Add target hook to allow merging stores of nonzero constants

[arsenm]

Summary

On GPU targets, materializing constants is cheap and stores are
expensive, so only doing this for zero vectors was silly.

Most of the new testcases aren't optimally merged, and are for
later improvements.

[hfinkel]

include/llvm/Target/TargetLowering.h

270

This does not explain well what this does. Cheaper than what?

[arsenm]

Update comment

[hfinkel]

LGTM.

[arsenm]

r238108

include/llvm/Target/TargetLowering.h

public:
   /// efficiently, casting the load to a smaller vector of larger types and
   /// loading is more efficient, however, this can be undone by optimizations in
   /// dag combiner.
   virtual bool isLoadBitCastBeneficial(EVT /* Load */,
                                        EVT /* Bitcast */) const {
     return true;
   }
 
+  /// Return true if it is expected to be cheaper to do a store of a non-zero
+  /// vector constant with the given size and type for the address space than to
+  /// store the individual scalar element constants.
+  virtual bool storeOfVectorConstantIsCheap(EVT MemVT,
+                                            unsigned NumElem,
+                                            unsigned AddrSpace) const {
+    return false;
+  }
+
   /// \brief Return true if it is cheap to speculate a call to intrinsic cttz.
   virtual bool isCheapToSpeculateCttz() const {
     return false;
   }
 
   /// \brief Return true if it is cheap to speculate a call to intrinsic ctlz.
   virtual bool isCheapToSpeculateCtlz() const {
     return false;

lib/CodeGen/SelectionDAG/DAGCombiner.cpp

for (unsigned i=0; i<LastConsecutiveStore+1; ++i) {
       // Find a legal type for the vector store.
       EVT Ty = EVT::getVectorVT(*DAG.getContext(), MemVT, i+1);
       if (TLI.isTypeLegal(Ty) &&
           allowableAlignment(DAG, TLI, Ty, FirstStoreAS, FirstStoreAlign)) {
         LastLegalVectorType = i + 1;
       }
     }
 
-    // We only use vectors if the constant is known to be zero and the
-    // function is not marked with the noimplicitfloat attribute.
-    if (NonZero || NoVectors)
+
+    // We only use vectors if the constant is known to be zero or the target
+    // allows it and the function is not marked with the noimplicitfloat
+    // attribute.
+    if (NoVectors) {
+      LastLegalVectorType = 0;
+    } else if (NonZero && !TLI.storeOfVectorConstantIsCheap(MemVT,
+                                                            LastLegalVectorType,
+                                                            FirstStoreAS)) {
       LastLegalVectorType = 0;
+    }
 
     // Check if we found a legal integer type to store.
     if (LastLegalType == 0 && LastLegalVectorType == 0)
       return false;
 
     bool UseVector = (LastLegalVectorType > LastLegalType) && !NoVectors;
     unsigned NumElem = UseVector ? LastLegalVectorType : LastLegalType;
 

lib/Target/R600/AMDGPUISelLowering.h

public:
 
   bool isFPImmLegal(const APFloat &Imm, EVT VT) const override;
   bool ShouldShrinkFPConstant(EVT VT) const override;
   bool shouldReduceLoadWidth(SDNode *Load,
                              ISD::LoadExtType ExtType,
                              EVT ExtVT) const override;
 
   bool isLoadBitCastBeneficial(EVT, EVT) const override;
+
+  bool storeOfVectorConstantIsCheap(EVT MemVT,
+                                    unsigned NumElem,
+                                    unsigned AS) const override;
   bool isCheapToSpeculateCttz() const override;
   bool isCheapToSpeculateCtlz() const override;
 
   SDValue LowerReturn(SDValue Chain, CallingConv::ID CallConv,
                       bool isVarArg,
                       const SmallVectorImpl<ISD::OutputArg> &Outs,
                       const SmallVectorImpl<SDValue> &OutVals,
                       SDLoc DL, SelectionDAG &DAG) const override;

lib/Target/R600/AMDGPUISelLowering.cpp

bool AMDGPUTargetLowering::isFAbsFree(EVT VT) const {
   return VT == MVT::f32 || VT == MVT::f64;
 }
 
 bool AMDGPUTargetLowering::isFNegFree(EVT VT) const {
   assert(VT.isFloatingPoint());
   return VT == MVT::f32 || VT == MVT::f64;
 }
 
