[clang] [CIR] Upstream EHScopeStack memory allocator (PR #152215)

[Morris Hafner via cfe-commits]

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@@ -33,6 +34,54 @@ using namespace clang::CIRGen;
 
 void EHScopeStack::Cleanup::anchor() {}
 
+/// Push an entry of the given size onto this protected-scope stack.
+char *EHScopeStack::allocate(size_t size) {
+  size = llvm::alignTo(size, ScopeStackAlignment);
+  if (!startOfBuffer) {
+    unsigned capacity = 1024;
+    while (capacity < size)
+      capacity *= 2;
+    startOfBuffer = new char[capacity];
+    startOfData = endOfBuffer = startOfBuffer + capacity;
+  } else if (static_cast<size_t>(startOfData - startOfBuffer) < size) {
+    unsigned currentCapacity = endOfBuffer - startOfBuffer;
+    unsigned usedCapacity = currentCapacity - (startOfData - startOfBuffer);
+
+    unsigned newCapacity = currentCapacity;
+    do {
+      newCapacity *= 2;
+    } while (newCapacity < usedCapacity + size);
+
+    char *newStartOfBuffer = new char[newCapacity];
+    char *newEndOfBuffer = newStartOfBuffer + newCapacity;
+    char *newStartOfData = newEndOfBuffer - usedCapacity;
+    memcpy(newStartOfData, startOfData, usedCapacity);
+    delete[] startOfBuffer;
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mmha wrote:

Can we use unique_ptr at least within this function?

https://github.com/llvm/llvm-project/pull/152215