Re: Fix PR ipa/60315 (inliner explosion)

[Jan Hubicka <hubicka at ucw dot cz>]

> > > Bootstrapped/regtested x86_64-linux, comitted.
> > 
> > Not with Ada apparently, resulting in 
> > 
> >                 === acats tests ===
> > FAIL:   c34007d
> > FAIL:   c34007g
> > FAIL:   c34007s
> > FAIL:   c37213j
> > FAIL:   c37213k
> > FAIL:   c37213l
> > FAIL:   ce2201g
> > FAIL:   cxa5a03
> > FAIL:   cxa5a04
> > FAIL:   cxa5a06
> > FAIL:   cxg2013
> > FAIL:   cxg2015
> > 
> The problem is that by redirection to noreturn, we end up freeing SSA name of the
> LHS but later we still process statements that refer it until they are removed as
> unreachable.
> The following patch fixes it. I tested it on x86_64-linux, but changed my mind.
> I think fixup_noreturn_call should do it instead, I will send updated patch after
> testing.
> 
> Honza

Actually after some additional invetstigation I decided to commit this patch.
fixup_noreturn_call already cares about the return value but differently than the
new Jakub's code.  We ought to unify it, but only for next stage1. 

Honza
> 
> Index: cgraph.c
> ===================================================================
> --- cgraph.c	(revision 208875)
> +++ cgraph.c	(working copy)
> @@ -1329,6 +1331,7 @@ gimple
>  cgraph_redirect_edge_call_stmt_to_callee (struct cgraph_edge *e)
>  {
>    tree decl = gimple_call_fndecl (e->call_stmt);
> +  tree lhs = gimple_call_lhs (e->call_stmt);
>    gimple new_stmt;
>    gimple_stmt_iterator gsi;
>  #ifdef ENABLE_CHECKING
> @@ -1471,6 +1474,22 @@ cgraph_redirect_edge_call_stmt_to_callee
>        update_stmt_fn (DECL_STRUCT_FUNCTION (e->caller->decl), new_stmt);
>      }
>  
> +  /* If the call becomes noreturn, remove the lhs.  */
> +  if (lhs && (gimple_call_flags (new_stmt) & ECF_NORETURN))
> +    {
> +      if (TREE_CODE (lhs) == SSA_NAME)
> +	{
> +          gsi = gsi_for_stmt (new_stmt);
> +
> +	  tree var = create_tmp_var (TREE_TYPE (lhs), NULL);
> +	  tree def = get_or_create_ssa_default_def
> +		      (DECL_STRUCT_FUNCTION (e->caller->decl), var);
> +	  gimple set_stmt = gimple_build_assign (lhs, def);
> +	  gsi_insert_before (&gsi, set_stmt, GSI_SAME_STMT);
> +	}
> +      gimple_call_set_lhs (new_stmt, NULL_TREE);
> +    }
> +
>    cgraph_set_call_stmt_including_clones (e->caller, e->call_stmt, new_stmt, false);
>  
>    if (cgraph_dump_file)