[PATCH] D133294: [Assignment Tracking][11/*] Update RemoveRedundantDbgInstrs

[Orlando Cazalet-Hyams via Phabricator via llvm-commits]

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Update the `RemoveRedundantDbgInstrs` utility to avoid sometimes losing information when deleting dbg.assign intrinsics.

`removeRedundantDbgInstrsUsingBackwardScan` - treat dbg.assign intrinsics that are not linked to any instruction just like dbg.values. That is, in a block of contiguous debug intrinsics, delete all other than the last definition for a fragment. Leave linked dbg.assign intrinsics in place.

`removeRedundantDbgInstrsUsingForwardScan` - this function has two changes. First, undef and unlinked dbg.assign intrinsics encountered in the entry block before any non-undef non-unlinked intrinsics for a given fragment are deleted. Second, don't delete linked dbg.assign intrinsics and don't the next intrinsic found even if it would otherwise be eligible for deletion.


https://reviews.llvm.org/D133294

Files:
  llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
  llvm/test/DebugInfo/Generic/assignment-tracking/remove-redundant.ll

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