[Bug tree-optimization/56195] [4.8 Regression] Error: incorrect register `%rdi' used with `l' suffix (at -O2)

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56195

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-05 16:40:17 UTC ---
I'd say the bug is in get_reload_reg.
Changing pseudo 118 in operand 0 of insn 90 on equiv 0
Changing address in insn 90 r59:DI -- no change
Changing pseudo 59 in address of insn 90 on equiv 0
      Creating newreg=137, assigning class GENERAL_REGS to address r137
         Choosing alt 1 in insn 90:  (0) r  (1) rm
         Reuse r137 for reload 0, change to class INDEX_REGS for r137
   90: flags:CCGC=cmp(r137:DI,[r137:DI])
    Inserting insn reload before:
  256: r137:DI=0


3065          if (get_reload_reg (type, mode, old, goal_alt[i], "", &new_reg)
3066              && type != OP_OUT)

calls it with
type=OP_IN, mode=SImode, original=const0_rtx, rclass=GENERAL_REGS
but returns new_reg = (reg:DI 137).
That is because:
      if (rtx_equal_p (curr_insn_input_reloads[i].input, original)
          && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class))
doesn't check any mode if original (and curr_insn_input_reloads[i].input) are
VOIDmode as in this case.  So, either this can be fixed by doing:
       if (rtx_equal_p (curr_insn_input_reloads[i].input, original)
-      && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class))
+      && in_class_p (curr_insn_input_reloads[i].reg, rclass, &new_class)
+      && GET_MODE (curr_insn_input_reloads[i].reg) == mode)
, or we could try better, if the GET_MODE (curr_insn_input_reloads[i].reg)
is wider than mode, see if we can create a lowpart subreg thereof and return
that, and only give up (i.e. continue looping) if creation of the lowpart
subreg for some reason failed.

Vlad, what do you think?