RFR: 8253524: C2: Refactor code that clones predicates during loop unswitching [v2]

[Tobias Hartmann]

On Wed, 23 Sep 2020 12:14:01 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> During unswitching, PhaseIdealLoop::create_slow_version_of_loop()
>> calls PhaseIdealLoop::clone_predicates_to_unswitched_loop() twice, one
>> for each loops, to clone some predicates above each loop. That code is
>> fragile as it (implicitly) requires the fast loop to be processed
>> first. I propose calling
>> PhaseIdealLoop::clone_predicates_to_unswitched_loop() a single time
>> and have it handle both loops in a single pass.
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   code style

Looks good.

src/hotspot/share/opto/loopPredicate.cpp line 298:

> 296: // Clone loop predicates to cloned loops when unswitching a loop.
> 297: void PhaseIdealLoop::clone_predicates_to_unswitched_loop(IdealLoopTree* loop, const Node_List& old_new, ProjNode*&
> iffast, ProjNode*& ifslow) { 298:   LoopNode* head  = loop->_head->as_Loop();

Extra whitespace after `head`

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Marked as reviewed by thartmann (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/317