[PATCH] D131942: [clang][Interp] Implement bool and nullptr literal expressions

[Erich Keane via Phabricator via cfe-commits]

erichkeane added inline comments.


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Comment at: clang/lib/AST/Interp/Disasm.cpp:26
 inline std::enable_if_t<!std::is_pointer<T>::value, T> ReadArg(Program &P,
-                                                               CodePtr OpPC) {
+                                                               CodePtr &OpPC) {
   return OpPC.read<T>();
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tbaeder wrote:
> erichkeane wrote:
> > Are you sure this isn't intentional that this is passed by value?  With a name like CodePtr, it certainly SOUNDS like it means to be passed by value.
> `CodePtr::read()` advances the pointer that `CodePtr` wraps , so copying just to call `read()` on it makes little sense. E.g. in https://github.com/llvm/llvm-project/blob/main/clang/lib/AST/Interp/Interp.cpp#L401-L412, `ReadArg` must advance the `CodePtr`, otherwise two consecutive `ReadArg` calls will read the same thing.
my point is; With a struct this small, the 'copy' is cheaper than a pass-by-ref.  However, if the pass-by-value causes the ReadArg to read the same thing, why was this not a problem before?  More importantly, what in this patch makes this change necessary?  


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Comment at: clang/test/AST/Interp/literals.cpp:14
+constexpr bool getTrue() { return true; }
+constexpr bool getFalse() { return false; }
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tbaeder wrote:
> erichkeane wrote:
> > can you also do a 'getNullptr'?  Also, a static-assert for all 3 of the functions as well.
> I can do a `getNull()`, but I can't call any of the functions yet, function calls aren't implemented yet.
ah, thanks for that clarificaiton. When doing the function-calls, please see if you can add that here as well.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D131942/new/

https://reviews.llvm.org/D131942