Enable REE pass by default for AArch64 at O2 or higher

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198424 138bc75d-0d04-0410-961f-82ee72b054a4
[AArch64] Support LDR/STR from/to S and D registers

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198425 138bc75d-0d04-0410-961f-82ee72b054a4
       * gcc.c-torture/execute/pr55875.c

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@198426 138bc75d-0d04-0410-961f-82ee72b054a4