1 files changed, 17 insertions, 1 deletions
diff --git a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 548454c633..8b382bc767 100644
--- a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -2314,13 +2314,29 @@ SDValue DAGTypeLegalizer::ExpandIntOp_TRUNCATE(SDNode *N) {
   return DAG.getNode(ISD::TRUNCATE, N->getDebugLoc(), N->getValueType(0), InL);
 }
 
+static const fltSemantics *EVTToAPFloatSemantics(EVT VT) {
+  switch (VT.getSimpleVT().SimpleTy) {
+  default: llvm_unreachable("Unknown FP format");
+  case MVT::f32:     return &APFloat::IEEEsingle;
+  case MVT::f64:     return &APFloat::IEEEdouble;
+  case MVT::f80:     return &APFloat::x87DoubleExtended;
+  case MVT::f128:    return &APFloat::IEEEquad;
+  case MVT::ppcf128: return &APFloat::PPCDoubleDouble;
+  }
+}
+
 SDValue DAGTypeLegalizer::ExpandIntOp_UINT_TO_FP(SDNode *N) {
   SDValue Op = N->getOperand(0);
   EVT SrcVT = Op.getValueType();
   EVT DstVT = N->getValueType(0);
   DebugLoc dl = N->getDebugLoc();
 
-  if (TLI.getOperationAction(ISD::SINT_TO_FP, SrcVT) == TargetLowering::Custom){
+  // The following optimization is valid only if every value in SrcVT (when
+  // treated as signed) is representable in DstVT.  Check that the mantissa
+  // size of DstVT is >= than the number of bits in SrcVT -1.
+  const fltSemantics *sem = EVTToAPFloatSemantics(DstVT);
+  if (APFloat::semanticsPrecision(*sem) >= SrcVT.getSizeInBits()-1 &&
+      TLI.getOperationAction(ISD::SINT_TO_FP, SrcVT) == TargetLowering::Custom){
     // Do a signed conversion then adjust the result.
     SDValue SignedConv = DAG.getNode(ISD::SINT_TO_FP, dl, DstVT, Op);
     SignedConv = TLI.LowerOperation(SignedConv, DAG);