https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95021
--- Comment #6 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 12 May 2020, hjl.tools at gmail dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95021 > > --- Comment #4 from H.J. Lu <hjl.tools at gmail dot com> --- > The problem is since df_lr_bb_local_compute has > > /* If the def is to only part of the reg, it does > not kill the other defs that reach here. */ > if (!(DF_REF_FLAGS (def) & (DF_REF_PARTIAL | DF_REF_CONDITIONAL))) > { > unsigned int dregno = DF_REF_REGNO (def); > bitmap_set_bit (&bb_info->def, dregno); > bitmap_clear_bit (&bb_info->use, dregno); > } > > it doesn't consider > > (insn 40 39 25 3 (set (subreg:SI (reg/v:DI 85 [ target ]) 4) > (subreg:SI (reg:V2DI 90) 0)) "x.i":17:7 -1 > (nil)) > > as a def. Which it isn't since it sets the upper half of reg:DI 85 only.
