Add an option to ignore unchecked() expressions

This new option, --ignoreUnchecked, can be useful for debugging whether
out-of-bounds reads/writes are taking place in code that normally should
not bounds-check for performance reasons.

Author: CountBleck

cli/index.js

@@ -320,6 +320,7 @@ export async function main(argv, options) {
   assemblyscript.setMemoryBase(compilerOptions, opts.memoryBase >>> 0);
   assemblyscript.setTableBase(compilerOptions, opts.tableBase >>> 0);
   assemblyscript.setSourceMap(compilerOptions, opts.sourceMap != null);
+  assemblyscript.setIgnoreUnchecked(compilerOptions, opts.ignoreUnchecked);
   assemblyscript.setNoUnsafe(compilerOptions, opts.noUnsafe);
   assemblyscript.setPedantic(compilerOptions, opts.pedantic);
   assemblyscript.setLowMemoryLimit(compilerOptions, opts.lowMemoryLimit >>> 0);

cli/options.json

@@ -98,6 +98,12 @@
     ],
     "type": "s"
   },
+  "ignoreUnchecked": {
+    "category": "Debugging",
+    "description": "Ignores unchecked() expressions.",
+    "type": "b",
+    "default": false
+  },
   "debug": {
     "category": "Debugging",
     "description": "Enables debug information in emitted binaries.",

src/builtins.ts

@@ -3588,7 +3588,7 @@ function builtin_unchecked(ctx: BuiltinContext): ExpressionRef {
   ) return module.unreachable();
   let flow = compiler.currentFlow;
   let alreadyUnchecked = flow.is(FlowFlags.UncheckedContext);
-  flow.set(FlowFlags.UncheckedContext);
+  if (!compiler.options.ignoreUnchecked) flow.set(FlowFlags.UncheckedContext);
   // eliminate unnecessary tees by preferring contextualType(=void)
   let expr = compiler.compileExpression(ctx.operands[0], ctx.contextualType);
   if (!alreadyUnchecked) flow.unset(FlowFlags.UncheckedContext);

src/compiler.ts

@@ -246,6 +246,8 @@ export class Options {
   exportTable: bool = false;
   /** If true, generates information necessary for source maps. */
   sourceMap: bool = false;
+  /** If true, unchecked() expressions are ignored. */
+  ignoreUnchecked: bool = false;
   /** If given, exports the start function instead of calling it implicitly. */
   exportStart: string | null = null;
   /** Static memory start offset. */

src/index-wasm.ts

@@ -102,6 +102,11 @@ export function setSourceMap(options: Options, sourceMap: bool): void {
   options.sourceMap = sourceMap;
 }
 
+/** Sets the `ignoreUnchecked` option. */
+export function setIgnoreUnchecked(options: Options, ignoreUnchecked: bool): void {
+  options.ignoreUnchecked = ignoreUnchecked;
+}
+
 /** Sets the `memoryBase` option. */
 export function setMemoryBase(options: Options, memoryBase: u32): void {
   options.memoryBase = memoryBase;