Hi all,
in this case:
…
int* p = …
int* q = p;
…
How can I know that data-flow from p to q,
i.e., which LLVM pass of header files could I use?
Thank you all.
hi,
Hi all,
in this case:
...
int* p = ...
int* q = p;
This will be eliminated by the "mem2reg" pass.
...
How can I know that data-flow from p to q,
i.e., which LLVM pass of header files could I use?
If you want something about "data-flow", there is a header named
"DataFlow.h": http://llvm.org/doxygen/DataFlow_8h.html
best regards
ether
Hi all,
in this case:
…
int* p = …
int* q = p;
…How can I know that data-flow from p to q,
i.e., which LLVM pass of header files could I use?
It’s not completely clear what sort of analysis you want. If you want reaching definitions for just SSA virtual register values, then you only need to follow the explicit def-use chains in the SSA graph (see the use_iterator of class llvm::Value, IIRC).
If you need to know if p and q point to the same memory object (assuming that the memory object is not eliminated by the mem2reg pass), then you need to either use the AliasAnalysis analysis group or a points-to analysis like DSA.
If you need reaching definitions analysis for all values (including those that travel into/out of memory objects), then you need a points-to analysis combined with a reaching definitions analysis. I do not think anyone has implemented such an analysis for LLVM yet, although a (relatively) simple one could probably be written on top of DSA.
– John T.