AnachronautandClaude Opus 5
fb335681d2
> load Asm.sbx
> run cosmos.asm
wrote cosmos.bin: program 7036, data 2448, labels 475
> run Asm.asm
wrote Asm.sbx: program 7533, data 4099, labels 555
Both byte for byte identical to what the host assembler builds from the
same source. The machine now builds the operating system it is running on,
and builds the thing that built it.
THE CHECK THAT MATTERS MOST IS THE THIRD ONE. A binary that matches could
still have come from an assembler wrong in some way this particular source
happens not to exercise. So Tests/native.sh boots the CosmOS that CosmOS
built and has THAT assemble CosmOS again - and the second generation is
identical to the first, down to the cycle count. It is a fixed point: the
machinery has been through itself. After this the host is a convenience
rather than a necessity.
WHAT STOOD IN THE WAY was not the assembler. It loaded, faulted at 7,780
cycles, and the fault was in CosmOS: a loaded program is staged at 0x8000
before being blitted into place, so the whole FILE has to fit in the 32,768
bytes above it. The assembler's file was 33,983, and 22K of that was
zeroed scratch buffers - because #Reserve emits what it reserves.
None of that is initialised data. It is scratch, wanted only while the
assembler runs, and while it runs everything above its own data is free.
So the buffers are a MAP now rather than declarations - Assembler/scratch.asm
writes down six addresses and the file carries none of it. 33,983 bytes
became 11,648, and the assembler could load itself.
The map has a file of its own because the reader and the label table both
need addresses out of it while neither includes the other.
The sizes are cut to the largest thing it is asked to build, and that turns
out not to be the operating system: the assembler is 555 labels and 11,648
bytes of output against CosmOS's 475 and 9,564. The hardest thing this
assembles is itself.
Also: sizing it for CosmOS meant raising the label table, and raising the
label table is what pushed the file over the staging limit. The two facts
only met because the first one was tried.
Speed, measured rather than guessed: CosmOS takes 80,168,646 cycles, which
is eighty seconds of emulated time and under a second under --fast. Most of
it is a straight walk of 475 label names, several thousand times. Sorting
or bucketing that is easy and was deliberately not written before there was
something to measure.
make run-cosmos now puts every source file on the disk, so the whole thing
can be done rather than read about.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
553 lines
12 KiB
NASM
553 lines
12 KiB
NASM
; The source reader: characters out of a file of any size.
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;
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; Everything else in the assembler sits on this, so it is the first thing built and the
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; thing most worth getting right. It hands out one character at a time and keeps a line
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; number, which is what lets an error say where it happened rather than only what it was.
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;
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; A FILE IS NEVER HELD WHOLE. It arrives a block at a time through osFileBlock, into one
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; buffer of 256 bytes, and is fetched again when the buffer runs out. That is why the
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; assembler can read a source file bigger than the memory it runs in - which cosmos.asm,
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; at 56,047 bytes, already is.
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;
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; The file is read TWICE, once per pass, and srcRewind is how the second pass starts over.
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; Nothing is kept between the passes but the label table.
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;
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; ---- A stack of readers ----
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;
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; #Include splices another file in where it stands, so the reader is a stack: srcInclude
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; puts the current file's whole state aside, opens the new one, and the end of that file
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; pops the old one back and carries on where it left off. Everything above works on "the
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; current file" and does not know the stack is there.
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;
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; THE WHOLE STATE GOES ASIDE, buffer and all, 293 bytes of it. Keeping only the position
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; and re-reading the block on the way back would be cheaper in memory and would cost a disk
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; read per pop; at six levels of nesting the copy costs less than the arithmetic to avoid it.
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; The buffer pointer survives the trip because it points into the buffer, which is always at
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; the same address - the state is saved from and restored to the same variables.
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;
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; A FILE IS INCLUDED ONCE. Including it twice is not an error, it just does nothing, which
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; is what lets two libraries depend on a third. The names are remembered for the length of
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; one pass and forgotten between them, because the second pass has to walk exactly the same
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; tree the first one did.
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;
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; Written by Anachronaut
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#Program
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; Opens the file DP0 names. Q is zero if it is there.
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;
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; The name is copied rather than pointed at, because the caller's copy is in the caller's
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; memory and every later block read has to name the file again - there being no such thing
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; as an open file to hold on to.
