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/Mips/MipsTargetMachine.h b/lib/Target/Mips/MipsTargetMachine.h
index c3428be..cd671cf 100644
--- a/lib/Target/Mips/MipsTargetMachine.h
+++ b/lib/Target/Mips/MipsTargetMachine.h
@@ -47,8 +47,8 @@
       return &InstrInfo.getRegisterInfo();
     }
 
-    virtual MipsTargetLowering   *getTargetLowering() const { 
-      return const_cast<MipsTargetLowering*>(&TLInfo); 
+    virtual const MipsTargetLowering *getTargetLowering() const { 
+      return &TLInfo;
     }
 
     // Pass Pipeline Configuration