RFR: 8311813: C1: Uninitialized PhiResolver::_loop field

[Aleksey Shipilev]

On Mon, 10 Jul 2023 23:47:56 GMT, Chad Rakoczy <duke at openjdk.org> wrote:

> [JDK-8311813](https://bugs.openjdk.org/browse/JDK-8311813)
> 
> Initialize `PhiResolver::_loop` field to `nullptr`
> 
> Additional testing:
> - [x] Linux x86_64 fastdebug `tier2`
> - [x] Linux x86_64 release `tier2`
> - [x] Linux x86_64 fastdebug `gtest:all`
> - [x] Linux x86_64 release `gtest:all`
> - [x] Linux x86_64 fastdebug `test/hotspot/jtreg/compiler/c1`
> - [x] Linux x86_64 release `test/hotspot/jtreg/compiler/c1`

Marked as reviewed by shade (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/14819#pullrequestreview-1525692733