https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86107
rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rsandifo at gcc dot gnu.org
--- Comment #4 from rsandifo at gcc dot gnu.org <rsandifo at gcc dot gnu.org>
---
(In reply to Uroš Bizjak from comment #2)
> For some reason, this part of x86_mitigate_rop:
>
> int n_uses;
> reg_class superclass = regrename_find_superclass (head, &n_uses,
> &unavailable);
> old_reg = head->regno;
> best_reg = find_rename_reg (head, superclass, &unavailable,
> old_reg, false);
> bool ok = regrename_do_replace (head, best_reg);
> gcc_assert (ok);
> if (dump_file)
> fprintf (dump_file, "Chain %d renamed as %s in %s\n", head->id,
> reg_names[best_reg], reg_class_names[superclass]);
>
> does not validate in regrename_do_replace.
>
> The compiler wants to rename:
>
> (insn 1264 1263 1265 5 (set (reg:DI 22 xmm1 [594])
> (reg:DI 3 bx [594])) "pr86107.c":15 85 {*movdi_internal}
> (expr_list:REG_DEAD (reg:DI 3 bx [594])
> (nil)))
>
> to:
>
> (set (reg:DI 22 xmm1 [594])
> (reg:DI 1 dx [594]))
>
> and fails validation of new instruction.
>
> The alternative 20 in *movdi_internal (*v->?r) is marked with
> preferred_for_speed attribute:
>
> (set (attr "preferred_for_speed")
> (cond [(eq_attr "alternative" "10,17,19")
> (symbol_ref "TARGET_INTER_UNIT_MOVES_FROM_VEC")
> (eq_attr "alternative" "11,18,20")
> (symbol_ref "TARGET_INTER_UNIT_MOVES_TO_VEC")
> ]
> (symbol_ref "true")))
>
> but should not fail verification even for !TARGET_INTER_UNIT_MOVES_TO_VEC
> targets. As a matter of fact, the compilation works with -mtune=intel.
This is by design when the insn belongs to a block that is being
optimised for speed rather than size. It isn't recog per se that
fails, but the validate_change stuff, which is designed for doing
optional optimisations rather than required changes.
