[X86,ISEL] Fix X86 increment chain dependence calculation

Merging Load-add-store pattern into a increment op previously dropped
the load's chain from the instructions dependence if the store is
chained to a TokenFactor.

llvm-svn: 293892

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
index 8ab4c061688..7f08d2dea9d 100644
--- a/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/llvm/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -1905,6 +1905,8 @@ static bool isLoadIncOrDecStore(StoreSDNode *StoreNode, unsigned Opc,
       SDValue Op = Chain.getOperand(i);
       if (Op == Load.getValue(1)) {
         ChainCheck = true;
+        // Drop Load, but keep its chain. No cycle check necessary.
+        ChainOps.push_back(Load.getOperand(0));
         continue;
       }