[PATCH] D96399: [X86][CodeGenPrepare] Try to reuse IV's incremented value instead of adding the offset

[Max Kazantsev via Phabricator via llvm-commits]

mkazantsev updated this revision to Diff 326626.
mkazantsev retitled this revision from "[X86][CodeGenPrepare] Try to reuse IV's incremented value instead of adding the offset (WIP)" to "[X86][CodeGenPrepare] Try to reuse IV's incremented value instead of adding the offset".
mkazantsev added a comment.

Added tests & safety checks against add/sub with `nuw/nsw` flags to avoid potential misuse of poisoned values. So far we conservatively restrain from optimizing such doubteous cases. Follow-up planned: try to prove flags is possible, if not - drop them (?).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D96399/new/

https://reviews.llvm.org/D96399

Files:
  llvm/lib/CodeGen/CodeGenPrepare.cpp
  llvm/test/CodeGen/X86/2020_12_02_decrementing_loop.ll
  llvm/test/CodeGen/X86/overflowing-iv.ll
  llvm/test/CodeGen/X86/uadd_inc_iv.ll
  llvm/test/CodeGen/X86/usub_inc_iv.ll

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