Merge 6abb92f2103a58d097620b4410054c5bb18c48ec into 12.0.1

[llvmbot]

Bugzilla Link	49871
Resolution	FIXED
Resolved on	May 11, 2021 20:49
Version	11.0
OS	Windows NT
Blocks	#48661
Reporter	LLVM Bugzilla Contributor
CC	@tstellar
Fixed by commit(s)	6abb92f aa97726

Extended Description

Please merge 6abb92f.

[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 #48926 .

[llvmbot]

assigned to @tstellar

[tstellar]

Hi Florian,

What is your opinion on backporting this?

https://reviews.llvm.org/rG6abb92f2103a58d097620b4410054c5bb18c48ec

[fhahn]

Hi Florian,

What is your opinion on backporting this?

https://reviews.llvm.org/rG6abb92f2103a58d097620b4410054c5bb18c48ec

I think that should be fine, given that it's small patch with a clear improvement. Please let me know if the patch does not apply cleanly, happy to help out.

[tstellar]

Merged: aa97726