revise array iteration optimization; add tests

src/codegen/compile.ml

@@ -29,8 +29,7 @@ let page_size = Int32.of_int (64*1024)
 let page_size64 = Int64.of_int32 page_size
 let page_size_bits = 16
 
-
-(* tentative tagging scheme *)
+(* Tentative tagging scheme *)
 
 module TaggingScheme = struct
  type bit = I | O
@@ -3240,7 +3239,7 @@ module MakeCompact (Num : BigNumType) : BigNumType = struct
           G.if1 I32Type
             (get_res ^^ compile_bitor_const (TaggingScheme.tag_of_typ Type.Int))
             (get_n ^^ compile_shrS_const (Int32.of_int (32 - BitTagged.ubits_of Type.Int)) ^^
-             Num.from_word30 env ^^ get_amount ^^ Num.compile_lsh env)
+             Num.from_word30 env ^^ get_amount ^^ Num.compile_lsh env) (* TBR: from_word30? *)
         )
         (get_n ^^ get_amount ^^ Num.compile_lsh env))
 
@@ -10383,7 +10382,7 @@ and compile_prim_invocation (env : E.t) ae p es at =
   | NextArrayOffset spacing, [e] ->
     let advance_by =
       match spacing with
-      | ElementSize -> Int32.shift_left Arr.element_size (32 - BitTagged.ubits_of Type.Int) (* 4 : Nat *)
+      | ElementSize
       | One -> Int32.shift_left 1l (32 - BitTagged.ubits_of Type.Int) (* 1 : Nat *) in
     SR.Vanilla,
     compile_exp_vanilla env ae e ^^ (* previous byte offset to array *)
@@ -10399,6 +10398,7 @@ and compile_prim_invocation (env : E.t) ae p es at =
     Tagged.load_forwarding_pointer env ^^
     compile_exp_vanilla env ae e2 ^^ (* byte offset *)
     BitTagged.untag_i32 env Type.Int ^^
+    compile_shl_const 2l ^^ (* effectively a multiplication by word_size *)
     (* Note: the below two lines compile to `i32.add; i32.load offset=OFFSET`
        with OFFSET = 13 with forwarding pointers and OFFSET = 9 without forwarding pointers,
        thus together also unskewing the pointer and skipping administrative
@@ -10409,10 +10409,8 @@ and compile_prim_invocation (env : E.t) ae p es at =
   | GetPastArrayOffset spacing, [e] ->
     let shift =
       match spacing with
-      | ElementSize ->
-         compile_shl_const 2l ^^ (* effectively a multiplication by word_size *)
-         BitTagged.tag_i32 env Type.Int
-      | One -> BigNum.from_word30 env in    (* make it a compact bignum *)
+      | ElementSize
+      | One -> BigNum.from_word30 env in    (* make it a compact bignum *) (* TBR: from_word30? *)
     SR.Vanilla,
     compile_exp_vanilla env ae e ^^ (* array *)
     Arr.len env ^^

test/run/array-iter-max.mo

@@ -0,0 +1,23 @@
+import Prim "mo:⛔";
+// test we can iterate over vals and keys of largest array
+let max_size = 2**29; // maximum array size
+let a = Prim.Array_tabulate<Nat>(max_size,func i = i+1);
+var c = 0;
+for (i in a.vals()) {
+ assert i == c+1; c += 1;
+}
+;
+assert c == max_size;
+Prim.debugPrint(debug_show c);
+var d = 0;
+for (k in a.keys()) {
+  assert k == d; d += 1;
+};
+assert d == max_size;
+Prim.debugPrint(debug_show d);
+
+Prim.Array_tabulate<Nat>(max_size+1,func i = i+1); // should trap
+
+//SKIP run
+//SKIP run-ir
+//SKIP run-low

test/run/mut-array-iter-max.mo

@@ -0,0 +1,23 @@
+import Prim "mo:⛔";
+// test we can iterate over vals and keys of largest mutable array
+let max_size = 2**29; // maximum array size
+let a = Prim.Array_init<Nat>(max_size, 666);
+var c = 0;
+for (v in a.vals()) {
+ assert v == 666; c += 1;
+}
+;
+assert c == max_size;
+Prim.debugPrint(debug_show c);
+var d = 0;
+for (k in a.keys()) {
+  assert k == d; d += 1;
+};
+assert d == max_size;
+Prim.debugPrint(debug_show d);
+
+Prim.Array_init<Nat>(max_size+1,0); // should trap
+
+//SKIP run
+//SKIP run-ir
+//SKIP run-low

test/run/ok/array-iter-max.wasm-run.ok

@@ -0,0 +1,17 @@
+536_870_912
+536_870_912
+RTS error: Array allocation too large
+Error: failed to run main module `_out/array-iter-max.wasm`
+
+Caused by:
+    0: failed to invoke command default
+    1: error while executing at wasm backtrace:
+         0: rts_trap
+         1: motoko_rts::trap_with_prefix::hb9fcc00b15d04524
+         2: motoko_rts::rts_trap_with::h22ec7878647e017a
+         3: motoko_rts::memory::alloc_array::h29955cba75599907
+         4: alloc_array
+         5: Array_tabulate
+         6: init
+         7: _start
+    2: wasm trap: unreachable

test/run/ok/array-iter-max.wasm-run.ret.ok

@@ -0,0 +1 @@
+Return code 134

test/run/ok/mut-array-iter-max.wasm-run.ok

@@ -0,0 +1,17 @@
+536_870_912
+536_870_912
+RTS error: Array allocation too large
+Error: failed to run main module `_out/mut-array-iter-max.wasm`
+
+Caused by:
+    0: failed to invoke command default
+    1: error while executing at wasm backtrace:
+         0: rts_trap
+         1: motoko_rts::trap_with_prefix::hb9fcc00b15d04524
+         2: motoko_rts::rts_trap_with::h22ec7878647e017a
+         3: motoko_rts::memory::alloc_array::h29955cba75599907
+         4: alloc_array
+         5: Array_init
+         6: init
+         7: _start
+    2: wasm trap: unreachable

test/run/ok/mut-array-iter-max.wasm-run.ret.ok

@@ -0,0 +1 @@
+Return code 134