[llvm-bugs] [Bug 49871] New: Merge 6abb92f2103a58d097620b4410054c5bb18c48ec into 12.0.0

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49871

            Bug ID: 49871
           Summary: Merge 6abb92f2103a58d097620b4410054c5bb18c48ec into
                    12.0.0
           Product: libraries
           Version: 11.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Scalar Optimizations
          Assignee: unassignedbugs at nondot.org
          Reporter: brad at comstyle.com
                CC: llvm-bugs at lists.llvm.org
            Blocks: 48902

Please merge
https://github.com/llvm/llvm-project/commit/6abb92f2103a58d097620b4410054c5bb18c48ec.

[SCCP] Avoid modifying AdditionalUsers while iterating over it

When run under valgrind, or with a malloc that poisons freed memory,
this can lead to segfaults or other problems.

To avoid modifying the AdditionalUsers DenseMap while still iterating,
save the instructions to be notified in a separate SmallPtrSet, and use
this to later call OperandChangedState on each instruction.

Fixes PR49582.


Referenced Bugs:

https://bugs.llvm.org/show_bug.cgi?id=48902
[Bug 48902] [meta] 12.0.0 Release Blockers
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