Use const qualifiers with TargetLowering. This eliminates several
const_casts, and it reinforces the design of the Target classes being
immutable.

SelectionDAGISel::IsLegalToFold is now a static member function, because
PIC16 uses it in an unconventional way. There is more room for API
cleanup here.

And PIC16's AsmPrinter no longer uses TargetLowering.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101635 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/Alpha/AlphaISelLowering.h b/lib/Target/Alpha/AlphaISelLowering.h
index b49aa9a..6919c38 100644
--- a/lib/Target/Alpha/AlphaISelLowering.h
+++ b/lib/Target/Alpha/AlphaISelLowering.h
@@ -68,13 +68,13 @@
 
     /// LowerOperation - Provide custom lowering hooks for some operations.
     ///
-    virtual SDValue LowerOperation(SDValue Op, SelectionDAG &DAG);
+    virtual SDValue LowerOperation(SDValue Op, SelectionDAG &DAG) const;
 
     /// ReplaceNodeResults - Replace the results of node with an illegal result
     /// type with new values built out of custom code.
     ///
     virtual void ReplaceNodeResults(SDNode *N, SmallVectorImpl<SDValue>&Results,
-                                    SelectionDAG &DAG);
+                                    SelectionDAG &DAG) const;
 
     // Friendly names for dumps
     const char *getTargetNodeName(unsigned Opcode) const;
@@ -83,7 +83,7 @@
                             CallingConv::ID CallConv, bool isVarArg,
                             const SmallVectorImpl<ISD::InputArg> &Ins,
                             DebugLoc dl, SelectionDAG &DAG,
-                            SmallVectorImpl<SDValue> &InVals);
+                            SmallVectorImpl<SDValue> &InVals) const;
 
     ConstraintType getConstraintType(const std::string &Constraint) const;
 
@@ -108,14 +108,14 @@
   private:
     // Helpers for custom lowering.
     void LowerVAARG(SDNode *N, SDValue &Chain, SDValue &DataPtr,
-                    SelectionDAG &DAG);
+                    SelectionDAG &DAG) const;
 
     virtual SDValue
       LowerFormalArguments(SDValue Chain,
                            CallingConv::ID CallConv, bool isVarArg,
                            const SmallVectorImpl<ISD::InputArg> &Ins,
                            DebugLoc dl, SelectionDAG &DAG,
-                           SmallVectorImpl<SDValue> &InVals);
+                           SmallVectorImpl<SDValue> &InVals) const;
 
     virtual SDValue
       LowerCall(SDValue Chain, SDValue Callee,
@@ -123,13 +123,13 @@
                 const SmallVectorImpl<ISD::OutputArg> &Outs,
                 const SmallVectorImpl<ISD::InputArg> &Ins,
                 DebugLoc dl, SelectionDAG &DAG,
-                SmallVectorImpl<SDValue> &InVals);
+                SmallVectorImpl<SDValue> &InVals) const;
 
     virtual SDValue
       LowerReturn(SDValue Chain,
                   CallingConv::ID CallConv, bool isVarArg,
                   const SmallVectorImpl<ISD::OutputArg> &Outs,
-                  DebugLoc dl, SelectionDAG &DAG);
+                  DebugLoc dl, SelectionDAG &DAG) const;
   };
 }