Add a low memory limit hint

cli/asc.js

@@ -247,6 +247,7 @@ exports.main = function main(argv, options, callback) {
   assemblyscript.setSourceMap(compilerOptions, args.sourceMap != null);
   assemblyscript.setNoUnsafe(compilerOptions, args.noUnsafe);
   assemblyscript.setPedantic(compilerOptions, args.pedantic);
+  assemblyscript.setLowMemoryLimit(compilerOptions, args.lowMemoryLimit >>> 0);
 
   // Add or override aliases if specified
   if (args.use) {

cli/asc.json

@@ -192,6 +192,12 @@
     "type": "S",
     "alias": "u"
   },
+  "lowMemoryLimit": {
+    "category": "Features",
+    "description": "Enforces very low (<64k) memory constraints.",
+    "default": 0,
+    "type": "i"
+  },
 
   "memoryBase": {
     "category": "Linking",

src/common.ts

@@ -154,6 +154,7 @@ export namespace CommonNames {
   export const ASC_TABLE_BASE = "ASC_TABLE_BASE";
   export const ASC_OPTIMIZE_LEVEL = "ASC_OPTIMIZE_LEVEL";
   export const ASC_SHRINK_LEVEL = "ASC_SHRINK_LEVEL";
+  export const ASC_LOW_MEMORY_LIMIT = "ASC_LOW_MEMORY_LIMIT";
   export const ASC_WASI = "ASC_WASI";
   export const ASC_FEATURE_SIGN_EXTENSION = "ASC_FEATURE_SIGN_EXTENSION";
   export const ASC_FEATURE_MUTABLE_GLOBALS = "ASC_FEATURE_MUTABLE_GLOBALS";

src/compiler.ts

@@ -219,6 +219,8 @@ export class Options {
   noUnsafe: bool = false;
   /** If true, enables pedantic diagnostics. */
   pedantic: bool = false;
+  /** Indicates a very low (<64k) memory limit. */
+  lowMemoryLimit: i32 = 0;
 
   /** Hinted optimize level. Not applied by the compiler itself. */
   optimizeLevelHint: i32 = 0;
@@ -361,7 +363,7 @@ export class Compiler extends DiagnosticEmitter {
       this.memoryOffset = i64_new(options.memoryBase);
       module.setLowMemoryUnused(false);
     } else {
-      if (options.optimizeLevelHint >= 2) {
+      if (options.optimizeLevelHint >= 2 && !options.lowMemoryLimit) {
         this.memoryOffset = i64_new(1024);
         module.setLowMemoryUnused(true);
       } else {
@@ -502,6 +504,16 @@ export class Compiler extends DiagnosticEmitter {
     // update the heap base pointer
     var memoryOffset = this.memoryOffset;
     memoryOffset = i64_align(memoryOffset, options.usizeType.byteSize);
+    var lowMemoryLimit32 = this.options.lowMemoryLimit;
+    if (lowMemoryLimit32) {
+      let lowMemoryLimit = i64_new(lowMemoryLimit32 & ~15);
+      if (i64_gt(memoryOffset, lowMemoryLimit)) {
+        this.error(
+          DiagnosticCode.Low_memory_limit_exceeded_by_static_data_0_1,
+          null, i64_to_string(memoryOffset), i64_to_string(lowMemoryLimit)
+        );
+      }
+    }
     this.memoryOffset = memoryOffset;
     module.removeGlobal(BuiltinNames.heap_base);
     if (this.runtimeFeatures & RuntimeFeatures.HEAP) {
@@ -526,7 +538,7 @@ export class Compiler extends DiagnosticEmitter {
     var isSharedMemory = options.hasFeature(Feature.THREADS) && options.sharedMemory > 0;
     module.setMemory(
       this.options.memoryBase /* is specified */ || this.memorySegments.length
-        ? i64_low(i64_shr_u(i64_align(memoryOffset, 0x10000), i64_new(16, 0)))
+        ? i64_low(i64_shr_u(i64_align(memoryOffset, 0x10000), i64_new(16)))
         : 0,
       isSharedMemory ? options.sharedMemory : Module.UNLIMITED_MEMORY,
       this.memorySegments,

src/diagnosticMessages.generated.ts

@@ -12,6 +12,7 @@ export enum DiagnosticCode {
   User_defined_0 = 102,
   Feature_0_is_not_enabled = 103,
   Function_0_is_possibly_called_virtually_which_is_not_yet_supported = 104,
+  Low_memory_limit_exceeded_by_static_data_0_1 = 105,
   Conversion_from_type_0_to_1_requires_an_explicit_cast = 200,
   Conversion_from_type_0_to_1_will_require_an_explicit_cast_when_switching_between_32_64_bit = 201,
   Type_0_cannot_be_changed_to_type_1 = 202,
@@ -165,6 +166,7 @@ export function diagnosticCodeToString(code: DiagnosticCode): string {
     case 102: return "User-defined: {0}";
     case 103: return "Feature '{0}' is not enabled.";
     case 104: return "Function '{0}' is possibly called virtually, which is not yet supported.";
+    case 105: return "Low memory limit exceeded by static data: {0} > {1}";
     case 200: return "Conversion from type '{0}' to '{1}' requires an explicit cast.";
     case 201: return "Conversion from type '{0}' to '{1}' will require an explicit cast when switching between 32/64-bit.";
     case 202: return "Type '{0}' cannot be changed to type '{1}'.";

