[cfe-dev] Adding lifetime begin/end to unnamed temporaries

[Arnaud A. de Grandmaison]

I am trying to implement the lifetime marker insertion for unnamed
temporaries in order to reduce stack consumption.

 

Inserting the lifetime.begin marker is the easy part; on the other hand,
inserting the lifetime.end gets a bit more complicated, as it involves
scoping , exception handling and lifetime extension.

 

Ideally, the lifetime.end marker should be inserted when the scope is
exited, after the cleanups have been run. The problem is that in some cases,
an object with a  trivial destructor for example, there is . no cleanup.
The existence of cleanups appears in the AST with the ExpWithCleanups, which
wraps the underlying MaterializeTemporaryExpr.

 

This is used in CodeGenFunction::EmitLValue to start a new RunCleanupsScope
when visiting an ExpWithCleanups. My problem is how can I add a
RunCleanupScope for MaterializeTemporaryExpr that are not part of an
ExpWithCleanups. I can not always add a new scope, because it would mess-up
the cleanup ordering --- when there are cleanups, the lifetime.end marker
should be emitted after the destructor.

 

Is there anything obvious I am missing ?

 

Any hints would be welcome. 

 

Cheers,

--

Arnaud A. de Grandmaison

 
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