SDAG: Make SelectCodeCommon return void

This means SelectCode unconditionally returns nullptr now. I'll follow
up with a change to make that return void as well, but it seems best
to keep that one very mechanical.

This is part of the work to have Select return void instead of an
SDNode *, which is in turn part of llvm.org/pr26808.

llvm-svn: 269136

llvm/include/llvm/CodeGen/SelectionDAGISel.h

@@ -274,9 +274,8 @@ public:
     llvm_unreachable("Tblgen should generate this!");
   }
 
-  SDNode *SelectCodeCommon(SDNode *NodeToMatch,
-                           const unsigned char *MatcherTable,
-                           unsigned TableSize);
+  void SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
+                        unsigned TableSize);
 
   /// \brief Return true if complex patterns for this target can mutate the
   /// DAG.
@@ -287,10 +286,10 @@ public:
 private:
 
   // Calls to these functions are generated by tblgen.
-  SDNode *Select_INLINEASM(SDNode *N);
-  SDNode *Select_READ_REGISTER(SDNode *N);
-  SDNode *Select_WRITE_REGISTER(SDNode *N);
-  SDNode *Select_UNDEF(SDNode *N);
+  void Select_INLINEASM(SDNode *N);
+  void Select_READ_REGISTER(SDNode *N);
+  void Select_WRITE_REGISTER(SDNode *N);
+  void Select_UNDEF(SDNode *N);
   void CannotYetSelect(SDNode *N);
 
 private:

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -2085,7 +2085,7 @@ bool SelectionDAGISel::IsLegalToFold(SDValue N, SDNode *U, SDNode *Root,
   return !findNonImmUse(Root, N.getNode(), U, Root, Visited, IgnoreChains);
 }
 
-SDNode *SelectionDAGISel::Select_INLINEASM(SDNode *N) {
+void SelectionDAGISel::Select_INLINEASM(SDNode *N) {
   SDLoc DL(N);
 
   std::vector<SDValue> Ops(N->op_begin(), N->op_end());
@@ -2094,11 +2094,11 @@ SDNode *SelectionDAGISel::Select_INLINEASM(SDNode *N) {
   const EVT VTs[] = {MVT::Other, MVT::Glue};
   SDValue New = CurDAG->getNode(ISD::INLINEASM, DL, VTs, Ops);
   New->setNodeId(-1);
-  return New.getNode();
+  ReplaceUses(N, New.getNode());
+  CurDAG->RemoveDeadNode(N);
 }
 
-SDNode
-*SelectionDAGISel::Select_READ_REGISTER(SDNode *Op) {
+void SelectionDAGISel::Select_READ_REGISTER(SDNode *Op) {
   SDLoc dl(Op);
   MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(Op->getOperand(1));
   const MDString *RegStr = dyn_cast<MDString>(MD->getMD()->getOperand(0));
@@ -2108,11 +2108,11 @@ SDNode
   SDValue New = CurDAG->getCopyFromReg(
                         Op->getOperand(0), dl, Reg, Op->getValueType(0));
   New->setNodeId(-1);
-  return New.getNode();
+  ReplaceUses(Op, New.getNode());
+  CurDAG->RemoveDeadNode(Op);
 }
 
-SDNode
-*SelectionDAGISel::Select_WRITE_REGISTER(SDNode *Op) {
+void SelectionDAGISel::Select_WRITE_REGISTER(SDNode *Op) {
   SDLoc dl(Op);
   MDNodeSDNode *MD = dyn_cast<MDNodeSDNode>(Op->getOperand(1));
   const MDString *RegStr = dyn_cast<MDString>(MD->getMD()->getOperand(0));
@@ -2122,11 +2122,17 @@ SDNode
   SDValue New = CurDAG->getCopyToReg(
                         Op->getOperand(0), dl, Reg, Op->getOperand(2));
   New->setNodeId(-1);
-  return New.getNode();
+  ReplaceUses(Op, New.getNode());
+  CurDAG->RemoveDeadNode(Op);
 }
 
-SDNode *SelectionDAGISel::Select_UNDEF(SDNode *N) {
-  return CurDAG->SelectNodeTo(N, TargetOpcode::IMPLICIT_DEF,N->getValueType(0));
+void SelectionDAGISel::Select_UNDEF(SDNode *N) {
+  SDNode *New =
+      CurDAG->SelectNodeTo(N, TargetOpcode::IMPLICIT_DEF, N->getValueType(0));
+  if (New != N) {
+    ReplaceUses(N, New);
+    CurDAG->RemoveDeadNode(N);
+  }
 }
 
