Decouple Array<T> from ArrayBufferView (#1121)

Author: dcodeIO

lib/loader/index.js

@@ -162,7 +162,7 @@ function postInstantiate(baseModule, instance) {
   /** Allocates a new array in the module's memory and returns its retained pointer. */
   function __allocArray(id, values) {
     const info = getInfo(id);
-    if (!(info & (ARRAYBUFFERVIEW | ARRAY))) throw Error("not an array: " + id + " @ " + info);
+    if (!(info & (ARRAYBUFFERVIEW | ARRAY))) throw Error("not an array: " + id + ", flags= " + info);
     const align = getValueAlign(info);
     const length = values.length;
     const buf = alloc(length << align, ARRAYBUFFER_ID);
@@ -188,7 +188,7 @@ function postInstantiate(baseModule, instance) {
     const U32 = new Uint32Array(memory.buffer);
     const id = U32[arr + ID_OFFSET >>> 2];
     const info = getInfo(id);
-    if (!(info & ARRAYBUFFERVIEW)) throw Error("not an array: " + id);
+    if (!(info & (ARRAYBUFFERVIEW | ARRAY))) throw Error("not an array: " + id + ", flags=" + info);
     const align = getValueAlign(info);
     var buf = U32[arr + ARRAYBUFFERVIEW_DATASTART_OFFSET >>> 2];
     const length = info & ARRAY

lib/loader/tests/build/default.wasm

@@ -7910,7 +7910,10 @@ export function compileRTTI(compiler: Compiler): void {
     if (instance !== abvInstance && instance.extends(abvPrototype)) {
       let valueType = instance.getArrayValueType();
       flags |= TypeinfoFlags.ARRAYBUFFERVIEW;
-      if (instance.extends(arrayPrototype)) flags |= TypeinfoFlags.ARRAY;
+      flags |= TypeinfoFlags.VALUE_ALIGN_0 * typeToRuntimeFlags(valueType);
+    } else if (instance.extends(arrayPrototype)) {
+      let valueType = instance.getArrayValueType();
+      flags |= TypeinfoFlags.ARRAY;
       flags |= TypeinfoFlags.VALUE_ALIGN_0 * typeToRuntimeFlags(valueType);
     } else if (instance.extends(setPrototype)) {
       let typeArguments = assert(instance.getTypeArgumentsTo(setPrototype));

lib/loader/tests/build/legacy.wasm

@@ -3751,25 +3751,37 @@ export class Class extends TypedElement {
   getArrayValueType(): Type {
     var current: Class = this;
     var program = this.program;
+    var arrayPrototype = program.arrayPrototype;
+    if (this.extends(arrayPrototype)) {
+      return this.getTypeArgumentsTo(arrayPrototype)![0];
+    }
     var abvInstance = program.arrayBufferViewInstance;
     while (current.base !== abvInstance) {
       current = assert(current.base);
     }
     var prototype = current.prototype;
-    if (prototype == program.arrayPrototype) {
-      return this.getTypeArgumentsTo(program.arrayPrototype)![0];
-    }
-    if (prototype == program.i8ArrayPrototype) return Type.i8;
-    if (prototype == program.i16ArrayPrototype) return Type.i16;
-    if (prototype == program.i32ArrayPrototype) return Type.i32;
-    if (prototype == program.i64ArrayPrototype) return Type.i64;
-    if (prototype == program.u8ArrayPrototype) return Type.u8;
-    if (prototype == program.u8ClampedArrayPrototype) return Type.u8;
-    if (prototype == program.u16ArrayPrototype) return Type.u16;
-    if (prototype == program.u32ArrayPrototype) return Type.u32;
-    if (prototype == program.u64ArrayPrototype) return Type.u64;
-    if (prototype == program.f32ArrayPrototype) return Type.f32;
-    if (prototype == program.f64ArrayPrototype) return Type.f64;
+    switch (prototype.name.charCodeAt(0)) {
+      case CharCode.F: {
+        if (prototype == program.f32ArrayPrototype) return Type.f32;
+        if (prototype == program.f64ArrayPrototype) return Type.f64;
+        break;
+      }
+      case CharCode.I: {
+        if (prototype == program.i8ArrayPrototype) return Type.i8;
+        if (prototype == program.i16ArrayPrototype) return Type.i16;
+        if (prototype == program.i32ArrayPrototype) return Type.i32;
+        if (prototype == program.i64ArrayPrototype) return Type.i64;
+        break;
+      }
+      case CharCode.U: {
+        if (prototype == program.u8ArrayPrototype) return Type.u8;
+        if (prototype == program.u8ClampedArrayPrototype) return Type.u8;
+        if (prototype == program.u16ArrayPrototype) return Type.u16;
+        if (prototype == program.u32ArrayPrototype) return Type.u32;
+        if (prototype == program.u64ArrayPrototype) return Type.u64;
+        break;
+      }
+    }
     assert(false);
     return Type.void;
   }

