[PATCH] D148001: [LICM] Reassociate & hoist sub expressions

[Serguei Katkov via Phabricator via llvm-commits]

skatkov accepted this revision.
skatkov added a comment.
This revision is now accepted and ready to land.

LGTM with comment for consideration - I do not insist.



================
Comment at: llvm/lib/Transforms/Scalar/LICM.cpp:2610
+  auto &DL = L.getHeader()->getModule()->getDataLayout();
+  bool ProvedNoOverflowAfterReassociate =
+      VariantSubtracted
----------------
Not sure it is more readable (may be only for me) but consider
```
// C1 - LV < C2 case, so we need C1 - C2 does not overflow.
if (VariantSubtracted && computeOverflowForSignedSub(InvariantOp, InvariantRHS, DL, AC,
                                         &ICmp, DT) != llvm::OverflowResult::NeverOverflows)
  return false;
// LV - C1 < C2 case, so we need C1 + C2 does not overflow.
if (!ValueSubrtacted && computeOverflowForSignedAdd(InvariantOp, InvariantRHS, DL, AC,
                                         &ICmp, DT) != llvm::OverflowResult::NeverOverflows)
  return false;
```


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