diff --git a/src/6502-c++.cpp b/src/6502-c++.cpp index 36e29e6..31627de 100644 --- a/src/6502-c++.cpp +++ b/src/6502-c++.cpp @@ -259,7 +259,7 @@ void fixup_16_bit_N_Z_flags(std::vector &instructions) // assuming A contains higher order byte and X contains lower order byte instructions.emplace_back(ASMLine::Type::Directive, "; BEGIN remove if next is lda"); instructions.emplace_back(ASMLine::Type::Directive, "; set CPU flags assuming A holds the higher order byte already"); - std::string set_flag_label = "flags_set_after_16_bit_op_" + std::to_string(instructions.size()); + std::string set_flag_label = "fixup_16_bit_op_flags" + std::to_string(instructions.size()); // if high order is negative, we know it's not 0 and it is negative instructions.emplace_back(mos6502::OpCode::bmi, Operand(Operand::Type::literal, set_flag_label)); // if it's not 0, then branch down, we know the result is not 0 and not negative @@ -268,8 +268,8 @@ void fixup_16_bit_N_Z_flags(std::vector &instructions) instructions.emplace_back(mos6502::OpCode::txa); // if low order is not negative, we know it's 0 or not 0 instructions.emplace_back(mos6502::OpCode::bpl, Operand(Operand::Type::literal, set_flag_label)); - // if low order byte is negative, shift right by one bit, then we'll get the proper Z/N flags - instructions.emplace_back(mos6502::OpCode::lsr); + // if low order byte is negative, just load 1, this will properly set the Z flag and leave C correct + instructions.emplace_back(mos6502::OpCode::lda, Operand(Operand::Type::literal, "#1")); instructions.emplace_back(ASMLine::Type::Label, set_flag_label); instructions.emplace_back(ASMLine::Type::Directive, "; END remove if next is lda, bcc, bcs"); } @@ -810,43 +810,7 @@ bool fix_long_branches(std::vector &instructions, int &branch_patch_cou } -bool fix_overwritten_flags(std::vector &instructions) -{ -// return false; - if (instructions.size() < 3) { - return false; - } - for (size_t op = 0; op < instructions.size(); ++op) { - if (instructions[op].is_comparison) { - auto op2 = op + 1; - while (op2 < instructions.size() - && !instructions[op2].is_comparison - && !instructions[op2].is_branch) { - ++op2; - } - - if (op2 < instructions.size() - && (op2 - op) > 1 - && instructions[op2 - 1].opcode != mos6502::OpCode::plp) { - if (instructions[op2].is_comparison) { - continue; - } - - if (instructions[op2].is_branch) { - // insert a pull of processor status before the branch - instructions.insert(std::next(std::begin(instructions), static_cast(op2)), mos6502(mos6502::OpCode::plp)); - // insert a push of processor status after the comparison - instructions.insert(std::next(std::begin(instructions), static_cast(op + 1)), mos6502(mos6502::OpCode::php)); - - return true; - } - } - } - } - - return false; -} void run(const Personality &personality, std::istream &input) { @@ -1008,13 +972,6 @@ void run(const Personality &personality, std::istream &input) } } - // it seems that with the move to AVR for the base, this - // fixup no longer makes sense, but I'm not going to remove it just yet - // until we have more complex C++ examples working -// while (fix_overwritten_flags(new_instructions)) { - // do it however many times it takes -// } - while (optimize(new_instructions)) { // do it however many times it takes }