X86: More efficient legalization of wide integer compares

[oota-llvm.git] / lib / CodeGen / SelectionDAG / LegalizeIntegerTypes.cpp

diff --git a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
index 3c7586db0abf0d7189e0261ac67a7404d4906023..ea537fff1688840dd704abd347cd412302fba166 100644 (file)
--- a/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
+++ b/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp
@@ -2634,6 +2634,7 @@ bool DAGTypeLegalizer::ExpandIntegerOperand(SDNode *N, unsigned OpNo) {
   case ISD::SCALAR_TO_VECTOR:  Res = ExpandOp_SCALAR_TO_VECTOR(N); break;
   case ISD::SELECT_CC:         Res = ExpandIntOp_SELECT_CC(N); break;
   case ISD::SETCC:             Res = ExpandIntOp_SETCC(N); break;
+  case ISD::SETCCE:            Res = ExpandIntOp_SETCCE(N); break;
   case ISD::SINT_TO_FP:        Res = ExpandIntOp_SINT_TO_FP(N); break;
   case ISD::STORE:   Res = ExpandIntOp_STORE(cast<StoreSDNode>(N), OpNo); break;
   case ISD::TRUNCATE:          Res = ExpandIntOp_TRUNCATE(N); break;
@@ -2761,6 +2762,47 @@ void DAGTypeLegalizer::IntegerExpandSetCCOperands(SDValue &NewLHS,
     return;
   }
 
+  if (LHSHi == RHSHi) {
+    // Comparing the low bits is enough.
+    NewLHS = Tmp1;
+    NewRHS = SDValue();
+    return;
+  }
+
+  // Lower with SETCCE if the target supports it.
+  // FIXME: Make all targets support this, then remove the other lowering.
+  if (TLI.getOperationAction(
+          ISD::SETCCE,
+          TLI.getTypeToExpandTo(*DAG.getContext(), LHSLo.getValueType())) ==
+      TargetLowering::Custom) {
+    // SETCCE can detect < and >= directly. For > and <=, flip operands and
+    // condition code.
+    bool FlipOperands = false;
+    switch (CCCode) {
+    case ISD::SETGT:  CCCode = ISD::SETLT;  FlipOperands = true; break;
+    case ISD::SETUGT: CCCode = ISD::SETULT; FlipOperands = true; break;
+    case ISD::SETLE:  CCCode = ISD::SETGE;  FlipOperands = true; break;
+    case ISD::SETULE: CCCode = ISD::SETUGE; FlipOperands = true; break;
+    default: break;
+    }
+    if (FlipOperands) {
+      std::swap(LHSLo, RHSLo);
+      std::swap(LHSHi, RHSHi);
+    }
+    // Perform a wide subtraction, feeding the carry from the low part into
+    // SETCCE. The SETCCE operation is essentially looking at the high part of
+    // the result of LHS - RHS. It is negative iff LHS < RHS. It is zero or
+    // positive iff LHS >= RHS.
+    SDVTList VTList = DAG.getVTList(LHSLo.getValueType(), MVT::Glue);
+    SDValue LowCmp = DAG.getNode(ISD::SUBC, dl, VTList, LHSLo, RHSLo);
+    SDValue Res =
+        DAG.getNode(ISD::SETCCE, dl, getSetCCResultType(LHSLo.getValueType()),
+                    LHSHi, RHSHi, LowCmp.getValue(1), DAG.getCondCode(CCCode));
+    NewLHS = Res;
+    NewRHS = SDValue();
+    return;
+  }
+
   NewLHS = TLI.SimplifySetCC(getSetCCResultType(LHSHi.getValueType()),
                              LHSHi, RHSHi, ISD::SETEQ, false,
                              DagCombineInfo, dl);
@@ -2825,6 +2867,24 @@ SDValue DAGTypeLegalizer::ExpandIntOp_SETCC(SDNode *N) {
                                 DAG.getCondCode(CCCode)), 0);
 }
 
+SDValue DAGTypeLegalizer::ExpandIntOp_SETCCE(SDNode *N) {
+  SDValue LHS = N->getOperand(0);
+  SDValue RHS = N->getOperand(1);
+  SDValue Carry = N->getOperand(2);
+  SDValue Cond = N->getOperand(3);
+  SDLoc dl = SDLoc(N);
+
+  SDValue LHSLo, LHSHi, RHSLo, RHSHi;
+  GetExpandedInteger(LHS, LHSLo, LHSHi);
+  GetExpandedInteger(RHS, RHSLo, RHSHi);
+
+  // Expand to a SUBE for the low part and a smaller SETCCE for the high.
+  SDVTList VTList = DAG.getVTList(LHSLo.getValueType(), MVT::Glue);
+  SDValue LowCmp = DAG.getNode(ISD::SUBE, dl, VTList, LHSLo, RHSLo, Carry);
+  return DAG.getNode(ISD::SETCCE, dl, N->getValueType(0), LHSHi, RHSHi,
+                     LowCmp.getValue(1), Cond);
+}
+
 SDValue DAGTypeLegalizer::ExpandIntOp_Shift(SDNode *N) {
   // The value being shifted is legal, but the shift amount is too big.
   // It follows that either the result of the shift is undefined, or the