From 1454b08a47a5e8c9b987280e12fea73271496e3f Mon Sep 17 00:00:00 2001
From: Yevgeny Rouban <yevgeny.rouban@azul.com>
Date: Fri, 1 Feb 2019 06:44:08 +0000
Subject: [PATCH] [SLPVectorizer] Get rid of IndexQueue array from
 vectorizeStores. NFCI.

Indices are checked as they are generated. No need to fill the whole array of indices.

Differential Revision: https://reviews.llvm.org/D57144

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@352839 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Vectorize/SLPVectorizer.cpp | 45 +++++++++-------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index b0157ee0f1c..d040f8eba86 100644
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -4746,38 +4746,29 @@ bool SLPVectorizerPass::vectorizeStores(ArrayRef<StoreInst *> Stores,
   BoUpSLP::ValueSet VectorizedStores;
   bool Changed = false;
 
-  // Do a quadratic search on all of the given stores in reverse order and find
-  // all of the pairs of stores that follow each other.
-  SmallVector<unsigned, 16> IndexQueue;
-  unsigned E = Stores.size();
-  IndexQueue.resize(E - 1);
-  for (unsigned I = E; I > 0; --I) {
-    unsigned Idx = I - 1;
-    // If a store has multiple consecutive store candidates, search Stores
-    // array according to the sequence: Idx-1, Idx+1, Idx-2, Idx+2, ...
-    // This is because usually pairing with immediate succeeding or preceding
-    // candidate create the best chance to find slp vectorization opportunity.
-    unsigned Offset = 1;
-    unsigned Cnt = 0;
-    for (unsigned J = 0; J < E - 1; ++J, ++Offset) {
-      if (Idx >= Offset) {
-        IndexQueue[Cnt] = Idx - Offset;
-        ++Cnt;
-      }
-      if (Idx + Offset < E) {
-        IndexQueue[Cnt] = Idx + Offset;
-        ++Cnt;
-      }
-    }
+  auto &&FindConsecutiveAccess =
+      [this, &Stores, &Heads, &Tails, &ConsecutiveChain] (int K, int Idx) {
+        if (!isConsecutiveAccess(Stores[K], Stores[Idx], *DL, *SE))
+          return false;
 
-    for (auto K : IndexQueue) {
-      if (isConsecutiveAccess(Stores[K], Stores[Idx], *DL, *SE)) {
         Tails.insert(Stores[Idx]);
         Heads.insert(Stores[K]);
         ConsecutiveChain[Stores[K]] = Stores[Idx];
+        return true;
+      };
+
+  // Do a quadratic search on all of the given stores in reverse order and find
+  // all of the pairs of stores that follow each other.
+  int E = Stores.size();
+  for (int Idx = E - 1; Idx >= 0; --Idx) {
+    // If a store has multiple consecutive store candidates, search according
+    // to the sequence: Idx-1, Idx+1, Idx-2, Idx+2, ...
+    // This is because usually pairing with immediate succeeding or preceding
+    // candidate create the best chance to find slp vectorization opportunity.
+    for (int Offset = 1, F = std::max(E - Idx, Idx + 1); Offset < F; ++Offset)
+      if ((Idx >= Offset && FindConsecutiveAccess(Idx - Offset, Idx)) ||
+          (Idx + Offset < E && FindConsecutiveAccess(Idx + Offset, Idx)))
         break;
-      }
-    }
   }
 
   // For stores that start but don't end a link in the chain:
-- 
2.40.0