[jdk17] RFR: 8269641: assert(tmp == _callprojs.fallthrough_catchproj) failed: allocation control projection

[Nils Eliasson]

When I investigated this bug I found out it was already fixed by JDK-8268405, or at least - it didn't happen any more. Since I had a good reproducer I took a look at why it happened and found two issues.

The noteable thing about the test case is that there are still allocations that isn't used. The initalizeNode lead to HaltNodes. This looks like a temporary state while the graph is simplified.

1) In macro.cpp - process_users_of_allocation - there was an assert that was wrong. We must assert before the replace_node - otherwise tmp will always be NULL and fail. Why this hasn't happened before is a mystery.

2) memnode.cpp - MemBarNode::remove - returns without doing anything if there are not exactly 2 outs. In this case there is a InitalizeNode that leads to a HaltNode. The memory uses has been removed - so the memory projection from the InitalizeNode is already removed.

If you want to check if this patch fixes the issue - you need to sync to jdk-17+26 - or before the fix for JDK-8268405.

Please review,
Nils Eliasson

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Commit messages:
 - Remove ws
 - Fix proj handling

Changes: https://git.openjdk.java.net/jdk17/pull/193/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17&pr=193&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8269641
  Stats: 10 lines in 2 files changed: 6 ins; 1 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk17/pull/193.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17 pull/193/head:pull/193

PR: https://git.openjdk.java.net/jdk17/pull/193