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.
185 lines
8.8 KiB
C
185 lines
8.8 KiB
C
/* flan_dyn — the dynamic-value runtime's ABI.
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*
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* This header is not compiled into a program. The build embeds the runtime's
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* .c files as strings and hands each one to clang on its own, with no include
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* path (see [Build.compile_c]), so runtime/flan_dyn.c declares everything it
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* defines and this file declares it a second time. That is the same standing
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* arrangement flan_escape_bytes and flan_dev_emit_str already live under —
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* "if either table changes, change both" — and it is made mechanical rather
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* than hopeful: test/dyn_ops.c includes this header and names every function
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* below, so a signature that drifts from the implementation is a link error in
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* `dune test` rather than a surprise at someone else's call site.
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*
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* Who reads it: the compiler lane, which emits calls to these names, and the
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* C tests. The whole of the boundary is here. What is behind it — the value
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* representation, the heap layout, the collector — is flan_dyn.c's business
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* and is argued in docs/SPIKE-DYNAMIC.md.
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*/
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#ifndef FLAN_DYN_H
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#define FLAN_DYN_H
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* A dynamic value. One machine word, always — the whole point of the type is
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* that a dyn local is a register or a stack slot and never a struct the ABI
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* has to agree about. NaN-boxed; see the design doc. */
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typedef uint64_t flan_dyn;
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/* ── Constructors ──────────────────────────────────────────────────── */
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flan_dyn flan_dyn_nil(void);
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flan_dyn flan_dyn_from_i64(int64_t x);
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flan_dyn flan_dyn_from_f64(double x);
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flan_dyn flan_dyn_from_bool(uint8_t b);
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/* Copies the bytes into the GC heap. The result is a text value, immutable
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* from that moment: nothing in this ABI writes into one. [p] may point
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* anywhere — a literal in .rodata, a frame slot, a slice the caller is about
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* to drop — because the bytes are copied before this returns. */
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flan_dyn flan_dyn_from_bytes(const uint8_t *p, int64_t n);
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flan_dyn flan_dyn_vec_new(void);
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/* ── Operations ────────────────────────────────────────────────────────
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*
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* Every one of these may trap, and a trap does not return: it prints a
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* sentence naming the operation, the tags it was given and the values, and
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* then takes flan_rt.c's [flan_trap] — which parks the program for inspection
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* in a dev session and ends it in a standalone build. The three that cannot
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* trap say so on their own line. */
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flan_dyn flan_dyn_add(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_sub(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_mul(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_div(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_rem(flan_dyn a, flan_dyn b);
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/* Answer a bool dyn. Numbers compare as numbers and text compares bytewise;
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* a mixture of the two, or anything else, traps. */
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flan_dyn flan_dyn_lt(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_le(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_gt(flan_dyn a, flan_dyn b);
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flan_dyn flan_dyn_ge(flan_dyn a, flan_dyn b);
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/* Structural, and the one operation in this file that never traps: two values
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* of unrelated tags are not an error, they are unequal. */
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flan_dyn flan_dyn_eq(flan_dyn a, flan_dyn b);
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/* Bytes of a text, elements of a vec. Anything else traps. */
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flan_dyn flan_dyn_len(flan_dyn v);
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/* Element of a vec, or the byte of a text as an int. Out of range traps. */
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flan_dyn flan_dyn_at(flan_dyn v, flan_dyn i);
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/* Vec only — a text is immutable and says so rather than being copied. */
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void flan_dyn_set_at(flan_dyn v, flan_dyn i, flan_dyn x);
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void flan_dyn_push(flan_dyn v, flan_dyn x);
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/* Structural, and per type it renders what typed [print] renders. Never
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* traps: every tag has a rendering, including nil. */
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void flan_dyn_print(flan_dyn v);
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/* ── The typed boundary ────────────────────────────────────────────────
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*
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* What an annotated parameter does with a dyn argument, and what a dyn
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* expression does where the checker wants a machine value. A tag that is not
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* the one asked for traps; there is no widening and no coercion here, which
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* is deliberate — see the doc's boundary section. */
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int64_t flan_dyn_need_i64(flan_dyn v);
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double flan_dyn_need_f64(flan_dyn v);
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uint8_t flan_dyn_need_bool(flan_dyn v);
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/* ── The collector ─────────────────────────────────────────────────────
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*
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* Mark-sweep, precise, and never moving. [flan_gc_init] is idempotent, and the
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* first allocation calls it if nobody else has — deliberately, because
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* flan_rt_init calling it would be flan_rt.c naming a symbol in flan_dyn.c,
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* and the whole of the droppability argument is that the dependency runs one
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* way only. So an emitted program need not call it at all; it is exported
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* because a test that wants a heap in a known state wants to say so.
