Implement reference counting (#592)

std/assembly/rt/stub.ts

@@ -0,0 +1,77 @@
+import { AL_MASK, BLOCK, BLOCK_OVERHEAD, BLOCK_MAXSIZE } from "rt/common";
+
+// @ts-ignore: decorator
+@lazy
+var startOffset: usize = (__heap_base + AL_MASK) & ~AL_MASK;
+
+// @ts-ignore: decorator
+@lazy
+var offset: usize = startOffset;
+
+// @ts-ignore: decorator
+@unsafe @global
+export function __alloc(size: usize, id: u32): usize {
+  if (size > BLOCK_MAXSIZE) unreachable();
+  var ptr = offset + BLOCK_OVERHEAD;
+  var newPtr = (ptr + max<usize>(size, 1) + AL_MASK) & ~AL_MASK;
+  var pagesBefore = memory.size();
+  if (newPtr > <usize>pagesBefore << 16) {
+    let pagesNeeded = ((newPtr - ptr + 0xffff) & ~0xffff) >>> 16;
+    let pagesWanted = max(pagesBefore, pagesNeeded); // double memory
+    if (memory.grow(pagesWanted) < 0) {
+      if (memory.grow(pagesNeeded) < 0) unreachable(); // out of memory
+    }
+  }
+  offset = newPtr;
+  var block = changetype<BLOCK>(ptr - BLOCK_OVERHEAD);
+  block.rtId = id;
+  block.rtSize = size;
+  return ptr;
+}
+
+// @ts-ignore: decorator
+@unsafe @global
+export function __realloc(ref: usize, size: usize): usize {
+  var block = changetype<BLOCK>(ref - BLOCK_OVERHEAD);
+  var oldSize = <usize>block.rtSize;
+  if (size > oldSize) {
+    let newRef = __alloc(size, block.rtId);
+    memory.copy(newRef, ref, oldSize);
+    ref = newRef;
+  } else {
+    block.rtSize = size;
+  }
+  return ref;
+}
+
+// @ts-ignore: decorator
+@unsafe @global
+export function __free(ref: usize): void {
+}
+
+// @ts-ignore: decorator
+@unsafe @global
+function __reset(): void { // special
+  offset = startOffset;
+}
+
+// @ts-ignore: decorator
+@global @unsafe
+export function __retain(ref: usize): usize {
+  return ref;
+}
+
+// @ts-ignore: decorator
+@global @unsafe
+export function __release(ref: usize): void {
+}
+
+// @ts-ignore: decorator
+@global @unsafe
+export function __visit(ref: usize, cookie: u32): void {
+}
+
+// @ts-ignore: decorator
+@global @unsafe
+export function __collect(): void {
+}