[AMDGPU] Combine add and adde, sub and sube

[rampitec]

Summary

If one of the arguments of adde/sube is zero we can fold another add/sub into it.

[rampitec]

Fixed operands in performAddCombine case.

[vpykhtin]

LGTM.

[rampitec]

Updated to follow parent revision using ADDCARRY/SUBCARRY.

llvm/trunk/lib/Target/AMDGPU/SIISelLowering.h

class SITargetLowering final : public AMDGPUTargetLowering {
   SDValue performMinMaxCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performFMed3Combine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performCvtPkRTZCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performExtractVectorEltCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
   unsigned getFusedOpcode(const SelectionDAG &DAG,
                           const SDNode *N0, const SDNode *N1) const;
   SDValue performAddCombine(SDNode *N, DAGCombinerInfo &DCI) const;
+  SDValue performAddCarrySubCarryCombine(SDNode *N, DAGCombinerInfo &DCI) const;
+  SDValue performSubCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performFAddCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performFSubCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performSetCCCombine(SDNode *N, DAGCombinerInfo &DCI) const;
   SDValue performCvtF32UByteNCombine(SDNode *N, DAGCombinerInfo &DCI) const;
 
   bool isLegalFlatAddressingMode(const AddrMode &AM) const;
   bool isLegalMUBUFAddressingMode(const AddrMode &AM) const;
 

llvm/trunk/lib/Target/AMDGPU/SIISelLowering.cpp

if (Subtarget->hasVOP3PInsts()) {
     setOperationAction(ISD::SELECT, MVT::v2f16, Custom);
   }
 
   for (MVT VT : { MVT::v4i16, MVT::v4f16, MVT::v2i8, MVT::v4i8, MVT::v8i8 }) {
     setOperationAction(ISD::SELECT, VT, Custom);
   }
 
   setTargetDAGCombine(ISD::ADD);
+  setTargetDAGCombine(ISD::ADDCARRY);
+  setTargetDAGCombine(ISD::SUB);
+  setTargetDAGCombine(ISD::SUBCARRY);
   setTargetDAGCombine(ISD::FADD);
   setTargetDAGCombine(ISD::FSUB);
   setTargetDAGCombine(ISD::FMINNUM);
   setTargetDAGCombine(ISD::FMAXNUM);
   setTargetDAGCombine(ISD::SMIN);
   setTargetDAGCombine(ISD::SMAX);
   setTargetDAGCombine(ISD::UMIN);
   setTargetDAGCombine(ISD::UMAX);
SDValue SITargetLowering::performAddCombine(SDNode *N,
   SDLoc SL(N);
   SDValue LHS = N->getOperand(0);
   SDValue RHS = N->getOperand(1);
 
   // add x, zext (setcc) => addcarry x, 0, setcc
   // add x, sext (setcc) => subcarry x, 0, setcc
   unsigned Opc = LHS.getOpcode();
   if (Opc == ISD::ZERO_EXTEND || Opc == ISD::SIGN_EXTEND ||
-      Opc == ISD::ANY_EXTEND)
+      Opc == ISD::ANY_EXTEND || Opc == ISD::ADDCARRY)
     std::swap(RHS, LHS);
 
