From dde785cd70a4a7418f310a0d86afcbfe3dd8dbfe Mon Sep 17 00:00:00 2001
From: Nadav Rotem <nrotem@apple.com>
Date: Thu, 6 Dec 2012 17:34:13 +0000
Subject: Fix a bug in the code that merges consecutive stores. Previously we
 did not check if loads that happen in between stores alias with the first
 store in the chain, only with the second store onwards.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169516 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/SelectionDAG/DAGCombiner.cpp | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

(limited to 'lib/CodeGen')

diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index a581fd8f23..6cd07c2c72 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -7613,9 +7613,9 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
     // information to check if it interferes with anything.
     SDNode *NextInChain = Index->getChain().getNode();
     while (1) {
-      if (isa<StoreSDNode>(NextInChain)) {
+      if (StoreSDNode *STn = dyn_cast<StoreSDNode>(NextInChain)) {
         // We found a store node. Use it for the next iteration.
-        Index = cast<StoreSDNode>(NextInChain);
+        Index = STn;
         break;
       } else if (LoadSDNode *Ldn = dyn_cast<LoadSDNode>(NextInChain)) {
         // Save the load node for later. Continue the scan.
@@ -7641,10 +7641,15 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
   // store memory address.
   unsigned LastConsecutiveStore = 0;
   int64_t StartAddress = StoreNodes[0].OffsetFromBase;
-  for (unsigned i = 1, e = StoreNodes.size(); i < e; ++i) {
-    int64_t CurrAddress = StoreNodes[i].OffsetFromBase;
-    if (CurrAddress - StartAddress != (ElementSizeBytes * i))
-      break;
+  for (unsigned i = 0, e = StoreNodes.size(); i < e; ++i) {
+
+    // Check that the addresses are consecutive starting from the second
+    // element in the list of stores.
+    if (i > 0) {
+      int64_t CurrAddress = StoreNodes[i].OffsetFromBase;
+      if (CurrAddress - StartAddress != (ElementSizeBytes * i))
+        break;
+    }
 
     bool Alias = false;
     // Check if this store interferes with any of the loads that we found.
@@ -7653,7 +7658,6 @@ bool DAGCombiner::MergeConsecutiveStores(StoreSDNode* St) {
         Alias = true;
         break;
       }
-
     // We found a load that alias with this store. Stop the sequence.
     if (Alias)
       break;
@@ -9746,9 +9750,9 @@ bool DAGCombiner::isAlias(LSBaseSDNode *Op0, LSBaseSDNode *Op1) {
   FindAliasInfo(Op1, Ptr1, Size1, SrcValue1, SrcValueOffset1,
                 SrcValueAlign1, SrcTBAAInfo1);
   return isAlias(Ptr0, Size0, SrcValue0, SrcValueOffset0,
-               SrcValueAlign0, SrcTBAAInfo0,
-               Ptr1, Size1, SrcValue1, SrcValueOffset1,
-               SrcValueAlign1, SrcTBAAInfo1);
+                 SrcValueAlign0, SrcTBAAInfo0,
+                 Ptr1, Size1, SrcValue1, SrcValueOffset1,
+                 SrcValueAlign1, SrcTBAAInfo1);
 }
 
 /// FindAliasInfo - Extracts the relevant alias information from the memory
-- 
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