This is the last remaining use of ConstantProp, migrate it to InstSimplify in the goal of removing ConstantProp.
Add -hexagon-instsimplify option to enable skipping of instsimplify in
tests that can't handle the extra optimization.
Differential Revision: https://reviews.llvm.org/D85047
This will remove suboptimal branching from the generated ll/sc loops.
The extra simplification pass affects a lot of testcases, which have
been modified to accommodate this change: either by modifying the
test to become immune to the CFG simplification, or (less preferablt)
by adding option -hexagon-initial-cfg-clenaup=0.
llvm-svn: 338774
Arthur Eubanks