SelectionDAG: Expand i64 = FP_TO_SINT i32

llvm-svn: 211108

1 files changed, 59 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index 48eb86c49c3..a4245a6016c 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3152,6 +3152,65 @@ void SelectionDAGLegalize::ExpandNode(SDNode *Node) {
                                 Node->getOperand(0), Node->getValueType(0), dl);
     Results.push_back(Tmp1);
     break;
+  case ISD::FP_TO_SINT: {
+    EVT VT = Node->getOperand(0).getValueType();
+    EVT NVT = Node->getValueType(0);
+
+    // FIXME: Only f32 to i64 conversions are supported.
+    if (VT != MVT::f32 || NVT != MVT::i64)
+      break;
+
+    // Expand f32 -> i64 conversion
+    // This algorithm comes from compiler-rt's implementation of fixsfdi:
+    // https://github.com/llvm-mirror/compiler-rt/blob/master/lib/builtins/fixsfdi.c
+    EVT IntVT = EVT::getIntegerVT(*DAG.getContext(),
+                                  VT.getSizeInBits());
+    SDValue ExponentMask = DAG.getConstant(0x7F800000, IntVT);
+    SDValue ExponentLoBit = DAG.getConstant(23, IntVT);
+    SDValue Bias = DAG.getConstant(127, IntVT);
+    SDValue SignMask = DAG.getConstant(APInt::getSignBit(VT.getSizeInBits()),
+                                       IntVT);
+    SDValue SignLowBit = DAG.getConstant(VT.getSizeInBits() - 1, IntVT);
+    SDValue MantissaMask = DAG.getConstant(0x007FFFFF, IntVT);
+
+    SDValue Bits = DAG.getNode(ISD::BITCAST, dl, IntVT, Node->getOperand(0));
+
+    SDValue ExponentBits = DAG.getNode(ISD::SRL, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, ExponentMask),
+        DAG.getZExtOrTrunc(ExponentLoBit, dl, TLI.getShiftAmountTy(IntVT)));
+    SDValue Exponent = DAG.getNode(ISD::SUB, dl, IntVT, ExponentBits, Bias);
+
+    SDValue Sign = DAG.getNode(ISD::SRA, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, SignMask),
+        DAG.getZExtOrTrunc(SignLowBit, dl, TLI.getShiftAmountTy(IntVT)));
+    Sign = DAG.getSExtOrTrunc(Sign, dl, NVT);
+
+    SDValue R = DAG.getNode(ISD::OR, dl, IntVT,
+        DAG.getNode(ISD::AND, dl, IntVT, Bits, MantissaMask),
+        DAG.getConstant(0x00800000, IntVT));
+
+    R = DAG.getZExtOrTrunc(R, dl, NVT);
+
+
+    R = DAG.getSelectCC(dl, Exponent, ExponentLoBit,
+       DAG.getNode(ISD::SHL, dl, NVT, R,
+                   DAG.getZExtOrTrunc(
+                      DAG.getNode(ISD::SUB, dl, IntVT, Exponent, ExponentLoBit),
+                      dl, TLI.getShiftAmountTy(IntVT))),
+       DAG.getNode(ISD::SRL, dl, NVT, R,
+                   DAG.getZExtOrTrunc(
+                      DAG.getNode(ISD::SUB, dl, IntVT, ExponentLoBit, Exponent),
+                      dl, TLI.getShiftAmountTy(IntVT))),
+       ISD::SETGT);
+
+    SDValue Ret = DAG.getNode(ISD::SUB, dl, NVT,
+        DAG.getNode(ISD::XOR, dl, NVT, R, Sign),
+        Sign);
+
+    Results.push_back(DAG.getSelectCC(dl, Exponent, DAG.getConstant(0, IntVT),
+        DAG.getConstant(0, NVT), Ret, ISD::SETLT));
+    break;
+  }
   case ISD::FP_TO_UINT: {
     SDValue True, False;
     EVT VT =  Node->getOperand(0).getValueType();