[mips] Move the code which does dag-combine for multiply-add/sub nodes to

derived class MipsSETargetLowering.

We shouldn't be generating madd/msub nodes if target is Mips16, since Mips16
doesn't have support for multipy-add/sub instructions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178404 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 197 insertions, 0 deletions

diff --git a/lib/Target/Mips/MipsSEISelLowering.cpp b/lib/Target/Mips/MipsSEISelLowering.cpp
index 5152419453..a97a693709 100644
--- a/lib/Target/Mips/MipsSEISelLowering.cpp
+++ b/lib/Target/Mips/MipsSEISelLowering.cpp
@@ -77,6 +77,9 @@ MipsSETargetLowering::MipsSETargetLowering(MipsTargetMachine &TM)
   setOperationAction(ISD::LOAD,               MVT::i32, Custom);
   setOperationAction(ISD::STORE,              MVT::i32, Custom);
 
+  setTargetDAGCombine(ISD::ADDE);
+  setTargetDAGCombine(ISD::SUBE);
+
   computeRegisterProperties();
 }
 
@@ -116,6 +119,200 @@ SDValue MipsSETargetLowering::LowerOperation(SDValue Op,
   return MipsTargetLowering::LowerOperation(Op, DAG);
 }
 
+// selectMADD -
+// Transforms a subgraph in CurDAG if the following pattern is found:
+//  (addc multLo, Lo0), (adde multHi, Hi0),
+// where,
+//  multHi/Lo: product of multiplication
+//  Lo0: initial value of Lo register
+//  Hi0: initial value of Hi register
+// Return true if pattern matching was successful.
+static bool selectMADD(SDNode *ADDENode, SelectionDAG *CurDAG) {
+  // ADDENode's second operand must be a flag output of an ADDC node in order
+  // for the matching to be successful.
+  SDNode *ADDCNode = ADDENode->getOperand(2).getNode();
+
+  if (ADDCNode->getOpcode() != ISD::ADDC)
+    return false;
+
+  SDValue MultHi = ADDENode->getOperand(0);
+  SDValue MultLo = ADDCNode->getOperand(0);
+  SDNode *MultNode = MultHi.getNode();
+  unsigned MultOpc = MultHi.getOpcode();
+
+  // MultHi and MultLo must be generated by the same node,
+  if (MultLo.getNode() != MultNode)
+    return false;
+
+  // and it must be a multiplication.
+  if (MultOpc != ISD::SMUL_LOHI && MultOpc != ISD::UMUL_LOHI)
+    return false;
+
+  // MultLo amd MultHi must be the first and second output of MultNode
+  // respectively.
+  if (MultHi.getResNo() != 1 || MultLo.getResNo() != 0)
+    return false;
+
+  // Transform this to a MADD only if ADDENode and ADDCNode are the only users
+  // of the values of MultNode, in which case MultNode will be removed in later
+  // phases.
+  // If there exist users other than ADDENode or ADDCNode, this function returns
+  // here, which will result in MultNode being mapped to a single MULT
+  // instruction node rather than a pair of MULT and MADD instructions being
+  // produced.
+  if (!MultHi.hasOneUse() || !MultLo.hasOneUse())
+    return false;
+
+  SDValue Chain = CurDAG->getEntryNode();
+  DebugLoc DL = ADDENode->getDebugLoc();
+
+  // Initialize accumulator.
+  SDValue ACCIn = CurDAG->getNode(MipsISD::InsertLOHI, DL, MVT::Untyped,
+                                  ADDCNode->getOperand(1),
+                                  ADDENode->getOperand(1));
+
+  // create MipsMAdd(u) node
+  MultOpc = MultOpc == ISD::UMUL_LOHI ? MipsISD::MAddu : MipsISD::MAdd;
+
+  SDValue MAdd = CurDAG->getNode(MultOpc, DL, MVT::Untyped,
+                                 MultNode->getOperand(0),// Factor 0
+                                 MultNode->getOperand(1),// Factor 1
+                                 ACCIn);
+
+  // replace uses of adde and addc here
+  if (!SDValue(ADDCNode, 0).use_empty()) {
+    SDValue LoIdx = CurDAG->getConstant(Mips::sub_lo, MVT::i32);
+    SDValue LoOut = CurDAG->getNode(MipsISD::ExtractLOHI, DL, MVT::i32, MAdd,
+                                    LoIdx);
+    CurDAG->ReplaceAllUsesOfValueWith(SDValue(ADDCNode, 0), LoOut);
+  }
+  if (!SDValue(ADDENode, 0).use_empty()) {
+    SDValue HiIdx = CurDAG->getConstant(Mips::sub_hi, MVT::i32);
+    SDValue HiOut = CurDAG->getNode(MipsISD::ExtractLOHI, DL, MVT::i32, MAdd,
+                                    HiIdx);
+    CurDAG->ReplaceAllUsesOfValueWith(SDValue(ADDENode, 0), HiOut);
+  }
+
+  return true;
+}
+
+// selectMSUB -
+// Transforms a subgraph in CurDAG if the following pattern is found:
+//  (addc Lo0, multLo), (sube Hi0, multHi),
+// where,
