Hi, On Fri, Mar 02, 2012 at 06:54:13PM +1300, Maxim Kuvyrkov wrote: > On 2/03/2012, at 1:53 AM, Martin Jambor wrote: > > > Hi, > > > > the following patch backports 4.5 behavior to 4.4 IPA-CP > > initialization when it decides which nodes need to be duplicated (we > > often say cloned, but cloning is an overloaded term in gcc) in order > > to modify them. In 4.5, this is decided by a new predicate called > > cgraph_only_called_directly_p which checks both node->needed and > > node->local.externally_visible, whereas 4.4 looks only at the needed > > flag. > > > > As described in the PR, this wrecks havoc for ipcp_update_callgraph > > which is the stage of the old IPA-CP when it undoes its decisions > > which turned out not to be safe. > > > > Bootstrapped and tested on x86_64-linux, OK for the branch? > > > > > ... > > Index: gcc/ipa-cp.c > > =================================================================== > > --- gcc/ipa-cp.c (revision 184662) > > +++ gcc/ipa-cp.c (working copy) > > @@ -508,7 +508,7 @@ ipcp_initialize_node_lattices (struct cg > > > > if (ipa_is_called_with_var_arguments (info)) > > type = IPA_BOTTOM; > > - else if (!node->needed) > > + else if (!node->needed && !node->local.externally_visible) > > type = IPA_TOP; > > /* When cloning is allowed, we can assume that externally visible > > functions > > are not called. We will compensate this by cloning later. */ > > Because this is for a branch, I would be more conservative and avoid any new > instances of IPA_TOP -- those that can be obtained from subsequent else-if > clauses. I.e., > > else if (!node->needed) > type = !node->local.externally_visible ? IPA_TOP : IPA_BOTTOM; >
That would be too conservative because it would mean we would never duplicate a node and thus never propagate constants into externally visible functions, even not at -O3 and we do want to keep doing that. I have committed my patch after it has been approved on IRC by Richi and Jakub. Thanks, Martin
