[AArch64][ISel] NFC: Change streaming mode only through 'changeStreamingMode'

This simplifies the code and unifies code-paths to use a single function
for emitting streaming-mode changes.

Author: sdesmalen-arm

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -6627,12 +6627,10 @@ SDValue AArch64TargetLowering::LowerFormalArguments(
   // make sure it is Glued to the last CopyFromReg value.
   if (IsLocallyStreaming) {
     const AArch64RegisterInfo *TRI = Subtarget->getRegisterInfo();
-    Chain = DAG.getNode(
-        AArch64ISD::SMSTART, DL, DAG.getVTList(MVT::Other, MVT::Glue),
-        {DAG.getRoot(),
-          DAG.getTargetConstant((int32_t)AArch64SVCR::SVCRSM, DL, MVT::i32),
-         DAG.getConstant(0, DL, MVT::i64), DAG.getConstant(1, DL, MVT::i64),
-         DAG.getRegisterMask(TRI->getSMStartStopCallPreservedMask()), Glue});
+    Chain =
+        changeStreamingMode(DAG, DL, /*Enable*/ true, DAG.getRoot(), Glue,
+                            DAG.getConstant(0, DL, MVT::i64), /*Entry*/ true);
+
     // Ensure that the SMSTART happens after the CopyWithChain such that its
     // chain result is used.
     for (unsigned I=0; I<InVals.size(); ++I) {
@@ -7884,11 +7882,9 @@ AArch64TargetLowering::LowerReturn(SDValue Chain, CallingConv::ID CallConv,
   // Emit SMSTOP before returning from a locally streaming function
   SMEAttrs FuncAttrs(MF.getFunction());
   if (FuncAttrs.hasStreamingBody() && !FuncAttrs.hasStreamingInterface()) {
-    Chain = DAG.getNode(
-        AArch64ISD::SMSTOP, DL, DAG.getVTList(MVT::Other, MVT::Glue), Chain,
-        DAG.getTargetConstant((int32_t)AArch64SVCR::SVCRSM, DL, MVT::i32),
-        DAG.getConstant(1, DL, MVT::i64), DAG.getConstant(0, DL, MVT::i64),
-        DAG.getRegisterMask(TRI->getSMStartStopCallPreservedMask()));
+    Chain = changeStreamingMode(
+        DAG, DL, /*Enable*/ false, Chain, /*Glue*/ SDValue(),
+        DAG.getConstant(1, DL, MVT::i64), /*Entry*/ true);
     Glue = Chain.getValue(1);
   }