Changes

[Attributor] Deduce dereferenceable based on accessed bytes map
Summary: This patch introduces the deduction based on load/store
instructions whose pointer operand is a non-inbounds GEP instruction. 
For example if we have,
``` void f(int *u){
u[0] = 0;
u[1] = 1;
u[2] = 2;
}
``` then u must be dereferenceable(12).
This patch is inspired by D64258
Reviewers: jdoerfert, spatel, hfinkel, RKSimon, sstefan1, xbolva00,
dtemirbulatov
Reviewed By: jdoerfert
Subscribers: jfb, lebedev.ri, xbolva00, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D70714