[cfe-dev] Analyzing the AST for variable usage

[Vedant Kumar via cfe-dev]

Hi Nat,

I'm not sure something like this exists. If I were to try it, I'd start by writing a llvm::FunctionPass which uses the alias analyzer. There's some documentation on this here:

    http://llvm.org/docs/AliasAnalysis.html#using-alias-analysis-results

In your example, it seems like you'd like to check if any loads/stores in your function may alias with 'p'.

vedant

> On Sep 9, 2015, at 1:05 PM, Nat! via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> 
> Hi
> 
> before I am writing this myself, I just wonder, if this functionality is maybe available somewhere (analyzer ?).
> 
> I want to know for every AST node, in a function, if any successor nodes access a memory area, that has been passed in by a (single) argument.
> 
> Or less abstract
> 
> ---
> struct foo
> {
>   char   space[ 20];
> };
> 
> 
> extern int  whatever( char *);
> 
> 
> void  f( struct foo *p)
> {
>   char   *q;
>   char   tmp[ 10];
> 
>   q = &p->space[ 10];
> loop:
>   whatever( q);
>   if( whatever( tmp))
>      goto loop;
> 
>   // here comes the first node, that does not touch p space
> 
>   whatever( tmp);
> }
> ---
> 
> 
> Ciao
>   Nat!
> 
> P.S. For my purposes it's really better do this on clang level than on llvm level.
> 
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