+bool AMDGPUTargetLowering:: storeOfVectorConstantIsCheap(EVT MemVT,
+                                                         unsigned NumElem,
+                                                         unsigned AS) const {
+  return true;
+}
+
 bool AMDGPUTargetLowering::isTruncateFree(EVT Source, EVT Dest) const {
   // Truncate is just accessing a subregister.
   return Dest.bitsLT(Source) && (Dest.getSizeInBits() % 32 == 0);
 }
 
 bool AMDGPUTargetLowering::isTruncateFree(Type *Source, Type *Dest) const {
   // Truncate is just accessing a subregister.
   return Dest->getPrimitiveSizeInBits() < Source->getPrimitiveSizeInBits() &&

test/CodeGen/R600/merge-stores.ll

+; RUN: llc -march=amdgcn -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=GCN %s
+; RUN: llc -march=amdgcn -mcpu=bonaire -verify-machineinstrs < %s | FileCheck -check-prefix=SI -check-prefix=GCN %s
+
+; Run with devices with different unaligned load restrictions.
+
+; TODO: Vector element tests
+; TODO: Non-zero base offset for load and store combinations
+; TODO: Same base addrspacecasted
+
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i8:
+; GCN: buffer_store_byte
+; GCN: buffer_store_byte
+; GCN: s_endpgm
+define void @merge_global_store_2_constants_i8(i8 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i8, i8 addrspace(1)* %out, i32 1
+
+  store i8 123, i8 addrspace(1)* %out.gep.1
+  store i8 456, i8 addrspace(1)* %out, align 2
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i8_natural_align:
+; GCN: buffer_store_byte
+; GCN: buffer_store_byte
+; GCN: s_endpgm
+define void @merge_global_store_2_constants_i8_natural_align(i8 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i8, i8 addrspace(1)* %out, i32 1
+
+  store i8 123, i8 addrspace(1)* %out.gep.1
+  store i8 456, i8 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i16:
+; GCN: buffer_store_dword v
+define void @merge_global_store_2_constants_i16(i16 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i16, i16 addrspace(1)* %out, i32 1
+
+  store i16 123, i16 addrspace(1)* %out.gep.1
+  store i16 456, i16 addrspace(1)* %out, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_0_i16:
+; GCN: buffer_store_dword v
+define void @merge_global_store_2_constants_0_i16(i16 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i16, i16 addrspace(1)* %out, i32 1
+
+  store i16 0, i16 addrspace(1)* %out.gep.1
+  store i16 0, i16 addrspace(1)* %out, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i16_natural_align:
+; GCN: buffer_store_short
+; GCN: buffer_store_short
+; GCN: s_endpgm
+define void @merge_global_store_2_constants_i16_natural_align(i16 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i16, i16 addrspace(1)* %out, i32 1
+
+  store i16 123, i16 addrspace(1)* %out.gep.1
+  store i16 456, i16 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i32:
+; SI-DAG: s_movk_i32 [[SLO:s[0-9]+]], 0x1c8
+; SI-DAG: s_movk_i32 [[SHI:s[0-9]+]], 0x7b
+; SI-DAG: v_mov_b32_e32 v[[LO:[0-9]+]], [[SLO]]
+; SI-DAG: v_mov_b32_e32 v[[HI:[0-9]+]], [[SHI]]
+; GCN: buffer_store_dwordx2 v{{\[}}[[LO]]:[[HI]]{{\]}}
+define void @merge_global_store_2_constants_i32(i32 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+
+  store i32 123, i32 addrspace(1)* %out.gep.1
+  store i32 456, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i32_f32:
+; GCN: buffer_store_dwordx2
