feat: speed up check_ir by caching sub, lub and check_typ tests (#5260)

Building CycleOps with check-ir on takes a long time with ir type checking turned on (the default)

```
real	1m31.395s
user	1m31.210s
sys	0m0.166s
```

Adding some naive caching of subtype, lub  and type well-formedness checks speeds this up quite a lot:

```
real	0m25.385s
user	0m25.236s
sys	0m0.148s
 ```

With no-check-ir, the time is:
```
real	0m12.299s
user	0m12.205s
sys	0m0.092s
```

(similar optimizations might improve the source typecheck.ml)

Proof:

Master:
```
crusso@crusso-Virtual-Machine:~/CycleOps$ time "/home/crusso/clean/motoko/bin/moc" "/home/crusso/CycleOps/canisters/cycleops/main.mo" "-o" "/home/crusso/CycleOps/.dfx/local/canisters/cycleops/cycleops.wasm" "-c" "--debug" "--idl" "--stable-types" "--public-metadata" "candid:service" "--public-metadata" "candid:args" "--actor-idl" "/home/crusso/CycleOps/.dfx/local/canisters/idl/" "--actor-alias" "cycleops" "bkyz2-fmaaa-aaaaa-qaaaq-cai" "--actor-alias" "internet_identity" "qhbym-qaaaa-aaaaa-aaafq-cai" "--actor-alias" "mock-management" "aaaaa-aa" "--actor-alias" "nns-cycles-minting" "rkp4c-7iaaa-aaaaa-aaaca-cai" "--actor-alias" "nns-genesis-token" "renrk-eyaaa-aaaaa-aaada-cai" "--actor-alias" "nns-governance" "rrkah-fqaaa-aaaaa-aaaaq-cai" "--actor-alias" "nns-identity" "rdmx6-jaaaa-aaaaa-aaadq-cai" "--actor-alias" "nns-ledger" "ryjl3-tyaaa-aaaaa-aaaba-cai" "--actor-alias" "nns-lifeline" "rno2w-sqaaa-aaaaa-aaacq-cai" "--actor-alias" "nns-registry" "rwlgt-iiaaa-aaaaa-aaaaa-cai" "--actor-alias" "nns-root" "r7inp-6aaaa-aaaaa-aaabq-cai" "--actor-alias" "nns-sns-wasm" "qaa6y-5yaaa-aaaaa-aaafa-cai" "--package" "account" ".vessel/account/a718d61a8a4086ce13056681567535f975ac0ddf/src" "--package" "account-identifier" ".vessel/account-identifier/d07f70f572fc0d4cfe44333276c92611de3e0d44/src" "--package" "array" ".vessel/array/v0.2.1/src" "--package" "base" ".vessel/base/moc-0.12.1/src" "--package" "base-0.7.3" ".vessel/base-0.7.3/aafcdee0c8328087aeed506e64aa2ff4ed329b47/src" "--package" "btree" ".vessel/btree/v0.3.4/src" "--package" "crypto" ".vessel/crypto/v0.3.1/src" "--package" "encoding" ".vessel/encoding/v0.4.1/src" "--package" "hash" ".vessel/hash/v0.1.1/src" "--package" "hashmap" ".vessel/hashmap/v8.0.0/src" "--package" "io" ".vessel/io/v0.3.2/src" "--package" "matchers" ".vessel/matchers/v1.2.0/src" "--package" "principal" ".vessel/principal/v0.2.6/src" "--package" "rand" ".vessel/rand/v0.2.1/src" "--package" "sha2" ".vessel/sha2/fb2d19d6d29406d3294a3f514d2b87f928f87bbf/src" "--package" "stable-buffer" ".vessel/stable-buffer/v1.3.0/src" "--package" "testing" ".vessel/testing/v0.1.3/src" "--package" "ulid" ".vessel/ulid/v0.1.3/src" "--enhanced-orthogonal-persistence"

real	1m29.139s
user	1m29.010s
sys	0m0.124s
```

