R600/SI: Fix offset folding in some cases with shifted pointers.

[arsenm]

Summary

Ordinarily (shl (add x, c1), c2) -> (add (shl x, c2), c1 << c2)
is only done if the add has one use. If the resulting constant
add can be folded into an addressing mode, force this to happen
for the pointer operand.

This ends up happening a lot because of how LDS objects are allocated.
Since the globals are allocated next to each other, acessing the first
element of the second object is directly indexed by a shifted pointer.

Depends on:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20140728/229124.html

[arsenm]

Ping

[arsenm]

r215739. I XFAILed the test since it also tests the other generic DAG combiner patch to do this with only 1 use

lib/Target/R600/SIISelLowering.h

 
   static SDValue performUCharToFloatCombine(SDNode *N,
                                             DAGCombinerInfo &DCI);
+  static SDValue performSHLPtrCombine(SDNode *N,
+                                      DAGCombinerInfo &DCI);
 
 public:
   SITargetLowering(TargetMachine &tm);

lib/Target/R600/SIISelLowering.cpp

 
   setTargetDAGCombine(ISD::UINT_TO_FP);
 
+  // All memory operations. Some folding on the pointer operand is done to help
+  // matching the constant offsets in the addressing modes.
+  setTargetDAGCombine(ISD::LOAD);
+  setTargetDAGCombine(ISD::STORE);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD);
+  setTargetDAGCombine(ISD::ATOMIC_STORE);
+  setTargetDAGCombine(ISD::ATOMIC_CMP_SWAP);
+  setTargetDAGCombine(ISD::ATOMIC_CMP_SWAP_WITH_SUCCESS);
+  setTargetDAGCombine(ISD::ATOMIC_SWAP);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_ADD);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_SUB);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_AND);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_OR);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_XOR);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_NAND);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_MIN);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_MAX);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_UMIN);
+  setTargetDAGCombine(ISD::ATOMIC_LOAD_UMAX);
+
   setSchedulingPreference(Sched::RegPressure);
 }
 

   return SDValue();
 }
 
+// (shl (add x, c1), c2) -> add (shl x, c2), (shl c1, c2)
+
+// This is a variant of
+// (mul (add x, c1), c2) -> add (mul x, c2), (mul c1, c2),
+//
+// The normal DAG combiner will do this, but only if the add has one use since
+// that would increase the number of instructions.
+//
+// This prevents us from seeing a constant offset that can be folded into a
+// memory instruction's addressing mode. If we know the resulting add offset of
+// a pointer can be folded into an addressing offset, we can replace the pointer
+// operand with the add of new constant offset. This eliminates one of the uses,
+// and may allow the remaining use to also be simplified.
+//
+SDValue SITargetLowering::performSHLPtrCombine(SDNode *N,
+                                               DAGCombinerInfo &DCI) {
+  SDValue N0 = N->getOperand(0);
+  SDValue N1 = N->getOperand(1);
+
+  if (N0.getOpcode() != ISD::ADD)
+    return SDValue();
+
+  const ConstantSDNode *CN1 = dyn_cast<ConstantSDNode>(N1);
+  if (!CN1)
+    return SDValue();
+
+  const ConstantSDNode *CAdd = dyn_cast<ConstantSDNode>(N0.getOperand(1));
+  if (!CAdd)
+    return SDValue();
+
+  // XXX: Do we need to check the right number of bits depending on the address
+  // space. I think they are all 16-bit offsets.
+
+  // If the resulting offset is > 16 bits, we can't fold it into the addressing
+  // mode offset.
+  APInt Offset = CAdd->getAPIntValue() << CN1->getAPIntValue();
+  if (!Offset.isIntN(16))
+    return SDValue();
+
+  SelectionDAG &DAG = DCI.DAG;
+  SDLoc SL(N);
+  EVT VT = N->getValueType(0);
+
+  SDValue ShlX = DAG.getNode(ISD::SHL, SL, VT, N0.getOperand(0), N1);
+  SDValue COffset = DAG.getConstant(Offset, MVT::i32);
+
+  return DAG.getNode(ISD::ADD, SL, VT, ShlX, COffset);
+}
+
 SDValue SITargetLowering::PerformDAGCombine(SDNode *N,
                                             DAGCombinerInfo &DCI) const {
   SelectionDAG &DAG = DCI.DAG;

