Delete a store whose input is a load from the same pointer:
x = load p
store x -> p
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@45398 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 6eaf7ae..242fffd 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -4223,7 +4223,7 @@
if (CombineToPreIndexedLoadStore(N) || CombineToPostIndexedLoadStore(N))
return SDOperand(N, 0);
- // FIXME: is there such a think as a truncating indexed store?
+ // FIXME: is there such a thing as a truncating indexed store?
if (ST->isTruncatingStore() && ST->getAddressingMode() == ISD::UNINDEXED &&
MVT::isInteger(Value.getValueType())) {
// See if we can simplify the input to this truncstore with knowledge that
@@ -4243,6 +4243,17 @@
return SDOperand(N, 0);
}
+ // If this is a load followed by a store to the same location, then the store
+ // is dead/noop.
+ if (LoadSDNode *Ld = dyn_cast<LoadSDNode>(Value)) {
+ if (Chain.Val == Ld && Ld->getBasePtr() == Ptr &&
+ ST->getAddressingMode() == ISD::UNINDEXED &&
+ ST->getStoredVT() == Ld->getLoadedVT()) {
+ // The store is dead, remove it.
+ return Chain;
+ }
+ }
+
return SDOperand();
}