Pull in r281586 from upstream llvm trunk (by Wei Mi):
Add some shortcuts in LazyValueInfo to reduce compile time of Correlated Value Propagation. The patch is to partially fix PR10584. Correlated Value Propagation queries LVI to check non-null for pointer params of each callsite. If we know the def of param is an alloca instruction, we know it is non-null and can return early from LVI. Similarly, CVP queries LVI to check whether pointer for each mem access is constant. If the def of the pointer is an alloca instruction, we know it is not a constant pointer. These shortcuts can reduce the cost of CVP significantly. Differential Revision: https://reviews.llvm.org/D18066
This significantly reduces memory usage and compilation time when
compiling a particular C++ source file of the graphics/colmap port.