Joseph Ferano
66a542277f
Work in progress: it builds and the runtime is exercised and green, but no Flan program can reach it yet — the checker half is not written, so (Map K V) is still refused where it is resolved. runtime/flan_rt.c is Odin's map, followed deliberately: open-addressed Robin Hood hashing at a 75% load factor, cache-line cell packing so no key or value straddles a line, and the probe loop kept to pointer-width integers. One type-erased runtime over (key size, value size) plus a hash and equality pair, the same arrangement the Vec runtime has over (size, align). Two departures from Odin, both deliberate and both commented where they are made. There are no tombstones, because removal is deferred by spec-memory.md, and that deletes the backward-shift loop entirely — it is the single largest reason this is shorter than the original. And the header does not stuff log2cap into the low bits of the data pointer: Odin does that because Raw_Map must be three words, whereas this header already carries an allocator, a generation and an epoch, so the tagging would buy nothing, cost a mask on every access, and make correctness depend on the block being 64-byte aligned rather than merely faster when it is. The scaffolding around it: a Map is 48 bytes and six words like a Vec, it crosses to the runtime by address because it is move-only and must be mutated in place, and it has a DWARF type showing all six fields. Tast.FnAddr is new — the address of a function, either one this compiler emitted or a runtime C symbol. It is not a function value: nothing in the surface language can produce one, name its type or call through it. Odin's Map_Info reaches its hash and equality pair exactly this way. reach.ml learns that edge, because a function reached only by address is invisible to the reachability walk otherwise, which is the same hazard handler-bind clauses already had. The hash and equality pair carries the transfer channel as its last parameter, because a pair emitted for a struct key is an ordinary Flan function and every Flan function's signature ends with one.
258 lines
13 KiB
OCaml
258 lines
13 KiB
OCaml
(** The typed IR: what the checker produces and what every backend consumes.
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Three backends share this — the tree-walking interpreter, dev redefinition
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and the release AOT build (plan.org, Compilation) — so everything a backend
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would otherwise have to re-derive is resolved here and nowhere else:
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- names are gone. A local is a slot index into the frame, a global is a
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name, and a call names its callee directly. No environment lookup.
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- field access is an index, not a string, and any auto-deref the source
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relied on is an explicit [Deref] node.
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- literals have a machine type. There is no untyped 1 past this point.
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- a struct literal lists every field in declaration order, with the omitted
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ones filled in as [Zero] — ZII is settled here rather than at runtime.
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- sugar is already gone from the AST; what is left is the small set below. *)
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type prim =
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(* arithmetic and comparison, per machine type — the operands carry their own
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kind at runtime, so one constructor covers every width *)
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| Add | Sub | Mul | Div | Rem
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| Eq | Ne | Lt | Le | Gt | Ge
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| Not
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(* bitwise, integers only. [Shr] is arithmetic on a signed type and logical
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on an unsigned one, which is what the operand's own kind already says. *)
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| BitAnd | BitOr | BitXor | Shl | Shr
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(* containers: fixed arrays and slices only at milestone 2 *)
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| Len | At | Slice
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(* the milestone-2 host primitives, plan.org. The four conversions are
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*text*: bytes->f64 parses "12.5", f64->bytes renders it — that is what
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calc-me's tokenizer and the prelude's printers each need. *)
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| Bytes | BytesToF64 | BytesToI64 | F64ToBytes | I64ToBytes
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(* (string b): the other direction of [Bytes], and the same non-instruction.
