Make cannotBePointer recurse through an Add when both of its
operands cannot be pointers. This lets canDisambiguatePointerOperand
identify the only viable base pointer of an outer Add even when the
offset side is itself an Add (or a deeper tree of Adds) whose leaves
are all clearly-non-pointer values, e.g.
%offset = add i64 (%a*%b), (%c*%d)
%result = add i64 %arg, %offset
Two unit tests cover the simple two-mul case and a deeper
four-mul binary-tree variant.
Introduce the ArithmeticToGEP canonicalisation pass. It detects
pointers (LLVM-typed pointer values, model pointers flagged by the
"revng.pointers" metadata, and pointer-tagged extract values) and
rewrites integer arithmetic computed on top of them as i8 GEPs,
followed by a ptrtoint when the original use needs an integer.
For each obvious pointer the pass also walks backwards through Add
chains and disambiguates the pointer operand of each Add when the
other operand cannot be a pointer, so the rewrite extends to integer
arithmetic that only later flows into a pointer use.
Alessandro Di Federico