[Bug bootstrap/65232] [5 Regression] bootstrap failure (ICE in change_symbol_block, at varasm.c:1230) on arm-linux-gnueabihf, in libstdc++ stage1

["aldyh at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65232

--- Comment #5 from Aldy Hernandez <aldyh at gcc dot gnu.org> ---
For the following symbol:

(symbol_ref:SI ("_ZTCSt9strstream8_So") [flags 0x82] <var_decl 0x7fffeecd4090
_ZTCSt9strstream8_So>)

We fail this assertion:

change_symbol_block (rtx symbol, struct object_block *block)
{
  if (block != SYMBOL_REF_BLOCK (symbol))
    {
      gcc_assert (SYMBOL_REF_BLOCK_OFFSET (symbol) < 0);
      SYMBOL_REF_BLOCK (symbol) = block;
    }
}

The symbol's block offset has been previously set (to 0) in place_block_symbol
here:

      if (snode->alias)
    {
      rtx target = DECL_RTL (snode->ultimate_alias_target ()->decl);

      gcc_assert (MEM_P (target)
              && GET_CODE (XEXP (target, 0)) == SYMBOL_REF
              && SYMBOL_REF_HAS_BLOCK_INFO_P (XEXP (target, 0)));
      target = XEXP (target, 0);
      place_block_symbol (target);
      SYMBOL_REF_BLOCK_OFFSET (symbol) = SYMBOL_REF_BLOCK_OFFSET (target);
      return;
    }

Interestingly, without the patch in r221040, snode->alias is not set, so a
different path is used to set the offset.

Be that as it may, the killer is that change_symbol_block() is being called on
mainline through do_assemble_alias -> make_decl_rtl, because the symbol is
considered an alias which it wasn't in r221040.

Honza?