R600: Implement 64bit SHL

v2: Use c++ style comment

Signed-off-by: Jan Vesely <jan.vesely@rutgers.edu>

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211157 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 0 deletions

diff --git a/lib/Target/R600/R600ISelLowering.cpp b/lib/Target/R600/R600ISelLowering.cpp
index beea54e14e..444190e179 100644
--- a/lib/Target/R600/R600ISelLowering.cpp
+++ b/lib/Target/R600/R600ISelLowering.cpp
@@ -157,6 +157,10 @@ R600TargetLowering::R600TargetLowering(TargetMachine &TM) :
   setOperationAction(ISD::UDIV, MVT::i64, Custom);
   setOperationAction(ISD::UREM, MVT::i64, Custom);
 
+  // We don't have 64-bit shifts. Thus we need either SHX i64 or SHX_PARTS i32
+  //  to be Legal/Custom in order to avoid library calls.
+  setOperationAction(ISD::SHL_PARTS, MVT::i32, Custom);
+
   setOperationAction(ISD::GlobalAddress, MVT::i32, Custom);
 
   setBooleanContents(ZeroOrNegativeOneBooleanContent);
@@ -552,6 +556,7 @@ SDValue R600TargetLowering::LowerOperation(SDValue Op, SelectionDAG &DAG) const
   default: return AMDGPUTargetLowering::LowerOperation(Op, DAG);
   case ISD::EXTRACT_VECTOR_ELT: return LowerEXTRACT_VECTOR_ELT(Op, DAG);
   case ISD::INSERT_VECTOR_ELT: return LowerINSERT_VECTOR_ELT(Op, DAG);
+  case ISD::SHL_PARTS: return LowerSHLParts(Op, DAG);
   case ISD::FCOS:
   case ISD::FSIN: return LowerTrig(Op, DAG);
   case ISD::SELECT_CC: return LowerSELECT_CC(Op, DAG);
@@ -905,6 +910,42 @@ SDValue R600TargetLowering::LowerTrig(SDValue Op, SelectionDAG &DAG) const {
       DAG.getConstantFP(3.14159265359, MVT::f32));
 }
 
+SDValue R600TargetLowering::LowerSHLParts(SDValue Op, SelectionDAG &DAG) const {
+  SDLoc DL(Op);
+  EVT VT = Op.getValueType();
+
+  SDValue Lo = Op.getOperand(0);
+  SDValue Hi = Op.getOperand(1);
+  SDValue Shift = Op.getOperand(2);
+  SDValue Zero = DAG.getConstant(0, VT);
+  SDValue One  = DAG.getConstant(1, VT);
+
+  SDValue Width  = DAG.getConstant(VT.getSizeInBits(), VT);
+  SDValue Width1 = DAG.getConstant(VT.getSizeInBits() - 1, VT);
+  SDValue BigShift  = DAG.getNode(ISD::SUB, DL, VT, Shift, Width);
+  SDValue CompShift = DAG.getNode(ISD::SUB, DL, VT, Width1, Shift);
+
+  // The dance around Width1 is necessary for 0 special case.
+  // Without it the CompShift might be 32, producing incorrect results in
+  // Overflow. So we do the shift in two steps, the alternative is to
+  // add a conditional to filter the special case.
+
+  SDValue Overflow = DAG.getNode(ISD::SRL, DL, VT, Lo, CompShift);
+  Overflow = DAG.getNode(ISD::SRL, DL, VT, Overflow, One);
+
+  SDValue HiSmall = DAG.getNode(ISD::SHL, DL, VT, Hi, Shift);
+  HiSmall = DAG.getNode(ISD::OR, DL, VT, HiSmall, Overflow);
+  SDValue LoSmall = DAG.getNode(ISD::SHL, DL, VT, Lo, Shift);
+
+  SDValue HiBig = DAG.getNode(ISD::SHL, DL, VT, Lo, BigShift);
+  SDValue LoBig = Zero;
+
+  Hi = DAG.getSelectCC(DL, Shift, Width, HiSmall, HiBig, ISD::SETULT);
+  Lo = DAG.getSelectCC(DL, Shift, Width, LoSmall, LoBig, ISD::SETULT);
+
+  return DAG.getNode(ISD::MERGE_VALUES, DL, DAG.getVTList(VT,VT), Lo, Hi);
+}
+
 SDValue R600TargetLowering::LowerFPTOUINT(SDValue Op, SelectionDAG &DAG) const {
   return DAG.getNode(
       ISD::SETCC,
diff --git a/lib/Target/R600/R600ISelLowering.h b/lib/Target/R600/R600ISelLowering.h
index ed12dab48b..a7d83742c1 100644
--- a/lib/Target/R600/R600ISelLowering.h
+++ b/lib/Target/R600/R600ISelLowering.h
@@ -60,6 +60,7 @@ private:
   SDValue LowerFPTOUINT(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerLOAD(SDValue Op, SelectionDAG &DAG) const;
   SDValue LowerTrig(SDValue Op, SelectionDAG &DAG) const;
+  SDValue LowerSHLParts(SDValue Op, SelectionDAG &DAG) const;
 
   SDValue stackPtrToRegIndex(SDValue Ptr, unsigned StackWidth,
                                           SelectionDAG &DAG) const;