This branch:

```
crusso@crusso-Virtual-Machine:~/CycleOps$ time "/home/crusso/clean/motoko/bin/moc" "/home/crusso/CycleOps/canisters/cycleops/main.mo" "-o" "/home/crusso/CycleOps/.dfx/local/canisters/cycleops/cycleops.wasm" "-c" "--debug" "--idl" "--stable-types" "--public-metadata" "candid:service" "--public-metadata" "candid:args" "--actor-idl" "/home/crusso/CycleOps/.dfx/local/canisters/idl/" "--actor-alias" "cycleops" "bkyz2-fmaaa-aaaaa-qaaaq-cai" "--actor-alias" "internet_identity" "qhbym-qaaaa-aaaaa-aaafq-cai" "--actor-alias" "mock-management" "aaaaa-aa" "--actor-alias" "nns-cycles-minting" "rkp4c-7iaaa-aaaaa-aaaca-cai" "--actor-alias" "nns-genesis-token" "renrk-eyaaa-aaaaa-aaada-cai" "--actor-alias" "nns-governance" "rrkah-fqaaa-aaaaa-aaaaq-cai" "--actor-alias" "nns-identity" "rdmx6-jaaaa-aaaaa-aaadq-cai" "--actor-alias" "nns-ledger" "ryjl3-tyaaa-aaaaa-aaaba-cai" "--actor-alias" "nns-lifeline" "rno2w-sqaaa-aaaaa-aaacq-cai" "--actor-alias" "nns-registry" "rwlgt-iiaaa-aaaaa-aaaaa-cai" "--actor-alias" "nns-root" "r7inp-6aaaa-aaaaa-aaabq-cai" "--actor-alias" "nns-sns-wasm" "qaa6y-5yaaa-aaaaa-aaafa-cai" "--package" "account" ".vessel/account/a718d61a8a4086ce13056681567535f975ac0ddf/src" "--package" "account-identifier" ".vessel/account-identifier/d07f70f572fc0d4cfe44333276c92611de3e0d44/src" "--package" "array" ".vessel/array/v0.2.1/src" "--package" "base" ".vessel/base/moc-0.12.1/src" "--package" "base-0.7.3" ".vessel/base-0.7.3/aafcdee0c8328087aeed506e64aa2ff4ed329b47/src" "--package" "btree" ".vessel/btree/v0.3.4/src" "--package" "crypto" ".vessel/crypto/v0.3.1/src" "--package" "encoding" ".vessel/encoding/v0.4.1/src" "--package" "hash" ".vessel/hash/v0.1.1/src" "--package" "hashmap" ".vessel/hashmap/v8.0.0/src" "--package" "io" ".vessel/io/v0.3.2/src" "--package" "matchers" ".vessel/matchers/v1.2.0/src" "--package" "principal" ".vessel/principal/v0.2.6/src" "--package" "rand" ".vessel/rand/v0.2.1/src" "--package" "sha2" ".vessel/sha2/fb2d19d6d29406d3294a3f514d2b87f928f87bbf/src" "--package" "stable-buffer" ".vessel/stable-buffer/v1.3.0/src" "--package" "testing" ".vessel/testing/v0.1.3/src" "--package" "ulid" ".vessel/ulid/v0.1.3/src" "--enhanced-orthogonal-persistence"
real	0m24.895s
user	0m24.784s
sys	0m0.111s
```

