Merge

8178500: Replace usages of round_to and round_down with align_up and align_down
Reviewed-by: rehn, tschatzl

8176506: C2: loop unswitching and unsafe accesses cause crash
Reviewed-by: vlivanov, mcberg, kvn, simonis

8160748: Inconsistent types for ideal_reg
Summary: Made ideal_reg consistently uint.
Reviewed-by: kvn, iveresov

8173770: Image conversion improvements
Reviewed-by: kvn, vlivanov, dlong, rhalade, mschoene, iignatyev

8168503: JEP 297: Unified arm32/arm64 Port
Reviewed-by: kvn, enevill, ihse, dholmes, erikj, coleenp, cjplummer