RFR: 8254369: Node::disconnect_inputs may skip precedences

[Xin Liu]

On Wed, 14 Oct 2020 23:37:34 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

>> src/hotspot/share/opto/node.cpp line 914:
>> 
>>> 912:   // Remove precedence edges if any exist
>>> 913:   // Note: Safepoints may have precedence edges, even during parsing
>>> 914:   for (uint i = len() - 1; i < len() && i >= req(); --i) {
>> 
>> i < len() check is not needed
>
> I got now why you need to scan reverse.

hi, @vnkozlov ,
Thank you to review it.

i <len() is there for protection.  Because is unsigned int, len() - 1 or --i might be underflow when len() 0 or req()
is 0.

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PR: https://git.openjdk.java.net/jdk/pull/664