Reapply 91904.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@91996 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 31 insertions, 8 deletions

diff --git a/lib/Target/PIC16/PIC16ISelLowering.cpp b/lib/Target/PIC16/PIC16ISelLowering.cpp
index c4f45fe157..4cf2b8bb89 100644
--- a/lib/Target/PIC16/PIC16ISelLowering.cpp
+++ b/lib/Target/PIC16/PIC16ISelLowering.cpp
@@ -1482,7 +1482,8 @@ bool PIC16TargetLowering::isDirectLoad(const SDValue Op) {
 // operand no. of the operand to be converted in 'MemOp'. Remember, PIC16 has 
 // no instruction that can operation on two registers. Most insns take
 // one register and one memory operand (addwf) / Constant (addlw).
-bool PIC16TargetLowering::NeedToConvertToMemOp(SDValue Op, unsigned &MemOp) {
+bool PIC16TargetLowering::NeedToConvertToMemOp(SDValue Op, unsigned &MemOp, 
+                      SelectionDAG &DAG) {
   // If one of the operand is a constant, return false.
   if (Op.getOperand(0).getOpcode() == ISD::Constant ||
       Op.getOperand(1).getOpcode() == ISD::Constant)
@@ -1491,11 +1492,33 @@ bool PIC16TargetLowering::NeedToConvertToMemOp(SDValue Op, unsigned &MemOp) {
   // Return false if one of the operands is already a direct
   // load and that operand has only one use.
   if (isDirectLoad(Op.getOperand(0))) {
-    if (Op.getOperand(0).hasOneUse())
-      return false;
-    else 
-      MemOp = 0;
+    if (Op.getOperand(0).hasOneUse()) {  
+      // Legal and profitable folding check uses the NodeId of DAG nodes.
+      // This NodeId is assigned by topological order. Therefore first 
+      // assign topological order then perform legal and profitable check.
+      // Note:- Though this ordering is done before begining with legalization,
+      // newly added node during legalization process have NodeId=-1 (NewNode)
+      // therefore before performing any check proper ordering of the node is
+      // required.
+      DAG.AssignTopologicalOrder();
+
+      // Direct load operands are folded in binary operations. But before folding
+      // verify if this folding is legal. Fold only if it is legal otherwise
+      // convert this direct load to a separate memory operation.
+      if(ISel->IsLegalAndProfitableToFold(Op.getOperand(0).getNode(), 
+                                         Op.getNode(), Op.getNode()))
+        return false;
+      else 
+        MemOp = 0;
+    }
   }
+
+  // For operations that are non-cummutative there is no need to check 
+  // for right operand because folding right operand may result in 
+  // incorrect operation. 
+  if (! SelectionDAG::isCommutativeBinOp(Op.getOpcode()))
+    return true;
+
   if (isDirectLoad(Op.getOperand(1))) {
     if (Op.getOperand(1).hasOneUse())
       return false;
@@ -1514,7 +1537,7 @@ SDValue PIC16TargetLowering::LowerBinOp(SDValue Op, SelectionDAG &DAG) {
   assert (Op.getValueType() == MVT::i8 && "illegal Op to lower");
 
   unsigned MemOp = 1;
-  if (NeedToConvertToMemOp(Op, MemOp)) {
+  if (NeedToConvertToMemOp(Op, MemOp, DAG)) {
     // Put one value on stack.
     SDValue NewVal = ConvertToMemOperand (Op.getOperand(MemOp), DAG, dl);
 
@@ -1533,7 +1556,7 @@ SDValue PIC16TargetLowering::LowerADD(SDValue Op, SelectionDAG &DAG) {
   assert (Op.getValueType() == MVT::i8 && "illegal add to lower");
   DebugLoc dl = Op.getDebugLoc();
   unsigned MemOp = 1;
-  if (NeedToConvertToMemOp(Op, MemOp)) {
+  if (NeedToConvertToMemOp(Op, MemOp, DAG)) {
     // Put one value on stack.
     SDValue NewVal = ConvertToMemOperand (Op.getOperand(MemOp), DAG, dl);
     
@@ -1574,7 +1597,7 @@ SDValue PIC16TargetLowering::LowerSUB(SDValue Op, SelectionDAG &DAG) {
                          DAG.getConstant(0-(C->getZExtValue()), MVT::i8));
     }
 
-  if (NeedToConvertToMemOp(Op, MemOp) ||
+  if (NeedToConvertToMemOp(Op, MemOp, DAG) ||
       (isDirectLoad(Op.getOperand(1)) && 
        (!isDirectLoad(Op.getOperand(0))) &&
        (Op.getOperand(0).getOpcode() != ISD::Constant)))