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/MSP430/MSP430TargetMachine.h b/lib/Target/MSP430/MSP430TargetMachine.h
index d93ac5c..68bde9a 100644
--- a/lib/Target/MSP430/MSP430TargetMachine.h
+++ b/lib/Target/MSP430/MSP430TargetMachine.h
@@ -50,8 +50,8 @@
     return &InstrInfo.getRegisterInfo();
   }
 
-  virtual MSP430TargetLowering *getTargetLowering() const {
-    return const_cast<MSP430TargetLowering*>(&TLInfo);
+  virtual const MSP430TargetLowering *getTargetLowering() const {
+    return &TLInfo;
   }
 
   virtual bool addInstSelector(PassManagerBase &PM, CodeGenOpt::Level OptLevel);