[ctor-eval] Stop if there are any memory.init instructions (#4442)

This tool depends (atm) on flattening memory segments. That is not compatible
with memory.init which cares about segment identities.

This changes flatten() only by adding the check for MemoryInit. The rest is
unchanged, although I saw the other two params are not needed and I removed
them while I was there.

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