[AMDGPU] SelectionDAG divergence tracking. Reviewer comments addressed.

Author: alex-t

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -2329,7 +2329,7 @@ SDValue SelectionDAG::getRegister(Register Reg, EVT VT) {
 
   auto *N = newSDNode<RegisterSDNode>(Reg, VTs);
   N->SDNodeBits.IsDivergent =
-      DivergentTarget ? TLI->isSDNodeSourceOfDivergence(N, FLI, UA) : false;
+      DivergentTarget && TLI->isSDNodeSourceOfDivergence(N, FLI, UA);
   CSEMap.InsertNode(N, IP);
   InsertNode(N);
   return SDValue(N, 0);
@@ -10931,8 +10931,7 @@ SDNode *SelectionDAG::UpdateNodeOperands(SDNode *N, SDValue Op) {
   // Now we update the operands.
   N->OperandList[0].set(Op);
 
-  if (DivergentTarget)
-    updateDivergence(N);
+  updateDivergence(N);
   // If this gets put into a CSE map, add it.
   if (InsertPos) CSEMap.InsertNode(N, InsertPos);
   return N;
@@ -10961,8 +10960,7 @@ SDNode *SelectionDAG::UpdateNodeOperands(SDNode *N, SDValue Op1, SDValue Op2) {
   if (N->OperandList[1] != Op2)
     N->OperandList[1].set(Op2);
 
-  if (DivergentTarget)
-    updateDivergence(N);
+  updateDivergence(N);
   // If this gets put into a CSE map, add it.
   if (InsertPos) CSEMap.InsertNode(N, InsertPos);
   return N;
@@ -11013,8 +11011,7 @@ UpdateNodeOperands(SDNode *N, ArrayRef<SDValue> Ops) {
     if (N->OperandList[i] != Ops[i])
       N->OperandList[i].set(Ops[i]);
 
-  if (DivergentTarget)
-    updateDivergence(N);
+  updateDivergence(N);
   // If this gets put into a CSE map, add it.
   if (InsertPos) CSEMap.InsertNode(N, InsertPos);
   return N;
@@ -11801,9 +11798,8 @@ void SelectionDAG::ReplaceAllUsesWith(SDValue FromN, SDValue To) {
       SDUse &Use = *UI;
       ++UI;
       Use.set(To);
-      if (DivergentTarget)
-        if (To->isDivergent() != From->isDivergent())
-          updateDivergence(User);
+      if (To->isDivergent() != From->isDivergent())
+        updateDivergence(User);
     } while (UI != UE && UI->getUser() == User);
     // Now that we have modified User, add it back to the CSE maps.  If it
     // already exists there, recursively merge the results together.
@@ -11860,9 +11856,8 @@ void SelectionDAG::ReplaceAllUsesWith(SDNode *From, SDNode *To) {
       SDUse &Use = *UI;
       ++UI;
       Use.setNode(To);
-      if (DivergentTarget)
-        if (To->isDivergent() != From->isDivergent())
-          updateDivergence(User);
+      if (To->isDivergent() != From->isDivergent())
+        updateDivergence(User);
     } while (UI != UE && UI->getUser() == User);
 
     // Now that we have modified User, add it back to the CSE maps.  If it
@@ -11914,9 +11909,8 @@ void SelectionDAG::ReplaceAllUsesWith(SDNode *From, const SDValue *To) {
       To_IsDivergent |= ToOp->isDivergent();
     } while (UI != UE && UI->getUser() == User);
 
-    if (DivergentTarget)
-      if (To_IsDivergent != From->isDivergent())
-        updateDivergence(User);
+    if (To_IsDivergent != From->isDivergent())
+      updateDivergence(User);
 
     // Now that we have modified User, add it back to the CSE maps.  If it
     // already exists there, recursively merge the results together.
@@ -11976,9 +11970,8 @@ void SelectionDAG::ReplaceAllUsesOfValueWith(SDValue From, SDValue To){
 
       ++UI;
       Use.set(To);
-      if (DivergentTarget)
-        if (To->isDivergent() != From->isDivergent())
-          updateDivergence(User);
+      if (To->isDivergent() != From->isDivergent())
+        updateDivergence(User);
     } while (UI != UE && UI->getUser() == User);
     // We are iterating over all uses of the From node, so if a use
     // doesn't use the specific value, no changes are made.
@@ -12062,6 +12055,8 @@ bool SelectionDAG::calculateDivergence(SDNode *N) {
 }
 
 void SelectionDAG::updateDivergence(SDNode *N) {
+  if (!DivergentTarget)
+    return;
   SmallVector<SDNode *, 16> Worklist(1, N);
   do {
     N = Worklist.pop_back_val();