perfaware/part1: Handle positive value IMM->Reg
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@ -15,7 +15,7 @@ copy /Y %script_dir%\listing_0040_challenge_movs %build_dir% 1>NUL
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REM Build
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REM ===========================================================================
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pushd %build_dir%
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cl %script_dir%\sim8086.c /W4 /WX /Z7 /nologo
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cl %script_dir%\sim8086.c /W4 /WX /Z7 /nologo || exit /b 1
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popd
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REM Tests
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@ -29,3 +29,8 @@ set listing_0038=%build_dir%\listing_0038_many_register_mov
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%build_dir%\sim8086.exe %listing_0038% > %listing_0038%_disassembled.asm
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nasm %listing_0038%_disassembled.asm
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fc %listing_0038% %listing_0038%_disassembled || exit /b 1
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set listing_0039=%build_dir%\listing_0039_more_movs
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%build_dir%\sim8086.exe %listing_0039% > %listing_0039%_disassembled.asm
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nasm %listing_0039%_disassembled.asm
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fc %listing_0039% %listing_0039%_disassembled || exit /b 1
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204
part1/sim8086.c
204
part1/sim8086.c
@ -189,34 +189,90 @@ enum S86_InstructionType {
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typedef struct S86_Instruction S86_Instruction;
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struct S86_Instruction {
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uint16_t op_mask;
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uint16_t op_bits;
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uint8_t op_mask0;
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uint8_t op_bits0;
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uint8_t op_mask1;
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uint8_t op_bits1;
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} S86_INSTRUCTIONS[S86_InstructionType_Count] = {
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[S86_InstructionType_MOVRegOrMemToOrFromReg] = {.op_mask = 0b1111'1100'0000'0000,
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.op_bits = 0b1000'1000'0000'0000},
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[S86_InstructionType_MOVRegOrMemToOrFromReg] = {.op_mask0 = 0b1111'1100,
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.op_bits0 = 0b1000'1000,
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.op_mask1 = 0b0000'0000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVImmediateToRegOrMem] = {.op_mask = 0b1111'1110'0011'1000,
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.op_bits = 0b1100'0110'0000'0000},
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[S86_InstructionType_MOVImmediateToRegOrMem] = {.op_mask0 = 0b1111'1110,
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.op_bits0 = 0b1100'0110,
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.op_mask1 = 0b0011'1000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVImmediateToReg] = {.op_mask = 0b1111'0000'0000'0000,
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.op_bits = 0b1011'0000'0000'0000},
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[S86_InstructionType_MOVImmediateToReg] = {.op_mask0 = 0b1111'0000,
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.op_bits0 = 0b1011'0000,
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.op_mask1 = 0b0000'0000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVMemToAccum] = {.op_mask = 0b1111'1110'0000'0000,
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.op_bits = 0b1010'0000'0000'0000},
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[S86_InstructionType_MOVMemToAccum] = {.op_mask0 = 0b1111'1110,
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.op_bits0 = 0b1010'0000,
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.op_mask1 = 0b0000'0000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVAccumToMem] = {.op_mask = 0b1111'1110'0000'0000,
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.op_bits = 0b1010'0010'0000'0000},
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[S86_InstructionType_MOVAccumToMem] = {.op_mask0 = 0b1111'1110,
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.op_bits0 = 0b1010'0010,
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.op_mask1 = 0b0000'0000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVRegOrMemToSegReg] = {.op_mask = 0b1111'1111'0010'0000,
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.op_bits = 0b1000'1110'0000'0000},
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[S86_InstructionType_MOVRegOrMemToSegReg] = {.op_mask0 = 0b1111'1111,
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.op_bits0 = 0b1000'1110,
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.op_mask1 = 0b0010'0000,
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.op_bits1 = 0b0000'0000},
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[S86_InstructionType_MOVSegRegToRegOrMem] = {.op_mask = 0b1111'1111'0010'0000,
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.op_bits = 0b1000'1100'0000'0000},
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[S86_InstructionType_MOVSegRegToRegOrMem] = {.op_mask0 = 0b1111'1111,
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.op_bits0 = 0b1000'1100,
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.op_mask1 = 0b0010'0000,
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.op_bits1 = 0b0000'0000},
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};
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typedef enum S86_OpDataSize S86_OpDataSize;
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enum S86_OpDataSize { S86_OpDataSize_Byte, S86_OpDataSize_Word };
