Store YGFloatOptional in 32 bits

Summary:
@public

After removing `-ffast-math`, `NaN` can again be used to represent `undefined`. That allows us to remove the additional flag from `YGFloatOptional`, and reduce memory usage.

Reviewed By: SidharthGuglani

Differential Revision: D13439611

fbshipit-source-id: 93e90f72f0415edb228b4e7d145e1fae35cc6b43

tests/YGFloatOptionalTest.cpp

@@ -10,11 +10,11 @@
 #include <yoga/YGFloatOptional.h>
 #include <yoga/YGValue.h>
 
-static const auto empty = YGFloatOptional{};
+constexpr auto empty = YGFloatOptional{};
-static const auto zero = YGFloatOptional{0.0f};
+constexpr auto zero = YGFloatOptional{0.0f};
-static const auto one = YGFloatOptional{1.0f};
+constexpr auto one = YGFloatOptional{1.0f};
-static const auto positive = YGFloatOptional{1234.5f};
+constexpr auto positive = YGFloatOptional{1234.5f};
-static const auto negative = YGFloatOptional{-9876.5f};
+constexpr auto negative = YGFloatOptional{-9876.5f};
 
 TEST(YGFloatOptional, value) {
   ASSERT_EQ(zero.getValue(), 0.0f);

yoga/YGFloatOptional.cpp

@@ -7,23 +7,13 @@
 #include "YGFloatOptional.h"
 #include <cstdlib>
 #include <iostream>
-#include "Yoga.h"
 #include "Yoga-internal.h"
+#include "Yoga.h"
 
 using namespace facebook;
 
-YGFloatOptional::YGFloatOptional(float value) {
-  if (yoga::isUndefined(value)) {
-    isUndefined_ = true;
-    value_ = 0;
-  } else {
-    value_ = value;
-    isUndefined_ = false;
-  }
-}
-
 float YGFloatOptional::getValue() const {
-  if (isUndefined_) {
+  if (isUndefined()) {
     // Abort, accessing a value of an undefined float optional
     std::cerr << "Tried to get value of an undefined YGFloatOptional\n";
     std::exit(EXIT_FAILURE);
@@ -31,53 +21,38 @@ float YGFloatOptional::getValue() const {
   return value_;
 }
 
-bool YGFloatOptional::operator==(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator==(YGFloatOptional op) const {
-  if (isUndefined_ == op.isUndefined()) {
+  return value_ == op.value_ || (isUndefined() && op.isUndefined());
-    return isUndefined_ || value_ == op.getValue();
-  }
-  return false;
 }
 
-bool YGFloatOptional::operator!=(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator!=(YGFloatOptional op) const {
   return !(*this == op);
 }
 
 bool YGFloatOptional::operator==(float val) const {
-  if (yoga::isUndefined(val) == isUndefined_) {
+  return value_ == val || (isUndefined() && yoga::isUndefined(val));
-    return isUndefined_ || val == value_;
-  }
-  return false;
 }
 
 bool YGFloatOptional::operator!=(float val) const {
   return !(*this == val);
 }
 
-YGFloatOptional YGFloatOptional::operator+(const YGFloatOptional& op) const {
+YGFloatOptional YGFloatOptional::operator+(YGFloatOptional op) const {
-  if (!isUndefined_ && !op.isUndefined_) {
+  return YGFloatOptional{value_ + op.value_};
-    return YGFloatOptional(value_ + op.value_);
-  }
-  return YGFloatOptional();
 }
 
-bool YGFloatOptional::operator>(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator>(YGFloatOptional op) const {
-  if (isUndefined_ || op.isUndefined_) {
-    return false;
-  }
   return value_ > op.value_;
 }
 
-bool YGFloatOptional::operator<(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator<(YGFloatOptional op) const {
-  if (isUndefined_ || op.isUndefined_) {
-    return false;
-  }
   return value_ < op.value_;
 }
 
-bool YGFloatOptional::operator>=(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator>=(YGFloatOptional op) const {
-  return *this == op || *this > op;
+  return *this > op || *this == op;
 }
 
-bool YGFloatOptional::operator<=(const YGFloatOptional& op) const {
+bool YGFloatOptional::operator<=(YGFloatOptional op) const {
-  return *this == op || *this < op;
+  return *this < op || *this == op;
 }

yoga/YGFloatOptional.h

@@ -6,37 +6,33 @@
  */
 #pragma once
 
+#include <cmath>
+#include <limits>
+
 struct YGFloatOptional {
  private:
-  float value_ = 0;
+  float value_ = std::numeric_limits<float>::quiet_NaN();
-  bool isUndefined_ = true;
 
  public:
-  explicit YGFloatOptional(float value);
+  explicit constexpr YGFloatOptional(float value) : value_(value) {}
-  YGFloatOptional() = default;
+  constexpr YGFloatOptional() = default;
 
   // Program will terminate if the value of an undefined is accessed. Please
   // make sure to check if the optional is defined before calling this function.
   // To check if float optional is defined, use `isUndefined()`.
   float getValue() const;
 
-  // Sets the value of float optional, and thus isUndefined is assigned false.
-  void setValue(float val) {
-    value_ = val;
-    isUndefined_ = false;
-  }
-
   bool isUndefined() const {
-    return isUndefined_;
+    return std::isnan(value_);
   }
 
-  YGFloatOptional operator+(const YGFloatOptional& op) const;
+  YGFloatOptional operator+(YGFloatOptional op) const;
-  bool operator>(const YGFloatOptional& op) const;
+  bool operator>(YGFloatOptional op) const;
-  bool operator<(const YGFloatOptional& op) const;
+  bool operator<(YGFloatOptional op) const;
-  bool operator>=(const YGFloatOptional& op) const;
+  bool operator>=(YGFloatOptional op) const;
-  bool operator<=(const YGFloatOptional& op) const;
+  bool operator<=(YGFloatOptional op) const;
-  bool operator==(const YGFloatOptional& op) const;
+  bool operator==(YGFloatOptional op) const;
-  bool operator!=(const YGFloatOptional& op) const;
+  bool operator!=(YGFloatOptional op) const;
 
   bool operator==(float val) const;
   bool operator!=(float val) const;

yoga/YGNode.cpp

@@ -211,7 +211,7 @@ YGFloatOptional YGNode::relativePosition(
 
   YGFloatOptional trailingPosition = getTrailingPosition(axis, axisSize);
   if (!trailingPosition.isUndefined()) {
-    trailingPosition.setValue(-1 * trailingPosition.getValue());
+    trailingPosition = YGFloatOptional{-1 * trailingPosition.getValue()};
   }
   return trailingPosition;
 }