8280283: Dead compiler code found during the JDK-8272058 code review

[anton-seoane]

This PR removes some dead code that was found during review for JDK-8272058.

target_addr_for_insn_or_null is never run with a ldrw to zr (i.e. a safepoint poll). This is just a remnant from global safepointing, before we moved to using thread-local handshakes. No safepoint polling code reaches this function. More information can be read in the original code review. Additionally, I have run tiers 1-6 to make sure this path did not exercise.

This changeset also cleans up the unused is_nop function, following the comments in the issue. Other dead code mentioned there has since been long disappered.

Testing: passes tiers 1-4

---

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-8280283: Dead compiler code found during the JDK-8272058 code review (Enhancement - P4)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/28473/head:pull/28473
$ git checkout pull/28473

Update a local copy of the PR:
$ git checkout pull/28473
$ git pull https://git.openjdk.org/jdk.git pull/28473/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 28473

View PR using the GUI difftool:
$ git pr show -t 28473

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/28473.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back aseoane! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@anton-seoane The following label will be automatically applied to this pull request:

• hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[anton-seoane]

/label add hotspot-compiler
/label remove hotspot

[openjdk]

@anton-seoane
The hotspot-compiler label was successfully added.

[openjdk]

@anton-seoane
The hotspot label was successfully removed.

[anton-seoane]

/touch

[openjdk]

@anton-seoane The pull request is being re-evaluated and the inactivity timeout has been reset.

[anton-seoane]

/issue add 8280283

[openjdk]

@anton-seoane This issue is referenced in the PR title - it will now be updated.

[anton-seoane]

/touch

Hey bot, please find my issue

[openjdk]

@anton-seoane The pull request is being re-evaluated and the inactivity timeout has been reset.

[mlbridge]

Webrevs

• 00: Full (749eda78)