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*
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* [flan_gc_collect] is a full collection on demand, which nothing in an
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* emitted program needs — collection happens inside allocation — and which
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* the tests and a break loop want. [flan_gc_live_bytes] is what the heap holds
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* after the last sweep, counted the way the trigger counts it. */
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void flan_gc_init(void);
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void flan_gc_collect(void);
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int64_t flan_gc_live_bytes(void);
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/* Roots, shadow-stack style, exactly as flan_dev.c's frame chain is: the
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* compiler emits a push per dyn local on entry and one pop for the lot on the
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* way out. The address is remembered, not the value, so a local that is
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* reassigned needs no second push.
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*
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* **The slot must hold a valid flan_dyn before it is pushed.** The collector
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* reads every registered address on every mark, and an uninitialised slot is a
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* word of stack garbage that will be decoded as a pointer. Storing nil first
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* is the whole of the contract; the compiler lane zeroes a slot at its
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* declaration anyway.
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*
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* A zeroed slot satisfies it, and this used to be the one thing in this header
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* decided by one side alone. It is checkable now that both sides exist:
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* flan_dyn.c's mark walks a value only when it is boxed, and boxed means the
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* quiet-NaN prefix is set, which the zero word does not have. So zero decodes
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* as the double 0.0 — an ordinary value, and never an address anything
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* follows. Both backends zero, and they are right to.
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*
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* Globals go through the same pair, pushed once at startup and never popped.
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*
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* [flan_dyn_root_pop] takes a count rather than an address because that is
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* what a function epilogue knows cheaply. Popping more than are pushed is
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* clamped at empty rather than being a second failure on top of the first. */
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void flan_dyn_root_push(flan_dyn *slot);
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void flan_dyn_root_pop(int64_t n);
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/* ── Extensions ────────────────────────────────────────────────────────
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*
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* Additions to the agreed ABI, none of which the compiler lane has to emit.
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* They are here because something in this repository needs them; each says
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* what. */
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/* The root stack, emptied. The counterpart of flan_dev.c's
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* [flan_dev_frames_reset] and there for its one caller: the merged dev build's
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* [main] is re-entered by longjmp, which pops no frame, so every root the
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* finished run pushed still points into stack the next run is about to write
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* over. Marking through those addresses would decode whatever the new run put
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* there. Called between runs, on the thread that runs them. */
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void flan_dyn_root_reset(void);
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/* The tag of a value, as a number and as the word that number is printed as.
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* The numbers are FLAN_DYN_TAG_* below. The break loop and the inspector want
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* both — a value's tag is the first thing anyone asks a stopped dyn program —
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* and the trap messages in flan_dyn.c are written from the same table, so a
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* message and an inspector cannot disagree about what to call a value. */
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#define FLAN_DYN_TAG_NIL 0
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#define FLAN_DYN_TAG_BOOL 1
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#define FLAN_DYN_TAG_INT 2
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#define FLAN_DYN_TAG_FLOAT 3
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#define FLAN_DYN_TAG_TEXT 4
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#define FLAN_DYN_TAG_VEC 5
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int32_t flan_dyn_tag(flan_dyn v);
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const char *flan_dyn_tag_name(int32_t tag);
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/* How many objects the heap holds, and the floor under the collection
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* trigger. Both are the tests': a live-bytes figure alone cannot tell a heap
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* that is collecting from one whose objects happen to be small, and a floor of
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* a megabyte would make the million-allocation case a megabyte of arithmetic
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* before it proved anything. Setting the floor takes effect at the next
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* allocation and never shrinks a heap by itself; pass 0 for the default. */
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int64_t flan_gc_count(void);
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void flan_gc_set_floor(int64_t bytes);
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#ifdef __cplusplus
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}
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#endif
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#endif /* FLAN_DYN_H */
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