mirror of https://github.com/bsnes-emu/bsnes.git
59 lines
1.5 KiB
C++
59 lines
1.5 KiB
C++
//ModRM functions
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//d7-d6 => mod
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//d5-d3 => reg
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//d2-d0 => mem
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auto V30MZ::getReg(Size size, uint8 modRM) -> uint16 {
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return size == Byte ? r.byte(modRM >> 3) : r.word(modRM >> 3);
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}
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auto V30MZ::setReg(Size size, uint8 modRM, uint16 data) -> void {
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if(size == Byte) r.byte(modRM >> 3) = data;
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if(size == Word) r.word(modRM >> 3) = data;
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}
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//
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auto V30MZ::getSeg(uint8 modRM) -> uint16 {
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return r.segment(modRM >> 3);
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}
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auto V30MZ::setSeg(uint8 modRM, uint16 data) -> void {
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r.segment(modRM >> 3) = data;
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}
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//
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auto V30MZ::getMemAddress(uint8 modRM) -> uint32 {
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if((modRM & 0xc7) == 0x06) return r.ds << 16 | fetch(Word);
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uint16 s = 0, a = 0;
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if((modRM & 0xc0) == 0x40) a = (int8)fetch(Byte);
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if((modRM & 0xc0) == 0x80) a = (int16)fetch(Word);
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switch(modRM & 7) {
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case 0: s = r.ds; a += r.bx + r.si; break;
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case 1: s = r.ds; a += r.bx + r.di; break;
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case 2: s = r.ss; a += r.bp + r.si; break;
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case 3: s = r.ss; a += r.bp + r.di; break;
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case 4: s = r.ds; a += r.si; break;
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case 5: s = r.ds; a += r.di; break;
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case 6: s = r.ss; a += r.bp; break;
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case 7: s = r.ds; a += r.bx; break;
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}
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return segment(s) << 16 | a;
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}
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auto V30MZ::getMem(Size size, uint8 modRM) -> uint32 {
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if(modRM >= 0xc0) return getReg(size, modRM << 3);
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auto addr = getMemAddress(modRM);
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return read(size, addr >> 16, addr);
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}
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auto V30MZ::setMem(Size size, uint8 modRM, uint16 data) -> void {
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if(modRM >= 0xc0) return setReg(size, modRM << 3, data);
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auto addr = getMemAddress(modRM);
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return write(size, addr >> 16, addr, data);
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}
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