   case ISD::UINT_TO_FP: {
     return performUCharToFloatCombine(N, DCI);
   }
+  case ISD::LOAD:
+  case ISD::STORE:
+  case ISD::ATOMIC_LOAD:
+  case ISD::ATOMIC_STORE:
+  case ISD::ATOMIC_CMP_SWAP:
+  case ISD::ATOMIC_CMP_SWAP_WITH_SUCCESS:
+  case ISD::ATOMIC_SWAP:
+  case ISD::ATOMIC_LOAD_ADD:
+  case ISD::ATOMIC_LOAD_SUB:
+  case ISD::ATOMIC_LOAD_AND:
+  case ISD::ATOMIC_LOAD_OR:
+  case ISD::ATOMIC_LOAD_XOR:
+  case ISD::ATOMIC_LOAD_NAND:
+  case ISD::ATOMIC_LOAD_MIN:
+  case ISD::ATOMIC_LOAD_MAX:
+  case ISD::ATOMIC_LOAD_UMIN:
+  case ISD::ATOMIC_LOAD_UMAX: { // TODO: Target mem intrinsics.
+    if (DCI.isBeforeLegalize())
+      break;
+
+    MemSDNode *MemNode = cast<MemSDNode>(N);
+    SDValue Ptr = MemNode->getBasePtr();
+
+    if (Ptr.getOpcode() == ISD::SHL &&
+        MemNode->getAddressSpace() != AMDGPUAS::PRIVATE_ADDRESS) {
+      SDValue NewPtr = performSHLPtrCombine(Ptr.getNode(), DCI);
+      if (NewPtr) {
+        SmallVector<SDValue, 8> NewOps;
+        for (unsigned I = 0, N = MemNode->getNumOperands(); I != N; ++I)
+          NewOps.push_back(MemNode->getOperand(I));
+
+        NewOps[N->getOpcode() == ISD::STORE ? 2 : 1] = NewPtr;
+        return SDValue(DAG.UpdateNodeOperands(MemNode, NewOps), 0);
+      }
+    }
+    break;
+  }
   }
-
   return AMDGPUTargetLowering::PerformDAGCombine(N, DCI);
 }
 