This branch (-no-check-ir):


```
crusso@crusso-Virtual-Machine:~/CycleOps$ time "/home/crusso/clean/motoko/bin/moc" "/home/crusso/CycleOps/canisters/cycleops/main.mo" "-o" "/home/crusso/CycleOps/.dfx/local/canisters/cycleops/cycleops.wasm" "-c" "--debug" "--idl" "--stable-types" "--public-metadata" "candid:service" "--public-metadata" "candid:args" "--actor-idl" "/home/crusso/CycleOps/.dfx/local/canisters/idl/" "--actor-alias" "cycleops" "bkyz2-fmaaa-aaaaa-qaaaq-cai" "--actor-alias" "internet_identity" "qhbym-qaaaa-aaaaa-aaafq-cai" "--actor-alias" "mock-management" "aaaaa-aa" "--actor-alias" "nns-cycles-minting" "rkp4c-7iaaa-aaaaa-aaaca-cai" "--actor-alias" "nns-genesis-token" "renrk-eyaaa-aaaaa-aaada-cai" "--actor-alias" "nns-governance" "rrkah-fqaaa-aaaaa-aaaaq-cai" "--actor-alias" "nns-identity" "rdmx6-jaaaa-aaaaa-aaadq-cai" "--actor-alias" "nns-ledger" "ryjl3-tyaaa-aaaaa-aaaba-cai" "--actor-alias" "nns-lifeline" "rno2w-sqaaa-aaaaa-aaacq-cai" "--actor-alias" "nns-registry" "rwlgt-iiaaa-aaaaa-aaaaa-cai" "--actor-alias" "nns-root" "r7inp-6aaaa-aaaaa-aaabq-cai" "--actor-alias" "nns-sns-wasm" "qaa6y-5yaaa-aaaaa-aaafa-cai" "--package" "account" ".vessel/account/a718d61a8a4086ce13056681567535f975ac0ddf/src" "--package" "account-identifier" ".vessel/account-identifier/d07f70f572fc0d4cfe44333276c92611de3e0d44/src" "--package" "array" ".vessel/array/v0.2.1/src" "--package" "base" ".vessel/base/moc-0.12.1/src" "--package" "base-0.7.3" ".vessel/base-0.7.3/aafcdee0c8328087aeed506e64aa2ff4ed329b47/src" "--package" "btree" ".vessel/btree/v0.3.4/src" "--package" "crypto" ".vessel/crypto/v0.3.1/src" "--package" "encoding" ".vessel/encoding/v0.4.1/src" "--package" "hash" ".vessel/hash/v0.1.1/src" "--package" "hashmap" ".vessel/hashmap/v8.0.0/src" "--package" "io" ".vessel/io/v0.3.2/src" "--package" "matchers" ".vessel/matchers/v1.2.0/src" "--package" "principal" ".vessel/principal/v0.2.6/src" "--package" "rand" ".vessel/rand/v0.2.1/src" "--package" "sha2" ".vessel/sha2/fb2d19d6d29406d3294a3f514d2b87f928f87bbf/src" "--package" "stable-buffer" ".vessel/stable-buffer/v1.3.0/src" "--package" "testing" ".vessel/testing/v0.1.3/src" "--package" "ulid" ".vessel/ulid/v0.1.3/src" "-no-check-ir" "--enhanced-orthogonal-persistence"
real	0m12.603s
user	0m12.500s
sys	0m0.102s
```

Author: crusso

Changelog.md

@@ -1,5 +1,9 @@
 # Motoko compiler changelog
 
+* motoko (`moc`)
+
+  * optimization: accelerate IR type checking with caching of sub, lub and check_typ tests (#5260). Reduces need for `-no-check-ir` flag.
+
 ## 0.14.12 (2025-06-12)
 
 * motoko (`moc`)

src/ir_def/check_ir.ml

@@ -14,6 +14,8 @@ module E = Ir_effect
 
 (* TODO: check escape of free mutables via actors *)
 
+
+
 (* Helpers *)
 
 let (==>) p q = not p || q
@@ -54,6 +56,9 @@ type con_env = T.ConSet.t
 
 type lvl = TopLvl | NotTopLvl
 
+module Set = Set.Make(T.Ord)
+module MapPair = Map.Make(T.OrdPair)
+
 type env =
   { flavor : Ir.flavor;
     lvl  : lvl;
@@ -64,6 +69,9 @@ type env =
     async : T.con option;
     seen : con_env ref;
     check_run : int;
+    check_typ_cache : Set.t ref;
+    sub_cache : bool MapPair.t ref;
+    lub_cache : T.typ MapPair.t ref;
   }
 
 let last_run : int ref = ref 0
@@ -82,8 +90,28 @@ let initial_env flavor : env =
                        | QueryCap c | AwaitCap c | AsyncCap c | CompositeCap c | CompositeAwaitCap c | SystemCap c -> Some c);
     seen = ref T.ConSet.empty;
     check_run;
+    check_typ_cache = ref Set.empty;
+    sub_cache = ref MapPair.empty;
+    lub_cache = ref MapPair.empty
   }
 
