[PATCH] D154055: [InstCombine] Preserve inbounds when folding select of GEP

[Nikita Popov via Phabricator via llvm-commits]

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The `select base, (gep base, offset)` to `gep base, select (0, offset)` fold used to drop `inbounds`, because the `gep base, 0` this introduces might not be inbounds. After the semantics change in D154051 <https://reviews.llvm.org/D154051>, such a GEP is always considered inbounds, in which allows us to preserve the flag here.

As the PhaseOrdering test demonstrates, this can result in major optimization improvements.

Depends on: D154051 <https://reviews.llvm.org/D154051>


https://reviews.llvm.org/D154055

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
  llvm/test/Transforms/InstCombine/select-gep.ll
  llvm/test/Transforms/InstCombine/stpncpy-1.ll
  llvm/test/Transforms/PhaseOrdering/gep-null-compare-in-loop.ll

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