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Eliminate branches from ABCD.

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This commit is contained in:
Thomas Harte 2022-05-12 15:25:01 -04:00
parent 79c5af755f
commit b7d1bff0c7
1 changed files with 5 additions and 3 deletions
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8
InstructionSets/M68k/Implementation/PerformImplementation.hpp
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@ -42,9 +42,11 @@ template <
// 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; const int unadjusted_result = destination + source + extend;
int result = (destination & 0xf) + (source & 0xf) + extend; int result = (destination & 0xf) + (source & 0xf) + extend;
if(result > 0x09) result += 0x06; result +=
result += (destination & 0xf0) + (source & 0xf0); (destination & 0xf0) +
if(result > 0x9f) result += 0x60; (source & 0xf0) +
(((9 - result) >> 4) & 0x06); // i.e. ((result > 0x09) ? 0x06 : 0x00);
result += ((0x9f - result) >> 4) & 0x60; // i.e. ((result > 0x9f) ? 0x60 : 0x00)
// Set all flags essentially as if this were normal addition. // Set all flags essentially as if this were normal addition.
status.zero_result |= result & 0xff; status.zero_result |= result & 0xff;