+define void @merge_global_store_2_constants_i32_f32(i32 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.1.bc = bitcast i32 addrspace(1)* %out.gep.1 to float addrspace(1)*
+  store float 1.0, float addrspace(1)* %out.gep.1.bc
+  store i32 456, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_f32_i32:
+; GCN: buffer_store_dwordx2
+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)*
+  store i32 123, i32 addrspace(1)* %out.gep.1.bc
+  store float 4.0, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_constants_i32:
+; GCN: buffer_store_dwordx4
+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
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+
+  store i32 123, i32 addrspace(1)* %out.gep.1
+  store i32 456, i32 addrspace(1)* %out.gep.2
+  store i32 333, i32 addrspace(1)* %out.gep.3
+  store i32 1234, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_constants_f32_order:
+; XGCN: buffer_store_dwordx4
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dwordx2 v
+define void @merge_global_store_4_constants_f32_order(float addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr float, float addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr float, float addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr float, float addrspace(1)* %out, i32 3
+
+  store float 8.0, float addrspace(1)* %out
+  store float 1.0, float addrspace(1)* %out.gep.1
+  store float 2.0, float addrspace(1)* %out.gep.2
+  store float 4.0, float addrspace(1)* %out.gep.3
+  ret void
+}
+
+; First store is out of order. Because of order of combines, the
+; consecutive store fails because only some of the stores have been
+; replaced with integer constant stores, and then won't merge because
+; the types are different.
+
+; GCN-LABEL: {{^}}merge_global_store_4_constants_f32:
+; XGCN: buffer_store_dwordx4
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+define void @merge_global_store_4_constants_f32(float addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr float, float addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr float, float addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr float, float addrspace(1)* %out, i32 3
+
+  store float 1.0, float addrspace(1)* %out.gep.1
+  store float 2.0, float addrspace(1)* %out.gep.2
+  store float 4.0, float addrspace(1)* %out.gep.3
+  store float 8.0, float addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_3_constants_i32:
+; SI-DAG: buffer_store_dwordx2
+; SI-DAG: buffer_store_dword
+; SI-NOT: buffer_store_dword
+; GCN: s_endpgm
+define void @merge_global_store_3_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
+
+  store i32 123, i32 addrspace(1)* %out.gep.1
+  store i32 456, i32 addrspace(1)* %out.gep.2
+  store i32 1234, i32 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_constants_i64:
+; XGCN: buffer_store_dwordx4
+; GCN: buffer_store_dwordx2
+; GCN: buffer_store_dwordx2
+define void @merge_global_store_2_constants_i64(i64 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i64, i64 addrspace(1)* %out, i64 1
+
+  store i64 123, i64 addrspace(1)* %out.gep.1
+  store i64 456, i64 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_constants_i64:
+; XGCN: buffer_store_dwordx4
+; XGCN: buffer_store_dwordx4
+
+; GCN: buffer_store_dwordx2
+; GCN: buffer_store_dwordx2
+; GCN: buffer_store_dwordx2
+; GCN: buffer_store_dwordx2