   Opc = RHS.getOpcode();
-  if (Opc == ISD::ZERO_EXTEND || Opc == ISD::SIGN_EXTEND ||
-      Opc == ISD::ANY_EXTEND) {
+  switch (Opc) {
+  default: break;
+  case ISD::ZERO_EXTEND:
+  case ISD::SIGN_EXTEND:
+  case ISD::ANY_EXTEND: {
     auto Cond = RHS.getOperand(0);
-    if (Cond.getOpcode() == ISD::SETCC) {
-      SDVTList VTList = DAG.getVTList(MVT::i32, MVT::i1);
-      SDValue Args[] = { LHS, DAG.getConstant(0, SL, MVT::i32), Cond };
-      Opc = (Opc == ISD::SIGN_EXTEND) ? ISD::SUBCARRY : ISD::ADDCARRY;
-      return DAG.getNode(Opc, SL, VTList, Args);
-    }
+    if (Cond.getOpcode() != ISD::SETCC) break;
+  case ISD::ADDCARRY: {
+    // add x, (addcarry y, 0, cc) => addcarry x, y, cc
+    auto C = dyn_cast<ConstantSDNode>(RHS.getOperand(1));
+    if (!C || C->getZExtValue() != 0) break;
+    SDValue Args[] = { LHS, RHS.getOperand(0), RHS.getOperand(2) };
+    return DAG.getNode(ISD::ADDCARRY, SDLoc(N), RHS->getVTList(), Args);
+  }
+  }
+  return SDValue();
+}
+
+SDValue SITargetLowering::performSubCombine(SDNode *N,
+                                            DAGCombinerInfo &DCI) const {
+  SelectionDAG &DAG = DCI.DAG;
+  EVT VT = N->getValueType(0);
+
+  if (VT != MVT::i32)
+    return SDValue();
+
+  SDLoc SL(N);
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+
+  unsigned Opc = LHS.getOpcode();
+  if (Opc != ISD::SUBCARRY)
+    std::swap(RHS, LHS);
+
+  if (LHS.getOpcode() == ISD::SUBCARRY) {
+    // sub (subcarry x, 0, cc), y => subcarry x, y, cc
+    auto C = dyn_cast<ConstantSDNode>(LHS.getOperand(1));
+    if (!C || C->getZExtValue() != 0)
+      return SDValue();
+    SDValue Args[] = { LHS.getOperand(0), RHS, LHS.getOperand(2) };
+    return DAG.getNode(ISD::SUBCARRY, SDLoc(N), LHS->getVTList(), Args);
+  }
+  return SDValue();
+}
+
+SDValue SITargetLowering::performAddCarrySubCarryCombine(SDNode *N,
+  DAGCombinerInfo &DCI) const {
+
+  if (N->getValueType(0) != MVT::i32)
+    return SDValue();
+
+  auto C = dyn_cast<ConstantSDNode>(N->getOperand(1));
+  if (!C || C->getZExtValue() != 0)
+    return SDValue();
+
+  SelectionDAG &DAG = DCI.DAG;
+  SDValue LHS = N->getOperand(0);
+
+  // addcarry (add x, y), 0, cc => addcarry x, y, cc
+  // subcarry (sub x, y), 0, cc => subcarry x, y, cc
+  unsigned LHSOpc = LHS.getOpcode();
+  unsigned Opc = N->getOpcode();
+  if ((LHSOpc == ISD::ADD && Opc == ISD::ADDCARRY) ||
+      (LHSOpc == ISD::SUB && Opc == ISD::SUBCARRY)) {
+    SDValue Args[] = { LHS.getOperand(0), LHS.getOperand(1), N->getOperand(2) };
+    return DAG.getNode(Opc, SDLoc(N), N->getVTList(), Args);
   }
   return SDValue();
 }
 
 SDValue SITargetLowering::performFAddCombine(SDNode *N,
                                              DAGCombinerInfo &DCI) const {
   if (DCI.getDAGCombineLevel() < AfterLegalizeDAG)
     return SDValue();

 
 SDValue SITargetLowering::PerformDAGCombine(SDNode *N,
                                             DAGCombinerInfo &DCI) const {
   switch (N->getOpcode()) {
   default:
     return AMDGPUTargetLowering::PerformDAGCombine(N, DCI);
   case ISD::ADD:
     return performAddCombine(N, DCI);
+  case ISD::SUB:
+    return performSubCombine(N, DCI);
+  case ISD::ADDCARRY:
+  case ISD::SUBCARRY:
+    return performAddCarrySubCarryCombine(N, DCI);
   case ISD::FADD:
     return performFAddCombine(N, DCI);
   case ISD::FSUB:
     return performFSubCombine(N, DCI);
   case ISD::SETCC:
     return performSetCCCombine(N, DCI);
   case ISD::FMAXNUM:
   case ISD::FMINNUM:

llvm/trunk/test/CodeGen/AMDGPU/combine-cond-add-sub.ll

bb:
   %v = load i32, i32 addrspace(1)* %gep, align 4
   %cmp = icmp ugt i32 %x, %y
   %ext = sext i1 %cmp to i32
   %add = add i32 %v, %ext
   store i32 %add, i32 addrspace(1)* %gep, align 4
   ret void
 }
 