+//  multHi/Lo: product of multiplication
+//  Lo0: initial value of Lo register
+//  Hi0: initial value of Hi register
+// Return true if pattern matching was successful.
+static bool selectMSUB(SDNode *SUBENode, SelectionDAG *CurDAG) {
+  // SUBENode's second operand must be a flag output of an SUBC node in order
+  // for the matching to be successful.
+  SDNode *SUBCNode = SUBENode->getOperand(2).getNode();
+
+  if (SUBCNode->getOpcode() != ISD::SUBC)
+    return false;
+
+  SDValue MultHi = SUBENode->getOperand(1);
+  SDValue MultLo = SUBCNode->getOperand(1);
+  SDNode *MultNode = MultHi.getNode();
+  unsigned MultOpc = MultHi.getOpcode();
+
+  // MultHi and MultLo must be generated by the same node,
+  if (MultLo.getNode() != MultNode)
+    return false;
+
+  // and it must be a multiplication.
+  if (MultOpc != ISD::SMUL_LOHI && MultOpc != ISD::UMUL_LOHI)
+    return false;
+
+  // MultLo amd MultHi must be the first and second output of MultNode
+  // respectively.
+  if (MultHi.getResNo() != 1 || MultLo.getResNo() != 0)
+    return false;
+
+  // Transform this to a MSUB only if SUBENode and SUBCNode are the only users
+  // of the values of MultNode, in which case MultNode will be removed in later
+  // phases.
+  // If there exist users other than SUBENode or SUBCNode, this function returns
+  // here, which will result in MultNode being mapped to a single MULT
+  // instruction node rather than a pair of MULT and MSUB instructions being
+  // produced.
+  if (!MultHi.hasOneUse() || !MultLo.hasOneUse())
+    return false;
+
+  SDValue Chain = CurDAG->getEntryNode();
+  DebugLoc DL = SUBENode->getDebugLoc();
+
+  // Initialize accumulator.
+  SDValue ACCIn = CurDAG->getNode(MipsISD::InsertLOHI, DL, MVT::Untyped,
+                                  SUBCNode->getOperand(0),
+                                  SUBENode->getOperand(0));
+
+  // create MipsSub(u) node
+  MultOpc = MultOpc == ISD::UMUL_LOHI ? MipsISD::MSubu : MipsISD::MSub;
+
+  SDValue MSub = CurDAG->getNode(MultOpc, DL, MVT::Glue,
+                                 MultNode->getOperand(0),// Factor 0
+                                 MultNode->getOperand(1),// Factor 1
+                                 ACCIn);
+
+  // replace uses of sube and subc here
+  if (!SDValue(SUBCNode, 0).use_empty()) {
+    SDValue LoIdx = CurDAG->getConstant(Mips::sub_lo, MVT::i32);
+    SDValue LoOut = CurDAG->getNode(MipsISD::ExtractLOHI, DL, MVT::i32, MSub,
+                                    LoIdx);
+    CurDAG->ReplaceAllUsesOfValueWith(SDValue(SUBCNode, 0), LoOut);
+  }
+  if (!SDValue(SUBENode, 0).use_empty()) {
+    SDValue HiIdx = CurDAG->getConstant(Mips::sub_hi, MVT::i32);
+    SDValue HiOut = CurDAG->getNode(MipsISD::ExtractLOHI, DL, MVT::i32, MSub,
+                                    HiIdx);
+    CurDAG->ReplaceAllUsesOfValueWith(SDValue(SUBENode, 0), HiOut);
+  }
+
+  return true;
+}
+
+static SDValue performADDECombine(SDNode *N, SelectionDAG &DAG,
+                                  TargetLowering::DAGCombinerInfo &DCI,
+                                  const MipsSubtarget *Subtarget) {
+  if (DCI.isBeforeLegalize())
+    return SDValue();
+
+  if (Subtarget->hasMips32() && N->getValueType(0) == MVT::i32 &&
+      selectMADD(N, &DAG))
+    return SDValue(N, 0);
+
+  return SDValue();
+}
+
+static SDValue performSUBECombine(SDNode *N, SelectionDAG &DAG,
+                                  TargetLowering::DAGCombinerInfo &DCI,
+                                  const MipsSubtarget *Subtarget) {
+  if (DCI.isBeforeLegalize())
+    return SDValue();
+
+  if (Subtarget->hasMips32() && N->getValueType(0) == MVT::i32 &&
+      selectMSUB(N, &DAG))
+    return SDValue(N, 0);
+
+  return SDValue();
+}
+
+SDValue
+MipsSETargetLowering::PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const {
+  SelectionDAG &DAG = DCI.DAG;
+
+  switch (N->getOpcode()) {
+  case ISD::ADDE:
+    return performADDECombine(N, DAG, DCI, Subtarget);
+  case ISD::SUBE:
+    return performSUBECombine(N, DAG, DCI, Subtarget);
+  default:
+    return MipsTargetLowering::PerformDAGCombine(N, DCI);
+  }
+}
+
 MachineBasicBlock *
 MipsSETargetLowering::EmitInstrWithCustomInserter(MachineInstr *MI,
                                                   MachineBasicBlock *BB) const {