+define void @merge_global_store_4_constants_i64(i64 addrspace(1)* %out) #0 {
+  %out.gep.1 = getelementptr i64, i64 addrspace(1)* %out, i64 1
+  %out.gep.2 = getelementptr i64, i64 addrspace(1)* %out, i64 2
+  %out.gep.3 = getelementptr i64, i64 addrspace(1)* %out, i64 3
+
+  store i64 123, i64 addrspace(1)* %out.gep.1
+  store i64 456, i64 addrspace(1)* %out.gep.2
+  store i64 333, i64 addrspace(1)* %out.gep.3
+  store i64 1234, i64 addrspace(1)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_adjacent_loads_i32:
+; GCN: buffer_load_dwordx2 [[LOAD:v\[[0-9]+:[0-9]+\]]]
+; GCN: buffer_store_dwordx2 [[LOAD]]
+define void @merge_global_store_2_adjacent_loads_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+
+  %lo = load i32, i32 addrspace(1)* %in
+  %hi = load i32, i32 addrspace(1)* %in.gep.1
+
+  store i32 %lo, i32 addrspace(1)* %out
+  store i32 %hi, i32 addrspace(1)* %out.gep.1
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_adjacent_loads_i32_nonzero_base:
+; GCN: buffer_load_dwordx2 [[LOAD:v\[[0-9]+:[0-9]+\]]], s{{\[[0-9]+:[0-9]+\]}}, 0 offset:8
+; GCN: buffer_store_dwordx2 [[LOAD]], s{{\[[0-9]+:[0-9]+\]}}, 0 offset:8
+define void @merge_global_store_2_adjacent_loads_i32_nonzero_base(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %in.gep.0 = getelementptr i32, i32 addrspace(1)* %in, i32 2
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 3
+
+  %out.gep.0 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+  %lo = load i32, i32 addrspace(1)* %in.gep.0
+  %hi = load i32, i32 addrspace(1)* %in.gep.1
+
+  store i32 %lo, i32 addrspace(1)* %out.gep.0
+  store i32 %hi, i32 addrspace(1)* %out.gep.1
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_2_adjacent_loads_shuffle_i32:
+; GCN: buffer_load_dword v
+; GCN: buffer_load_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+define void @merge_global_store_2_adjacent_loads_shuffle_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+
+  %lo = load i32, i32 addrspace(1)* %in
+  %hi = load i32, i32 addrspace(1)* %in.gep.1
+
+  store i32 %hi, i32 addrspace(1)* %out
+  store i32 %lo, i32 addrspace(1)* %out.gep.1
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_i32:
+; GCN: buffer_load_dwordx4 [[LOAD:v\[[0-9]+:[0-9]+\]]]
+; GCN: buffer_store_dwordx4 [[LOAD]]
+define void @merge_global_store_4_adjacent_loads_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+  %in.gep.2 = getelementptr i32, i32 addrspace(1)* %in, i32 2
+  %in.gep.3 = getelementptr i32, i32 addrspace(1)* %in, i32 3
+
+  %x = load i32, i32 addrspace(1)* %in
+  %y = load i32, i32 addrspace(1)* %in.gep.1
+  %z = load i32, i32 addrspace(1)* %in.gep.2
+  %w = load i32, i32 addrspace(1)* %in.gep.3
+
+  store i32 %x, i32 addrspace(1)* %out
+  store i32 %y, i32 addrspace(1)* %out.gep.1
+  store i32 %z, i32 addrspace(1)* %out.gep.2
+  store i32 %w, i32 addrspace(1)* %out.gep.3
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_3_adjacent_loads_i32:
+; SI-DAG: buffer_load_dwordx2
+; SI-DAG: buffer_load_dword v
+; GCN: s_waitcnt
+; SI-DAG: buffer_store_dword v
+; SI-DAG: buffer_store_dwordx2 v
+; GCN: s_endpgm
+define void @merge_global_store_3_adjacent_loads_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+  %in.gep.2 = getelementptr i32, i32 addrspace(1)* %in, i32 2
+
+  %x = load i32, i32 addrspace(1)* %in
+  %y = load i32, i32 addrspace(1)* %in.gep.1
