mu/subx/ex1.2.subx

## first program: same as https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html
# Just return 42.
#
# To run:
#   $ subx translate ex1.2.subx ex1
#   $ subx run ex1

== 0x08048054  # code segment, after leaving room for ELF header
# instruction                     effective address                                           operand     displacement    immediate
# op          subop               mod             rm32          base      index     scale     r32
# 1-3 bytes   3 bits              2 bits          3 bits        3 bits    3 bits    2 bits    2 bits      0/1/2/4 bytes   0/1/2/4 bytes
  bb                                                                                                                      2a/imm32          # copy 42 to EBX
  # exit(EBX)
  b8                                                                                                                      1/imm32           # copy 1 to EAX
  cd                                                                                                                      0x80/imm8         # int 80h

# vim:ft=subx
4303 - subx: first real transform We'll see if this is useful. Mostly just stretching our legs. 2018-07-01 07:01:13 +00:00			`## first program: same as https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html`
4351 2018-07-16 14:55:07 +00:00			`# Just return 42.`
4303 - subx: first real transform We'll see if this is useful. Mostly just stretching our legs. 2018-07-01 07:01:13 +00:00			`#`
			`# To run:`
			`# $ subx translate ex1.2.subx ex1`
			`# $ subx run ex1`

4350 Reorganize layers to introduce the translation workflow right at the start. We also avoid duplicating parsing code. Programs are always parsed into the `program` data structure. 2018-07-16 05:59:02 +00:00			`== 0x08048054 # code segment, after leaving room for ELF header`
4424 Clean up format of example programs. 2018-07-26 19:19:02 +00:00			`# instruction effective address operand displacement immediate`
			`# op subop mod rm32 base index scale r32`
			`# 1-3 bytes 3 bits 2 bits 3 bits 3 bits 3 bits 2 bits 2 bits 0/1/2/4 bytes 0/1/2/4 bytes`
4431 - operate exclusively in hex Was confusing having numbers without an explicit base sometimes be hex and sometimes not, based on their metadata. By convention I don't bother with the '0x' for instructions, or for single-digit numbers that are equal to their decimal representation. But I could and it would still work. 2018-07-27 05:32:57 +00:00			`bb 2a/imm32 # copy 42 to EBX`
4325 2018-07-08 06:13:25 +00:00			`# exit(EBX)`
4424 Clean up format of example programs. 2018-07-26 19:19:02 +00:00			`b8 1/imm32 # copy 1 to EAX`
4431 - operate exclusively in hex Was confusing having numbers without an explicit base sometimes be hex and sometimes not, based on their metadata. By convention I don't bother with the '0x' for instructions, or for single-digit numbers that are equal to their decimal representation. But I could and it would still work. 2018-07-27 05:32:57 +00:00			`cd 0x80/imm8 # int 80h`
4303 - subx: first real transform We'll see if this is useful. Mostly just stretching our legs. 2018-07-01 07:01:13 +00:00
			`# vim:ft=subx`