Tyker marked an inline comment as done.
Tyker added inline comments.
================
Comment at: clang/lib/Serialization/ASTReader.cpp:9635
+ if (IsExpr) {
+ Base = APValue::LValueBase(ReadExpr(F), CallIndex, Version);
+ ElemTy = Base.get<const Expr *>()->getType();
----------------
Tyker wrote:
> rsmith wrote:
> > This is problematic.
> >
> > `ReadExpr` will read a new copy of the expression, creating a distinct
> > object. But in the case where we reach this when deserializing (for a
> > `MaterializeTemporaryExpr`), we need to refer to the existing
> > `MaterializeTemporaryExpr` in the initializer of its lifetime-extending
> > declaration. We will also need to serialize the `ASTContext`'s
> > `MaterializedTemporaryValues` collection so that the temporaries
> > lifetime-extended in a constant initializer get properly handled.
> >
> > That all sounds very messy, so I think we should reconsider the model that
> > we use for lifetime-extended materialized temporaries. As a half-baked idea:
> >
> > * When we lifetime-extend a temporary, create a
> > `MaterializedTemporaryDecl` to hold its value, and modify
> > `MaterializeTemporaryExpr` to refer to the `MaterializedTemporaryDecl`
> > rather than to just hold the subexpression for the temporary.
> > * Change the `LValueBase` representation to denote the declaration rather
> > than the expression.
> > * Store the constant evaluated value for a materialized temporary on the
> > `MaterializedTemporaryDecl` rather than on a side-table in the `ASTContext`.
> >
> > With that done, we should verify that all remaining `Expr*`s used as
> > `LValueBase`s are either only transiently used during evaluation or don't
> > have these kinds of identity problems.
> Would it be possible to adapt serialization/deserialization so that they make
> sure that `MaterializeTemporaryExpr` are unique.
> by:
>
> - When serializing `MaterializeTemporaryExpr` serialize a key obtained from
> the pointer to the expression as it is unique.
> - When deserializing `MaterializeTemporaryExpr` deserializing the key, and
> than have a cache for previously deserialized expression that need to be
> unique.
>
> This would make easier adding new `Expr` that require uniqueness and seem
> less complicated.
> What do you think ?
i added a review that does the refactoring https://reviews.llvm.org/D69360.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D63640/new/
https://reviews.llvm.org/D63640
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