[Mlir-commits] [mlir] [MLIR][Bytecode] Enforce alignment requirements (PR #157004)

[Mehdi Amini]

================
@@ -117,6 +119,57 @@ TEST(Bytecode, MultiModuleWithResource) {
   checkResourceAttribute(*roundTripModule);
 }
 
+TEST(Bytecode, AlignmentFailure) {
+  MLIRContext context;
+  Builder builder(&context);
+  ParserConfig parseConfig(&context);
+  OwningOpRef<Operation *> module =
+      parseSourceString<Operation *>(irWithResources, parseConfig);
+  ASSERT_TRUE(module);
+
+  // Write the module to bytecode.
+  MockOstream ostream;
+  EXPECT_CALL(ostream, reserveExtraSpace).WillOnce([&](uint64_t space) {
+    ostream.buffer = std::make_unique<std::byte[]>(space);
+    ostream.size = space;
+  });
+  ASSERT_TRUE(succeeded(writeBytecodeToFile(module.get(), ostream)));
+
+  // Create copy of buffer which is not aligned to requested resource alignment.
+  std::string buffer((char *)ostream.buffer.get(),
+                     (char *)ostream.buffer.get() + ostream.size);
+  size_t bufferSize = buffer.size();
+
+  // Increment into the buffer until we get to a power of 2 alignment that is
+  // not 32 bit aligned.
+  size_t pad = 0;
+  while (true) {
+    if (llvm::isAddrAligned(Align(2), &buffer[pad]) &&
+        !llvm::isAddrAligned(Align(32), &buffer[pad]))
+      break;
+
+    pad++;
+    buffer.reserve(bufferSize + pad);
----------------
joker-eph wrote:

This should be after the loop.

If this is meant to help with the next iteration accessing buffer[pad], then it should be a resize instead of reserve I believe.
You may also use `buffer.data() + pad` to avoid dereferencing anything.

https://github.com/llvm/llvm-project/pull/157004