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Corrects SBCD carry.

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This commit is contained in:
Thomas Harte 2019-12-17 22:16:02 -05:00
parent e969b386f1
commit a3e64cae41
1 changed files with 15 additions and 16 deletions
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31
Processors/68000/Implementation/68000Implementation.hpp
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@ -390,6 +390,7 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
const uint8_t destination = destination()->halves.low.halves.low; const uint8_t destination = destination()->halves.low.halves.low;
// Perform the BCD add by evaluating the two nibbles separately. // Perform the BCD add by evaluating the two nibbles separately.
const int unadjusted_result = destination + source + (extend_flag_ ? 1 : 0);
int result = (destination & 0xf) + (source & 0xf) + (extend_flag_ ? 1 : 0); int result = (destination & 0xf) + (source & 0xf) + (extend_flag_ ? 1 : 0);
if(result > 0x09) result += 0x06; if(result > 0x09) result += 0x06;
result += (destination & 0xf0) + (source & 0xf0); result += (destination & 0xf0) + (source & 0xf0);
@ -399,8 +400,6 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
zero_result_ |= result & 0xff; zero_result_ |= result & 0xff;
extend_flag_ = carry_flag_ = uint_fast32_t(result & ~0xff); extend_flag_ = carry_flag_ = uint_fast32_t(result & ~0xff);
negative_flag_ = result & 0x80; negative_flag_ = result & 0x80;
const int unadjusted_result = destination + source + (extend_flag_ ? 1 : 0);
overflow_flag_ = ~unadjusted_result & result & 0x80; overflow_flag_ = ~unadjusted_result & result & 0x80;
// Store the result. // Store the result.
@ -1530,21 +1529,21 @@ template <class T, bool dtack_is_implicit, bool signal_will_perform> void Proces
overflow_flag_ = carry_flag_ = 0; overflow_flag_ = carry_flag_ = 0;
break; break;
#define sbcd() \ #define sbcd() \
/* Perform the BCD arithmetic by evaluating the two nibbles separately. */ \ /* Perform the BCD arithmetic by evaluating the two nibbles separately. */ \
int result = (destination & 0xf) - (source & 0xf) - (extend_flag_ ? 1 : 0); \
if((result & 0x1f) > 0x09) result -= 0x06; \
result += (destination & 0xf0) - (source & 0xf0); \
if((result & 0x1ff) > 0x99) result -= 0x60; \
\
/* Set all flags essentially as if this were normal subtraction. */ \
zero_result_ |= result & 0xff; \
extend_flag_ = carry_flag_ = decltype(carry_flag_)(result & ~0xff); \
negative_flag_ = result & 0x80; \
const int unadjusted_result = destination - source - (extend_flag_ ? 1 : 0); \ const int unadjusted_result = destination - source - (extend_flag_ ? 1 : 0); \
overflow_flag_ = unadjusted_result & ~result & 0x80; \ int result = (destination & 0xf) - (source & 0xf) - (extend_flag_ ? 1 : 0); \
\ if((result & 0x1f) > 0x09) result -= 0x06; \
/* Store the result. */ \ result += (destination & 0xf0) - (source & 0xf0); \
extend_flag_ = carry_flag_ = decltype(carry_flag_)((result & 0x1ff) > 0x99); \
if(carry_flag_) result -= 0x60; \
\
/* Set all flags essentially as if this were normal subtraction. */ \
zero_result_ |= result & 0xff; \
negative_flag_ = result & 0x80; \
overflow_flag_ = unadjusted_result & ~result & 0x80; \
\
/* Store the result. */ \
destination()->halves.low.halves.low = uint8_t(result); destination()->halves.low.halves.low = uint8_t(result);
/* /*