From d9d86cb7386daf050ecb6c329109ac3b61587852 Mon Sep 17 00:00:00 2001
From: Nirav Dave <niravd@google.com>
Date: Wed, 16 May 2018 16:47:54 +0000
Subject: [PATCH] [DAG] Defer merge store cycle checking to just before merge.
 NFCI.

llvm-svn: 332489
---
 llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 28 +++++++++++++------
 1 file changed, 20 insertions(+), 8 deletions(-)

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index aeea99894d6d..8a7b2f6f98b9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -13473,14 +13473,6 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode *St) {
       continue;
     }
 
-    // Check that we can merge these candidates without causing a cycle
-    if (!checkMergeStoreCandidatesForDependencies(StoreNodes,
-                                                  NumConsecutiveStores)) {
-      StoreNodes.erase(StoreNodes.begin(),
-                       StoreNodes.begin() + NumConsecutiveStores);
-      continue;
-    }
-
     // The node with the lowest store address.
     LLVMContext &Context = *DAG.getContext();
     const DataLayout &DL = DAG.getDataLayout();
@@ -13576,6 +13568,12 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode *St) {
         continue;
       }
 
+      // Check that we can merge these candidates without causing a cycle.
+      if (!checkMergeStoreCandidatesForDependencies(StoreNodes, NumElem)) {
+        StoreNodes.erase(StoreNodes.begin(), StoreNodes.begin() + NumElem);
+        continue;
+      }
+
       bool Merged = MergeStoresOfConstantsOrVecElts(
           StoreNodes, MemVT, NumElem, true, UseVector, LastIntegerTrunc);
       RV |= Merged;
@@ -13634,6 +13632,14 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode *St) {
         continue;
       }
 
+      // Check that we can merge these candidates without causing a cycle.
+      if (!checkMergeStoreCandidatesForDependencies(StoreNodes,
+                                                    NumStoresToMerge)) {
+        StoreNodes.erase(StoreNodes.begin(),
+                         StoreNodes.begin() + NumStoresToMerge);
+        continue;
+      }
+
       bool Merged = MergeStoresOfConstantsOrVecElts(
           StoreNodes, MemVT, NumStoresToMerge, false, true, false);
       if (!Merged) {
@@ -13803,6 +13809,12 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode *St) {
       continue;
     }
 
+    // Check that we can merge these candidates without causing a cycle.
+    if (!checkMergeStoreCandidatesForDependencies(StoreNodes, NumElem)) {
+      StoreNodes.erase(StoreNodes.begin(), StoreNodes.begin() + NumElem);
+      continue;
+    }
+
     // Find if it is better to use vectors or integers to load and store
     // to memory.
     EVT JointMemOpVT;