[wasm] Fix page size constant + test limits on max pages.

BUG=chromium:801604
R=bbudge@chromium.org,titzer@chromium.org

Change-Id: I5fa57d5f8ea288d7aef7d466cbf11df46c4dcd1d
Reviewed-on: https://chromium-review.googlesource.com/869468Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Brad Nelson <bradnelson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50665}

src/wasm/wasm-js.cc

@@ -826,7 +826,7 @@ void WebAssemblyMemoryGrow(const v8::FunctionCallbackInfo<v8::Value>& args) {
     return;
   }
   uint32_t old_size =
-      old_buffer->byte_length()->Number() / i::wasm::kSpecMaxWasmMemoryPages;
+      old_buffer->byte_length()->Number() / i::wasm::kWasmPageSize;
   int64_t new_size64 = old_size + delta_size;
   if (delta_size < 0 || max_size64 < new_size64 || new_size64 < old_size) {
     thrower.RangeError(new_size64 < old_size ? "trying to shrink memory"

test/mjsunit/wasm/memory-size.js

@@ -7,6 +7,9 @@
 load("test/mjsunit/wasm/wasm-constants.js");
 load("test/mjsunit/wasm/wasm-module-builder.js");
 
+var kV8MaxWasmMemoryPages = 32767;  // ~ 2 GiB
+var kSpecMaxWasmMemoryPages = 65536;  // 4 GiB
+
 (function testMemorySizeZero() {
   print("testMemorySizeZero()");
   var builder = new WasmModuleBuilder();
@@ -29,3 +32,38 @@ load("test/mjsunit/wasm/wasm-module-builder.js");
   var module = builder.instantiate();
   assertEquals(size, module.exports.memory_size());
 })();
+
+(function testMemorySizeSpecMaxOk() {
+  print("testMemorySizeV8Max()");
+  var builder = new WasmModuleBuilder();
+  builder.addMemory(1, kSpecMaxWasmMemoryPages, true);
+  builder.addFunction("memory_size", kSig_i_v)
+         .addBody([kExprMemorySize, kMemoryZero])
+         .exportFunc();
+  var module = builder.instantiate();
+  assertEquals(1, module.exports.memory_size());
+})();
+
+(function testMemorySizeV8MaxPlus1Throws() {
+  print("testMemorySizeV8MaxPlus1Throws()");
+  var builder = new WasmModuleBuilder();
+  builder.addMemory(kV8MaxWasmMemoryPages + 1,
+                    kV8MaxWasmMemoryPages + 1, false);
+  builder.addFunction("memory_size", kSig_i_v)
+         .addBody([kExprMemorySize, kMemoryZero])
+         .exportFunc();
+  assertThrows(() => builder.instantiate());
+})();
+
+(function testMemorySpecMaxOk() {
+  print("testMemoryInitialMaxOk()");
+  var mem = new WebAssembly.Memory(
+      {initial: 1, maximum: kSpecMaxWasmMemoryPages});
+  assertThrows(() => builder.instantiate());
+})();
+
+(function testMemoryInitialMaxPlus1Throws() {
+  print("testMemoryInitialMaxOk()");
+  assertThrows(() => new WebAssembly.Memory(
+      {initial: kV8WasmMaxMemoryPages + 1}));
+})();