+  %z = load i32, i32 addrspace(1)* %in.gep.2
+
+  store i32 %x, i32 addrspace(1)* %out
+  store i32 %y, i32 addrspace(1)* %out.gep.1
+  store i32 %z, i32 addrspace(1)* %out.gep.2
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_f32:
+; GCN: buffer_load_dwordx4 [[LOAD:v\[[0-9]+:[0-9]+\]]]
+; GCN: buffer_store_dwordx4 [[LOAD]]
+define void @merge_global_store_4_adjacent_loads_f32(float addrspace(1)* %out, float addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr float, float addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr float, float addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr float, float addrspace(1)* %out, i32 3
+  %in.gep.1 = getelementptr float, float addrspace(1)* %in, i32 1
+  %in.gep.2 = getelementptr float, float addrspace(1)* %in, i32 2
+  %in.gep.3 = getelementptr float, float addrspace(1)* %in, i32 3
+
+  %x = load float, float addrspace(1)* %in
+  %y = load float, float addrspace(1)* %in.gep.1
+  %z = load float, float addrspace(1)* %in.gep.2
+  %w = load float, float addrspace(1)* %in.gep.3
+
+  store float %x, float addrspace(1)* %out
+  store float %y, float addrspace(1)* %out.gep.1
+  store float %z, float addrspace(1)* %out.gep.2
+  store float %w, float addrspace(1)* %out.gep.3
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_i32_nonzero_base:
+; GCN: buffer_load_dwordx4 [[LOAD:v\[[0-9]+:[0-9]+\]]], s{{\[[0-9]+:[0-9]+\]}}, 0 offset:44
+; GCN: buffer_store_dwordx4 [[LOAD]], s{{\[[0-9]+:[0-9]+\]}}, 0 offset:28
+define void @merge_global_store_4_adjacent_loads_i32_nonzero_base(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %in.gep.0 = getelementptr i32, i32 addrspace(1)* %in, i32 11
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 12
+  %in.gep.2 = getelementptr i32, i32 addrspace(1)* %in, i32 13
+  %in.gep.3 = getelementptr i32, i32 addrspace(1)* %in, i32 14
+  %out.gep.0 = getelementptr i32, i32 addrspace(1)* %out, i32 7
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 8
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 9
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 10
+
+  %x = load i32, i32 addrspace(1)* %in.gep.0
+  %y = load i32, i32 addrspace(1)* %in.gep.1
+  %z = load i32, i32 addrspace(1)* %in.gep.2
+  %w = load i32, i32 addrspace(1)* %in.gep.3
+
+  store i32 %x, i32 addrspace(1)* %out.gep.0
+  store i32 %y, i32 addrspace(1)* %out.gep.1
+  store i32 %z, i32 addrspace(1)* %out.gep.2
+  store i32 %w, i32 addrspace(1)* %out.gep.3
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_inverse_i32:
+; GCN: buffer_load_dwordx4 [[LOAD:v\[[0-9]+:[0-9]+\]]]
+; GCN: s_barrier
+; GCN: buffer_store_dwordx4 [[LOAD]]
+define void @merge_global_store_4_adjacent_loads_inverse_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+  %in.gep.2 = getelementptr i32, i32 addrspace(1)* %in, i32 2
+  %in.gep.3 = getelementptr i32, i32 addrspace(1)* %in, i32 3
+
+  %x = load i32, i32 addrspace(1)* %in
+  %y = load i32, i32 addrspace(1)* %in.gep.1
+  %z = load i32, i32 addrspace(1)* %in.gep.2
+  %w = load i32, i32 addrspace(1)* %in.gep.3
+
+  ; Make sure the barrier doesn't stop this
+  tail call void @llvm.AMDGPU.barrier.local() #1
+
+  store i32 %w, i32 addrspace(1)* %out.gep.3
+  store i32 %z, i32 addrspace(1)* %out.gep.2
+  store i32 %y, i32 addrspace(1)* %out.gep.1
+  store i32 %x, i32 addrspace(1)* %out
+
+  ret void
+}
+
