[PATCH] D116499: [SCEV] Compute exit count from overflow check expressed w/ x.with.overflow intrinsics

[Philip Reames via Phabricator via llvm-commits]

reames added inline comments.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:8101
+    if (EVI->getNumIndices() == 1 && EVI->getIndices()[0] == 1)
+      if (auto *WO = dyn_cast<WithOverflowInst>(EVI->getAggregateOperand())) {
+        const APInt *C;
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nikic wrote:
> I'd write these three conditions as `match(ExitCond, m_ExtractValue<1>(m_WithOverflowInst(WO))`.
Thanks, this is *much* cleaner.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:8111
+          if (!ExitIfTrue)
+            Pred = ICmpInst::getInversePredicate(Pred);
+          auto *LHS = getSCEV(WO->getLHS());
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nikic wrote:
> I didn't spot where this case is tested. Can you please add one where the successors are swapped? I see some tests using `xor -1`, but that doesn't appear to be supported by SCEV right now.
Oops, you're right.  Will be covered by @sadd_symbolic_swapped once the change is pushed.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D116499/new/

https://reviews.llvm.org/D116499