[DAG] Make MergeStores generate legalized stores. NFCI.

Realized merged stores as truncstores if store will be realized as
such by legalization.

llvm-svn: 305467

1 files changed, 21 insertions, 4 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index bcec40e4f29..b5e1b492e96 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -12461,10 +12461,27 @@ bool DAGCombiner::MergeStoresOfConstantsOrVecElts(
 
   LSBaseSDNode *FirstInChain = StoreNodes[0].MemNode;
   SDValue NewChain = getMergeStoreChains(StoreNodes, NumStores);
-  SDValue NewStore = DAG.getStore(NewChain, DL, StoredVal,
-                                  FirstInChain->getBasePtr(),
-                                  FirstInChain->getPointerInfo(),
-                                  FirstInChain->getAlignment());
+
+  // make sure we use trunc store if it's necessary to be legal.
+  SDValue NewStore;
+  if (TLI.isTypeLegal(StoredVal.getValueType())) {
+    NewStore = DAG.getStore(NewChain, DL, StoredVal, FirstInChain->getBasePtr(),
+                            FirstInChain->getPointerInfo(),
+                            FirstInChain->getAlignment());
+  } else { // Must be realized as a trunc store
+    EVT LegalizedStoredValueTy =
+        TLI.getTypeToTransformTo(*DAG.getContext(), StoredVal.getValueType());
+    unsigned LegalizedStoreSize = LegalizedStoredValueTy.getSizeInBits();
+    ConstantSDNode *C = cast<ConstantSDNode>(StoredVal);
+    SDValue ExtendedStoreVal =
+        DAG.getConstant(C->getAPIntValue().zextOrTrunc(LegalizedStoreSize), DL,
+                        LegalizedStoredValueTy);
+    NewStore = DAG.getTruncStore(
+        NewChain, DL, ExtendedStoreVal, FirstInChain->getBasePtr(),
+        FirstInChain->getPointerInfo(), StoredVal.getValueType() /*TVT*/,
+        FirstInChain->getAlignment(),
+        FirstInChain->getMemOperand()->getFlags());
+  }
 
   // Replace all merged stores with the new store.
   for (unsigned i = 0; i < NumStores; ++i)