+; GCN-LABEL: {{^}}add_adde:
+; GCN: v_cmp_gt_u32_e{{32|64}} [[CC:[^,]+]], v{{[0-9]+}}, v{{[0-9]+}}
+; GCN: v_addc_u32_e{{32|64}} v{{[0-9]+}}, {{[^,]+}}, v{{[0-9]+}}, v{{[0-9]+}}, [[CC]]
+; GCN-NOT: v_cndmask
+; GCN-NOT: v_add
+
+define amdgpu_kernel void @add_adde(i32 addrspace(1)* nocapture %arg, i32 %a) {
+bb:
+  %x = tail call i32 @llvm.amdgcn.workitem.id.x()
+  %y = tail call i32 @llvm.amdgcn.workitem.id.y()
+  %gep = getelementptr inbounds i32, i32 addrspace(1)* %arg, i32 %x
+  %v = load i32, i32 addrspace(1)* %gep, align 4
+  %cmp = icmp ugt i32 %x, %y
+  %ext = zext i1 %cmp to i32
+  %adde = add i32 %v, %ext
+  %add2 = add i32 %adde, %a
+  store i32 %add2, i32 addrspace(1)* %gep, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}adde_add:
+; GCN: v_cmp_gt_u32_e{{32|64}} [[CC:[^,]+]], v{{[0-9]+}}, v{{[0-9]+}}
+; GCN: v_addc_u32_e{{32|64}} v{{[0-9]+}}, {{[^,]+}}, v{{[0-9]+}}, v{{[0-9]+}}, [[CC]]
+; GCN-NOT: v_cndmask
+; GCN-NOT: v_add
+
+define amdgpu_kernel void @adde_add(i32 addrspace(1)* nocapture %arg, i32 %a) {
+bb:
+  %x = tail call i32 @llvm.amdgcn.workitem.id.x()
+  %y = tail call i32 @llvm.amdgcn.workitem.id.y()
+  %gep = getelementptr inbounds i32, i32 addrspace(1)* %arg, i32 %x
+  %v = load i32, i32 addrspace(1)* %gep, align 4
+  %cmp = icmp ugt i32 %x, %y
+  %ext = zext i1 %cmp to i32
+  %add = add i32 %v, %a
+  %adde = add i32 %add, %ext
+  store i32 %adde, i32 addrspace(1)* %gep, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}sub_sube:
+; GCN: v_cmp_gt_u32_e{{32|64}} [[CC:[^,]+]], v{{[0-9]+}}, v{{[0-9]+}}
+; GCN: v_subb_u32_e{{32|64}} v{{[0-9]+}}, {{[^,]+}}, v{{[0-9]+}}, v{{[0-9]+}}, [[CC]]
+; GCN-NOT: v_cndmask
+; GCN-NOT: v_sub
+
+define amdgpu_kernel void @sub_sube(i32 addrspace(1)* nocapture %arg, i32 %a) {
+bb:
+  %x = tail call i32 @llvm.amdgcn.workitem.id.x()
+  %y = tail call i32 @llvm.amdgcn.workitem.id.y()
+  %gep = getelementptr inbounds i32, i32 addrspace(1)* %arg, i32 %x
+  %v = load i32, i32 addrspace(1)* %gep, align 4
+  %cmp = icmp ugt i32 %x, %y
+  %ext = sext i1 %cmp to i32
+  %adde = add i32 %v, %ext
+  %sub = sub i32 %adde, %a
+  store i32 %sub, i32 addrspace(1)* %gep, align 4
+  ret void
+}
+
+; GCN-LABEL: {{^}}sube_sub:
+; GCN: v_cmp_gt_u32_e{{32|64}} [[CC:[^,]+]], v{{[0-9]+}}, v{{[0-9]+}}
+; GCN: v_subb_u32_e{{32|64}} v{{[0-9]+}}, {{[^,]+}}, v{{[0-9]+}}, v{{[0-9]+}}, [[CC]]
+; GCN-NOT: v_cndmask
+; GCN-NOT: v_sub
+
+define amdgpu_kernel void @sube_sub(i32 addrspace(1)* nocapture %arg, i32 %a) {
+bb:
+  %x = tail call i32 @llvm.amdgcn.workitem.id.x()
+  %y = tail call i32 @llvm.amdgcn.workitem.id.y()
+  %gep = getelementptr inbounds i32, i32 addrspace(1)* %arg, i32 %x
+  %v = load i32, i32 addrspace(1)* %gep, align 4
+  %cmp = icmp ugt i32 %x, %y
+  %ext = sext i1 %cmp to i32
+  %sub = sub i32 %v, %a
+  %adde = add i32 %sub, %ext
+  store i32 %adde, i32 addrspace(1)* %gep, align 4
+  ret void
+}
+
 declare i32 @llvm.amdgcn.workitem.id.x() #0
 
 declare i32 @llvm.amdgcn.workitem.id.y() #0
 
 attributes #0 = { nounwind readnone speculatable }