8328085: C2: Use after free in PhaseChaitin::Register_Allocate()

[reinrich]

This change removes the ResourceMark from PhaseChaitin::merge_multidefs() because it frees memory that is used in the caller method PhaseChaitin::Register_Allocate.
My comment on the JBS item explains the details.

Testing

I was able to reproduce the issue on ppc64le but not on x86_64 running applications/ctw/modules/java_desktop.java. The issue didn't reproduce with this pr.

ResourceArea Sizes

I've traced maximum ResourceArea size after returning from PhaseChaitin::merge_multidefs() (see first commit).
I haven't found a significant difference.
Below you can see the last trace line from each run.

x86_64: 3 Runs Dacapo Tomcat 5 Iterations

Baseline

Run 1: [24.222s][info][newcode] New maximum for resource area size: 3274 KB
Run 2: [21.317s][info][newcode] New maximum for resource area size: 3274 KB
Run 3: [37.400s][info][newcode] New maximum for resource area size: 3336 KB

PR

Run 1: [35.002s][info][newcode] New maximum for resource area size: 3363 KB
Run 2: [21.332s][info][newcode] New maximum for resource area size: 3274 KB
Run 3: [36.050s][info][newcode] New maximum for resource area size: 3286 KB

x86_64: 3 Runs applications/ctw/modules/java_desktop.java

Baseline

Run 1: [29.876s][info][newcode] New maximum for resource area size: 3143 KB
Run 2: [29.631s][info][newcode] New maximum for resource area size: 3111 KB
Run 3: [29.227s][info][newcode] New maximum for resource area size: 3142 KB

PR

Run 1: [29.755s][info][newcode] New maximum for resource area size: 3175 KB
Run 2: [28.964s][info][newcode] New maximum for resource area size: 3143 KB
Run 3: [28.863s][info][newcode] New maximum for resource area size: 3143 KB

PPC: 3 Runs Dacapo Tomcat 5 Iterations

Baseline

Run 1: [20.041s][info][newcode] New maximum for resource area size: 3474 KB
Run 2: [20.581s][info][newcode] New maximum for resource area size: 3474 KB
Run 3: [20.367s][info][newcode] New maximum for resource area size: 3474 KB

PR

Run 1: [20.520s][info][newcode] New maximum for resource area size: 3506 KB
Run 2: [20.918s][info][newcode] New maximum for resource area size: 3506 KB
Run 3: [20.994s][info][newcode] New maximum for resource area size: 3505 KB

PPC: 3 Runs applications/ctw/modules/java_desktop.java

Baseline

Run 1: [71.992s][info][newcode] New maximum for resource area size: 3483 KB
Run 2: [55.808s][info][newcode] New maximum for resource area size: 3483 KB
Run 3: [29.252s][info][newcode] New maximum for resource area size: 1684 KB

PR

Run 1: [55.996s][info][newcode] New maximum for resource area size: 3515 KB
Run 2: [30.384s][info][newcode] New maximum for resource area size: 2849 KB
Run 3: [65.671s][info][newcode] New maximum for resource area size: 3547 KB

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8328085: C2: Use after free in PhaseChaitin::Register_Allocate() (Bug - P3)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/22200/head:pull/22200
$ git checkout pull/22200

Update a local copy of the PR:
$ git checkout pull/22200
$ git pull https://git.openjdk.org/jdk.git pull/22200/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 22200

View PR using the GUI difftool:
$ git pr show -t 22200

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/22200.diff

[bridgekeeper]

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[openjdk]

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[openjdk]

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