https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110206
--- Comment #15 from Uroš Bizjak <ubizjak at gmail dot com> --- Created attachment 55537 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55537&action=edit Proposed patch. v2 patch in testing. This version prevents emission of invalid REG_EQUAL note in cprop.cc/try_replace_reg when original, non-simplified RTX contains SUBREG. The patch is in effect an one-liner: @@ -795,7 +796,8 @@ try_replace_reg (rtx from, rtx to, rtx_insn *insn) /* If we've failed perform the replacement, have a single SET to a REG destination and don't yet have a note, add a REG_EQUAL note to not lose information. */ - if (!success && note == 0 && set != 0 && REG_P (SET_DEST (set))) + if (!success && note == 0 && set != 0 && REG_P (SET_DEST (set)) + && !contains_paradoxical_subreg_p (SET_SRC (set))) note = set_unique_reg_note (insn, REG_EQUAL, copy_rtx (src)); } but we have to move contains_paradoxical_subreg_p to rtlanal.cc.
