Index: llvm/trunk/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
+++ llvm/trunk/lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
@@ -628,7 +628,7 @@
 
 bool Vectorizer::vectorizeInstructions(ArrayRef<Instruction *> Instrs) {
   DEBUG(dbgs() << "LSV: Vectorizing " << Instrs.size() << " instructions.\n");
-  SmallSetVector<int, 16> Heads, Tails;
+  SmallVector<int, 16> Heads, Tails;
   int ConsecutiveChain[64];
 
   // Do a quadratic search on all of the given stores and find all of the pairs
@@ -647,8 +647,8 @@
             continue; // Should not insert.
         }
 
-        Tails.insert(j);
-        Heads.insert(i);
+        Tails.push_back(j);
+        Heads.push_back(i);
         ConsecutiveChain[i] = j;
       }
     }
@@ -660,21 +660,21 @@
   for (int Head : Heads) {
     if (InstructionsProcessed.count(Instrs[Head]))
       continue;
-    bool longerChainExists = false;
+    bool LongerChainExists = false;
     for (unsigned TIt = 0; TIt < Tails.size(); TIt++)
       if (Head == Tails[TIt] &&
           !InstructionsProcessed.count(Instrs[Heads[TIt]])) {
-        longerChainExists = true;
+        LongerChainExists = true;
         break;
       }
-    if (longerChainExists)
+    if (LongerChainExists)
       continue;
 
     // We found an instr that starts a chain. Now follow the chain and try to
     // vectorize it.
     SmallVector<Instruction *, 16> Operands;
     int I = Head;
-    while (I != -1 && (Tails.count(I) || Heads.count(I))) {
+    while (I != -1 && (is_contained(Tails, I) || is_contained(Heads, I))) {
       if (InstructionsProcessed.count(Instrs[I]))
         break;
 
Index: llvm/trunk/test/Transforms/LoadStoreVectorizer/AMDGPU/multiple_tails.ll
===================================================================
--- llvm/trunk/test/Transforms/LoadStoreVectorizer/AMDGPU/multiple_tails.ll
+++ llvm/trunk/test/Transforms/LoadStoreVectorizer/AMDGPU/multiple_tails.ll
@@ -0,0 +1,64 @@
+; RUN: opt -mtriple=amdgcn-amd-amdhsa -basicaa -load-store-vectorizer -S -o - %s | FileCheck %s
+
+target datalayout = "e-p:32:32-p1:64:64-p2:64:64-p3:32:32-p4:64:64-p5:32:32-i64:64-v16:16-v24:32-v32:32-v48:64-v96:128-v192:256-v256:256-v512:512-v1024:1024-v2048:2048-n32:64"
+
+; Checks that there is no crash when there are multiple tails
+; for a the same head starting a chain.
+@0 = internal addrspace(3) global [16384 x i32] undef
+
+; CHECK-LABEL: @no_crash(
+; CHECK: store <2 x i32> zeroinitializer
+; CHECK: store i32 0
+; CHECK: store i32 0
+
+define void @no_crash(i32 %arg) {
+  %tmp2 = add i32 %arg, 14
+  %tmp3 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %tmp2
+  %tmp4 = add i32 %arg, 15
+  %tmp5 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %tmp4
+
+  store i32 0, i32 addrspace(3)* %tmp3, align 4
+  store i32 0, i32 addrspace(3)* %tmp5, align 4
+  store i32 0, i32 addrspace(3)* %tmp5, align 4
+  store i32 0, i32 addrspace(3)* %tmp5, align 4
+
+  ret void
+}
+
+; Check adjiacent memory locations are properly matched and the
+; longest chain vectorized
+
+; CHECK-LABEL: @interleave_get_longest
+; CHECK: load <2 x i32>
+; CHECK: load i32
+; CHECK: store <2 x i32> zeroinitializer
+; CHECK: load i32
+; CHECK: load <2 x i32>
+; CHECK: load i32
+; CHECK: load i32
+
+define void @interleave_get_longest(i32 %arg) {
+  %a1 = add i32 %arg, 1
+  %a2 = add i32 %arg, 2
+  %a3 = add i32 %arg, 3
+  %a4 = add i32 %arg, 4
+  %tmp1 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %arg
+  %tmp2 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %a1
+  %tmp3 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %a2
+  %tmp4 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %a3
+  %tmp5 = getelementptr [16384 x i32], [16384 x i32] addrspace(3)* @0, i32 0, i32 %a4
+
+  %l1 = load i32, i32 addrspace(3)* %tmp2, align 4
+  %l2 = load i32, i32 addrspace(3)* %tmp1, align 4
+  store i32 0, i32 addrspace(3)* %tmp2, align 4
+  store i32 0, i32 addrspace(3)* %tmp1, align 4
+  %l3 = load i32, i32 addrspace(3)* %tmp2, align 4
+  %l4 = load i32, i32 addrspace(3)* %tmp3, align 4
+  %l5 = load i32, i32 addrspace(3)* %tmp4, align 4
+  %l6 = load i32, i32 addrspace(3)* %tmp5, align 4
+  %l7 = load i32, i32 addrspace(3)* %tmp5, align 4
+  %l8 = load i32, i32 addrspace(3)* %tmp5, align 4
+
+  ret void
+}
+
Index: llvm/trunk/test/Transforms/LoadStoreVectorizer/X86/subchain-interleaved.ll
===================================================================
--- llvm/trunk/test/Transforms/LoadStoreVectorizer/X86/subchain-interleaved.ll
+++ llvm/trunk/test/Transforms/LoadStoreVectorizer/X86/subchain-interleaved.ll
@@ -85,3 +85,33 @@
   ret void
 }
 
+; FIXME: If the chain is too long and TLI says misaligned is not fast,
+; then LSV fails to vectorize anything in that chain.
+; To reproduce below, add a tmp5 (ptr+4) and load tmp5 into l6 and l7.
+
+; CHECK-LABEL: @interleave_get_longest
+; CHECK: load <3 x i32>
+; CHECK: load i32
+; CHECK: store <2 x i32> zeroinitializer
+; CHECK: load i32
+; CHECK: load i32
+; CHECK: load i32
+
+define void @interleave_get_longest(i32* noalias %ptr) {
+  %tmp1 = getelementptr i32, i32* %ptr, i64 0
+  %tmp2 = getelementptr i32, i32* %ptr, i64 1
+  %tmp3 = getelementptr i32, i32* %ptr, i64 2
+  %tmp4 = getelementptr i32, i32* %ptr, i64 3
+
+  %l1 = load i32, i32* %tmp2, align 4
+  %l2 = load i32, i32* %tmp1, align 4
+  store i32 0, i32* %tmp2, align 4
+  store i32 0, i32* %tmp1, align 4
+  %l3 = load i32, i32* %tmp2, align 4
+  %l4 = load i32, i32* %tmp3, align 4
+  %l5 = load i32, i32* %tmp4, align 4
+  %l6 = load i32, i32* %tmp4, align 4
+  %l7 = load i32, i32* %tmp4, align 4
+
+  ret void
+}