Make variable argument intrinsics behave correctly in a Win64 CC function.

Summary:
This change makes the variable argument intrinsics, `llvm.va_start` and
`llvm.va_copy`, and the `va_arg` instruction behave as they do on Windows
inside a `CallingConv::X86_64_Win64` function. It's needed for a Clang patch
I have to add support for GCC's `__builtin_ms_va_list` constructs.

Reviewers: nadav, asl, eugenis

CC: llvm-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D1622

llvm-svn: 245990

2 files changed, 55 insertions, 48 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 552f92bbd46..be08ca8c0b2 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3099,57 +3099,13 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
     Results.push_back(Tmp1);
     break;
   }
-  case ISD::VAARG: {
-    const Value *V = cast<SrcValueSDNode>(Node->getOperand(2))->getValue();
-    EVT VT = Node->getValueType(0);
-    Tmp1 = Node->getOperand(0);
-    Tmp2 = Node->getOperand(1);
-    unsigned Align = Node->getConstantOperandVal(3);
-
-    SDValue VAListLoad =
-        DAG.getLoad(TLI.getPointerTy(DAG.getDataLayout()), dl, Tmp1, Tmp2,
-                    MachinePointerInfo(V), false, false, false, 0);
-    SDValue VAList = VAListLoad;
-
-    if (Align > TLI.getMinStackArgumentAlignment()) {
-      assert(((Align & (Align-1)) == 0) && "Expected Align to be a power of 2");
-
-      VAList = DAG.getNode(ISD::ADD, dl, VAList.getValueType(), VAList,
-                           DAG.getConstant(Align - 1, dl,
-                                           VAList.getValueType()));
-
-      VAList = DAG.getNode(ISD::AND, dl, VAList.getValueType(), VAList,
-                           DAG.getConstant(-(int64_t)Align, dl,
-                                           VAList.getValueType()));
-    }
-
-    // Increment the pointer, VAList, to the next vaarg
-    Tmp3 = DAG.getNode(ISD::ADD, dl, VAList.getValueType(), VAList,
-                       DAG.getConstant(DAG.getDataLayout().getTypeAllocSize(
-                                           VT.getTypeForEVT(*DAG.getContext())),
-                                       dl, VAList.getValueType()));
-    // Store the incremented VAList to the legalized pointer
-    Tmp3 = DAG.getStore(VAListLoad.getValue(1), dl, Tmp3, Tmp2,
-                        MachinePointerInfo(V), false, false, 0);
-    // Load the actual argument out of the pointer VAList
-    Results.push_back(DAG.getLoad(VT, dl, Tmp3, VAList, MachinePointerInfo(),
-                                  false, false, false, 0));
+  case ISD::VAARG:
+    Results.push_back(DAG.expandVAArg(Node));
     Results.push_back(Results[0].getValue(1));
     break;
-  }
-  case ISD::VACOPY: {
-    // This defaults to loading a pointer from the input and storing it to the
-    // output, returning the chain.
-    const Value *VD = cast<SrcValueSDNode>(Node->getOperand(3))->getValue();
-    const Value *VS = cast<SrcValueSDNode>(Node->getOperand(4))->getValue();
-    Tmp1 = DAG.getLoad(TLI.getPointerTy(DAG.getDataLayout()), dl,
-                       Node->getOperand(0), Node->getOperand(2),
-                       MachinePointerInfo(VS), false, false, false, 0);
-    Tmp1 = DAG.getStore(Tmp1.getValue(1), dl, Tmp1, Node->getOperand(1),
-                        MachinePointerInfo(VD), false, false, 0);
-    Results.push_back(Tmp1);
+  case ISD::VACOPY:
+    Results.push_back(DAG.expandVACopy(Node));
     break;
-  }
   case ISD::EXTRACT_VECTOR_ELT:
     if (Node->getOperand(0).getValueType().getVectorNumElements() == 1)
       // This must be an access of the only element.  Return it.
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 0d73bc5e65d..82537eb8923 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1855,6 +1855,57 @@ SDValue SelectionDAG::getShiftAmountOperand(EVT LHSTy, SDValue Op) {
   return getZExtOrTrunc(Op, SDLoc(Op), ShTy);
 }
 
+SDValue SelectionDAG::expandVAArg(SDNode *Node) {
+  SDLoc dl(Node);
+  const TargetLowering &TLI = getTargetLoweringInfo();
+  const Value *V = cast<SrcValueSDNode>(Node->getOperand(2))->getValue();
+  EVT VT = Node->getValueType(0);
+  SDValue Tmp1 = Node->getOperand(0);
+  SDValue Tmp2 = Node->getOperand(1);
+  unsigned Align = Node->getConstantOperandVal(3);
+
+  SDValue VAListLoad =
+    getLoad(TLI.getPointerTy(getDataLayout()), dl, Tmp1, Tmp2,
+            MachinePointerInfo(V), false, false, false, 0);
+  SDValue VAList = VAListLoad;
+
+  if (Align > TLI.getMinStackArgumentAlignment()) {
+    assert(((Align & (Align-1)) == 0) && "Expected Align to be a power of 2");
+
+    VAList = getNode(ISD::ADD, dl, VAList.getValueType(), VAList,
+                     getConstant(Align - 1, dl, VAList.getValueType()));
+
+    VAList = getNode(ISD::AND, dl, VAList.getValueType(), VAList,
+                     getConstant(-(int64_t)Align, dl, VAList.getValueType()));
+  }
+
+  // Increment the pointer, VAList, to the next vaarg
+  Tmp1 = getNode(ISD::ADD, dl, VAList.getValueType(), VAList,
+                 getConstant(getDataLayout().getTypeAllocSize(
+                                               VT.getTypeForEVT(*getContext())),
+                             dl, VAList.getValueType()));
+  // Store the incremented VAList to the legalized pointer
+  Tmp1 = getStore(VAListLoad.getValue(1), dl, Tmp1, Tmp2,
+                  MachinePointerInfo(V), false, false, 0);
+  // Load the actual argument out of the pointer VAList
+  return getLoad(VT, dl, Tmp1, VAList, MachinePointerInfo(),
+                 false, false, false, 0);
+}
+
+SDValue SelectionDAG::expandVACopy(SDNode *Node) {
+  SDLoc dl(Node);
+  const TargetLowering &TLI = getTargetLoweringInfo();
+  // This defaults to loading a pointer from the input and storing it to the
+  // output, returning the chain.
+  const Value *VD = cast<SrcValueSDNode>(Node->getOperand(3))->getValue();
+  const Value *VS = cast<SrcValueSDNode>(Node->getOperand(4))->getValue();
+  SDValue Tmp1 = getLoad(TLI.getPointerTy(getDataLayout()), dl,
+                         Node->getOperand(0), Node->getOperand(2),
+                         MachinePointerInfo(VS), false, false, false, 0);
+  return getStore(Tmp1.getValue(1), dl, Tmp1, Node->getOperand(1),
+                  MachinePointerInfo(VD), false, false, 0);
+}
+
 /// CreateStackTemporary - Create a stack temporary, suitable for holding the
 /// specified value type.
 SDValue SelectionDAG::CreateStackTemporary(EVT VT, unsigned minAlign) {