ce8928f2e4
This is the first of two patches to address PR46753. We basically allow mem2reg to promote allocas that are used in doppable instructions, for now that means `llvm.assume`. The uses of the alloca (or a bitcast or zero offset GEP from there) are replaced by `undef` in the droppable instructions. Reviewed By: Tyker Differential Revision: https://reviews.llvm.org/D83976