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See check.ml's "string" case for why it is unchecked. *)
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| StrOfBytes
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(* No surface name: the structural printer is the only thing that builds
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these. U64ToBytes because u64 is not i64 with a flag, EscapeBytes for a
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string nested inside a printed structure. *)
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| U64ToBytes | EscapeBytes
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| WriteStdout | Exit | Argv
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(* A call into the runtime's C, named by symbol. The argument and result
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LLVM types come off the expression nodes themselves, so one constructor
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covers every entry point the allocator and container runtime has and the
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backend grows one arm rather than one per operation — which matters
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because spec-memory.md's runtime is type-erased and therefore *is* a list
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of C entry points. A string or slice argument crosses as ptr+len, the
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same rule as every other shim here. No transfer guard follows one: a
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transfer cannot cross a C frame. *)
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| Rt of string
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(* spec-memory.md, "Alignment": a property of the type, computed at the call
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site, passed as a parameter to the type-erased allocator — all three, and
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they are not alternatives. The checker builds these at the site where the
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concrete element type is known and the backend fills in the number from
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the same layout calculator DWARF uses. *)
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| SizeOf of Types.t
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| AlignOf of Types.t
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(* The address of any expression, not only of a place: the element a [push]
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copies may be a computed value, and the runtime takes it by pointer
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because it is type-erased. The backend already spills a non-place to a
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temporary for exactly this. *)
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| AddrOf
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| Cast of Types.t
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type expr = { e : expr_kind; ty : Types.t; loc : Loc.t }
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and expr_kind =
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| Int of int64 * Types.ikind
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| Float of float * Types.fkind
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| Bool of bool
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| Str of string
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| Unit
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| Zero of Types.t (* ZII: all-bytes-zero of this type *)
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| Uninit of Types.t (* the explicit opt-out *)
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| Local of int (* slot index into the frame *)
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| Global of string
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| Prim of prim * expr list
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| Call of string * expr list (* direct call; no first-class fns yet *)
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(* The address of a function the compiler emitted, by symbol. Not a function
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*value*: nothing in the surface language can produce one, name its type or
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call through it, and its only consumers are runtime entry points that take
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a procedure the way spec-memory.md's type-erased allocator does. The Map's
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hash and equality pair is what wanted it — Odin's [Map_Info] is two
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contextless [proc] fields reached exactly this way — and a handler-bind
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clause is the same arrangement with the symbol carried on [hframe]
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instead. Its Flan type is [Alloc]: an opaque pointer-width value with no
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user-writable constructor, which is all any backend needs to know. *)
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| FnAddr of fnref
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| Do of expr list
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| Let of (int * expr) list * expr list
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| If of expr * expr * expr
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| While of expr * expr list
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| Return of expr option
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| Set of place * expr
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| Field of expr * int (* target is already a struct value *)
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| Addr of place
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| Deref of expr
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| Make of string * expr list (* struct literal, every field, in order *)
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| Arr of expr list (* fixed-array literal *)
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| Some_ of expr
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| None_
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| Match of expr * arm list
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(* (some x): unwrap Some, else early-return None from the enclosing function.
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An early return, not an expression that can fail — hence its own node. *)
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| UnwrapSome of expr
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(* Conditions, spec-conditions.md. [Signal] walks the handler stack and
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returns Unit whatever it finds — with nothing matching it is a no-op, so
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nothing here alters control flow. [HandlerBind] pushes one frame per
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clause, runs its body, and pops them; each clause was lifted into its own
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function by the checker, so what is left is the frame and the call. *)
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| Signal of sigkind * int * expr (* how, the type id, the condition *)
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| Handled of hframe list * expr list
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(* The transfer, spec-conditions.md §3–§6. [RestartCase] pushes one frame per
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clause, runs its body, and pops them; if a transfer arrives naming one of
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*its* frames it runs that clause instead, and the whole form yields either
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way. [InvokeRestart] looks the name up on the restart stack, writes the
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frame it found into the transfer channel and leaves — it has type Never,
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so nothing follows it.
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[InvokeRestart]'s arguments are already evaluated: the checker binds each
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to a slot and wraps the node in a [Let], so what is left here is a list of
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locals to copy into the frame. Two reasons, and both matter. An argument
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that transfers on its own must be guarded before this one aims the
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channel; and a call written in an argument has to be on the walk [Reach]
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and [Load] already do, which a list hanging off a node they treat as a
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leaf would not be. [rsig] is the argument types as written, and [rsig_id]
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their hash — §3's run-time check, since the name is resolved on a stack
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nothing static can see. *)
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| RestartCase of rclause list * expr
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(* (with-allocator A BODY...) — spec-memory.md. It rebinds the current
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allocator for its dynamic extent and releases nothing. Its own node
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because the restore has to happen on the *transfer* path too: a body that
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errors, or a restart taken from inside it, must not leave the context
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allocator pointing at a region the handler knows nothing about. *)
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| WithAlloc of expr * expr list
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(* name id, name, arguments, their spelling, its hash, where *)
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| InvokeRestart of int * string * expr list * string * int * Loc.t
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(* [Serror] is §2's diverging variant: the same lookup, type Never, and with
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nothing transferring the program stops rather than carrying on. *)
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(* Which symbol table the address comes out of. [Flanfn] is a function this
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compiler emitted and is therefore name-mangled and reachability-tracked;
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[Rtfn] is a C entry point in flan_rt.c, spelled as written. The two are
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interchangeable at the call site because a Flan function's emitted signature
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is its parameters followed by the transfer channel, and the runtime's
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matching typedef spells that last pointer out. *)
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and fnref = Flanfn of string | Rtfn of string
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and sigkind = Ssignal | Serror
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and place =
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| Plocal of int
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| Pglobal of string
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| Pfield of expr * int
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| Pindex of expr * expr list
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| Pderef of expr
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(* A pushed handler: which condition type it matches, and the lifted function
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that runs when one is signalled. *)
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and hframe = { htype : int; hfn : string }
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(* A restart clause. [rname_id] is what [invoke-restart] matches by name; the
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body is a branch in the function that wrote it, because unlike a handler a
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clause runs at the restart-case, which is where it was written.
