This is part of an effort to remove ConstantExpr based
representations of `vscale` so that its LangRef definiton can
be relaxed to accommodate a less strict definition of constant.
Differential Revision: https://reviews.llvm.org/D144891
This patch extends SCEVParameterRewriter to support rewriting unknown
epxressions to arbitrary SCEV expressions. It will be used by further
patches.
Reviewed By: reames
Differential Revision: https://reviews.llvm.org/D67176
This makes it usable from outside of SCEV,
while previously it was internal to the ScalarEvolution.cpp
In particular, i want to use it in an WIP alloca promotion helper pass,
to analyze if some SCEV is a multiple of some other SCEV.