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typedef struct S86_InstructionStream {
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uint8_t bytes[6];
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uint8_t size;
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} S86_InstructionStream;
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typedef struct S86_BufferIterator {
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S86_Buffer buffer;
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size_t index;
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} S86_BufferIterator;
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S86_BufferIterator S86_BufferIteratorInit(S86_Buffer buffer)
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{
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S86_BufferIterator result = {0};
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result.buffer = buffer;
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return result;
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}
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bool S86_BufferIteratorHasMoreBytes(S86_BufferIterator it)
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{
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bool result = S86_BufferIsValid(it.buffer) && it.index < it.buffer.size;
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return result;
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}
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uint8_t S86_BufferIteratorPeekByte(S86_BufferIterator it)
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{
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S86_ASSERT(S86_BufferIsValid(it.buffer));
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S86_ASSERT(it.index < it.buffer.size);
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uint8_t result = it.buffer.data[it.index];
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return result;
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}
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uint8_t S86_BufferIteratorNextByte(S86_BufferIterator *it)
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{
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S86_ASSERT(it);
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S86_ASSERT(S86_BufferIsValid(it->buffer));
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S86_ASSERT(it->index < it->buffer.size);
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uint8_t result = it->buffer.data[it->index++];
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return result;
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}
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int main(int argc, char **argv)
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{
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if (argc != 2) {
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@ -257,31 +313,58 @@ int main(int argc, char **argv)
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}
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S86_PrintLn(S86_STR8("bits 16"));
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S86_ASSERT(buffer.size % 2 == 0); // We expect 2 byte instructions
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S86_BufferIterator buffer_it = S86_BufferIteratorInit(buffer);
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while (S86_BufferIteratorHasMoreBytes(buffer_it)) {
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for (size_t buffer_index = 0; buffer_index < buffer.size; buffer_index += 2) {
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uint8_t byte0 = (uint8_t)buffer.data[buffer_index + 0];
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uint8_t byte1 = (uint8_t)buffer.data[buffer_index + 1];
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uint16_t byte01 = (uint16_t)byte0 << 8 | (uint16_t)byte1 << 0;
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S86_InstructionStream stream = {0};
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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S86_InstructionType instruction_type = S86_InstructionType_Count;
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// NOTE: Match the assembly bytes to the desired instruction
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// =====================================================================
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S86_InstructionType instruction_type = S86_InstructionType_Count;
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S86_Instruction const *instruction = NULL;
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for (size_t instruction_index = 0;
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instruction_type == S86_InstructionType_Count && instruction_index < S86_ARRAY_UCOUNT(S86_INSTRUCTIONS);
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instruction_index++)
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{
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S86_Instruction instruction = S86_INSTRUCTIONS[instruction_index];
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if ((byte01 & instruction.op_mask) == instruction.op_bits)
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S86_Instruction *item = S86_INSTRUCTIONS + instruction_index;
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// NOTE: Check first instruction byte
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// =================================================================
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if ((stream.bytes[0] & item->op_mask0) != item->op_bits0)
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continue;
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// NOTE Check multi-byte instruction
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// =================================================================
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// If the matched instruction has a bit mask for the 2nd byte, this
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// is a multi-byte instruction. Check if the 2nd byte checks out.
