[LLVMdev] LLVM Value Tracking Analysis

[Duncan Sands]

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.

Ciao, Duncan.