[CodeMoverUtils] Enhance isSafeToMoveBefore() when control flow equivalence is satisfied
With improved analysis in determining CFG equivalence that does
not require strict dominance and post-dominance conditions, we
now relax isSafeToMoveBefore() such that an instruction I can
be moved before InsertPoint even if they do not strictly dominate
each other, as long as they follow the same control flow path.
For example, we can move Instruction 0 before Instruction 1,
and vice versa.
if (cond1) // Instruction 0: %add = add i32 1, 2 if (cond1) // Instruction 1: %add2 = add i32 2, 1
Reviewed By: Whitney
Differential Revision: https://reviews.llvm.org/D110456