[llvm-commits] [llvm] r47252 - /llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp

[Bill Wendling]

What are the bugs?

-bw

On Feb 17, 2008, at 6:31 PM, Owen Anderson wrote:

> Author: resistor
> Date: Sun Feb 17 20:31:23 2008
> New Revision: 47252
>
> URL: http://llvm.org/viewvc/llvm-project?rev=47252&view=rev
> Log:
> Fix bugs that Chris noticed in my last patch.
>
> Modified:
>     llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
>
> Modified: llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/ 
> BasicAliasAnalysis.cpp?rev=47252&r1=47251&r2=47252&view=diff
>
> ====================================================================== 
> ========
> --- llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp (original)
> +++ llvm/trunk/lib/Analysis/BasicAliasAnalysis.cpp Sun Feb 17  
> 20:31:23 2008
> @@ -250,22 +250,30 @@
>      const Value *Object = getUnderlyingObject(P);
>      // Allocations and byval arguments are "new" objects.
>      if (Object &&
> -        (isa<AllocationInst>(Object) ||
> -         (isa<Argument>(Object) &&
> -                                 (cast<Argument>(Object)- 
> >hasByValAttr() ||
> -                                  cast<Argument>(Object)- 
> >hasNoAliasAttr())))) {
> +        (isa<AllocationInst>(Object) || isa<Argument>(Object))) {
>        // Okay, the pointer is to a stack allocated (or effectively  
> so, for
>        // for noalias parameters) object.  If we can prove that
>        // the pointer never "escapes", then we know the call cannot  
> clobber it,
>        // because it simply can't get its address.
> -      if (!AddressMightEscape(Object))
> -        return NoModRef;
> +      if (isa<AllocationInst>(Object) ||
> +          cast<Argument>(Object)->hasByValAttr() ||
> +          cast<Argument>(Object)->hasNoAliasAttr())
> +        if (!AddressMightEscape(Object)) {
> +          for (CallSite::arg_iterator CI = CS.arg_begin(), CE =  
> CS.arg_end();
> +              CI != CE; ++CI)
> +            if (getUnderlyingObject(CI->get()) == P)
> +              return AliasAnalysis::getModRefInfo(CS, P, Size);
> +
> +          return NoModRef;
> +        }
>
>        // If this is a tail call and P points to a stack location,  
> we know that
>        // the tail call cannot access or modify the local stack.
> -      if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
> -        if (CI->isTailCall() && !isa<MallocInst>(Object))
> -          return NoModRef;
> +      if (isa<AllocationInst>(Object) ||
> +          cast<Argument>(Object)->hasByValAttr())
> +        if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction()))
> +          if (CI->isTailCall() && !isa<MallocInst>(Object))
> +            return NoModRef;
>      }
>    }
>
>
>
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