https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91469
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Uroš Bizjak from comment #3) > STV converts the register in address: > > (insn 14 56 15 3 (parallel [ > (set (reg/v:SI 90 [ f ]) > (umax:SI (reg/v:SI 92 [ _23 ]) > (mem:SI (plus:SI (mult:SI (reg/v:SI 92 [ _23 ]) > (const_int 4 [0x4])) > (symbol_ref:SI ("d") [flags 0x2] <var_decl > 0x7f4bf0fcbcf0 d>)) [1 d S4 A32]))) > (clobber (reg:CC 17 flags)) > ]) 973 {*umaxsi3_1} > (expr_list:REG_UNUSED (reg:CC 17 flags) > (nil))) > > which is certainly wrong. Yes, it does that via general_scalar_chain::make_vector_copies when replacing all uses: for (ref = DF_REG_USE_CHAIN (regno); ref; ref = DF_REF_NEXT_REG (ref)) if (bitmap_bit_p (insns, DF_REF_INSN_UID (ref))) { rtx_insn *insn = DF_REF_INSN (ref); replace_with_subreg_in_insn (insn, reg, vreg); if (dump_file) fprintf (dump_file, " Replaced r%d with r%d in insn %d\n", regno, REGNO (vreg), INSN_UID (insn)); } I think we need to disqualify this instruction from being STVed because of the address-use of the reg. I've seen code to do that that probably needs extending to cover {U,S}{MIN,MAX}. Looking.