[LV] Prefer DenseMap::lookup over find (NFC)

[artagnon]

Apart from the stylistic improvement, lookup has the nice property of returning a default-constructed object on failure-to-find, while find returns the end iterator, which cannot be dereferenced.

[llvmbot]

@llvm/pr-subscribers-vectorizers

@llvm/pr-subscribers-llvm-transforms

Author: Ramkumar Ramachandra (artagnon)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/141809.diff

1 Files Affected:

• (modified) llvm/lib/Transforms/Vectorize/LoopVectorize.cpp (+4-4)

diff --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 05b5764ffcafc..4baa7907178c7 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -2566,9 +2566,9 @@ static Value *getExpandedStep(const InductionDescriptor &ID,
     return C->getValue();
   if (auto *U = dyn_cast<SCEVUnknown>(Step))
     return U->getValue();
-  auto I = ExpandedSCEVs.find(Step);
-  assert(I != ExpandedSCEVs.end() && "SCEV must be expanded at this point");
-  return I->second;
+  auto *V = ExpandedSCEVs.lookup(Step);
+  assert(V && "SCEV must be expanded at this point");
+  return V;
 }
 
 /// Knowing that loop \p L executes a single vector iteration, add instructions
@@ -10160,7 +10160,7 @@ preparePlanForEpilogueVectorLoop(VPlan &Plan, Loop *L,
     if (!ExpandR)
       continue;
     auto *ExpandedVal =
-        Plan.getOrAddLiveIn(ExpandedSCEVs.find(ExpandR->getSCEV())->second);
+        Plan.getOrAddLiveIn(ExpandedSCEVs.lookup(ExpandR->getSCEV()));
     ExpandR->replaceAllUsesWith(ExpandedVal);
     if (Plan.getTripCount() == ExpandR)
       Plan.resetTripCount(ExpandedVal);

[fhahn]

LGTM, thanks