Implement a DAGCombine in MipsISelLowering.cpp which transforms the following

pattern:

(add v0, (add v1, abs_lo(tjt))) => (add (add v0, v1), abs_lo(tjt))

"tjt" is a TargetJumpTable node. 

llvm-svn: 158419

2 files changed, 34 insertions, 4 deletions

diff --git a/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp b/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
index 62f7cdea3c0..b0513c31278 100644
--- a/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
+++ b/llvm/lib/Target/Mips/MipsISelDAGToDAG.cpp
@@ -335,11 +335,11 @@ SelectAddr(SDNode *Parent, SDValue Addr, SDValue &Base, SDValue &Offset) {
     //  lui $2, %hi($CPI1_0)
     //  lwc1 $f0, %lo($CPI1_0)($2)
     if (Addr.getOperand(1).getOpcode() == MipsISD::Lo) {
-      SDValue LoVal = Addr.getOperand(1);
-      if (isa<ConstantPoolSDNode>(LoVal.getOperand(0)) ||
-          isa<GlobalAddressSDNode>(LoVal.getOperand(0))) {
+      SDValue LoVal = Addr.getOperand(1), Opnd0 = LoVal.getOperand(0);
+      if (isa<ConstantPoolSDNode>(Opnd0) || isa<GlobalAddressSDNode>(Opnd0) ||
+          isa<JumpTableSDNode>(Opnd0)) {
         Base = Addr.getOperand(0);
-        Offset = LoVal.getOperand(0);
+        Offset = Opnd0;
         return true;
       }
     }
diff --git a/llvm/lib/Target/Mips/MipsISelLowering.cpp b/llvm/lib/Target/Mips/MipsISelLowering.cpp
index aa777f7c2c1..1ea1a671279 100644
--- a/llvm/lib/Target/Mips/MipsISelLowering.cpp
+++ b/llvm/lib/Target/Mips/MipsISelLowering.cpp
@@ -295,6 +295,7 @@ MipsTargetLowering(MipsTargetMachine &TM)
   setTargetDAGCombine(ISD::SELECT);
   setTargetDAGCombine(ISD::AND);
   setTargetDAGCombine(ISD::OR);
+  setTargetDAGCombine(ISD::ADD);
 
   setMinFunctionAlignment(HasMips64 ? 3 : 2);
 
@@ -733,6 +734,33 @@ static SDValue PerformORCombine(SDNode *N, SelectionDAG& DAG,
                      DAG.getConstant(SMSize0, MVT::i32), And0.getOperand(0));
 }
 
+static SDValue PerformADDCombine(SDNode *N, SelectionDAG& DAG,
+                                 TargetLowering::DAGCombinerInfo &DCI,
+                                 const MipsSubtarget* Subtarget) {
+  // (add v0, (add v1, abs_lo(tjt))) => (add (add v0, v1), abs_lo(tjt))
+
+  if (DCI.isBeforeLegalizeOps())
+    return SDValue();
+
+  SDValue Add = N->getOperand(1);
+
+  if (Add.getOpcode() != ISD::ADD)
+    return SDValue();
+
+  SDValue Lo = Add.getOperand(1);
+
+  if ((Lo.getOpcode() != MipsISD::Lo) ||
+      (Lo.getOperand(0).getOpcode() != ISD::TargetJumpTable))
+    return SDValue();
+
+  EVT ValTy = N->getValueType(0);
+  DebugLoc DL = N->getDebugLoc();
+
+  SDValue Add1 = DAG.getNode(ISD::ADD, DL, ValTy, N->getOperand(0),
+                             Add.getOperand(0));
+  return DAG.getNode(ISD::ADD, DL, ValTy, Add1, Lo);
+}
+
 SDValue  MipsTargetLowering::PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI)
   const {
   SelectionDAG &DAG = DCI.DAG;
@@ -753,6 +781,8 @@ SDValue  MipsTargetLowering::PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI)
     return PerformANDCombine(N, DAG, DCI, Subtarget);
   case ISD::OR:
     return PerformORCombine(N, DAG, DCI, Subtarget);
+  case ISD::ADD:
+    return PerformADDCombine(N, DAG, DCI, Subtarget);
   }
 
   return SDValue();