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[rparams] are the slots §3's parameters are bound to, in order, with their
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types; the invoker stores into a buffer this frame owns and the clause loads
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them from it. [rsig] is how those types are spelled and [rsig_id] its hash:
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what the two ends compare, since neither can see the other. *)
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and rclause =
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{ rname_id : int; rname : string; rparams : (int * Types.t) list;
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rsig : string; rsig_id : int; rbody : expr list }
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(* [binds] are the slots the pattern's fields are bound to, in field order. *)
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and arm = { acase : string option; binds : int list; abody : expr list }
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type field = { fname : string; fty : Types.t }
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type structure = { sname : string; fields : field list }
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type variant = { vname : string; vfields : field list }
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type union = { uname : string; cases : variant list }
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type fn = {
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name : string;
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params : Types.t list; (* bound to slots 0 .. n-1, in order *)
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slots : Types.t array; (* the frame: one entry per slot *)
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(* What the source called each slot, parallel to [slots]. [None] is a slot
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the compiler made up and no one wrote a name for -- [dotimes]'s hidden
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bound, the pair (min) and (max) evaluate their operands into, the slot a
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tail expression goes through. Names are otherwise gone from this IR (see
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the header); this is the one exception, and it exists so a debug build can
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emit a [!DILocalVariable] that says [lo] where the source said [lo]. A
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backend is free to ignore it entirely -- nothing is *resolved* through it,
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and a slot is still only ever referred to by index. *)
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snames : string option array;
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ret : Types.t;
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body : expr list;
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(* The defers again, innermost first. [body] already has them spliced onto
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the normal exit path; this is the same list for the *transfer* exit path,
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which leaves through a landing block the backend builds and no form in
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[body] can reach. spec-conditions.md §5: they run, and errdefer does not. *)
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fdefers : expr list;
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(* Set on a function the checker made up rather than one anyone wrote: a
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handler-bind clause, lifted out of the function named here. It is reached
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by address from that function's body and from nowhere else, so it needs no
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cell and no registry slot, and a redefinition of the parent carries its
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own copy. *)
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fparent : string option;
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floc : Loc.t;
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}
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(* [gfolded] is the difference between a constant whose value the *checker*
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consumed — an array length, decided before any type resolves — and one that
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is only ever read at run time. The first is in the program's shape and can
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never be reloaded; the second is just bytes in memory and can. Nothing else
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can tell them apart afterwards, so it is recorded here. *)
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type global = {
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gname : string;
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gty : Types.t;
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ginit : expr;
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gconst : bool;
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gfolded : bool;
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}
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(* A foreign function: no body, and [esym] is the symbol the linker sees. The
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aggregate calling convention is not modelled here — a C shim flattens every
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struct that crosses the boundary, so clang classifies it per target and
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nothing in the backend has to know x86-64 from arm64 from wasm32. *)
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type extern = {
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ename : string; (* the Flan name, e.g. rl/init-window *)
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esym : string; (* the C symbol *)
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eparams : Types.t list;
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eret : Types.t;
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}
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type program = {
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structs : structure list;
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unions : union list;
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globals : global list; (* in declaration order *)
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externs : extern list;
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fns : fn list;
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(* The C the program's own (declare-c ...) forms generated, if any: one
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translation unit, compiled into the build like a package's hand-written
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.c file. It is on the program rather than beside it so that every driver
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— the CLI, the REPL, the acceptance table — carries it without knowing
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it exists. See [Shim]. *)
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(* The generated FFI shim, in parts keyed by the declaration each serves,
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with "" for the shared preamble. Parts rather than one string so that
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[Reach.link] can drop a wrapper whose binding nothing reachable calls. *)
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cshim : (string * string) list;
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}
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let field_index (s : structure) name =
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let rec go i = function
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| [] -> None
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| f :: rest -> if String.equal f.fname name then Some i else go (i + 1) rest
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in
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go 0 s.fields
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