[PATCH] Fix merges of non-zero vector stores

[Matt Arsenault]

 Now actually stores the non-zero constant instead of 0.
I somehow forgot to include this part with r238108.
   
The test change was just an independent instruction order swap,
so just add another check line to satisfy CHECK-NEXT.

http://reviews.llvm.org/D10326

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/R600/merge-stores.ll
  test/CodeGen/X86/2012-11-28-merge-store-alias.ll

Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -387,6 +387,13 @@
       unsigned SequenceNum;
     };
 
+    /// This is a helper function for MergeStoresOfConstantsOrVecElts. Returns a
+    /// constant build_vector of the stored constant values in Stores.
+    SDValue getMergedConstantVectorStore(SelectionDAG &DAG,
+                                         SDLoc SL,
+                                         ArrayRef<MemOpLink> Stores,
+                                         EVT Ty) const;
+
     /// This is a helper function for MergeConsecutiveStores. When the source
     /// elements of the consecutive stores are all constants or all extracted
     /// vector elements, try to merge them into one larger store.
@@ -10576,6 +10583,17 @@
 };
 } // namespace
 
+SDValue DAGCombiner::getMergedConstantVectorStore(SelectionDAG &DAG,
+                                                  SDLoc SL,
+                                                  ArrayRef<MemOpLink> Stores,
+                                                  EVT Ty) const {
+  SmallVector<SDValue, 8> BuildVector;
+
+  for (const MemOpLink &Store : Stores)
+    BuildVector.push_back(cast<StoreSDNode>(Store.MemNode)->getValue());
+  return DAG.getNode(ISD::BUILD_VECTOR, SL, Ty, BuildVector);
+}
+
 bool DAGCombiner::MergeStoresOfConstantsOrVecElts(
                   SmallVectorImpl<MemOpLink> &StoreNodes, EVT MemVT,
                   unsigned NumElem, bool IsConstantSrc, bool UseVector) {
@@ -10606,12 +10624,7 @@
     EVT Ty = EVT::getVectorVT(*DAG.getContext(), MemVT, NumElem);
     assert(TLI.isTypeLegal(Ty) && "Illegal vector store");
     if (IsConstantSrc) {
-      // A vector store with a constant source implies that the constant is
-      // zero; we only handle merging stores of constant zeros because the zero
-      // can be materialized without a load.
-      // It may be beneficial to loosen this restriction to allow non-zero
-      // store merging.
-      StoredVal = DAG.getConstant(0, DL, Ty);
+      StoredVal = getMergedConstantVectorStore(DAG, DL, StoreNodes, Ty);
     } else {
       SmallVector<SDValue, 8> Ops;
       for (unsigned i = 0; i < NumElem ; ++i) {
Index: test/CodeGen/R600/merge-stores.ll
===================================================================
--- test/CodeGen/R600/merge-stores.ll
+++ test/CodeGen/R600/merge-stores.ll
@@ -89,7 +89,11 @@
 }
 
 ; GCN-LABEL: {{^}}merge_global_store_2_constants_f32_i32:
-; GCN: buffer_store_dwordx2
+; SI-DAG: s_mov_b32 [[SLO:s[0-9]+]], 4.0
+; SI-DAG: s_movk_i32 [[SHI:s[0-9]+]], 0x7b{{$}}
+; SI-DAG: v_mov_b32_e32 v[[VLO:[0-9]+]], [[SLO]]
+; SI-DAG: v_mov_b32_e32 v[[VHI:[0-9]+]], [[SHI]]
+; GCN: buffer_store_dwordx2 v{{\[}}[[VLO]]:[[VHI]]{{\]}}
 define void @merge_global_store_2_constants_f32_i32(float addrspace(1)* %out) #0 {
   %out.gep.1 = getelementptr float, float addrspace(1)* %out, i32 1
   %out.gep.1.bc = bitcast float addrspace(1)* %out.gep.1 to i32 addrspace(1)*
@@ -99,7 +103,11 @@
 }
 
 ; GCN-LABEL: {{^}}merge_global_store_4_constants_i32:
-; GCN: buffer_store_dwordx4
+; GCN-DAG: v_mov_b32_e32 v[[HI:[0-9]+]], 0x14d{{$}}
+; GCN-DAG: v_mov_b32_e32 v{{[0-9]+}}, 0x1c8{{$}}
+; GCN-DAG: v_mov_b32_e32 v{{[0-9]+}}, 0x7b{{$}}
+; GCN-DAG: v_mov_b32_e32 v[[LO:[0-9]+]], 0x4d2{{$}}
+; GCN: buffer_store_dwordx4 v{{\[}}[[LO]]:[[HI]]{{\]}}
 define void @merge_global_store_4_constants_i32(i32 addrspace(1)* %out) #0 {
   %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
   %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
Index: test/CodeGen/X86/2012-11-28-merge-store-alias.ll
===================================================================
--- test/CodeGen/X86/2012-11-28-merge-store-alias.ll
+++ test/CodeGen/X86/2012-11-28-merge-store-alias.ll
@@ -3,6 +3,7 @@
 ; CHECK: merge_stores_can
 ; CHECK: callq foo
 ; CHECK: xorps %xmm0, %xmm0
+; CHECK-NEXT: movl 36(%rsp), %ebp
 ; CHECK-NEXT: movups  %xmm0
 ; CHECK: callq foo
 ; CHECK: ret

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