RFR (M): 7173340: C2: code cleanup: use PhaseIterGVN::replace_edge(Node*, int, Node*) where applicable

[Vladimir Kozlov]

Vladimir,

Next code is wrong, use_clone edge update should be after use node update since 
it is used there:

!       _igvn.replace_edge_of(use_clone, LoopNode::LoopBackControl, C->top());
!       _igvn.rehash_node_delayed(use); // Multiple edge updates
         use->set_req(LoopNode::EntryControl, 
use_clone->in(LoopNode::LoopBackControl));
         use->set_req(LoopNode::LoopBackControl, C->top());

Could you also define rehash_node_delayed() first and use it in 
replace_edge_of() and delete_edge_of() methods since it is not required to have 
set_req() and del_req() before _worklist.push()?

It was my suggestion to use 'edge' in new methods name but I think it is not 
accurate. Methods update only input edges so it would be better to call methods 
replace_input_of() and delete_input_of().

Thanks,
Vladimir

Vladimir Ivanov wrote:
> http://cr.openjdk.java.net/~vi/7173340/webrev.01/
> 
> The idea is to replace the following patterns with a single call to
> a corresponding method from PhaseIterGVN:
>   1) igvn.hash_delete(n);
>      n->set_req(i, in);
>      igvn._worklist.push(n);
> 
>   2) hash_delete(n);
>      n->del_req(i);
>      _worklist.push(n);
> 
>   3) hash_delete(n);
>      _worklist.push(n);
>  to
>   1) PhaseIterGVN::replace_edge_of(Node*, int, Node*)
>   2) PhaseIterGVN::delete_edge_of(Node*, int)
>   3) PhaseIterGVN::rehash_node_delayed(Node*)
> 
> I reordered code in some places, but it should be safe. Please, confirm.
> 
> Testing: VM tests, VM regression tests
> 
> Thanks!
> 
> Best regards,
> Vladimir Ivanov