70 lines
3.2 KiB
Text
70 lines
3.2 KiB
Text
# Internals: Nga Virtual Machine
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## Overview
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At the heart of RETRO is a simple MISC (minimal instruction
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set computer) processor for a dual stack architecture.
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This is a very simple and straightforward system. There are
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30 instructions. The memory is a linear array of signed 32
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bit values. And there are two stacks: one for data and one
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for return addresses.
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## Instrution Table
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Column:
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0 - opcode value
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1 - Muri assembly name
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2 - Full name
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3 - Data Stack Usage
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4 - Address Stack Usage
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+--------------------------------------------------+
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| 0 .. nop - - |
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| 1 li lit -n - |
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| 2 du dup n-nn - |
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| 3 dr drop n- - |
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| 4 sw swap xy-yx - |
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| 5 pu push n- -n |
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| 6 po pop -n n- |
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| 7 ju jump a- - |
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| 8 ca call a- -A |
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| 9 cc conditional call af- -A |
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| 10 re return - A- |
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| 11 eq equality xy-f - |
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| 12 ne inequality xy-f - |
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| 13 lt less than xy-f - |
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| 14 gt greater than xy-f - |
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| 15 fe fetch a-n - |
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| 16 st store na- - |
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| 17 ad addition xy-n - |
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| 18 su subtraction xy-n - |
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| 19 mu multiplication xy-n - |
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| 20 di divide & remainder xy-rq - |
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| 21 an bitwise and xy-n - |
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| 22 or bitwise or xy-n - |
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| 23 xo bitwise xor xy-n - |
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| 24 sh shift xy-n - |
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| 25 zr zero return n-n | n- - |
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| 26 en end - - |
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| 27 ie i/o enumerate -n - |
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| 28 iq i/o query n-xy - |
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| 29 ii i/o invoke ...n- - |
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| Each `li` will push the value in the following |
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| cell to the data stack. |
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+--------------------------------------------------+
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| li du mu .. |
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| i lidumu.. 00000001:00000010:00010011:00000000 |
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| data for li |
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| d 2 00000000:00000000:00000000:00000010 |
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| Assembler Directives Instruction Bundles |
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| ======================== ==================== |
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| : label Combine instruction |
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| i bundle names in groups of 4 |
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| d numeric-data |
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| r ref-to-address-by-name Use only .. after |
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| s null-terminated string ju, ca, cc, re, zr |
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+--------------------------------------------------+
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