Joseph Ferano
675241e226
defunion parsed and its shape checked; naming the type and constructing a
value were both refused as milestone 6. They are not any more.
A union is Types.Named, exactly as a struct is, so every path that carries a
type -- a field, a parameter, a slot, a copy -- learns nothing about unions.
Which table the name is in is the only thing that tells the two apart.
The layout is a tag then room for the largest case, with the alignment the
widest member of any case needs: %"U" = type { i32, [k x iA] }, and one
named %"U.C" per case laid over the blob. That is C's
struct { int tag; union { ... } u; } byte for byte, which is the requirement
the macro expander's Form will arrive with.
A value is (U.C {.field value ...}), or U.C on its own when the case has no
fields. Construction goes through the struct-literal syntax already there, so
parse.ml is untouched: the dot is a symbol constituent and U.C reads as one
name.
Tags are declaration order from zero, so an all-bytes-zero union is the first
declared case with a zeroed payload -- the same rule that makes an Option's
zero a None, and it makes case order part of a union's contract.
A move-only field in a case is refused in the same words a struct's is, and a
union is refused as a map key: the payload past the case in hand is
indeterminate, so hashing the blob would make two equal values hash
differently.
294 lines
14 KiB
OCaml
294 lines
14 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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(* A union value: the union's name, the case's name, and every field of that
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case in declaration order with the omitted ones filled in as [Zero] — the
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same ZII rule [Make] carries, and settled here for the same reason. It is
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its own node rather than a [Make] over a synthesised struct because the
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value's *type* is the union and its payload is a byte blob the case is
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reinterpreted into; a backend that saw only [Make] would have to rederive
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which of the two it was looking at. *)
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| MakeCase of string * string * expr list
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(* One field of one case of a union value, by index. The case name is on the
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node because the payload is untyped bytes: [Field]'s index alone cannot
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say which case struct the blob is being read as. [match] is the only thing
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that proves the case, so this is only ever built under an arm that
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checked the tag — and by [Render], which reads a field only after the same
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comparison. One node, so the payload layout is known in exactly one place
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in each backend rather than once per reader. *)
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| CaseField of expr * string * int
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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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(* The declared position of a case, which is its tag, and the case itself. Tags
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are declaration order from zero, so an all-bytes-zero union is the first
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case with a zeroed payload — the same rule that makes an [Option]'s zero a
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[None], and the reason case order is part of a union's contract. *)
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let case_index (u : union) name =
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let rec go i = function
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| [] -> None
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| (c : variant) :: rest ->
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if String.equal c.vname name then Some (i, c) else go (i + 1) rest
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in
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go 0 u.cases
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let vfield_index (c : variant) name =
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let rec go i = function
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| [] -> None
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| (f : field) :: rest ->
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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 c.vfields
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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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