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srcOpen:
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SETD.1 SrcTopName
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CALL srcKeepName ; Kept apart, so that each pass can open it again.
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CALL srcRestart
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RET
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; Back to the top of the tree: the first file, no includes taken yet, nothing on the stack.
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; This is what starts each pass.
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srcRestart:
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RSTA
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SETD.0 SrcDepth
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STA.0
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SETD.0 IncCount
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STA.0
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SETD.0 SrcTopName
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SETD.1 SrcName
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CALL srcKeepName
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CALL srcRewind
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RET
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; Back to the first character, for the second pass.
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srcRewind:
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SETD.0 SrcIndex
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CALL numZero
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SETD.0 SrcAt
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CALL numZero
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SETD.0 SrcCount
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CALL numZero
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RSTA
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SETD.0 SrcEnded
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STA.0
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; The line number counts from one, the way an editor does.
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SETD.0 SrcLine
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CALL numZero
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SETD.0 SrcLine
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CALL numStep
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; Ask how big it is, which is both the answer to "is it there" and the thing that says
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; when to stop asking for blocks.
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SETD.0 SrcName
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SWI osFileInfo
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BNQ srcRewindNo
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PSHD.3
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POPB
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POPA
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SETD.0 SrcBlocks
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STA.0
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INCD.0
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STB.0
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RSTA
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RSTB
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CCF
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ADD ; Q is zero: it is there.
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RET
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srcRewindNo:
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INIA 0d1
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SETD.0 SrcEnded
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STA.0
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RSTA
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INIB 0d1
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CCF
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ADD ; Q is not zero: it is not.
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RET
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; The next character of the file, into SrcChar. Q is zero if there was one, and something
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; else at the end of the file.
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srcNext:
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SETD.0 SrcEnded
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LDA.0
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BNA srcAtEnd
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; Is the buffer used up? SrcAt counts how far into it we have read and SrcCount how many
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; of its bytes are the file's, which is 256 for every block but a short last one.
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SETD.0 SrcAt
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SETD.2 SrcCount
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CALL numCompare
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BNQ srcHaveByte
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CALL srcLoad
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BNQ srcAtEnd
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srcHaveByte:
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SETD.1 SrcPointer
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LDD.0.1
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LDA.0
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INCD.0
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STD.0.1
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SETD.0 SrcChar
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STA.0
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SETD.0 SrcAt
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CALL numStep
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; A newline is what makes the next character part of the next line. Counting it here,
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; as it is handed out, means the line number always describes the character just given.
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SETD.0 SrcChar
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LDA.0
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INIB 0x0A
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XOR
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BNQ srcNextDone
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SETD.0 SrcLine
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CALL numStep
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srcNextDone:
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RSTA
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RSTB
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CCF
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ADD ; Q is zero: there was a character.
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RET
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srcAtEnd:
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; This file is finished. If it was included by another, that one is not: it goes back on
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; and the next character comes from where it left off, which is what makes an include
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; read as though the text had been written there.
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INIA 0d1
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SETD.0 SrcEnded
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STA.0
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SETD.0 SrcDepth
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LDA.0
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BRA srcNothingLeft
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CALL srcPop
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BRI srcNext
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srcNothingLeft:
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RSTA
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INIB 0d1
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CCF
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ADD ; Q is not zero: there is no more source anywhere.
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RET
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; ---- The stack ----
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; Opens the file named at DP0 as though its text were written here. Q is zero if the
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; reader is now inside it, or if it had already been included and there is nothing to do.
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srcInclude:
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SETD.1 IncWanted
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CALL srcKeepName
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CALL srcSeenAlready
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BRQ srcIncludeSkip
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SETD.0 SrcDepth
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LDA.0
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SETD.2 SrcDepthLimit
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LDB.2
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CCF
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SUB
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BNC srcTooDeep
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CALL srcRemember
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CALL srcPush
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SETD.0 IncWanted
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SETD.1 SrcName
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CALL srcKeepName
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CALL srcRewind
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BNQ srcIncludeGone
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RET ; Q is zero, out of srcRewind.
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srcIncludeSkip:
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RSTA
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RSTB
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CCF
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ADD ; Already in, so this line does nothing at all.
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RET
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srcIncludeGone:
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; The file is not there. The stack is left as it is: the caller stops the assembly, and
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; unwinding for the sake of tidiness would only hide where it happened.
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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srcTooDeep:
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SETD.0 TooDeepText
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SWI osPrintString
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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; Puts the current file aside and makes room for another.