src/diagnosticMessages.json

@@ -4,6 +4,7 @@
   "User-defined: {0}": 102,
   "Feature '{0}' is not enabled.": 103,
   "Function '{0}' is possibly called virtually, which is not yet supported.": 104,
+  "Low memory limit exceeded by static data: {0} > {1}": 105,
 
   "Conversion from type '{0}' to '{1}' requires an explicit cast.": 200,
   "Conversion from type '{0}' to '{1}' will require an explicit cast when switching between 32/64-bit.": 201,

src/glue/js/i64.d.ts

@@ -29,6 +29,7 @@ declare function i64_not(value: i64): i64;
 
 declare function i64_eq(left: i64, right: i64): bool;
 declare function i64_ne(left: i64, right: i64): bool;
+declare function i64_gt(left: i64, right: i64): bool;
 
 declare function i64_align(value: i64, alignment: i32): i64;
 

src/glue/js/i64.js

@@ -85,6 +85,10 @@ global.i64_ne = function(left, right) {
   return left.ne(right);
 };
 
+global.i64_gt = function(left, right) {
+  return left.gt(right);
+};
+
 global.i64_align = function(value, alignment) {
   assert(alignment && (alignment & (alignment - 1)) == 0);
   var mask = Long.fromInt(alignment - 1);

src/glue/wasm/i64.ts

@@ -125,6 +125,12 @@ function i64_ne(left: i64, right: i64): bool {
   return left != right;
 }
 
+// @ts-ignore: decorator
+@global
+function i64_gt(left: i64, right: i64): bool {
+  return left > right;
+}
+
 // @ts-ignore: decorator
 @global
 function i64_align(value: i64, alignment: i64): i64 {

src/index.ts

@@ -109,6 +109,11 @@ export function setNoUnsafe(options: Options, noUnsafe: bool): void {
   options.noUnsafe = noUnsafe;
 }
 
+/** Sets the `lowMemoryLimit` option. */
+export function setLowMemoryLimit(options: Options, lowMemoryLimit: i32): void {
+  options.lowMemoryLimit = lowMemoryLimit;
+}
+
 /** Sign extension operations. */
 export const FEATURE_SIGN_EXTENSION = Feature.SIGN_EXTENSION;
 /** Mutable global imports and exports. */

src/program.ts

@@ -741,6 +741,8 @@ export class Program extends DiagnosticEmitter {
       i64_new(options.optimizeLevelHint, 0));
     this.registerConstantInteger(CommonNames.ASC_SHRINK_LEVEL, Type.i32,
       i64_new(options.shrinkLevelHint, 0));
+    this.registerConstantInteger(CommonNames.ASC_LOW_MEMORY_LIMIT, Type.i32,
+      i64_new(options.lowMemoryLimit, 0));
 
     // register feature hints
     this.registerConstantInteger(CommonNames.ASC_FEATURE_SIGN_EXTENSION, Type.bool,

std/assembly/index.d.ts

@@ -52,6 +52,8 @@ declare const ASC_TABLE_BASE: i32;
 declare const ASC_OPTIMIZE_LEVEL: i32;
 /** Provided shrinkLevel option. */
 declare const ASC_SHRINK_LEVEL: i32;
+/** Provided lowMemoryLimit option. */
+declare const ASC_LOW_MEMORY_LIMIT: i32;
 /** Whether the sign extension feature is enabled. */
 declare const ASC_FEATURE_SIGN_EXTENSION: bool;
 /** Whether the mutable globals feature is enabled. */

std/assembly/rt/tlsf.ts

@@ -433,6 +433,10 @@ function addMemory(root: Root, start: usize, end: usize): bool {
 
