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

[kkojima at gcc dot gnu.org]

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

--- Comment #89 from Kazumoto Kojima <kkojima at gcc dot gnu.org> ---
Created attachment 34159
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=34159&action=edit
a reduced c++ test case (-O2 -std=gnu++11)

Here is related lines of lra-constraints.c:

4906      save = emit_spill_move (true, new_reg, original_reg);
4907      if (NEXT_INSN (save) != NULL_RTX)
4908        {
4909          lra_assert (! call_save_p);

where

(gdb) p call_save_p
$2 = true
(gdb) call debug_rtx(new_reg)    
(reg:DC 270)
(gdb) call debug_rtx(original_reg)
(reg:DC 220 [+8 ])

and emit_spill_move emits 3 instructions

(insn 106 0 107 (clobber (reg:DC 270)) -1
     (nil))

(insn 107 106 108 (parallel [
            (set (subreg:DF (reg:DC 270) 0)
                (subreg:DF (reg:DC 220 [+8 ]) 0))
            (use (reg:SI 154 fpscr0))
            (clobber (scratch:SI))
        ]) -1
     (nil))

(insn 108 107 0 (parallel [
            (set (subreg:DF (reg:DC 270) 8)
                (subreg:DF (reg:DC 220 [+8 ]) 8))
            (use (reg:SI 154 fpscr0))
            (clobber (scratch:SI))
        ]) -1
     (nil))

with emit_move_complex function in expr.c.