Interim report of the Grant Program 2020 of Ruby Association

Summary

I have implemented mini mruby compiler in order to cover major syntax of Ruby for microcontroller.

I submit this document as the interim report of the Grant Program 2020 of Ruby Association.

It consists of three parts:

• The first part is explaining my outcome as of today
• The second is a summary of difference between mruby2 and mruby3 in terms of syntax and VM code
• The third is a TODO list which I should implement by the deadline of the final report

Submit date

January 15th, 2021

Implementations so far

This link shows the progress of the period: https://github.com/hasumikin/mmruby/compare/9c776f4...9670063

OP codes relating to conditional jump

• if (unless) elsif then end
• if modifier, unless modifier
• while/until, break, next, redo
• case when then end
• and, or, ||, &&

OP codes relating to block (IREP) and conditional block (like while)

• OP_BLOCK
• OP_ENTER (setups only mandatory parameters)
• Generating nested IREP records
• Keywords which control block things like next break redo

Investigation of differences between mruby2 and mruby3

NEW OP codes

• OP_LOADI16
• OP_LOADI32
• OP_LOADL16
• OP_LOADSYM16

OP codes whose spec is amended

• OP_SETUPVAR
• OP_GETUPVAR
• Relative value of operand for JMP (used to be absolute value)

IREP record structure

• Abolishment of ISEQ’s 4-byte-alignment
• 2 bytes for representing number of literal/symbol (used to be 4 bytes)
• Literal kinds:
• 0x00 for string literal
• 0x01 abolished (used to be for string-formed integer)
• 0x02 abolished (used to be for string-formed float)
• 0x03 for integer which is more than 0x7FFFFFFF or less than -0x80000000
• 0x04 ??? (to be studied)
• 0x05 for float whose width is 8 bytes

TODO from now

• Parsing and generating lambda, yield, class, def, alias, rescue, ensure
• Improvement generating block parameters to generate def sentence
• Correspondence to mruby3
• Reducing RAM consumption