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srcPush:
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CALL srcSlot
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SETD.0 SrcState
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SETD.1 SrcSlot
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LDD.1.1
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CALL srcCopyState
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SETD.0 SrcDepth
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LDA.0
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INCA
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STA.0
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RET
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; And takes it back.
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srcPop:
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SETD.0 SrcDepth
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LDA.0
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DECA
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STA.0
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CALL srcSlot
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SETD.1 SrcSlot
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LDD.0.1
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SETD.1 SrcState
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CALL srcCopyState
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RET
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; Puts one character back, so that the next read produces it again. The character itself
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; is in A, because whether it was a newline decides whether a line goes back too.
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;
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; The tokenizer holds one character of lookahead, and at an #Include that character belongs
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; to the file about to be put aside. Undoing the read is how it stays with that file: when
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; the file is opened again the character is simply still there, and nothing has to be
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; carried across the include or handed back at some moment chosen by the reader.
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;
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; CARRYING IT ACROSS WAS THE OBVIOUS THING AND IT WAS WRONG. A file runs out in the middle
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; of whatever the tokenizer happens to be doing, so handing the character back then injects
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; it into the middle of a word: `start:` came back as `s` and then `tart:`, which assembles
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; into a file that looks entirely reasonable.
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srcStepBack:
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INIB 0x0A
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XOR
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BNQ srcStepBackAt
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SETD.0 SrcLine
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SETD.2 SrcOne
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CALL numTake ; A newline not yet read has not started a line either.
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srcStepBackAt:
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SETD.0 SrcAt
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SETD.2 SrcOne
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CALL numTake
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SETD.0 SrcPointer
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SETD.2 SrcOne
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CALL numTake
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RET
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; Where the slot for the current depth is, into SrcSlot.
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srcSlot:
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SETD.0 SrcSlot
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SETD.2 ScratchSrcStack
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CALL numSet ; WHERE the stack is, not what is in it.
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SETD.0 SrcSlotLeft
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SETD.2 SrcDepth
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LDA.2
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STA.0
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srcSlotLoop:
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SETD.0 SrcSlotLeft
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LDA.0
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BRA srcSlotDone
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DECA
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STA.0
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SETD.0 SrcSlot
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SETD.2 SrcStateBytes
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CALL numAdd
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BRI srcSlotLoop
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srcSlotDone:
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RET
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; The whole reader state, from DP0 to DP1.
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srcCopyState:
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SETD.2 SrcCopyFrom
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STD.0.2
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SETD.2 SrcCopyTo
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STD.1.2
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SETD.0 SrcCopyLeft
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SETD.2 SrcStateBytes
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CALL numSet
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srcCopyLoop:
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SETD.1 SrcCopyFrom
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LDD.0.1
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LDA.0
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SETD.1 SrcCopyTo
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LDD.0.1
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STA.0
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SETD.0 SrcCopyFrom
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CALL numStep
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SETD.0 SrcCopyTo
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CALL numStep
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SETD.0 SrcCopyLeft
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SETD.2 SrcOne
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CALL numTake
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SETD.0 SrcCopyLeft
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LDA.0
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INCD.0
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LDB.0
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OR
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BNQ srcCopyLoop
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RET
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; ---- Which files have been in ----
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; Q is zero if IncWanted has already been included in this pass.
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srcSeenAlready:
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RSTA
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SETD.0 IncLeft
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STA.0
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srcSeenLoop:
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SETD.0 IncLeft
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LDA.0
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SETD.2 IncCount
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LDB.2
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CCF
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SUB
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BRQ srcSeenNo
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CALL srcSeenSlot
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SETD.1 IncSlot
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LDD.0.1
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SETD.1 IncWanted
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CALL sameText
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BRQ srcSeenYes
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SETD.0 IncLeft
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LDA.0
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INCA
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STA.0
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BRI srcSeenLoop
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srcSeenYes:
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RSTA
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RSTB
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CCF
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ADD
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RET
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srcSeenNo:
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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; Writes IncWanted down as having been included.
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srcRemember:
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SETD.0 IncLeft
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SETD.2 IncCount
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LDA.2
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STA.0
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CALL srcSeenSlot
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SETD.0 IncWanted
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SETD.1 IncSlot
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LDD.1.1
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CALL srcKeepName
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SETD.0 IncCount
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LDA.0
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INCA
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STA.0
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RET
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; Where name number IncLeft sits, into IncSlot. Fixed fields of 23 bytes: there are few of
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; these and they are short, so an arena would cost more code than it saved.
