[Bug rtl-optimization/57281] [4.9 Regression] x86_64-linux loop fails to terminate at -O3 -m32

[ebotcazou at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57281

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ebotcazou at gcc dot gnu.org

--- Comment #5 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
> postreload leaves a REG_DEAD note on the
> 
> (insn 19 78 21 4 (parallel [
>             (set (mem:DI (reg/f:SI 3 bx [orig:68 D.1736 ] [68]) [4 *_18+0 S8
> A64])
>                 (sign_extend:DI (reg:SI 0 ax [orig:75 b ] [75])))
>             (clobber (reg:CC 17 flags))
>             (clobber (reg:SI 1 dx [80]))
>         ]) t.c:9 137 {extendsidi2_1}
>      (expr_list:REG_UNUSED (reg:SI 1 dx [80])
>         (expr_list:REG_DEAD (reg:SI 0 ax [orig:75 b ] [75])
>             (nil))))
> 
> which is bogus.

Leaving REG_DEAD/REG_UNUSED notes at the end of a pass is OK, it's up to the
next pass using them to make sure they are valid by invoking DF.