src/builtins.ts

@@ -2,13 +2,13 @@
 
 import { BLOCK_MAXSIZE } from "./rt/common";
 import { COMPARATOR, SORT } from "./util/sort";
-import { ArrayBufferView } from "./arraybuffer";
 import { joinBooleanArray, joinIntegerArray, joinFloatArray, joinStringArray, joinReferenceArray } from "./util/string";
 import { idof, isArray as builtin_isArray } from "./builtins";
 import { E_INDEXOUTOFRANGE, E_INVALIDLENGTH, E_EMPTYARRAY, E_HOLEYARRAY } from "./util/error";
 
 /** Ensures that the given array has _at least_ the specified backing size. */
 function ensureSize(array: usize, minSize: usize, alignLog2: u32): void {
+  // depends on the fact that Arrays mimic ArrayBufferView
   var oldCapacity = changetype<ArrayBufferView>(array).byteLength;
   if (minSize > <usize>oldCapacity >>> alignLog2) {
     if (minSize > BLOCK_MAXSIZE >>> alignLog2) throw new RangeError(E_INVALIDLENGTH);
@@ -24,12 +24,17 @@ function ensureSize(array: usize, minSize: usize, alignLog2: u32): void {
   }
 }
 
-export class Array<T> extends ArrayBufferView {
+export class Array<T> {
   [key: number]: T;
 
-  // Implementing ArrayBufferView isn't strictly necessary here but is done to allow glue code
+  // Mimicking ArrayBufferView isn't strictly necessary here but is done to allow glue code
   // to work with typed and normal arrays interchangeably. Technically, normal arrays do not need
-  // `dataStart` (equals `data`) and `dataLength` (equals computed `data.byteLength`).
+  // `dataStart` (equals `buffer`) and `byteLength` (equals computed `buffer.byteLength`), but the
+  // block is 16 bytes anyway so it's fine to have a couple extra fields in there.
+
+  private buffer: ArrayBuffer;
+  private dataStart: usize;
+  private byteLength: i32;
 
   // Also note that Array<T> with non-nullable T must guard against uninitialized null values
   // whenever an element is accessed. Otherwise, the compiler wouldn't be able to guarantee
@@ -49,7 +54,13 @@ export class Array<T> extends ArrayBufferView {
   }
 
   constructor(length: i32 = 0) {
-    super(length, alignof<T>());
+    if (<u32>length > <u32>BLOCK_MAXSIZE >>> alignof<T>()) throw new RangeError(E_INVALIDLENGTH);
+    var bufferSize = <usize>length << alignof<T>();
+    var buffer = __alloc(bufferSize, idof<ArrayBuffer>());
+    memory.fill(buffer, 0, bufferSize);
+    this.buffer = changetype<ArrayBuffer>(buffer); // retains
+    this.dataStart = buffer;
+    this.byteLength = <i32>bufferSize;
     this.length_ = length;
   }
 
