Function return values can be constructed directly in variables or passed
directly into return statements, without even an elidable copy in between.
This is how the C++17 mandatory copy elision AST behaves. The behavior we'll
have in such cases is the "old" behavior that we've had before we've
implemented destructor inlining and proper lifetime extension support.
Differential Revision: https://reviews.llvm.org/D44755
llvm-svn: 328253
This patch uses the newly added CFGCXXRecordTypedCall element at the call site
of the caller to construct the return value within the callee directly into the
caller's stack frame. This way it is also capable of populating the temporary
destructor and lifetime extension maps for the temporary, which allows
temporary destructors and lifetime extension to work correctly.
This patch does not affect temporaries that were returned from conservatively
evaluated functions.
Differential Revision: https://reviews.llvm.org/D44124
llvm-svn: 327345
Don't enable c++-temp-dtor-inlining by default yet, due to this reference
counting pointe problem.
Otherwise the new mode seems stable and allows us to incrementally fix C++
problems in much less hacky ways.
Differential Revision: https://reviews.llvm.org/D43804
llvm-svn: 326461
Automatic destructors are missing in the CFG in situations like
const int &x = C().x;
For now it's better to disable construction inlining, because inlining
constructors while doing nothing on destructors is very bad.
Differential Revision: https://reviews.llvm.org/D43689
llvm-svn: 326240
This patch uses the reference to MaterializeTemporaryExpr stored in the
construction context since r326014 in order to model that expression correctly.
When modeling MaterializeTemporaryExpr, instead of copying the raw memory
contents from the sub-expression's rvalue to a completely new temporary region,
that we conjure up for the lack of better options, we now have the better
option to recall the region into which the object was originally constructed
and declare that region to be the value of the expression, which is semantically
correct.
This only works when the construction context is available, which is worked on
independently.
The temporary region's liveness (in the sense of removeDeadBindings) is extended
until the MaterializeTemporaryExpr is resolved, in order to keep the store
bindings around, because it wouldn't be referenced from anywhere else in the
program state.
Differential Revision: https://reviews.llvm.org/D43497
llvm-svn: 326236
When constructing a temporary object region, which represents the result of
MaterializeTemporaryExpr, track down the sub-expression for which the temporary
is necessary with a trick similar to the approach used in CodeGen, namely
by using Expr::skipRValueSubobjectAdjustments().
Then, create the temporary object region with type of that sub-expression.
That type would propagate further in a path-sensitive manner.
During destruction of lifetime-extened temporaries, consult the type of
the temporary object region, rather than the type of the lifetime-extending
variable, in order to call the correct destructor (fixes pr17001) and,
at least, not to crash by trying to call a destructor of a plain type
(fixes pr19539).
rdar://problem/29131302
rdar://problem/29131576
Differential Revision: https://reviews.llvm.org/D26839
llvm-svn: 288263
Artem Dergachev