[Bug rtl-optimization/124041] [16 regression] ICE in lra_eliminate_regs_1, at lra-eliminations.cc:665 since r16-1565

[rdapp at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124041

--- Comment #14 from Robin Dapp <rdapp at gcc dot gnu.org> ---
Just for the record, this is what I tried (and what causes miscompiles):

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 8c8c9d69a96..a7ef1402267 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -4369,11 +4369,19 @@ curr_insn_transform (bool check_only_p)
          continue;

        old = op = *curr_id->operand_loc[i];
+       machine_mode outer_mode = GET_MODE (old);
+       bool subreg_p = false;
        if (GET_CODE (old) == SUBREG)
-         old = SUBREG_REG (old);
+         {
+           old = SUBREG_REG (old);
+           subreg_p = true;
+         }
        subst = get_equiv_with_elimination (old, curr_insn);
        original_subreg_reg_mode[i] = VOIDmode;
        equiv_substition_p[i] = false;
+       if (subreg_p && HARD_REGISTER_P (subst)
+           && !targetm.hard_regno_mode_ok (REGNO (subst), outer_mode))
+         continue;
        if (subst != old)
          {
            equiv_substition_p[i] = true;