Operation” section above).
The SF, ZF, and PF flags are set according to the result. The OF flag is undefined. The SF, ZF, and PF flags are set according to the result. The OF flag is undefined.
*/ */
const uint8_t old_al = al;
const auto old_carry = status.carry;
status.carry = 0;
if((al & 0x0f) > 0x09 || status.auxiliary_carry) { if((al & 0x0f) > 0x09 || status.auxiliary_carry) {
status.carry |= al > 0xf9; status.carry = old_carry | (al > 0xf9);
al += 0x06; al += 0x06;
status.auxiliary_carry = 1; status.auxiliary_carry = 1;
} else { } else {
status.auxiliary_carry = 0; status.auxiliary_carry = 0;
} }
if((al & 0xf0) > 0x90 || status.carry) { if(old_al > 0x99 || old_carry) {
al += 0x60; al += 0x60;
status.carry = 1; status.carry = 1;
} else { } else {