[PATCH] D148536: [Assignment Tracking] Fix fragment error for some DSE-shortened stores

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

Orlando created this revision.
Orlando added reviewers: jmorse, paulkirth.
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`shortenAssignment` inserts dbg.assigns with fragments describing the dead part of a shortened store after each dbg.assign linked to the store.

Without this patch it doesn't take into account that the dead part of a shortened store may be outside the bounds of a variable of a linked dbg.assign. It also doesn't correctly account for a non-zero offset in the address modifying `DIExpression` of the dbg.assign (which is possible for fragments now even though whole variables currently cannot have a non-zero offset in their alloca).

Fix this by moving the dead slice into variable-space and performing an intersect of that adjusted slice with the existing fragment.

This fixes a verifier error reported when building chromium with assignment tracking enabled: https://ci.chromium.org/ui/p/fuchsia/builders/ci/clang_toolchain.ci.core.x64-release/b8784000953022145169/overview


https://reviews.llvm.org/D148536

Files:
  llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
  llvm/test/DebugInfo/Generic/assignment-tracking/dse/dse-after-memcpyopt-merge.ll
  llvm/test/DebugInfo/Generic/assignment-tracking/dse/shorten-offset.ll
  llvm/test/DebugInfo/Generic/assignment-tracking/dse/shorten.ll

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