Simplify floating-point comparisons with NaN in Optimizing.

This change was suggested by Ian.

Also, simplify some art::HFloatConstant and
art::HDoubleConstant methods.

Change-Id: I7908df23581a7f61c8ec79c290fe5f70798ac3be
diff --git a/compiler/optimizing/nodes.h b/compiler/optimizing/nodes.h
index 5fc0470..53bff91 100644
--- a/compiler/optimizing/nodes.h
+++ b/compiler/optimizing/nodes.h
@@ -2094,15 +2094,16 @@
   size_t ComputeHashCode() const OVERRIDE { return static_cast<size_t>(GetValue()); }
 
   bool IsMinusOne() const OVERRIDE {
-    return bit_cast<uint32_t, float>(AsFloatConstant()->GetValue()) ==
-        bit_cast<uint32_t, float>((-1.0f));
+    return bit_cast<uint32_t, float>(value_) == bit_cast<uint32_t, float>((-1.0f));
   }
   bool IsZero() const OVERRIDE {
-    return AsFloatConstant()->GetValue() == 0.0f;
+    return value_ == 0.0f;
   }
   bool IsOne() const OVERRIDE {
-    return bit_cast<uint32_t, float>(AsFloatConstant()->GetValue()) ==
-        bit_cast<uint32_t, float>(1.0f);
+    return bit_cast<uint32_t, float>(value_) == bit_cast<uint32_t, float>(1.0f);
+  }
+  bool IsNaN() const {
+    return std::isnan(value_);
   }
 
   DECLARE_INSTRUCTION(FloatConstant);
@@ -2132,15 +2133,16 @@
   size_t ComputeHashCode() const OVERRIDE { return static_cast<size_t>(GetValue()); }
 
   bool IsMinusOne() const OVERRIDE {
-    return bit_cast<uint64_t, double>(AsDoubleConstant()->GetValue()) ==
-        bit_cast<uint64_t, double>((-1.0));
+    return bit_cast<uint64_t, double>(value_) == bit_cast<uint64_t, double>((-1.0));
   }
   bool IsZero() const OVERRIDE {
-    return AsDoubleConstant()->GetValue() == 0.0;
+    return value_ == 0.0;
   }
   bool IsOne() const OVERRIDE {
-    return bit_cast<uint64_t, double>(AsDoubleConstant()->GetValue()) ==
-        bit_cast<uint64_t, double>(1.0);
+    return bit_cast<uint64_t, double>(value_) == bit_cast<uint64_t, double>(1.0);
+  }
+  bool IsNaN() const {
+    return std::isnan(value_);
   }
 
   DECLARE_INSTRUCTION(DoubleConstant);