constify InstCombine::foldAllocaCmp.  NFC.

This is part of an effort to constify ValueTracking.cpp.  This change is
to methods which need const Value* instead of Value* to go with the upcoming
changes to ValueTracking.

llvm-svn: 278528
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index ea6827c..c555ff8 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -541,7 +541,8 @@
 
   Instruction *foldGEPICmp(GEPOperator *GEPLHS, Value *RHS,
                            ICmpInst::Predicate Cond, Instruction &I);
-  Instruction *foldAllocaCmp(ICmpInst &ICI, AllocaInst *Alloca, Value *Other);
+  Instruction *foldAllocaCmp(ICmpInst &ICI, const AllocaInst *Alloca,
+                             const Value *Other);
   Instruction *foldCmpLoadFromIndexedGlobal(GetElementPtrInst *GEP,
                                             GlobalVariable *GV, CmpInst &ICI,
                                             ConstantInt *AndCst = nullptr);