+; TODO: Re-packing of loaded register required. Maybe an IR pass
+; should catch this?
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_shuffle_i32:
+; GCN: buffer_load_dword v
+; GCN: buffer_load_dword v
+; GCN: buffer_load_dword v
+; GCN: buffer_load_dword v
+; GCN: s_barrier
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+define void @merge_global_store_4_adjacent_loads_shuffle_i32(i32 addrspace(1)* %out, i32 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+  %in.gep.1 = getelementptr i32, i32 addrspace(1)* %in, i32 1
+  %in.gep.2 = getelementptr i32, i32 addrspace(1)* %in, i32 2
+  %in.gep.3 = getelementptr i32, i32 addrspace(1)* %in, i32 3
+
+  %x = load i32, i32 addrspace(1)* %in
+  %y = load i32, i32 addrspace(1)* %in.gep.1
+  %z = load i32, i32 addrspace(1)* %in.gep.2
+  %w = load i32, i32 addrspace(1)* %in.gep.3
+
+  ; Make sure the barrier doesn't stop this
+  tail call void @llvm.AMDGPU.barrier.local() #1
+
+  store i32 %w, i32 addrspace(1)* %out
+  store i32 %z, i32 addrspace(1)* %out.gep.1
+  store i32 %y, i32 addrspace(1)* %out.gep.2
+  store i32 %x, i32 addrspace(1)* %out.gep.3
+
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_i8:
+; GCN: buffer_load_dword [[LOAD:v[0-9]+]]
+; GCN: buffer_store_dword [[LOAD]]
+; GCN: s_endpgm
+define void @merge_global_store_4_adjacent_loads_i8(i8 addrspace(1)* %out, i8 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i8, i8 addrspace(1)* %out, i8 1
+  %out.gep.2 = getelementptr i8, i8 addrspace(1)* %out, i8 2
+  %out.gep.3 = getelementptr i8, i8 addrspace(1)* %out, i8 3
+  %in.gep.1 = getelementptr i8, i8 addrspace(1)* %in, i8 1
+  %in.gep.2 = getelementptr i8, i8 addrspace(1)* %in, i8 2
+  %in.gep.3 = getelementptr i8, i8 addrspace(1)* %in, i8 3
+
+  %x = load i8, i8 addrspace(1)* %in, align 4
+  %y = load i8, i8 addrspace(1)* %in.gep.1
+  %z = load i8, i8 addrspace(1)* %in.gep.2
+  %w = load i8, i8 addrspace(1)* %in.gep.3
+
+  store i8 %x, i8 addrspace(1)* %out, align 4
+  store i8 %y, i8 addrspace(1)* %out.gep.1
+  store i8 %z, i8 addrspace(1)* %out.gep.2
+  store i8 %w, i8 addrspace(1)* %out.gep.3
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_global_store_4_adjacent_loads_i8_natural_align:
+; GCN: buffer_load_ubyte
+; GCN: buffer_load_ubyte
+; GCN: buffer_load_ubyte
+; GCN: buffer_load_ubyte
+; GCN: buffer_store_byte
+; GCN: buffer_store_byte
+; GCN: buffer_store_byte
+; GCN: buffer_store_byte
+; GCN: s_endpgm
+define void @merge_global_store_4_adjacent_loads_i8_natural_align(i8 addrspace(1)* %out, i8 addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i8, i8 addrspace(1)* %out, i8 1
+  %out.gep.2 = getelementptr i8, i8 addrspace(1)* %out, i8 2
+  %out.gep.3 = getelementptr i8, i8 addrspace(1)* %out, i8 3
+  %in.gep.1 = getelementptr i8, i8 addrspace(1)* %in, i8 1
+  %in.gep.2 = getelementptr i8, i8 addrspace(1)* %in, i8 2
+  %in.gep.3 = getelementptr i8, i8 addrspace(1)* %in, i8 3
+
+  %x = load i8, i8 addrspace(1)* %in
+  %y = load i8, i8 addrspace(1)* %in.gep.1
+  %z = load i8, i8 addrspace(1)* %in.gep.2
+  %w = load i8, i8 addrspace(1)* %in.gep.3
+
+  store i8 %x, i8 addrspace(1)* %out
+  store i8 %y, i8 addrspace(1)* %out.gep.1
+  store i8 %z, i8 addrspace(1)* %out.gep.2
+  store i8 %w, i8 addrspace(1)* %out.gep.3
+  ret void
+}
+
+; This works once AA is enabled on the subtarget
+; GCN-LABEL: {{^}}merge_global_store_4_vector_elts_loads_v4i32:
