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* 4695Kartik Agaram2018-10-141-18/+18
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* 4694Kartik Agaram2018-10-131-9/+9
| | | | Check for duplicate docstrings.
* 4693Kartik Agaram2018-10-131-9/+9
| | | | | | | | Add the standard mnemonic for each opcode. We aren't ever going to have complete docs of the subset of the x86 ISA we support, so we need to help readers cross-correlate with the complete docs.
* 4689Kartik Agaram2018-10-121-64/+0
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* 4688Kartik Agaram2018-10-121-28/+28
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* 4687Kartik Agaram2018-10-121-11/+11
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* 4686Kartik Agaram2018-10-121-5/+5
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* 4685Kartik Agaram2018-10-121-1/+1
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* 4634Kartik Agaram2018-10-011-91/+91
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* 4503Kartik Agaram2018-09-221-0/+23
| | | | Include LEA (load effective address) in the SubX subset of x86 ISA.
* 4584 - discrepancy between SubX and native x86Kartik Agaram2018-09-211-7/+12
| | | | | | | | | | | | | | | | | | | | | | | | | One of the more painful things I had to debug with machine code. Tricks I used can be seen in ex10.subx: - printing argv[1] in various places - printing a single 'X' in various places to count how many times we get to different instructions - exiting with the current value of EAX in various places I repeatedly went down the wrong trail in several ways: - forgetting that the problem lay in native runs, and accidentally switching to subx runs during debugging. - forgetting to pass commandline args, because ex10 doesn't check its argv - writing the wrong comment for an instruction, and then miscalculating the set of registers that need to be saved. - forgetting that syscalls clobber EAX. Debugging native runs is hard, because you have to write non-trivial code to instrument the binary, and instrumentation can itself be buggy. When we finally tracked it down, I recognized the problem immediately. I'd meant to confirm the behavior of opcode 8a against bare metal, and then forgot. In any case, opcode 8a was inconsistent with 88. Sloppy.
* 4578 - subx: implement inc/dec operationsKartik Agaram2018-09-211-17/+6
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* 4547Kartik Agaram2018-09-161-1/+1
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* 4538Kartik Agaram2018-09-071-2/+2
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* 4537Kartik Agaram2018-09-071-4/+5
| | | | | | | | | | | | | | | Streamline the factorial function; we don't need to save a stack variable into a register before operating on it. All instructions can take a stack variable directly. In the process we found two bugs: a) Opcode f7 was not implemented correctly. It was internally consistent but I'd never validated it against a natively running program. Turns out it encodes multiple instructions, not just 'not'. b) The way we look up imm32 operands was sometimes reading them before disp8/disp32 operands.
* 4527 - reading commandline argumentsKartik Agaram2018-08-301-1/+60
| | | | | | | | | | | The new example ex9 doesn't yet work natively. In the process I've emulated the kernel's role in providing args, implemented a couple of instructions acting on 8-bit operands (useful for ASCII string operations), and begun the start of the standard library (ascii_length is the same as strlen). At the level of SubX we're just only going to support ASCII.
* 4469Kartik Agaram2018-08-031-0/+589