tbaeder marked 3 inline comments as done.
tbaeder added inline comments.
================
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>();
----------------
erichkeane wrote:
> 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?
Nothing in this patch, if you e.g. take this code:
```
constexpr int func() { return 5; }
```
and run it with `clang++ -std=c++20 -fexperimental-new-constant-interpreter`,
the constant interpreter runs into an assertion while evaluating the bytecode
for that function. Switching `ReadArg` to take the codeptr by reference fixes
that. So I could probably postpone the change to a later patch but it's one of
the first problems I ran into while working on the codebase.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D131942/new/
https://reviews.llvm.org/D131942
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