test/CodeGen/R600/shl_add_ptr.ll

+; RUN: llc -march=r600 -mcpu=SI -verify-machineinstrs < %s | FileCheck -check-prefix=SI %s
+
+; Test that doing a shift of a pointer with a constant add will be
+; folded into the constant offset addressing mode even if the add has
+; multiple uses. This is relevant to accessing 2 separate, adjacent
+; LDS globals.
+
+
+declare i32 @llvm.r600.read.tidig.x() #1
+
+@lds0 = addrspace(3) global [512 x float] zeroinitializer, align 4
+@lds1 = addrspace(3) global [512 x float] zeroinitializer, align 4
+
+
+; Make sure the (add tid, 2) << 2 gets folded into the ds's offset as (tid << 2) + 8
+
+; SI-LABEL: @load_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_READ_B32 {{v[0-9]+}}, [[PTR]], 0x8, [M0]
+; SI: S_ENDPGM
+define void @load_shl_base_lds_0(float addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x float] addrspace(3)* @lds0, i32 0, i32 %idx.0
+  %val0 = load float addrspace(3)* %arrayidx0, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  store float %val0, float addrspace(1)* %out
+  ret void
+}
+
+; Make sure once the first use is folded into the addressing mode, the
+; remaining add use goes through the normal shl + add constant fold.
+
+; SI-LABEL: @load_shl_base_lds_1
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_READ_B32 [[RESULT:v[0-9]+]], [[PTR]], 0x8, [M0]
+; SI: V_ADD_I32_e32 [[ADDUSE:v[0-9]+]], 8, v{{[0-9]+}}
+; SI-DAG: BUFFER_STORE_DWORD [[RESULT]]
+; SI-DAG: BUFFER_STORE_DWORD [[ADDUSE]]
+; SI: S_ENDPGM
+define void @load_shl_base_lds_1(float addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x float] addrspace(3)* @lds0, i32 0, i32 %idx.0
+  %val0 = load float addrspace(3)* %arrayidx0, align 4
+  %shl_add_use = shl i32 %idx.0, 2
+  store i32 %shl_add_use, i32 addrspace(1)* %add_use, align 4
+  store float %val0, float addrspace(1)* %out
+  ret void
+}
+
+; The two globals are placed adjacent in memory, so the same base
+; pointer can be used with an offset into the second one.
+
+; SI-LABEL: @load_shl_base_lds_2
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI-NEXT: DS_READ_B32 {{v[0-9]+}}, [[PTR]], 0x100, [M0]
+; SI-NEXT: DS_READ_B32 {{v[0-9]+}}, [[PTR]], 0x900, [M0]
+; SI: S_ENDPGM
+define void @load_shl_base_lds_2(float addrspace(1)* %out) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 64
+  %arrayidx0 = getelementptr inbounds [512 x float] addrspace(3)* @lds0, i32 0, i32 %idx.0
+  %val0 = load float addrspace(3)* %arrayidx0, align 4
+  %arrayidx1 = getelementptr inbounds [512 x float] addrspace(3)* @lds1, i32 0, i32 %idx.0
+  %val1 = load float addrspace(3)* %arrayidx1, align 4
+  %sum = fadd float %val0, %val1
+  store float %sum, float addrspace(1)* %out, align 4
+  ret void
+}
+
+; SI-LABEL: @store_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_WRITE_B32 [[PTR]], {{v[0-9]+}}, 0x8 [M0]
+; SI: S_ENDPGM
+define void @store_shl_base_lds_0(float addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x float] addrspace(3)* @lds0, i32 0, i32 %idx.0
+  store float 1.0, float addrspace(3)* %arrayidx0, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+
+; --------------------------------------------------------------------------------
+; Atomics.
+
+@lds2 = addrspace(3) global [512 x i32] zeroinitializer, align 4
+
+; define void @atomic_load_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+;   %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+;   %idx.0 = add nsw i32 %tid.x, 2
+;   %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+;   %val = load atomic i32 addrspace(3)* %arrayidx0 seq_cst, align 4
+;   store i32 %val, i32 addrspace(1)* %out, align 4
+;   store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+;   ret void
+; }
+
+
+; SI-LABEL: @atomic_cmpxchg_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_CMPST_RTN_B32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_cmpxchg_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use, i32 %swap) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %pair = cmpxchg i32 addrspace(3)* %arrayidx0, i32 7, i32 %swap seq_cst monotonic
+  %result = extractvalue { i32, i1 } %pair, 0
+  store i32 %result, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_swap_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_WRXCHG_RTN_B32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_swap_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw xchg i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_add_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_ADD_RTN_U32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_add_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw add i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_sub_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_SUB_RTN_U32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_sub_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw sub i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_and_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_AND_RTN_B32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_and_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw and i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_or_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_OR_RTN_B32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_or_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw or i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_xor_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_XOR_RTN_B32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_xor_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw xor i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; define void @atomic_nand_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+;   %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+;   %idx.0 = add nsw i32 %tid.x, 2
+;   %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+;   %val = atomicrmw nand i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+;   store i32 %val, i32 addrspace(1)* %out, align 4
+;   store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+;   ret void
+; }
+
+; SI-LABEL: @atomic_min_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_MIN_RTN_I32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_min_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw min i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_max_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_MAX_RTN_I32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_max_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw max i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_umin_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_MIN_RTN_U32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_umin_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw umin i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+; SI-LABEL: @atomic_umax_shl_base_lds_0
+; SI: V_LSHLREV_B32_e32 [[PTR:v[0-9]+]], 2, {{v[0-9]+}}
+; SI: DS_MAX_RTN_U32 {{v[0-9]+}}, [[PTR]], {{v[0-9]+}}, 0x8
+; SI: S_ENDPGM
+define void @atomic_umax_shl_base_lds_0(i32 addrspace(1)* %out, i32 addrspace(1)* %add_use) #0 {
+  %tid.x = tail call i32 @llvm.r600.read.tidig.x() #1
+  %idx.0 = add nsw i32 %tid.x, 2
+  %arrayidx0 = getelementptr inbounds [512 x i32] addrspace(3)* @lds2, i32 0, i32 %idx.0
+  %val = atomicrmw umax i32 addrspace(3)* %arrayidx0, i32 3 seq_cst
+  store i32 %val, i32 addrspace(1)* %out, align 4
+  store i32 %idx.0, i32 addrspace(1)* %add_use, align 4
+  ret void
+}
+
+attributes #0 = { nounwind }
+attributes #1 = { nounwind readnone }