[NFC][LLVMContext] Clean up DenseMapInfo classes used for APInt & APFloat.

DenseMapAPIntKeyInfo looks like a redundant definition because it
mirrors the default used by DenseMap when not specified.

Replacing DenseMapAPFloatKeyInfo with a specialisation of
DenseMapInfo allows DenseMap<T> to be more easily used when T is
an aggregate type containing an APFloat.

Author: paulwalker-arm

llvm/lib/IR/LLVMContextImpl.h

@@ -73,9 +73,7 @@ class StringRef;
 class TypedPointerType;
 class ValueHandleBase;
 
-using DenseMapAPIntKeyInfo = DenseMapInfo<APInt>;
-
-struct DenseMapAPFloatKeyInfo {
+template <> struct DenseMapInfo<APFloat> {
   static inline APFloat getEmptyKey() { return APFloat(APFloat::Bogus(), 1); }
   static inline APFloat getTombstoneKey() {
     return APFloat(APFloat::Bogus(), 2);
@@ -1489,11 +1487,9 @@ class LLVMContextImpl {
 
   DenseMap<unsigned, std::unique_ptr<ConstantInt>> IntZeroConstants;
   DenseMap<unsigned, std::unique_ptr<ConstantInt>> IntOneConstants;
-  DenseMap<APInt, std::unique_ptr<ConstantInt>, DenseMapAPIntKeyInfo>
-      IntConstants;
+  DenseMap<APInt, std::unique_ptr<ConstantInt>> IntConstants;
 
-  DenseMap<APFloat, std::unique_ptr<ConstantFP>, DenseMapAPFloatKeyInfo>
-      FPConstants;
+  DenseMap<APFloat, std::unique_ptr<ConstantFP>> FPConstants;
 
   FoldingSet<AttributeImpl> AttrsSet;
   FoldingSet<AttributeListImpl> AttrsLists;