Joseph Ferano
c2d378957e
x86 is what flan dev takes by default and dyn is the iteration feature, so a backend that refused dyn meant the two halves of the dev loop could not be in the same program. The refusal was one arm of is_agg, and it said the true thing: it was never the representation that was missing. A dyn is uint64_t, a scalar in both calling conventions, classified by every rule this file already had; every operation on one is a Tast.Rt primitive and call_rt has always known how to make one of those. What the lane actually cost was the collector's root discipline. Which is emit.ml's, reused rather than rewritten: Emit.dyn_roots counts the roots for both backends now, so the pushes and the pops balance because one counter decides both ends, and the two backends root the same nodes because there is one counter and not two. A zeroed frame slot per dyn slot and per dyn-producing call, minted beside the channel and outside every scoped -- the bump allocator reclaims at the end of a statement and a slot minted in the body would be handed out again while the collector still held its address. Pushed from the body buffer, not the prologue's, because a call clobbers the registers the prologue is still spilling from. And one pop in the epilogue, which is the whole of why this backend needed no landing-pad work for it: there is exactly one epilogue, and the return, the fall-through and the transfer exit all arrive at it. emit.ml needs the same pop at five separate rets. The ABI point the dyn handoff left open for the integrator is settled by reading the other side rather than by agreeing: flan_dyn.c's mark follows a value only when the quiet-NaN prefix is set, and the zero word does not have it, so a zeroed root decodes as the double 0.0 and is never an address anything dereferences. Zero is safe for a reason. The header says so now. And one line in dev.ml that was never x86's: the merged dev host resets the condition stacks and the frame chain between runs, because main is re-entered by longjmp and pops no frame -- and it never reset the root stack, so every root a finished run pushed still named stack the next run was about to write over. That gap was an LLVM dev build's too. Verification, and one of the numbers is new. @x86: MATCH 129 -> 135, DIFFER 0, REFUSED 0 -- the five dyn programs off survey.sh's llvmonly list, which is gone rather than empty, plus p13. dune test --force green, with --x86 acceptance rows beside the LLVM ones for all five dyn programs, dyn-boundary asserted on the same exit 134 and the same sentence on both. p13-dyn-collect.flan is the one that is not a formality. Nothing else in this repository allocates past flan_dyn.c's one-megabyte floor, so nothing else collects even once, so a program whose roots are entirely wrong passes every output test there is -- the handoff wrote that about the stub and it outlived the stub. p13 allocates several megabytes of garbage while holding live values across it: at forty times the corpus size it peaks at 4MB of RSS, which is the collector running many times over, and both backends still print the same four lines.
What is in here, and what is still true
These are the documents that are written once and read occasionally: the reasons behind the code, the
reports from finished investigations, and the record of individual work sessions. The documents that are
edited every day stay at the repository root, because source comments cite them by bare filename from
dozens of places and a path that moves is a path that rots. So plan.org, NEXT.md, spec-memory.md
and spec-conditions.md are one directory up, and everything here points back at them.
A note on how to read the citations below: a document in this directory that says plan.org means the
one at the repository root. Nothing in docs/ is named for a file at the root, so there is no ambiguity,
and rewriting a hundred prose mentions into ../plan.org would have cost more in readability than it
bought in precision.
If you have thirty seconds
Read BUILT.md. It is by far the largest document here and it is the one that pays: it holds the
reason behind every part of the compiler that exists, from why nothing is ever dlclosed to why the
printer is a compile-time walk over a type rather than a runtime function. It is current, it is
maintained, and deleting it would mean deriving all of it again. If you want to know why a thing is the
shape it is, the answer is in here.
After that, ../NEXT.md at the root for what is actually in flight, and REFERENCES.md here for
where the evidence comes from — the reference clones on this machine, what each one answers, and the
standing rule that a claim in these notes was read out of a clone rather than recalled.
The current documents
| File | What it is |
|---|---|
BUILT.md |
Why the parts that exist are shaped the way they are. The longest and the most load-bearing document in the repository. Current. |
DISCUSS.md |
Open questions, raised and deliberately not answered. Nothing in it is a decision or a task; entries that have since been answered say so and point at where the answer landed. Current, though it is half archive by now. |
PORTING.md |
What the author's game, siam-farmer, needs from Flan that Flan does not have yet, measured against the code that exists rather than against a plan. It is the requirements document the language is actually steering by. Current. |
REFERENCES.md |
The reference clones under ~/Repositories, what each one is consulted for, and the specific files and lines already cited from them. Current. |
The reports
| File | What it is |
|---|---|
SPIKE-GENERICS.md |
Milestone 5's parametric polymorphism, run early and out of order as a spike. The spike succeeded and generics landed, so this is the report of finished work rather than a live plan — but its findings about where the cost falls are still the reason the implementation looks the way it does. Historical, findings still stand. |
overview.md |
The first brainstorm, from before the language had S-expressions. It says in its own first line that it is superseded and no longer accurate. Kept for history only; its table of what changed is the only part worth reading. Superseded. |
handoffs/
One report per work session, each written by whoever held the branch at the time. They are the
operational record: what was attempted, what was measured, what was decided without being able to ask,
and what was left open for the next lane. They are all historical the moment they are written — a handoff
describes a session that has ended — but they are cited by name from source comments and from NEXT.md,
because the reasoning behind a guard or a calling convention is often only written down once and this is
where it was written.
Six of them are the hand-written x86-64 backend, read in the order the work happened:
handoffs/HANDOFF-x86-rt.md set the remaining-items list that the four after it close, handoffs/HANDOFF-x86-redef.md
built the redefinition emitter, handoffs/HANDOFF-x86-aggregates.md took that across the struct boundary,
handoffs/HANDOFF-x86-guards.md settled the two guards nothing reaches, handoffs/HANDOFF-x86-debug.md added debug
information, and handoffs/HANDOFF-x86-cost.md measured what the backend costs and set the survey running on its
own so a refusal cannot sit unnoticed again.
The other six sessions are unrelated to each other. handoffs/HANDOFF-arith.md is why a divide by zero is a condition
rather than a SIGFPE. handoffs/HANDOFF-raylib-ports.md is the running record of the last two raylib example
ports, whose lasting findings were folded into PORTING.md, and handoffs/HANDOFF-cimport-ptr.md is the arm
cimport.ml's header check had been promising in a comment and not implementing — which is what those two ports
found, worked around and wrote up. handoffs/HANDOFF-devtest-noise.md is the linker
error dune test used to print on every run. handoffs/HANDOFF-emacs-flake.md is the test_emacs flake that
turned out to be SIGPIPE killing the daemon mid-reply, and it is worth reading for the two mechanisms it
rules out as much as for the one it found. handoffs/HANDOFF-tidy.md is this reorganisation.