[PATCH] D156702: Add support for GEP of GEP instruction combining when types do not exactly match

[Simeon Krastnikov via Phabricator via llvm-commits]

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InstCombine can combine a GEP of a GEP into a single one if the type of the source pointer matches the source element type of the outer pointer. However, in certain cases the source pointer may have had one or more of its indices folded (as `CreateGEP` calls `FoldGEP`) and thus have a different resulting type than the source element type, leading to a missed optimization. This patch attempts to handle this case by "unfolding" the source GEP by incrementally appending zero indices until its type matches.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D156702

Files:
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/InstCombine/gepgep-after-fold.ll

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