@@ -498,6 +509,6 @@ export class Array<T> extends ArrayBufferView {
         cur += sizeof<usize>();
       }
     }
-    // automatically visits ArrayBufferView (.buffer) next
+    __visit(changetype<usize>(this.buffer), cookie);
   }
 }

src/program.ts

@@ -85,7 +85,7 @@
   if
    i32.const 1104
    i32.const 1168
-   i32.const 93
+   i32.const 104
    i32.const 41
    call $~lib/builtins/abort
    unreachable
@@ -98,7 +98,7 @@
   if
    i32.const 1216
    i32.const 1168
-   i32.const 97
+   i32.const 108
    i32.const 39
    call $~lib/builtins/abort
    unreachable
@@ -113,7 +113,7 @@
   if
    i32.const 1104
    i32.const 1168
-   i32.const 93
+   i32.const 104
    i32.const 41
    call $~lib/builtins/abort
    unreachable

std/assembly/array.ts

@@ -122,7 +122,7 @@
   if
    i32.const 96
    i32.const 160
-   i32.const 93
+   i32.const 104
    i32.const 41
    call $~lib/builtins/abort
    unreachable
@@ -138,7 +138,7 @@
    call $~lib/rt/stub/__release
    i32.const 208
    i32.const 160
-   i32.const 97
+   i32.const 108
    i32.const 39
    call $~lib/builtins/abort
    unreachable
@@ -188,7 +188,7 @@
   if
    i32.const 96
    i32.const 160
-   i32.const 93
+   i32.const 104
    i32.const 41
    call $~lib/builtins/abort
    unreachable

tests/compiler/assert-nonnull.optimized.wat

@@ -605,8 +605,8 @@
   f64.const 0
   f64.const 0
   f64.const 12
-  f64.const 24
-  f64.const 24
+  f64.const 25
+  f64.const 25
   call $~lib/builtins/trace
   i32.const 1216
   i32.const 1216

tests/compiler/assert-nonnull.untouched.wat

@@ -1563,9 +1563,9 @@
   local.set $1
   i32.const 12
   local.set $6
-  i32.const 24
+  i32.const 25
   local.set $7
-  i32.const 24
+  i32.const 25
   local.set $8
   i32.const 128
   i32.const 5

tests/compiler/builtins.optimized.wat

@@ -4,7 +4,7 @@
  (type $i32_i32_=>_i32 (func (param i32 i32) (result i32)))
  (memory $0 1)
  (data (i32.const 1024) "\1c\00\00\00\01\00\00\00\01\00\00\00\1c\00\00\00I\00n\00v\00a\00l\00i\00d\00 \00l\00e\00n\00g\00t\00h")
- (data (i32.const 1072) "&\00\00\00\01\00\00\00\01\00\00\00&\00\00\00~\00l\00i\00b\00/\00a\00r\00r\00a\00y\00b\00u\00f\00f\00e\00r\00.\00t\00s")
+ (data (i32.const 1072) "\1a\00\00\00\01\00\00\00\01\00\00\00\1a\00\00\00~\00l\00i\00b\00/\00a\00r\00r\00a\00y\00.\00t\00s")
  (global $~lib/rt/stub/startOffset (mut i32) (i32.const 0))
  (global $~lib/rt/stub/offset (mut i32) (i32.const 0))
  (export "memory" (memory $0))
@@ -123,23 +123,14 @@
   i32.const 4
   i32.const 4
   call $~lib/rt/stub/__alloc
-  i32.const 16
-  i32.const 5
-  call $~lib/rt/stub/__alloc
-  local.set $0
   i32.const 0
   i32.const 0
   call $~lib/rt/stub/__alloc
   local.set $1
-  local.get $0
-  i32.eqz
-  if
-   i32.const 12
-   i32.const 2
-   call $~lib/rt/stub/__alloc
-   local.set $0
-  end
-  local.get $0
+  i32.const 16
+  i32.const 5
+  call $~lib/rt/stub/__alloc
+  local.tee $0
   i32.const 0
   i32.store
   local.get $0
@@ -149,6 +140,9 @@
   i32.const 0
   i32.store offset=8
   local.get $0
+  i32.const 0
+  i32.store offset=12
+  local.get $0
   i32.load
   drop
   local.get $0
@@ -164,15 +158,12 @@
   i32.const 0
   i32.store offset=12
   local.get $0
-  i32.const 0
-  i32.store offset=12
-  local.get $0
   i32.store
  )
  (func $~start (; 3 ;)
-  i32.const 1136
+  i32.const 1120
   global.set $~lib/rt/stub/startOffset
-  i32.const 1136
+  i32.const 1120
   global.set $~lib/rt/stub/offset
  )
 )