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srcSeenSlot:
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SETD.0 IncSlot
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SETD.2 ScratchIncNames
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CALL numSet
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SETD.0 IncSlotLeft
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SETD.2 IncLeft
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LDA.2
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STA.0
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srcSeenSlotLoop:
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SETD.0 IncSlotLeft
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LDA.0
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BRA srcSeenSlotDone
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DECA
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STA.0
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INIA 0d23
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SETD.0 IncSlot
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CALL numAddByte
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BRI srcSeenSlotLoop
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srcSeenSlotDone:
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RET
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; Fetches the block SrcIndex names, and steps SrcIndex past it. Q is zero if there was one.
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;
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; Running off the end is not a failure here: osFileBlock answers three for a block past the
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; end of the file, which is how a reader finds out it has finished. Any other refusal is a
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; real one, and both come back the same way because there is nothing useful to do about
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; either except stop.
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srcLoad:
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SETD.0 SrcName
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SETD.1 SrcBuffer
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SETD.2 SrcIndex
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LDA.2
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INCD.2
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LDB.2
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SWI osFileBlock
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BNQ srcLoadNo
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; DP3 says how many of the block's bytes belong to the file: a whole 256 except in a
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; short last one, which is why it comes back in a pointer and not a register.
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PSHD.3
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POPB
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POPA
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SETD.0 SrcCount
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STA.0
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INCD.0
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STB.0
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SETD.0 SrcAt
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CALL numZero
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SETD.0 SrcIndex
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CALL numStep
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; The walking pointer starts at the front of the buffer again.
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SETD.0 SrcBuffer
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SETD.1 SrcPointer
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STD.0.1
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RSTA
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RSTB
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CCF
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ADD
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RET
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srcLoadNo:
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RSTA
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INIB 0d1
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CCF
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ADD
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RET
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; Copies the name at DP0 into DP1, up to 22 characters of it and the zero after them,
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; which is as long as a name on this filesystem may be.
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srcKeepName:
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INIA 0d22
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SETD.2 SrcLeft
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STA.2
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srcKeepLoop:
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LDA.0
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BRA srcKeepEnd
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STA.1
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INCD.0
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INCD.1
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LDA.2
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DECA
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STA.2
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BNA srcKeepLoop
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srcKeepEnd:
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RSTA
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STA.1 ; The zero that makes it a string.
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RET
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#Data
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; ---- The current file, as one block so that it can be put aside in one piece ----
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;
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SrcState:
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SrcName:
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#Reserve 0d23
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SrcBlocks:
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0x00 0x00
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SrcIndex:
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0x00 0x00
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SrcCount:
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0x00 0x00
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SrcAt:
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0x00 0x00
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SrcLine:
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0x00 0x00
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SrcPointer:
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0x00 0x00
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SrcEnded:
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0x00
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; One block, which is the whole of what a source file costs in memory however big it is.
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SrcBuffer:
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#Reserve 0d256
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; 292 bytes: a name of 23, six numbers of two, one single byte, and the buffer. NOTHING MAY
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; BE ADDED IN THE MIDDLE OF THE BLOCK ABOVE without changing this to match.
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SrcStateBytes:
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0x01 0x24
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SrcDepthLimit:
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0d6
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SrcOne:
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0x00 0x01
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SrcChar:
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0x00
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SrcLeft:
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0x00
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SrcDepth:
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0x00
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SrcSlot:
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0x00 0x00
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SrcSlotLeft:
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0x00
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SrcCopyFrom:
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0x00 0x00
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SrcCopyTo:
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0x00 0x00
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SrcCopyLeft:
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0x00 0x00
|
|
|
|
; The file the assembly started from, so that each pass can open it again.
|
|
SrcTopName:
|
|
#Reserve 0d23
|
|
|
|
IncWanted:
|
|
#Reserve 0d23
|
|
IncCount:
|
|
0x00
|
|
IncLeft:
|
|
0x00
|
|
IncSlot:
|
|
0x00 0x00
|
|
IncSlotLeft:
|
|
0x00
|
|
|
|
TooDeepText:
|
|
"included files are nested deeper than this assembler will follow
|
|
"
|
|
|
|
|