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

4 files changed, 77 insertions, 58 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) {
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 0ade9654b29..0f8736f311e 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -484,8 +484,7 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
   // VASTART needs to be custom lowered to use the VarArgsFrameIndex
   setOperationAction(ISD::VASTART           , MVT::Other, Custom);
   setOperationAction(ISD::VAEND             , MVT::Other, Expand);
-  if (Subtarget->is64Bit() && !Subtarget->isTargetWin64()) {
-    // TargetInfo::X86_64ABIBuiltinVaList
+  if (Subtarget->is64Bit()) {
     setOperationAction(ISD::VAARG           , MVT::Other, Custom);
     setOperationAction(ISD::VACOPY          , MVT::Other, Custom);
   } else {
@@ -15153,7 +15152,8 @@ SDValue X86TargetLowering::LowerVASTART(SDValue Op, SelectionDAG &DAG) const {
   const Value *SV = cast<SrcValueSDNode>(Op.getOperand(2))->getValue();
   SDLoc DL(Op);
 
-  if (!Subtarget->is64Bit() || Subtarget->isTargetWin64()) {
+  if (!Subtarget->is64Bit() ||
+      Subtarget->isCallingConvWin64(MF.getFunction()->getCallingConv())) {
     // vastart just stores the address of the VarArgsFrameIndex slot into the
     // memory location argument.
     SDValue FR = DAG.getFrameIndex(FuncInfo->getVarArgsFrameIndex(), PtrVT);
@@ -15203,10 +15203,13 @@ SDValue X86TargetLowering::LowerVASTART(SDValue Op, SelectionDAG &DAG) const {
 SDValue X86TargetLowering::LowerVAARG(SDValue Op, SelectionDAG &DAG) const {
   assert(Subtarget->is64Bit() &&
          "LowerVAARG only handles 64-bit va_arg!");
-  assert((Subtarget->isTargetLinux() ||
-          Subtarget->isTargetDarwin()) &&
-          "Unhandled target in LowerVAARG");
   assert(Op.getNode()->getNumOperands() == 4);
+
+  MachineFunction &MF = DAG.getMachineFunction();
+  if (Subtarget->isCallingConvWin64(MF.getFunction()->getCallingConv()))
+    // The Win64 ABI uses char* instead of a structure.
+    return DAG.expandVAArg(Op.getNode());
+
   SDValue Chain = Op.getOperand(0);
   SDValue SrcPtr = Op.getOperand(1);
   const Value *SV = cast<SrcValueSDNode>(Op.getOperand(2))->getValue();
@@ -15234,8 +15237,7 @@ SDValue X86TargetLowering::LowerVAARG(SDValue Op, SelectionDAG &DAG) const {
   if (ArgMode == 2) {
     // Sanity Check: Make sure using fp_offset makes sense.
     assert(!Subtarget->useSoftFloat() &&
-           !(DAG.getMachineFunction().getFunction()->hasFnAttribute(
-               Attribute::NoImplicitFloat)) &&
+           !(MF.getFunction()->hasFnAttribute(Attribute::NoImplicitFloat)) &&
            Subtarget->hasSSE1());
   }
 
@@ -15264,8 +15266,14 @@ SDValue X86TargetLowering::LowerVAARG(SDValue Op, SelectionDAG &DAG) const {
 
 static SDValue LowerVACOPY(SDValue Op, const X86Subtarget *Subtarget,
                            SelectionDAG &DAG) {
-  // X86-64 va_list is a struct { i32, i32, i8*, i8* }.
+  // X86-64 va_list is a struct { i32, i32, i8*, i8* }, except on Windows,
+  // where a va_list is still an i8*.
   assert(Subtarget->is64Bit() && "This code only handles 64-bit va_copy!");
+  if (Subtarget->isCallingConvWin64(
+        DAG.getMachineFunction().getFunction()->getCallingConv()))
+    // Probably a Win64 va_copy.
+    return DAG.expandVACopy(Op.getNode());
+
   SDValue Chain = Op.getOperand(0);
   SDValue DstPtr = Op.getOperand(1);
   SDValue SrcPtr = Op.getOperand(2);
@@ -20034,7 +20042,7 @@ X86TargetLowering::EmitVAStartSaveXMMRegsWithCustomInserter(
   int64_t RegSaveFrameIndex = MI->getOperand(1).getImm();
   int64_t VarArgsFPOffset = MI->getOperand(2).getImm();
 
-  if (!Subtarget->isTargetWin64()) {
+  if (!Subtarget->isCallingConvWin64(F->getFunction()->getCallingConv())) {
     // If %al is 0, branch around the XMM save block.
     BuildMI(MBB, DL, TII->get(X86::TEST8rr)).addReg(CountReg).addReg(CountReg);
     BuildMI(MBB, DL, TII->get(X86::JE_1)).addMBB(EndMBB);
diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index d296474abe1..eb2a5b3653c 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -2863,6 +2863,8 @@ struct VarArgAMD64Helper : public VarArgHelper {
   }
 
   void visitVAStartInst(VAStartInst &I) override {
+    if (F.getCallingConv() == CallingConv::X86_64_Win64)
+      return;
     IRBuilder<> IRB(&I);
     VAStartInstrumentationList.push_back(&I);
     Value *VAListTag = I.getArgOperand(0);
@@ -2875,6 +2877,8 @@ struct VarArgAMD64Helper : public VarArgHelper {
   }
 
   void visitVACopyInst(VACopyInst &I) override {
+    if (F.getCallingConv() == CallingConv::X86_64_Win64)
+      return;
     IRBuilder<> IRB(&I);
     Value *VAListTag = I.getArgOperand(0);
     Value *ShadowPtr = MSV.getShadowPtr(VAListTag, IRB.getInt8Ty(), IRB);