[clang] [clang][Interp] Support arbitrary precision constants (PR #79747)

[Aaron Ballman via cfe-commits]

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@@ -263,6 +263,30 @@ template <bool Signed> class IntegralAP final {
       *R = IntegralAP(A.V.lshr(ShiftAmount));
   }
 
+  // === Serialization support ===
+  size_t bytesToSerialize() const {
+    // 1 byte for the BitWidth followed by N bytes for the actual APInt.
+    // FIXME: Is 1 byte enough? APInt::getBitWidth() returns an unsigned.
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AaronBallman wrote:

I don't think one byte is sufficient if this will end up underpinning `_BitInt`.

https://github.com/llvm/llvm-project/pull/79747