Add ISD::UNDEF node

Teach the SelectionDAG code how to expand and promote it
Have PPC32 LowerCallTo generate ISD::UNDEF for int arg regs used up by fp
  arguments, but not shadowing their value.  This allows us to do the right
  thing with both fixed and vararg floating point arguments.

llvm-svn: 20988

2 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 5f8a21aca0f..52449ef376a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -219,6 +219,23 @@ SDOperand SelectionDAGLegalize::LegalizeOp(SDOperand Op) {
     if (Tmp1 != Node->getOperand(0))
       Result = DAG.getImplicitDef(Tmp1, cast<RegSDNode>(Node)->getReg());
     break;
+  case ISD::UNDEF: {
+    MVT::ValueType VT = Op.getValueType();
+    switch (TLI.getOperationAction(ISD::UNDEF, VT)) {
+    case Expand:
+    case Promote:
+      if (MVT::isInteger(VT))
+        Result = DAG.getConstant(0, VT);
+      else if (MVT::isFloatingPoint(VT))
+        Result = DAG.getConstantFP(0, VT);
+      else
+        assert(0 && "Unknown value type!");
+      break;
+    case Legal:
+      break;
+    }
+    break;
+  }
   case ISD::Constant:
     // We know we don't need to expand constants here, constants only have one
     // value and we check that it is fine above.
@@ -1018,6 +1035,9 @@ SDOperand SelectionDAGLegalize::PromoteOp(SDOperand Op) {
     std::cerr << "NODE: "; Node->dump(); std::cerr << "\n";
     assert(0 && "Do not know how to promote this operator!");
     abort();
+  case ISD::UNDEF:
+    Result = DAG.getNode(ISD::UNDEF, NVT);
+    break;
   case ISD::Constant:
     Result = DAG.getNode(ISD::ZERO_EXTEND, NVT, Op);
     assert(isa<ConstantSDNode>(Result) && "Didn't constant fold zext?");
@@ -1574,6 +1594,10 @@ void SelectionDAGLegalize::ExpandOp(SDOperand Op, SDOperand &Lo, SDOperand &Hi){
     std::cerr << "NODE: "; Node->dump(); std::cerr << "\n";
     assert(0 && "Do not know how to expand this operator!");
     abort();
+  case ISD::UNDEF:
+    Lo = DAG.getNode(ISD::UNDEF, NVT);
+    Hi = DAG.getNode(ISD::UNDEF, NVT);
+    break;
   case ISD::Constant: {
     uint64_t Cst = cast<ConstantSDNode>(Node)->getValue();
     Lo = DAG.getConstant(Cst, NVT);
diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index edc5b8c6f5e..023848a9f91 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -1112,6 +1112,7 @@ const char *SDNode::getOperationName() const {
   case ISD::CopyToReg:     return "CopyToReg";
   case ISD::CopyFromReg:   return "CopyFromReg";
   case ISD::ImplicitDef:   return "ImplicitDef";
+  case ISD::UNDEF:         return "undef";
 
   case ISD::ADD:    return "add";
   case ISD::SUB:    return "sub";