+; GCN: buffer_load_dwordx4 [[LOAD:v\[[0-9]+:[0-9]+\]]]
+; XGCN: buffer_store_dwordx4 [[LOAD]]
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+; GCN: buffer_store_dword v
+define void @merge_global_store_4_vector_elts_loads_v4i32(i32 addrspace(1)* %out, <4 x i32> addrspace(1)* %in) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(1)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(1)* %out, i32 2
+  %out.gep.3 = getelementptr i32, i32 addrspace(1)* %out, i32 3
+  %vec = load <4 x i32>, <4 x i32> addrspace(1)* %in
+
+  %x = extractelement <4 x i32> %vec, i32 0
+  %y = extractelement <4 x i32> %vec, i32 1
+  %z = extractelement <4 x i32> %vec, i32 2
+  %w = extractelement <4 x i32> %vec, i32 3
+
+  store i32 %x, i32 addrspace(1)* %out
+  store i32 %y, i32 addrspace(1)* %out.gep.1
+  store i32 %z, i32 addrspace(1)* %out.gep.2
+  store i32 %w, i32 addrspace(1)* %out.gep.3
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_local_store_2_constants_i8:
+; GCN: ds_write_b8
+; GCN: ds_write_b8
+; GCN: s_endpgm
+define void @merge_local_store_2_constants_i8(i8 addrspace(3)* %out) #0 {
+  %out.gep.1 = getelementptr i8, i8 addrspace(3)* %out, i32 1
+
+  store i8 123, i8 addrspace(3)* %out.gep.1
+  store i8 456, i8 addrspace(3)* %out, align 2
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_local_store_2_constants_i32:
+; GCN-DAG: s_movk_i32 [[SLO:s[0-9]+]], 0x1c8
+; GCN-DAG: s_movk_i32 [[SHI:s[0-9]+]], 0x7b
+; GCN-DAG: v_mov_b32_e32 v[[LO:[0-9]+]], [[SLO]]
+; GCN-DAG: v_mov_b32_e32 v[[HI:[0-9]+]], [[SHI]]
+; GCN: ds_write2_b32 v{{[0-9]+}}, v[[LO]], v[[HI]] offset1:1{{$}}
+define void @merge_local_store_2_constants_i32(i32 addrspace(3)* %out) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(3)* %out, i32 1
+
+  store i32 123, i32 addrspace(3)* %out.gep.1
+  store i32 456, i32 addrspace(3)* %out
+  ret void
+}
+
+; GCN-LABEL: {{^}}merge_local_store_4_constants_i32:
+; GCN: ds_write_b32
+; GCN: ds_write_b32
+; GCN: ds_write_b32
+; GCN: ds_write_b32
+define void @merge_local_store_4_constants_i32(i32 addrspace(3)* %out) #0 {
+  %out.gep.1 = getelementptr i32, i32 addrspace(3)* %out, i32 1
+  %out.gep.2 = getelementptr i32, i32 addrspace(3)* %out, i32 2
+  %out.gep.3 = getelementptr i32, i32 addrspace(3)* %out, i32 3
+
+  store i32 123, i32 addrspace(3)* %out.gep.1
+  store i32 456, i32 addrspace(3)* %out.gep.2
+  store i32 333, i32 addrspace(3)* %out.gep.3
+  store i32 1234, i32 addrspace(3)* %out
+  ret void
+}
+
+declare void @llvm.AMDGPU.barrier.local() #1
+
+attributes #0 = { nounwind }
+attributes #1 = { noduplicate nounwind }

test/CodeGen/R600/store.ll

 ; EG: STORE_RAW
 ; EG: STORE_RAW
 ; EG: STORE_RAW
 ; EG: STORE_RAW
 ; CM: STORE_DWORD
 ; CM: STORE_DWORD
 ; CM: STORE_DWORD
 ; CM: STORE_DWORD
-; SI: buffer_store_dwordx2
-; SI: buffer_store_dwordx2
+; SI: buffer_store_dwordx4
 define void @i128-const-store(i32 addrspace(1)* %out) {
 entry:
   store i32 1, i32 addrspace(1)* %out, align 4
   %arrayidx2 = getelementptr inbounds i32, i32 addrspace(1)* %out, i64 1
   store i32 1, i32 addrspace(1)* %arrayidx2, align 4
   %arrayidx4 = getelementptr inbounds i32, i32 addrspace(1)* %out, i64 2
   store i32 2, i32 addrspace(1)* %arrayidx4, align 4
   %arrayidx6 = getelementptr inbounds i32, i32 addrspace(1)* %out, i64 3
   store i32 2, i32 addrspace(1)* %arrayidx6, align 4
   ret void
 }