[PATCH] D23473: [LSV] Use a set rather than an ArraySlice at the end of getVectorizablePrefix. NFC

[Justin Lebar via llvm-commits]

jlebar created this revision.
jlebar added a reviewer: asbirlea.
jlebar added subscribers: arsenm, llvm-commits.
Herald added a subscriber: mzolotukhin.

This avoids a small O(n^2) loop.

https://reviews.llvm.org/D23473

Files:
  llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp

Index: llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
===================================================================
--- llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
+++ llvm/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
@@ -517,12 +517,11 @@
   // ChainInstrs[0, ChainInstrIdx).  This is the largest vectorizable prefix of
   // Chain.  (Recall that Chain is in address order, but ChainInstrs is in BB
   // order.)
-  auto VectorizableChainInstrs =
-      makeArrayRef(ChainInstrs.data(), ChainInstrIdx);
-  unsigned ChainIdx, ChainLen;
-  for (ChainIdx = 0, ChainLen = Chain.size(); ChainIdx < ChainLen; ++ChainIdx) {
-    Instruction *I = Chain[ChainIdx];
-    if (!is_contained(VectorizableChainInstrs, I))
+  SmallPtrSet<Instruction *, 16> VectorizableChainInstrs(
+      ChainInstrs.begin(), ChainInstrs.begin() + ChainInstrIdx);
+  unsigned ChainIdx = 0;
+  for (unsigned ChainLen = Chain.size(); ChainIdx < ChainLen; ++ChainIdx) {
+    if (!VectorizableChainInstrs.count(Chain[ChainIdx]))
       break;
   }
   return Chain.slice(0, ChainIdx);


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