From 70d695801a2bd5eed4bd6ea05d40516e6e6fa276 Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Wed, 26 Jun 2013 23:44:45 +0000
Subject: [PATCH] SLP: When searching for vectorization opportunities scan the
 blocks in post-order because we grow chains upwards.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185041 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Vectorize/SLPVectorizer.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/lib/Transforms/Vectorize/SLPVectorizer.cpp b/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 3c1dc78bc40..6ffd34bbf5a 100644
--- a/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -1377,8 +1377,10 @@ struct SLPVectorizer : public FunctionPass {
     // he store instructions.
     FuncSLP R(&F, SE, DL, TTI, AA, LI, DT);
 
-    for (Function::iterator it = F.begin(), e = F.end(); it != e; ++it) {
-      BasicBlock *BB = it;
+    // Scan the blocks in the function in post order.
+    for (po_iterator<BasicBlock*> it = po_begin(&F.getEntryBlock()),
+         e = po_end(&F.getEntryBlock()); it != e; ++it) {
+      BasicBlock *BB = *it;
 
       // Vectorize trees that end at reductions.
       Changed |= vectorizeChainsInBlock(BB, R);