[Bug target/55212] [SH] Switch to LRA

["kkojima at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55212

--- Comment #70 from Kazumoto Kojima <kkojima at gcc dot gnu.org> ---
I'd like to apply the revised patches below to sh-lra branch for
looking at the problems easily.  Oleg, is it OK for you?

c#55: Fixup the result of decompose_mem_address when INDEX_REG_CLASS
  is a single register class.
c#59: Introduce target hook which disables the substitution of pseudos
  with equivalent memory values.
c#61: Define SH specific HARD_REGNO_CALLER_SAVE_MODE target macro.
c#66: Make *addsi3_compact insn_and_split and add an alternative
  which will split to (set a c) and (set (plus a b)) after reload.

I omit c#29 patch which touches lra-constraints.c and may impact on
other targets.  That patch would make it hard to compare with other
targets.  c#55 and c#59 also touch lra-constraints.c but those changes
unlikely impact on other targets.  Fortunately the test case c#28
doesn't ICE anymore without c#29.