From 1cb26cb141f6394a763ee06e2a1704f160d6440b Mon Sep 17 00:00:00 2001 From: Thomas Harte Date: Mon, 9 Oct 2023 16:40:50 -0400 Subject: [PATCH] Pull add/sub distinction into templates. --- .../Implementation/PerformImplementation.hpp | 16 +++++----- Numeric/Carry.hpp | 31 ++++++++++++++++--- .../Implementation/6502Implementation.hpp | 8 ++--- 3 files changed, 38 insertions(+), 17 deletions(-) diff --git a/InstructionSets/x86/Implementation/PerformImplementation.hpp b/InstructionSets/x86/Implementation/PerformImplementation.hpp index 70b6de0c8..1978a54a0 100644 --- a/InstructionSets/x86/Implementation/PerformImplementation.hpp +++ b/InstructionSets/x86/Implementation/PerformImplementation.hpp @@ -408,8 +408,8 @@ void adc(IntT &destination, IntT source, Status &status) { */ const IntT result = destination + source + status.carry_bit(); - status.carry = Numeric::carried_out() - 1>(destination, source, result); - status.auxiliary_carry = Numeric::carried_in<4>(destination, source, result); + status.carry = Numeric::carried_out() - 1>(destination, source, result); + status.auxiliary_carry = Numeric::carried_in(destination, source, result); status.sign = result & top_bit(); status.zero = status.parity = result; status.overflow = overflow(destination, source, result); @@ -427,8 +427,8 @@ void add(IntT &destination, IntT source, Status &status) { */ const IntT result = destination + source; - status.carry = Numeric::carried_out() - 1>(destination, source, result); - status.auxiliary_carry = Numeric::carried_in<4>(destination, source, result); + status.carry = Numeric::carried_out() - 1>(destination, source, result); + status.auxiliary_carry = Numeric::carried_in(destination, source, result); status.sign = result & top_bit(); status.zero = status.parity = result; status.overflow = overflow(destination, source, result); @@ -446,8 +446,8 @@ void sbb(IntT &destination, IntT source, Status &status) { */ const IntT result = destination - source - status.carry_bit(); - status.carry = !Numeric::carried_out() - 1>(destination, IntT(~source), result); - status.auxiliary_carry = !Numeric::carried_in<4>(destination, IntT(~source), result); + status.carry = Numeric::carried_out() - 1>(destination, source, result); + status.auxiliary_carry = Numeric::carried_in(destination, source, result); status.sign = result & top_bit(); status.zero = status.parity = result; status.overflow = overflow(destination, source, result); @@ -465,8 +465,8 @@ void sub(IntT &destination, IntT source, Status &status) { */ const IntT result = destination - source; - status.carry = !Numeric::carried_out() - 1>(destination, IntT(~source), result); - status.auxiliary_carry = !Numeric::carried_in<4>(destination, IntT(~source), result); + status.carry = Numeric::carried_out() - 1>(destination, source, result); + status.auxiliary_carry = Numeric::carried_in(destination, source, result); status.sign = result & top_bit(); status.zero = status.parity = result; status.overflow = overflow(destination, source, result); diff --git a/Numeric/Carry.hpp b/Numeric/Carry.hpp index fd17ed357..4896220b9 100644 --- a/Numeric/Carry.hpp +++ b/Numeric/Carry.hpp @@ -11,19 +11,40 @@ namespace Numeric { -/// @returns @c true if there was carry out of @c bit when @c source1 and @c source2 were added, producing @c result. -template bool carried_out(IntT source1, IntT source2, IntT result) { +/// @returns @c true if there, from @c bit there was +/// • carry after calculating @c lhs + @c rhs if @c is_add is true; or +/// • borrow after calculating @c lhs - @c rhs if @c is_add is false; +/// producing @c result. +template bool carried_out(IntT lhs, IntT rhs, IntT result) { // 0 and 0 => didn't. // 0 and 1 or 1 and 0 => did if 0. // 1 and 1 => did. - return IntT(1 << bit) & (source1 | source2) & ((source1 & source2) | ~result); + if constexpr (!is_add) { + rhs = ~rhs; + } + const bool carry = IntT(1 << bit) & (lhs | rhs) & ((lhs & rhs) | ~result); + if constexpr (!is_add) { + return !carry; + } else { + return carry; + } } +// ~carried_out<>(d, ~s, r) + /// @returns @c true if there was carry into @c bit when @c source1 and @c source2 were added, producing @c result. -template bool carried_in(IntT source1, IntT source2, IntT result) { +template bool carried_in(IntT lhs, IntT rhs, IntT result) { // 0 and 0 or 1 and 1 => did if 1 // 0 and 1 or 1 and 0 => did if 0 - return IntT(1 << bit) & (source1 ^ source2 ^ result); + if constexpr (!is_add) { + rhs = ~rhs; + } + const bool carry = IntT(1 << bit) & (lhs ^ rhs ^ result); + if constexpr (!is_add) { + return !carry; + } else { + return carry; + } } } diff --git a/Processors/6502/Implementation/6502Implementation.hpp b/Processors/6502/Implementation/6502Implementation.hpp index bd8dbd502..caa9c71e5 100644 --- a/Processors/6502/Implementation/6502Implementation.hpp +++ b/Processors/6502/Implementation/6502Implementation.hpp @@ -327,7 +327,7 @@ template void Proces // All flags are set based only on the decimal result. flags_.zero_result = result; - flags_.carry = Numeric::carried_out<7>(a_, operand_, result); + flags_.carry = Numeric::carried_out(a_, operand_, result); flags_.negative_result = result; flags_.overflow = (( (result ^ a_) & (result ^ operand_) ) & 0x80) >> 1; @@ -343,7 +343,7 @@ template void Proces // on a 6502 additional borrow isn't propagated but on a 65C02 it is. // This difference affects invalid BCD numbers only — valid numbers will // never be less than -9 so adding 10 will always generate carry. - if(!Numeric::carried_in<4>(a_, operand_, result)) { + if(!Numeric::carried_in(a_, operand_, result)) { if constexpr (is_65c02(personality)) { result += 0xfa; } else { @@ -377,7 +377,7 @@ template void Proces if(flags_.decimal && has_decimal_mode(personality)) { uint8_t result = a_ + operand_ + flags_.carry; flags_.zero_result = result; - flags_.carry = Numeric::carried_out<7>(a_, operand_, result); + flags_.carry = Numeric::carried_out(a_, operand_, result); // General ADC logic: // @@ -390,7 +390,7 @@ template void Proces // // So if that carry already happened, fix up the bottom without permitting another; // otherwise permit the carry to happen (and check whether carry then rippled out of bit 7). - if(Numeric::carried_in<4>(a_, operand_, result)) { + if(Numeric::carried_in(a_, operand_, result)) { result = (result & 0xf0) | ((result + 0x06) & 0x0f); } else if((result & 0xf) > 0x9) { flags_.carry |= result >= 0x100 - 0x6;