 /** Grows memory to fit at least another block of the specified size. */
 function growMemory(root: Root, size: usize): void {
+  if (ASC_LOW_MEMORY_LIMIT) {
+    unreachable();
+    return;
+  }
   // Here, both rounding performed in searchBlock ...
   const halfMaxSize = BLOCK_MAXSIZE >> 1;
   if (size < halfMaxSize) { // don't round last fl
@@ -462,7 +466,7 @@ function prepareSize(size: usize): usize {
 export function maybeInitialize(): Root {
   var root = ROOT;
   if (!root) {
-    const rootOffset = (__heap_base + AL_MASK) & ~AL_MASK;
+    let rootOffset = (__heap_base + AL_MASK) & ~AL_MASK;
     let pagesBefore = memory.size();
     let pagesNeeded = <i32>((((rootOffset + ROOT_SIZE) + 0xffff) & ~0xffff) >>> 16);
     if (pagesNeeded > pagesBefore && memory.grow(pagesNeeded - pagesBefore) < 0) unreachable();
@@ -475,7 +479,14 @@ export function maybeInitialize(): Root {
         SETHEAD(root, fl, sl, null);
       }
     }
-    addMemory(root, (rootOffset + ROOT_SIZE + AL_MASK) & ~AL_MASK, memory.size() << 16);
+    let memStart = (rootOffset + ROOT_SIZE + AL_MASK) & ~AL_MASK;
+    if (ASC_LOW_MEMORY_LIMIT) {
+      const memEnd = <usize>ASC_LOW_MEMORY_LIMIT & ~AL_MASK;
+      if (memStart <= memEnd) addMemory(root, memStart, memEnd);
+      else unreachable(); // low memory limit already exceeded
+    } else {
+      addMemory(root, memStart, memory.size() << 16);
+    }
     ROOT = root;
   }
   return root;

tests/compiler/do.optimized.wat

@@ -813,7 +813,7 @@
   if
    i32.const 0
    i32.const 1072
-   i32.const 490
+   i32.const 501
    i32.const 13
    call $~lib/builtins/abort
    unreachable
@@ -883,7 +883,7 @@
     if
      i32.const 0
      i32.const 1072
-     i32.const 502
+     i32.const 513
      i32.const 19
      call $~lib/builtins/abort
      unreachable
@@ -899,7 +899,7 @@
   if
    i32.const 0
    i32.const 1072
-   i32.const 510
+   i32.const 521
    i32.const 13
    call $~lib/builtins/abort
    unreachable

tests/compiler/do.untouched.wat

@@ -21,6 +21,7 @@
  (table $0 1 funcref)
  (global $do/ran (mut i32) (i32.const 0))
  (global $~lib/rt/tlsf/ROOT (mut i32) (i32.const 0))
+ (global $~lib/ASC_LOW_MEMORY_LIMIT i32 (i32.const 0))
  (global $~lib/rt/tlsf/collectLock (mut i32) (i32.const 0))
  (global $~lib/gc/gc.auto (mut i32) (i32.const 1))
  (global $~started (mut i32) (i32.const 0))
@@ -1164,7 +1165,9 @@
    global.get $~lib/heap/__heap_base
    i32.const 15
    i32.add
-   i32.const -16
+   i32.const 15
+   i32.const -1
+   i32.xor
    i32.and
    local.set $1
    memory.size
@@ -1273,7 +1276,6 @@
      br $for-loop|0
     end
    end
-   local.get $0
    local.get $1
    i32.const 1572
    i32.add
@@ -1283,6 +1285,9 @@
    i32.const -1
    i32.xor
    i32.and
+   local.set $5
+   local.get $0
+   local.get $5
    memory.size
    i32.const 16
    i32.shl
@@ -1302,7 +1307,7 @@
   if
    i32.const 112
    i32.const 64
-   i32.const 457
+   i32.const 461
    i32.const 29
    call $~lib/builtins/abort
    unreachable
@@ -1693,7 +1698,7 @@
   if
    i32.const 0
    i32.const 64
-   i32.const 490
+   i32.const 501
    i32.const 13
    call $~lib/builtins/abort
    unreachable
@@ -1734,7 +1739,7 @@
      if
       i32.const 0
       i32.const 64
-      i32.const 502
+      i32.const 513
       i32.const 19
       call $~lib/builtins/abort
       unreachable
@@ -1753,7 +1758,7 @@
     if
      i32.const 0
      i32.const 64
-     i32.const 507
+     i32.const 518
      i32.const 17
      call $~lib/builtins/abort
      unreachable
@@ -1770,7 +1775,7 @@
   if
    i32.const 0
    i32.const 64
-   i32.const 510
+   i32.const 521
    i32.const 13
    call $~lib/builtins/abort
    unreachable

tests/compiler/extends-baseaggregate.optimized.wat

@@ -679,7 +679,7 @@
   if
    i32.const 1184
    i32.const 1136
-   i32.const 457
+   i32.const 461
    i32.const 29
    call $~lib/builtins/abort
    unreachable
@@ -908,7 +908,7 @@
   if
    i32.const 0
    i32.const 1136
-   i32.const 490
+   i32.const 501
    i32.const 13
    call $~lib/builtins/abort
    unreachable
@@ -1000,7 +1000,7 @@
     if
      i32.const 0
      i32.const 1136
-     i32.const 502
+     i32.const 513
      i32.const 19
      call $~lib/builtins/abort
      unreachable
@@ -1016,7 +1016,7 @@
   if
    i32.const 0
    i32.const 1136
-   i32.const 510
+   i32.const 521
    i32.const 13
    call $~lib/builtins/abort
    unreachable
@@ -1131,7 +1131,7 @@
   if
    i32.const 0
    i32.const 1136
-   i32.const 570
+   i32.const 581
    i32.const 2
    call $~lib/builtins/abort
    unreachable