Subzero: Fix floating-point constant pooling.

src/IceGlobalContext.cpp

 //===- subzero/src/IceGlobalContext.cpp - Global context defs -------------===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file defines aspects of the compilation that persist across
@@ skipping 22 matching lines @@
 template <> struct hash<Ice::RelocatableTuple> {
   size_t operator()(const Ice::RelocatableTuple &Key) const {
     return hash<Ice::IceString>()(Key.Name) +
            hash<Ice::RelocOffsetT>()(Key.Offset);
   }
 };
 } // end of namespace std
 
 namespace Ice {
 
+namespace {
+
+// Define the key comparison function for the constant pool's
+// unordered_map, but only for key types of interest: integer types,
+// floating point types, and the special RelocatableTuple.
+template <typename KeyType, class Enable = void> struct KeyCompare {};
+
+template <typename KeyType>
+struct KeyCompare<KeyType,
+                  typename std::enable_if<
+                      std::is_integral<KeyType>::value ||
+                      std::is_same<KeyType, RelocatableTuple>::value>::type> {
+  bool operator()(const KeyType &Value1, const KeyType &Value2) const {
+    return Value1 == Value2;
+  }
+};
+template <typename KeyType>
+struct KeyCompare<KeyType, typename std::enable_if<
+                               std::is_floating_point<KeyType>::value>::type> {
+  bool operator()(const KeyType &Value1, const KeyType &Value2) const {
+    return !memcmp(&Value1, &Value2, sizeof(KeyType));
+  }
+};
+
 // TypePool maps constants of type KeyType (e.g. float) to pointers to
 // type ValueType (e.g. ConstantFloat).
 template <Type Ty, typename KeyType, typename ValueType> class TypePool {
   TypePool(const TypePool &) = delete;
   TypePool &operator=(const TypePool &) = delete;
 
 public:
   TypePool() : NextPoolID(0) {}
   ValueType *getOrAdd(GlobalContext *Ctx, KeyType Key) {
     auto Iter = Pool.find(Key);
     if (Iter != Pool.end())
       return Iter->second;
     ValueType *Result = ValueType::create(Ctx, Ty, Key, NextPoolID++);
     Pool[Key] = Result;
     return Result;
   }
   ConstantList getConstantPool() const {
     ConstantList Constants;
     Constants.reserve(Pool.size());
     for (auto &I : Pool)
       Constants.push_back(I.second);
     return Constants;
   }
 
 private:
-  typedef std::unordered_map<KeyType, ValueType *> ContainerType;
+  // Use the default hash function, and a custom key comparison
+  // function.  The key comparison function for floating point
+  // variables can't use the default == based implementation because
+  // of special C++ semantics regarding +0.0, -0.0, and NaN
+  // comparison.  However, it's OK to use the default hash for
+  // floating point values because KeyCompare is the final source of
+  // truth - in the worst case a "false" collision must be resolved.
+  typedef std::unordered_map<KeyType, ValueType *, std::hash<KeyType>,
+                             KeyCompare<KeyType>> ContainerType;
   ContainerType Pool;
   uint32_t NextPoolID;
 };
 
 // UndefPool maps ICE types to the corresponding ConstantUndef values.
 class UndefPool {
   UndefPool(const UndefPool &) = delete;
   UndefPool &operator=(const UndefPool &) = delete;
 
 public:
   UndefPool() : NextPoolID(0), Pool(IceType_NUM) {}
 
   ConstantUndef *getOrAdd(GlobalContext *Ctx, Type Ty) {
     if (Pool[Ty] == nullptr)
       Pool[Ty] = ConstantUndef::create(Ctx, Ty, NextPoolID++);
     return Pool[Ty];
   }
 
 private:
   uint32_t NextPoolID;
   std::vector<ConstantUndef *> Pool;
 };
 
+} // end of anonymous namespace
+
 // The global constant pool bundles individual pools of each type of
 // interest.
 class ConstantPool {
   ConstantPool(const ConstantPool &) = delete;
   ConstantPool &operator=(const ConstantPool &) = delete;
 
 public:
   ConstantPool() {}
   TypePool<IceType_f32, float, ConstantFloat> Floats;
   TypePool<IceType_f64, double, ConstantDouble> Doubles;
@@ skipping 639 matching lines @@
   Ctx = Func->getContext();
   Active =
       Func->getFocusedTiming() || Ctx->getFlags().getSubzeroTimingEnabled();
   if (Active)
     Ctx->pushTimer(ID, StackID);
 }
 
 ICE_TLS_DEFINE_FIELD(GlobalContext::ThreadContext *, GlobalContext, TLS);
 
 } // end of namespace Ice