1 files changed, 75 insertions, 0 deletions
diff --git a/clang/lib/AST/ByteCode/BitcastBuffer.cpp b/clang/lib/AST/ByteCode/BitcastBuffer.cpp
index 0cc97b0b6bf1..fbd500fd8f5f 100644
--- a/clang/lib/AST/ByteCode/BitcastBuffer.cpp
+++ b/clang/lib/AST/ByteCode/BitcastBuffer.cpp
@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 #include "BitcastBuffer.h"
+#include "llvm/ADT/STLExtras.h"
 
 using namespace clang;
 using namespace clang::interp;
@@ -60,6 +61,80 @@ BitcastBuffer::copyBits(Bits BitOffset, Bits BitWidth, Bits FullBitWidth,
   return Out;
 }
 
+bool BitcastBuffer::allInitialized() const {
+  return rangeInitialized(Bits::zero(), FinalBitSize);
+}
+
+void BitcastBuffer::markInitialized(Bits Offset, Bits Length) {
+  if (Length.isZero())
+    return;
+
+  BitRange Element(Offset, Offset + Length - Bits(1));
+  if (InitializedBits.empty()) {
+    InitializedBits.push_back(Element);
+    return;
+  }
+
+  assert(InitializedBits.size() >= 1);
+  // Common case of just appending.
+  Bits End = InitializedBits.back().End;
+  if (End <= Offset) {
+    // Merge this range with the last one.
+    // In the best-case scenario, this means we only ever have
+    // one single bit range covering all bits.
+    if (End == (Offset - Bits(1))) {
+      InitializedBits.back().End = Element.End;
+      return;
+    }
+
+    // Otherwise, we can simply append.
+    InitializedBits.push_back(Element);
+  } else {
+    // Insert sorted.
+    auto It = std::upper_bound(InitializedBits.begin(), InitializedBits.end(),
+                               Element);
+    InitializedBits.insert(It, Element);
+  }
+
+#ifndef NDEBUG
+  // Ensure ranges are sorted and non-overlapping.
+  assert(llvm::is_sorted(InitializedBits));
+  for (unsigned I = 1; I != InitializedBits.size(); ++I) {
+    [[maybe_unused]] auto Prev = InitializedBits[I - 1];
+    [[maybe_unused]] auto Cur = InitializedBits[I];
+    assert(Prev.End.N < Cur.Start.N);
+  }
+#endif
+}
+
+bool BitcastBuffer::rangeInitialized(Bits Offset, Bits Length) const {
+  if (Length.isZero())
+    return true;
+
+  BitRange Range(Offset, Offset + Length - Bits(1));
+  Bits Sum;
+  bool FoundStart = false;
+  for (BitRange BR : InitializedBits) {
+    if (FoundStart) {
+      if (BR.contains(Range.End)) {
+        Sum += (Range.End - BR.Start + Bits(1));
+        break;
+      }
+
+      // Else, BR is completely inside Range.
+      Sum += BR.size();
+    }
+    if (BR.contains(Range.Start)) {
+      Sum += (BR.End - Range.Start + Bits(1));
+      FoundStart = true;
+    }
+  }
+
+  // Note that Sum can be larger than Range, e.g. when Range is fully
+  // contained in one range.
+  return Sum >= Range.size();
+}
+
 #if 0
   template<typename T>
   static std::string hex(T t) {