[Target] Use isNullConstant (NFC)

Author: kazutakahirata

llvm/lib/Target/AMDGPU/AMDGPUISelDAGToDAG.cpp

@@ -1579,13 +1579,9 @@ bool AMDGPUDAGToDAGISel::SelectMUBUFOffset(SDValue Addr, SDValue &SRsrc,
 
 bool AMDGPUDAGToDAGISel::SelectBUFSOffset(SDValue ByteOffsetNode,
                                           SDValue &SOffset) const {
-  if (Subtarget->hasRestrictedSOffset()) {
-    if (auto SOffsetConst = dyn_cast<ConstantSDNode>(ByteOffsetNode)) {
-      if (SOffsetConst->isZero()) {
-        SOffset = CurDAG->getRegister(AMDGPU::SGPR_NULL, MVT::i32);
-        return true;
-      }
-    }
+  if (Subtarget->hasRestrictedSOffset() && isNullConstant(ByteOffsetNode)) {
+    SOffset = CurDAG->getRegister(AMDGPU::SGPR_NULL, MVT::i32);
+    return true;
   }
 
   SOffset = ByteOffsetNode;

llvm/lib/Target/AMDGPU/SIISelLowering.cpp

@@ -8181,12 +8181,8 @@ SDValue SITargetLowering::LowerINTRINSIC_WO_CHAIN(SDValue Op,
 // SGPR_NULL to avoid generating an extra s_mov with zero.
 static SDValue selectSOffset(SDValue SOffset, SelectionDAG &DAG,
                              const GCNSubtarget *Subtarget) {
-  if (Subtarget->hasRestrictedSOffset())
-    if (auto SOffsetConst = dyn_cast<ConstantSDNode>(SOffset)) {
-      if (SOffsetConst->isZero()) {
-        return DAG.getRegister(AMDGPU::SGPR_NULL, MVT::i32);
-      }
-    }
+  if (Subtarget->hasRestrictedSOffset() && isNullConstant(SOffset))
+    return DAG.getRegister(AMDGPU::SGPR_NULL, MVT::i32);
   return SOffset;
 }
 

llvm/lib/Target/MSP430/MSP430ISelLowering.cpp

@@ -1149,15 +1149,10 @@ SDValue MSP430TargetLowering::LowerSETCC(SDValue Op, SelectionDAG &DAG) const {
   // but they are different from CMP.
   // FIXME: since we're doing a post-processing, use a pseudoinstr here, so
   // lowering & isel wouldn't diverge.
-  bool andCC = false;
-  if (ConstantSDNode *RHSC = dyn_cast<ConstantSDNode>(RHS)) {
-    if (RHSC->isZero() && LHS.hasOneUse() &&
-        (LHS.getOpcode() == ISD::AND ||
-         (LHS.getOpcode() == ISD::TRUNCATE &&
-          LHS.getOperand(0).getOpcode() == ISD::AND))) {
-      andCC = true;
-    }
-  }
+  bool andCC = isNullConstant(RHS) && LHS.hasOneUse() &&
+               (LHS.getOpcode() == ISD::AND ||
+                (LHS.getOpcode() == ISD::TRUNCATE &&
+                 LHS.getOperand(0).getOpcode() == ISD::AND));
   ISD::CondCode CC = cast<CondCodeSDNode>(Op.getOperand(2))->get();
   SDValue TargetCC;
   SDValue Flag = EmitCMP(LHS, RHS, TargetCC, CC, dl, DAG);