[LLVMdev] LLVM Value Tracking Analysis

[Xin Tong]

On Sat, Mar 3, 2012 at 5:26 PM, Duncan Sands <baldrick at free.fr> wrote:
> Hi Xin,
>
>> It seems to me that LLVM does not do too much on value range analysis.
>>   i.e. what are the value constraints on a variable at a given point in
>> the program. The closest thing i can find is the ValueTracking API,
>> which can do some simple analysis on the value of a variables. Am I
>> missing something/Is there a plan on the implementation of a more
>> powerful value range analysis ?
>
> as far as I know there have been two implementations of this kind of thing
> in the past, but they were each removed in turn.  IIRC, this was due to them
> significantly increasing compilation time without a sufficient improvement in
> the quality of code to justify the compile time cost.  Currently the closest
> thing is the correlated value propagation pass, but I doubt it will be useful
> for
> you.

The correlated value propagation pass is what is currently in the
ValueTrack.cpp file ? do you know when the two implementations are
removed ? and where i can get them ? and how difficult is it to bring
them up to the current src tree.

Thanks

Xin
>
> Ciao, Duncan.
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