ymandel added inline comments.
================
Comment at:
clang-tools-extra/clang-tidy/performance/UnnecessaryCopyInitialization.cpp:98-101
auto Matches =
match(findAll(declStmt(has(varDecl(equalsNode(&InitializingVar))))
.bind("declStmt")),
+ Body, Context);
----------------
flx wrote:
> ymandel wrote:
> > Consider inspecting the `DeclContext`s instead, which should be much more
> > efficient than searching the entire block. Pass the `FunctionDecl` as an
> > argument instead of `Body`, since it is a `DeclContext`. e.g. `const
> > DeclContext &Fun`
> >
> > Then, either
> > 1. Call `Fun.containsDecl(InitializingVar)`, or
> > 2. Search through the contexts yourself; something like:
> > ```
> > DeclContext* DC = InitializingVar->getDeclContext();
> > while (DC != nullptr && DC != &Fun)
> > DC = DC->getLexicalParent();
> > if (DC == nullptr)
> > // The reference or pointer is not initialized anywhere witin the
> > function. We
> > // assume its pointee is not modified then.
> > return true;
> > ```
> Are #1 and #2 equivalent? From the implementation and comment I cannot tell
> whether #1 would cover cases where the variable is not declared directly in
> the function, but in child block:
>
> ```
> void Fun() {
> {
> var i;
> {
> i.usedHere();
> }
> }
> }
> ```
>
> I'm also reading this as an optimization to more quickly determine whether we
> can stop here. We still need to find the matches for the next steps, but I
> think I could then limit matching to the DeclContext I found here. Is this
> correct? For this I would actually need the DeclContext result from #2.
A. I think you're right that #2 is more suited to what you need. I wasn't sure,
so included both. Agreed that the comments are ambiguous.
B. yes, this is just an optimization. it may be premature for that matter; just
that match can be expensive and this seemed a more direct expression of the
algorithm.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D103021/new/
https://reviews.llvm.org/D103021
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