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bool instruction_matched = true;
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if (item->op_mask1) {
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// TODO: This assumes the iterator is valid
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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instruction_matched = (stream.bytes[stream.size - 1] & item->op_mask1) == item->op_bits1;
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}
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if (instruction_matched) {
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instruction_type = instruction_index;
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instruction = item;
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}
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}
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// NOTE: Disassemble bytes to assembly mnemonics
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// =================================================================
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S86_ASSERT(instruction_type != S86_InstructionType_Count && "Unknown instruction");
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switch (instruction_type) {
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case S86_InstructionType_MOVRegOrMemToOrFromReg: {
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uint8_t d = (byte0 & 0b0000'0010) >> 1;
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uint8_t w = (byte0 & 0b0000'0001) >> 0;
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uint8_t mod = (byte1 & 0b1100'0000) >> 6;
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uint8_t reg = (byte1 & 0b0011'1000) >> 3;
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uint8_t rm = (byte1 & 0b0000'0111) >> 0;
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// NOTE: Instruction does not have opcode bits in the 2nd byte
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S86_ASSERT(stream.size == 1);
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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uint8_t d = (stream.bytes[0] & 0b0000'0010) >> 1;
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uint8_t w = (stream.bytes[0] & 0b0000'0001) >> 0;
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uint8_t mod = (stream.bytes[1] & 0b1100'0000) >> 6;
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uint8_t reg = (stream.bytes[1] & 0b0011'1000) >> 3;
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uint8_t rm = (stream.bytes[1] & 0b0000'0111) >> 0;
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S86_ASSERT(d < 2);
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S86_ASSERT(w < 2);
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S86_ASSERT(mod < 4);
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@ -309,11 +392,72 @@ int main(int argc, char **argv)
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} break;
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case S86_InstructionType_MOVImmediateToRegOrMem: {
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S86_ASSERT(stream.size == 2);
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uint8_t w = (stream.bytes[0] & 0b0000'0001) >> 0;
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uint8_t mod = (stream.bytes[1] & 0b1100'0000) >> 6;
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uint8_t rm = (stream.bytes[1] & 0b0000'0111) >> 0;
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uint16_t displacement = 0;
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if (mod == 0b01) {
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// 8 bit displacement
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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displacement = stream.bytes[stream.size - 1];
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} else if (mod == 0b10) {
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// 16 bit displacement
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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displacement = (uint16_t)stream.bytes[2] << 0 | (uint16_t)stream.bytes[3] << 8;
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} else {
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// NOTE: We can't have register-to-register (mod == 0b11)
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// as this instruction is an immediate to register/memory
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S86_ASSERT(mod == 0b00);
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}
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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uint16_t data = stream.bytes[stream.size - 1];
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if (w) { // 16 bit data
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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data |= (uint16_t)(stream.bytes[stream.size - 1]) << 8;
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}
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S86_Str8 effective_address_registers;
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switch (rm) {
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case 0b000: effective_address_registers = S86_STR8("bx + si"); break;
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case 0b001: effective_address_registers = S86_STR8("bx + di"); break;
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case 0b010: effective_address_registers = S86_STR8("bp + si"); break;
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case 0b011: effective_address_registers = S86_STR8("bp + di"); break;
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case 0b100: effective_address_registers = S86_STR8("si"); break;
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case 0b101: effective_address_registers = S86_STR8("di"); break;
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case 0b110: effective_address_registers = S86_STR8("??"); S86_ASSERT(!"Unhandled instruction"); break;
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case 0b111: effective_address_registers = S86_STR8("bx"); break;
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default: S86_ASSERT(!"Invalid rm value, must be 3 bits"); break;
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}
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S86_ASSERT(!"Unhandled instruction");
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} break;
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case S86_InstructionType_MOVImmediateToReg: {
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S86_ASSERT(!"Unhandled instruction");
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// NOTE: Parse opcode control bits
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// =============================================================
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S86_ASSERT(stream.size == 1);
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uint8_t w = (stream.bytes[0] & 0b0000'1000) >> 4;
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uint8_t reg = (stream.bytes[0] & 0b0000'0111) >> 0;
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// NOTE: Parse data payload
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// =============================================================
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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uint16_t data = stream.bytes[stream.size - 1];
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if (w) { // 16 bit data
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stream.bytes[stream.size++] = S86_BufferIteratorNextByte(&buffer_it);
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data |= (uint16_t)(stream.bytes[stream.size - 1]) << 8;
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}
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// NOTE: Disassemble
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// =============================================================
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S86_Str8 dest_register = REGISTER_FIELD_ENCODING[w][reg];
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S86_PrintLnFmt("mov %.*s, %u", S86_STR8_FMT(dest_register), data);
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} break;
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case S86_InstructionType_MOVMemToAccum: {
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BIN
project.rdbg
BIN
project.rdbg
Binary file not shown.
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