1 files changed, 72 insertions, 0 deletions
diff --git a/src/ir/memory-utils.cpp b/src/ir/memory-utils.cpp
new file mode 100644
index 000000000..b7c92fe9e
--- /dev/null
+++ b/src/ir/memory-utils.cpp
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2022 WebAssembly Community Group participants
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "ir/memory-utils.h"
+#include "wasm.h"
+
+namespace wasm::MemoryUtils {
+
+bool flatten(Module& wasm) {
+  // The presence of any MemoryInit instructions is a problem because they care
+  // about segment identity, which flattening gets rid of ( when it merges them
+  // all into one big segment).
+  ModuleUtils::ParallelFunctionAnalysis<bool> analysis(
+    wasm, [&](Function* func, bool& hasMemoryInit) {
+      if (func->imported()) {
+        return;
+      }
+      hasMemoryInit = FindAll<MemoryInit>(func->body).list.size() > 0;
+    });
+
+  for (auto& [func, hasMemoryInit] : analysis.map) {
+    if (hasMemoryInit) {
+      return false;
+    }
+  }
+
+  auto& memory = wasm.memory;
+
+  if (memory.segments.size() == 0) {
+    return true;
+  }
+
+  std::vector<char> data;
+  for (auto& segment : memory.segments) {
+    if (segment.isPassive) {
+      return false;
+    }
+    auto* offset = segment.offset->dynCast<Const>();
+    if (!offset) {
+      return false;
+    }
+  }
+  for (auto& segment : memory.segments) {
+    auto* offset = segment.offset->dynCast<Const>();
+    Index start = offset->value.getInteger();
+    Index end = start + segment.data.size();
+    if (end > data.size()) {
+      data.resize(end);
+    }
+    std::copy(segment.data.begin(), segment.data.end(), data.begin() + start);
+  }
+  memory.segments.resize(1);
+  memory.segments[0].offset->cast<Const>()->value = Literal(int32_t(0));
+  memory.segments[0].data.swap(data);
+
+  return true;
+}
+
+} // namespace wasm::MemoryUtils