[cfe-dev] Lazy bindings

[Zhongxing Xu]

Sorry, this email is unfinished. I accidentally clicked 'send' button.

On Sun, Dec 14, 2008 at 6:13 PM, Zhongxing Xu <xuzhongxing at gmail.com> wrote:

> In current static analysis implementation, big array initializations takes
> a very long time, because we create regions for every elements no matter if
> it is used at all. Lazy binding is desirable for such cases. That is, when
> the decl stmt is visited, only a VarRegion is created for the array.
> ElementRegions will be created when it is first time read or written.
>
> We have to distinguish the following cases if a region is not in
> regionbindings:
> * it is assigned unknown value (a.k.a. killed, we remove its binding in
> such case)
> * it is not initialized and it is local, we should return undefined value
> for it
> * it is not initialized and it is global, we should return symbolic value
> for it
>
> A tentative logic is proposed as follows:
>
> Retrieve(Loc L)
>   if L is in bindings
>     return bind(L)
>   else
>     if L is not field or element
>       return UnknownVal               // we initialize scalar variable, so
> it must be killed.
>     else
>       if L is in killset
>         return UnknownVal
>       else
>         if L is on the stack or heap
>           return UndefinedVal
>         else
>
>
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