Index: clang/lib/AST/Interp/ByteCodeEmitter.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeEmitter.cpp
+++ clang/lib/AST/Interp/ByteCodeEmitter.cpp
@@ -206,6 +206,25 @@
   }
 }
 
+template <>
+void emit(Program &P, std::vector<std::byte> &Code, const Floating &Val,
+          bool &Success) {
+  size_t Size = Val.bytesToSerialize();
+
+  if (Code.size() + Size > std::numeric_limits<unsigned>::max()) {
+    Success = false;
+    return;
+  }
+
+  // Access must be aligned!
+  size_t ValPos = align(Code.size());
+  Size = align(Size);
+  assert(aligned(ValPos + Size));
+  Code.resize(ValPos + Size);
+
+  Val.serialize(Code.data() + ValPos);
+}
+
 template <typename... Tys>
 bool ByteCodeEmitter::emitOp(Opcode Op, const Tys &... Args, const SourceInfo &SI) {
   bool Success = true;
Index: clang/lib/AST/Interp/Floating.h
===================================================================
--- clang/lib/AST/Interp/Floating.h
+++ clang/lib/AST/Interp/Floating.h
@@ -124,6 +124,26 @@
     llvm::StoreIntToMemory(API, (uint8_t *)Buff, bitWidth() / 8);
   }
 
+  size_t bytesToSerialize() const {
+    return sizeof(llvm::fltSemantics *) +
+           (APFloat::semanticsSizeInBits(F.getSemantics()) / 8);
+  }
+
+  void serialize(std::byte *Buff) const {
+    // Semantics followed by an APInt.
+    *reinterpret_cast<const llvm::fltSemantics **>(Buff) = &F.getSemantics();
+
+    llvm::APInt API = F.bitcastToAPInt();
+    llvm::StoreIntToMemory(API, (uint8_t *)(Buff + sizeof(void *)),
+                           bitWidth() / 8);
+  }
+
+  static Floating deserialize(const std::byte *Buff) {
+    const llvm::fltSemantics *Sem;
+    std::memcpy((void *)&Sem, Buff, sizeof(void *));
+    return bitcastFromMemory(Buff + sizeof(void *), *Sem);
+  }
+
   // -------
 
   static APFloat::opStatus add(const Floating &A, const Floating &B,
Index: clang/lib/AST/Interp/Interp.h
===================================================================
--- clang/lib/AST/Interp/Interp.h
+++ clang/lib/AST/Interp/Interp.h
@@ -1895,6 +1895,12 @@
   }
 }
 
+template <> inline Floating ReadArg<Floating>(InterpState &S, CodePtr &OpPC) {
+  Floating F = Floating::deserialize(OpPC.Ptr);
+  OpPC += align(F.bytesToSerialize());
+  return F;
+}
+
 } // namespace interp
 } // namespace clang
 
Index: clang/lib/AST/Interp/Source.h
===================================================================
--- clang/lib/AST/Interp/Source.h
+++ clang/lib/AST/Interp/Source.h
@@ -60,6 +60,7 @@
   /// Constructor used by Function to generate pointers.
   CodePtr(const std::byte *Ptr) : Ptr(Ptr) {}
   /// Pointer into the code owned by a function.
+public:
   const std::byte *Ptr;
 };
 
Index: clang/test/AST/Interp/floats.cpp
===================================================================
--- clang/test/AST/Interp/floats.cpp
+++ clang/test/AST/Interp/floats.cpp
@@ -140,4 +140,11 @@
 
 namespace LongDouble {
   constexpr long double ld = 3.1425926539;
+
+  constexpr long double f() {
+    const long double L = __LDBL_MAX__;
+
+    return L;
+  };
+  static_assert(f() == __LDBL_MAX__);
 }