RFR: 8257211: C2: Enable call devirtualization during post-parse phase [v3]

[Vladimir Ivanov]

On Wed, 2 Dec 2020 20:57:53 GMT, Nils Eliasson <neliasso at openjdk.org> wrote:

>> Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Minor cleanup in comments
>
> src/hotspot/share/opto/multnode.cpp line 66:
> 
>> 64: }
>> 65: 
>> 66: ProjNode* MultiNode::proj_out_or_null(uint which_proj, bool is_io_use) const {
> 
> This MultiNode::proj_out_or_null and the MultiNode::proj_out_or_null above are very similar but with a few differences. The only use of this method has is_io_use false.
> 
> I feel that there might be a risk of mixup in the future. Perhaps a different name can help? I don't have a better solution so I don't require you to fix this.

I considered merging them and introduce `is_io_use` as an optional argument, but was concerned that code which currently effectively doesn't care about the flavor of projection it gets (regular or IO) may fail. 
(I suspect it may be a lurking bug when it happens, but wanted to play it safe here.)

Since as you pointed out there's only a single use site, I can just inline the code there. What do you think?

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PR: https://git.openjdk.java.net/jdk/pull/1550