AnachronautandClaude Opus 5
4fd8bf7b3f
DPUP takes an immediate, so an offset of one is legal and does exactly the right thing. It is also three bytes where INCD is two, and reads as "offset the pointer up by one" where INCD reads as "step the pointer". 56 of them across 15 files: the system, the assembler, the editor, and eight test programs. CosmOS is 9,564 bytes to 9,537, the native assembler 11,648 to 11,635, and every program in the repository together 49 bytes lighter. The worst offender was numbers.asm, written this week, where every sixteen bit helper reaches the low byte and comes back the long way round. It is the file every other part of the assembler includes, so it is the first thing anybody reads when they go looking - and it was teaching them the long way. Pattern matched off sbfs.asm rather than off the instruction table I had just embedded in two programs. THIS IS NOT TWO WAYS TO DO ONE THING. DPUP takes an arbitrary number, so one is inevitably among them; INCD earns its place by making the common case a byte cheaper. The overlap is structural and the choice is a usage question, which is a linter's job rather than an ISA's - "DPUP.n 0d01: INCD.n does this in a byte less" is a mechanical rule with no judgement in it. Nothing needed re-recording, which was not a foregone conclusion: cosmosBreak prints the system addresses the registers happened to hold, and they did not move. Both assemblers still produce identical bytes and CosmOS still builds itself to a fixed point. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
37 lines
1.0 KiB
NASM
37 lines
1.0 KiB
NASM
; Tests MVSD, which copies the Stack Pointer into a Data Pointer.
|
|
;
|
|
; The Stack Pointer still cannot be written, so this does not let a program move the
|
|
; Stack. It lets a program find it, which is what reading anything already on the Stack
|
|
; requires. Without it, the manual's claim that a Data Pointer can be aimed at the Stack
|
|
; is not something a program can actually act on: there is no way to learn where the
|
|
; Stack is without already knowing.
|
|
;
|
|
; An interrupt handler needs this to reach its own frame, which is how a fault handler
|
|
; steps over the byte that failed and carries on.
|
|
;
|
|
; Correct output is:
|
|
; OK
|
|
|
|
#Program
|
|
|
|
start:
|
|
; Push two bytes, then go looking for them.
|
|
INIA 0d79 ; 'O'
|
|
PSHA
|
|
INIA 0d75 ; 'K'
|
|
PSHA
|
|
|
|
; The Stack Pointer points at the next free slot, so the byte pushed last sits one
|
|
; above it, and the one before that sits two above.
|
|
MVSD.0
|
|
INCD.0
|
|
LDA.0 ; 'K', the last one pushed.
|
|
INCD.0
|
|
LDB.0 ; 'O', the one before it.
|
|
|
|
OUTB 0x00
|
|
OUTA 0x00
|
|
INIA 0x0A
|
|
OUTA 0x00
|
|
HALT
|