[PATCH] D100137: [JumpThreading] merge debug info when merging select+br

[Nick Desaulniers via Phabricator via llvm-commits]

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Jump threading can replace select then unconditional branch with
conditional branch, but when doing so looses debug info. This is a text
book case for merging debug info locations.

This destructive transform is eventually leading to a failed Verifier
run during full LTO builds of the Linux kernel with CFI and KCOV
enabled.

Link: b/184085493
Link: https://bugs.llvm.org/show_bug.cgi?id=39531
Link: https://www.llvm.org/docs/HowToUpdateDebugInfo.html#when-to-merge-instruction-locations
Signed-off-by: Nick Desaulniers <ndesaulniers at google.com>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100137

Files:
  llvm/lib/Transforms/Scalar/JumpThreading.cpp
  llvm/test/Transforms/JumpThreading/branch-debug-info2.ll

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