[clang] [clang][bytecode] Add opaque pointers to support type-only pointers (PR #213017)

[Oliver Hunt via cfe-commits]

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@@ -1221,3 +1254,172 @@ IntPointer IntPointer::baseCast(const interp::Context &Ctx,
                                               std::nullopt, RD, false);
   return {T.getTypePtr(), Value + BaseLayoutOffset.getQuantity()};
 }
+
+std::optional<size_t>
+OpaquePointer::computeLayoutOffset(const ASTContext &ASTCtx) const {
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ojhunt wrote:

I just had a dream of a faster access path in the interpreter, ah well :(

I wish there was some direct way to verify compatible layout, oh well.

Can bitfields effect this? you can't in principle get the offset of a bit field but I don't know if it's possible to construct a code path that could reach here in such a position. In principle I would expect sema to have already rejected that before evaluation happens.

https://github.com/llvm/llvm-project/pull/213017