https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61578
--- Comment #30 from Vladimir Makarov <vmakarov at gcc dot gnu.org> --- (In reply to Dominik Vogt from comment #29) > I think I understand what's going on: > > Consider the patched code in match_reloads(): > > + = (ins[1] < 0 && REG_P (in_rtx) > + && (int) REGNO (in_rtx) < lra_new_regno_start > + && find_regno_note (curr_insn, REG_DEAD, REGNO (in_rtx)) > + ? lra_create_new_reg (inmode, in_rtx, goal_class, "") > + : lra_create_new_reg_with_unique_value (outmode, out_rtx, > + goal_class, "")); > > (1) This code normally makes a unique copy of the register in in_rtx, but if > the register is marked as REG_DEAD in the curr_insn, it just makes a copy of > the register using lra_create_new_reg(), with the same .val and .offset in > the reg_info structure. > > (2) Further down in match_reloads, new insns are generated and stored in > *before and *after. However, the new "after" insn still references the old > register. In other words, in step (1) the code has made the assumption that > the old register is no longer used, then generates an insn that uses it > after it was marked as REG_DEAD. > > (3) Based on the bogus decision in (1), the condition in lra-lives.c decides > that the two registers are identical copies and can be mapped to the same > hard register: > > + && (((src_regno >= FIRST_PSEUDO_REGISTER > + && (! sparseset_bit_p (pseudos_live, src_regno) > + || (dst_regno >= FIRST_PSEUDO_REGISTER > + && lra_reg_val_equal_p (src_regno, > + lra_reg_info[dst_regno].val, > + > lra_reg_info[dst_regno].offset)) Sorry for breaking s390 port and thanks for the analysis. I'll try to fix it on this week.