+let sub env t1 t2 =
+  if t1 == t2 then true else
+  match MapPair.find_opt (t1, t2) !(env.sub_cache) with
+  | Some b -> b
+  | None ->
+    let b = T.sub t1 t2 in
+    env.sub_cache := MapPair.add (t1, t2) b !(env.sub_cache);
+    b
+
+let lub env t1 t2 =
+  if t1 == t2 then t1 else
+  match MapPair.find_opt (t1, t2) !(env.lub_cache) with
+  | Some t -> t
+  | None ->
+    let t = T.lub t1 t2 in
+    env.lub_cache := MapPair.add (t1, t2) t !(env.lub_cache);
+    t
 
 (* More error bookkeeping *)
 
@@ -125,7 +153,7 @@ let disjoint_union env at fmt env1 env2 =
 
 (* FIX ME: these error reporting functions are eager and will construct unnecessary type strings !*)
 let check_sub env at t1 t2 =
-  if not (T.sub t1 t2) then
+  if not (sub env t1 t2) then
     error env at "subtype violation:\n  %s\n  %s\n"
       (T.string_of_typ_expand t1) (T.string_of_typ_expand t2)
 
@@ -317,7 +345,7 @@ and check_typ_bounds env (tbs : T.bind list) typs at : unit =
     error env at "too few type arguments";
   List.iter2
     (fun tb typ ->
-      check env at (T.sub typ (T.open_ typs tb.T.bound))
+      check env at (sub env typ (T.open_ typs tb.T.bound))
         "type argument does not match parameter bound")
     tbs typs
 
@@ -326,6 +354,11 @@ and check_inst_bounds env tbs typs at =
   List.iter (check_typ env) typs;
   check_typ_bounds env tbs typs at
 
+let check_typ env typ =
+  if Set.mem typ !(env.check_typ_cache) then () else
+  check_typ env typ;
+  env.check_typ_cache := Set.add typ !(env.check_typ_cache);
+
 (* Literals *)
 
 open Ir
@@ -968,7 +1001,7 @@ and check_case env t_pat t {it = {pat; exp}; _} =
   let ve = check_pat env pat in
   check_sub env pat.at t_pat pat.note;
   check_exp (adjoin_vals env ve) exp;
-  check env pat.at (T.sub (typ exp) t) "bad case"
+  check env pat.at (sub env (typ exp) t) "bad case"
 
 (* Arguments *)
 
@@ -1003,7 +1036,7 @@ and gather_pat env const ve0 pat : val_env =
       List.fold_left go ve (pats_of_obj_pat pfs)
     | AltP (pat1, pat2) ->
       let ve1, ve2 = go ve pat1, go ve pat2 in
-      let common i1 i2 = { typ = T.lub i1.typ i2.typ; loc_known = i1.loc_known && i2.loc_known; const = i1.const && i2.const } in
+      let common i1 i2 = { typ = lub env i1.typ i2.typ; loc_known = i1.loc_known && i2.loc_known; const = i1.const && i2.const } in
       T.Env.merge (fun _ -> Lib.Option.map2 common) ve1 ve2
     | OptP pat1
     | TagP (_, pat1) ->
@@ -1053,7 +1086,7 @@ and check_pat env pat : val_env =
     t <: pat2.note;
     if T.Env.(keys ve1 <> keys ve2) then
         error env pat.at "set of bindings differ for alternative pattern";
-    let common i1 i2 = { typ = T.lub i1.typ i2.typ; loc_known = i1.loc_known && i2.loc_known; const = i1.const && i2.const } in
+    let common i1 i2 = { typ = lub env i1.typ i2.typ; loc_known = i1.loc_known && i2.loc_known; const = i1.const && i2.const } in
     T.Env.merge (fun _ -> Lib.Option.map2 common) ve1 ve2
 
 and check_pats at env pats ve : val_env =