Re-land part of r354244 "[DAGCombiner] Eliminate dead stores to stack."

This part introduces the lifetime node.

llvm-svn: 354578

3 files changed, 44 insertions, 10 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index dd284430645..156f772654d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -6506,6 +6506,36 @@ SDValue SelectionDAG::getMemIntrinsicNode(unsigned Opcode, const SDLoc &dl,
   return SDValue(N, 0);
 }
 
+SDValue SelectionDAG::getLifetimeNode(bool IsStart, const SDLoc &dl,
+                                      SDValue Chain, int FrameIndex,
+                                      int64_t Size, int64_t Offset) {
+  const unsigned Opcode = IsStart ? ISD::LIFETIME_START : ISD::LIFETIME_END;
+  const auto VTs = getVTList(MVT::Other);
+  SDValue Ops[2] = {
+      Chain,
+      getFrameIndex(FrameIndex,
+                    getTargetLoweringInfo().getFrameIndexTy(getDataLayout()),
+                    true)};
+
+  FoldingSetNodeID ID;
+  AddNodeIDNode(ID, Opcode, VTs, Ops);
+  ID.AddInteger(FrameIndex);
+  ID.AddInteger(Size);
+  ID.AddInteger(Offset);
+  void *IP = nullptr;
+  if (SDNode *E = FindNodeOrInsertPos(ID, dl, IP))
+    return SDValue(E, 0);
+
+  LifetimeSDNode *N = newSDNode<LifetimeSDNode>(
+      Opcode, dl.getIROrder(), dl.getDebugLoc(), VTs, Size, Offset);
+  createOperands(N, Ops);
+  CSEMap.InsertNode(N, IP);
+  InsertNode(N);
+  SDValue V(N, 0);
+  NewSDValueDbgMsg(V, "Creating new node: ", this);
+  return V;
+}
+
 /// InferPointerInfo - If the specified ptr/offset is a frame index, infer a
 /// MachinePointerInfo record from it.  This is particularly useful because the
 /// code generator has many cases where it doesn't bother passing in a
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 75f7cc08aa9..1b75dc7d2e5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -6373,8 +6373,11 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
     if (TM.getOptLevel() == CodeGenOpt::None)
       return nullptr;
 
+    const int64_t ObjectSize =
+        cast<ConstantInt>(I.getArgOperand(0))->getSExtValue();
+    Value *const ObjectPtr = I.getArgOperand(1);
     SmallVector<Value *, 4> Allocas;
-    GetUnderlyingObjects(I.getArgOperand(1), Allocas, *DL);
+    GetUnderlyingObjects(ObjectPtr, Allocas, *DL);
 
     for (SmallVectorImpl<Value*>::iterator Object = Allocas.begin(),
            E = Allocas.end(); Object != E; ++Object) {
@@ -6390,15 +6393,13 @@ SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I, unsigned Intrinsic) {
       if (SI == FuncInfo.StaticAllocaMap.end())
         return nullptr;
 
-      int FI = SI->second;
-
-      SDValue Ops[2];
-      Ops[0] = getRoot();
-      Ops[1] =
-          DAG.getFrameIndex(FI, TLI.getFrameIndexTy(DAG.getDataLayout()), true);
-      unsigned Opcode = (IsStart ? ISD::LIFETIME_START : ISD::LIFETIME_END);
-
-      Res = DAG.getNode(Opcode, sdl, MVT::Other, Ops);
+      const int FrameIndex = SI->second;
+      int64_t Offset;
+      if (GetPointerBaseWithConstantOffset(
+              ObjectPtr, Offset, DAG.getDataLayout()) != LifetimeObject)
+        Offset = -1; // Cannot determine offset from alloca to lifetime object.
+      Res = DAG.getLifetimeNode(IsStart, sdl, getRoot(), FrameIndex, ObjectSize,
+                                Offset);
       DAG.setRoot(Res);
     }
     return nullptr;
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
index 490b2f9957e..365286309ea 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGDumper.cpp
@@ -709,6 +709,9 @@ void SDNode::print_details(raw_ostream &OS, const SelectionDAG *G) const {
        << " -> "
        << ASC->getDestAddressSpace()
        << ']';
+  } else if (const LifetimeSDNode *LN = dyn_cast<LifetimeSDNode>(this)) {
+    if (LN->hasOffset())
+      OS << "<" << LN->getOffset() << " to " << LN->getOffset() + LN->getSize() << ">";
   }
 
   if (VerboseDAGDumping) {