Fix PR6497, a bug where we'd fold a load into an addc

node which has a flag.  That flag in turn was used by an
already-selected adde which turned into an ADC32ri8 which
used a selected load which was chained to the load we
folded.  This flag use caused us to form a cycle.  Fix
this by not ignoring chains in IsLegalToFold even in
cases where the isel thinks it can.

llvm-svn: 97791

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
index b9ec4c46f3b..f426fb1f3fa 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
@@ -1485,7 +1485,14 @@ bool SelectionDAGISel::IsLegalToFold(SDValue N, SDNode *U, SDNode *Root,
       break;
     Root = FU;
     VT = Root->getValueType(Root->getNumValues()-1);
+    
+    // If our query node has a flag result with a use, we've walked up it.  If
+    // the user (which has already been selected) has a chain or indirectly uses
+    // the chain, our WalkChainUsers predicate will not consider it.  Because of
+    // this, we cannot ignore chains in this predicate.
+    IgnoreChains = false;
   }
+  
 
   SmallPtrSet<SDNode*, 16> Visited;
   return !findNonImmUse(Root, N.getNode(), U, Root, Visited, IgnoreChains);