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Re: PR other/51165: add new adress_escapes predicate


On Mon, Jan 16, 2012 at 3:29 PM, Aldy Hernandez <aldyh@redhat.com> wrote:
> As discussed in the PR, the problem here is that we are using
> ptr_deref_may_alias_global_p() to determine if a dereferenced address
> escapes, whereas we were previously using the now non existent
> is_call_clobbered. ?The function ptr_deref_may_alias_global_p() does not
> understand SSA_NAMEs, whereas is_call_clobbered did.
>
> Richi suggested using may_be_aliased() for DECLs.
>
> The patch below abstracts an address_escapes_p() predicate for more generic
> use into the aliasing code. ?Using this instead of
> ptr_deref_may_alias_global_p() fixes all 4 TM memory optimization
> regressions. ?TM logging is now back in business.
>
> Is this what you had in mind? ?OK for trunk?

Not really - you handle both ptr and *ptr in the same predicate and
call both "address escaped".  What I suggested was sth like

/* Return true, if the memory access X may alias with a global variable.  */

bool
access_may_refer_to_global_p (tree x)
{
  x = get_base_address (x);
  if (DECL_P (x))
    return is_global_var (x);
  else if (TREE_CODE (x) == MEM_REF
             || TREE_CODE (x) == TARGET_MEM_REF)
    return ptr_deref_may_alias_global_p (TREE_OPERAND (x, 0));
  return true;
}

Richard.


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