 /// GetVBR - decode a vbr encoding whose top bit is set.
@@ -2706,9 +2712,9 @@ public:
 };
 } // end anonymous namespace
 
-SDNode *SelectionDAGISel::
-SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
-                 unsigned TableSize) {
+void SelectionDAGISel::SelectCodeCommon(SDNode *NodeToMatch,
+                                        const unsigned char *MatcherTable,
+                                        unsigned TableSize) {
   // FIXME: Should these even be selected?  Handle these cases in the caller?
   switch (NodeToMatch->getOpcode()) {
   default:
@@ -2736,17 +2742,25 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
   case ISD::LIFETIME_START:
   case ISD::LIFETIME_END:
     NodeToMatch->setNodeId(-1); // Mark selected.
-    return nullptr;
+    return;
   case ISD::AssertSext:
   case ISD::AssertZext:
     CurDAG->ReplaceAllUsesOfValueWith(SDValue(NodeToMatch, 0),
                                       NodeToMatch->getOperand(0));
     CurDAG->RemoveDeadNode(NodeToMatch);
-    return nullptr;
-  case ISD::INLINEASM: return Select_INLINEASM(NodeToMatch);
-  case ISD::READ_REGISTER: return Select_READ_REGISTER(NodeToMatch);
-  case ISD::WRITE_REGISTER: return Select_WRITE_REGISTER(NodeToMatch);
-  case ISD::UNDEF:     return Select_UNDEF(NodeToMatch);
+    return;
+  case ISD::INLINEASM:
+    Select_INLINEASM(NodeToMatch);
+    return;
+  case ISD::READ_REGISTER:
+    Select_READ_REGISTER(NodeToMatch);
+    return;
+  case ISD::WRITE_REGISTER:
+    Select_WRITE_REGISTER(NodeToMatch);
+    return;
+  case ISD::UNDEF:
+    Select_UNDEF(NodeToMatch);
+    return;
   }
 
   assert(!NodeToMatch->isMachineOpcode() && "Node already selected!");
@@ -3360,7 +3374,7 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
         // NodeToMatch was eliminated by CSE when the target changed the DAG.
         // We will visit the equivalent node later.
         DEBUG(dbgs() << "Node was eliminated by CSE\n");
-        return nullptr;
+        return;
       }
 
       // If the node had chain/glue results, update our notion of the current
@@ -3428,7 +3442,11 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
       if (IsMorphNodeTo) {
         // Update chain uses.
         UpdateChains(NodeToMatch, InputChain, ChainNodesMatched, true);
-        return Res;
+        if (Res != NodeToMatch) {
+          ReplaceUses(NodeToMatch, Res);
+          CurDAG->RemoveDeadNode(NodeToMatch);
+        }
+        return;
       }
       continue;
     }
@@ -3477,9 +3495,7 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
              "Didn't replace all uses of the node?");
       CurDAG->RemoveDeadNode(NodeToMatch);
 
-      // FIXME: We just return here, which interacts correctly with SelectRoot
-      // above.  We should fix this to not return an SDNode* anymore.
-      return nullptr;
+      return;
     }
     }
 
@@ -3491,7 +3507,7 @@ SelectCodeCommon(SDNode *NodeToMatch, const unsigned char *MatcherTable,
     while (1) {
       if (MatchScopes.empty()) {
         CannotYetSelect(NodeToMatch);
-        return nullptr;
+        return;
       }
 
       // Restore the interpreter state back to the point where the scope was

llvm/utils/TableGen/DAGISelMatcherEmitter.cpp

@@ -841,8 +841,9 @@ void llvm::EmitMatcherTable(const Matcher *TheMatcher,
   MatcherEmitter.EmitHistogram(TheMatcher, OS);
 
   OS << "  #undef TARGET_VAL\n";
-  OS << "  return SelectCodeCommon(N, MatcherTable,sizeof(MatcherTable));\n}\n";
-  OS << '\n';
+  OS << "  SelectCodeCommon(N, MatcherTable,sizeof(MatcherTable));\n";
+  OS << "  return nullptr;\n";
+  OS << "}\n";
 
   // Next up, emit the function for node and pattern predicates:
   MatcherEmitter.EmitPredicateFunctions(OS);