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lips/README.md
Connor Olding 9a2335fab1 a little more info
2015-11-23 20:42:19 -08:00

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lips

An assembler for the MIPS R4300i architecture, written in Lua.

Not for production. Much of the code and syntax is untested and likely to change. Even this README is incomplete.

Syntax

(TODO)

A derivative of CajeASM's syntax.

Instructions

Instructions were primarily referenced from the N64 Toolkit: Opcodes.

A more in-depth look at instructions for MIPS IV processors in general is given by the MIPS IV Instruction Set manual.

There's also a brief and incomplete overview of MIPS instructions. First-time writers of MIPS assembly may find this the most useful.

Unimplemented

  • CACHE

  • ERET

  • TLBP, TLBR, TLBWI, TLBWR

  • BC1F, BC1FL, BC1T, BC1TL

Unimplemented Pseudo-Instructions

Besides implied arguments for existing instructions, there are:

  • ABS, MUL, DIV, REM

  • NAND, NANDI, NORI, ROL, ROR

  • SEQ, SEQI, SEQIU, SEQU

  • SGE, SGEI, SGEIU, SGEU

  • SGT, SGTI, SGTIU, SGTU

  • SLE, SLEI, SLEIU, SLEU

  • SNE, SNEI, SNEIU, SNEU

  • BEQI, BNEI, BGE, BGEI, BLE, BLEI, BLT, BLTI, BGT, BGTI

Registers

In order of numerical value, with intended usage:

  • R0: always zero; cannot be written to. 'zero' is an acceptable alias.

  • AT: assembler temporary. used by various pseudo-instructions. user may use freely if they're wary.

  • V0, V1: subroutine return values.

  • A0 A1 A2 A3: subroutine arguments.

  • T0 T1 T2 T3 T4 T5 T6 T7: temporary registers.

  • S0 S1 S2 S3 S4 S5 S6 S7: saved registers.

  • T8 T9: more temporary registers.

  • K0 K1: kernel registers. not recommended to use outside of kernel code.

  • GP: global pointer.

  • SP: stack pointer.

  • FP: frame pointer. 'S8' is an acceptable alias.

  • RA: subroutine return address.

  • REG#: whereas # is a decimal number from 0 to 31. aliased to the appropriate register. eg: REG0 is R0, REG1 is at, REG2 is V0.

  • F#: coproccesor 1 registers, whereas # is a decimal number from 0 to 31.

Unimplemented

all coprocessor 0 registers:

Index,     Random,    EntryLo0,     EntryLo1,
Context,   PageMask,  Wired,        RESERVED,
BadVAddr,  Count,     EntryHi,      Compare,
Status,    Cause,     ExceptionPC,  PRId,
Config,    LLAddr,    WatchLo,      WatchHi,
XContext,  RESERVED,  RESERVED,     RESERVED,
RESERVED,  RESERVED,  RESERVED,     CacheErr,
TagLo,     TagHi,     ErrorEPC,     RESERVED

Directives

  • BYTE: writes a list of 8-bit numbers until end-of-line. be wary of potential alignment issues.

  • HALFWORD: writes a list of 16-bit numbers until end-of-line. be wary of potential alignment issues.

  • WORD: writes a list of 32-bit numbers until end-of-line.

  • SKIP: takes one or two arguments.

  • ORG: change the current address for writing to; seeking. for now, this is untested and likely to cause performance issues.

Unimplemented

  • ALIGN: takes one or two arguments. unlike some other assemblers, ALIGN only affects the first immediately following datum.

  • FLOAT: writes a list of 32-bit floating point numbers until end-of-line. this may not get implemented due to a lack of aliasing in vanilla Lua, and thus accuracy issues.

  • ASCII: writes a string using its characters' ASCII values.

  • ASCIIZ: same as ASCII, but with a null byte added to the end.

  • INC, INCASM, INCLUDE: include an external assembly file as-is at this position.

  • INCBIN: write an external binary file as-is at this position.