FloatOptional GCC build fix and more constexpr (#39796)

Summary:
X-link: facebook/yoga#1411

Pull Request resolved: #39796

X-link: facebook/yoga#1414

GCC flags that `isUndefined()` is not declared `constexpr` but that `unwrapOrDefault()` is. `std::isnan` is not constexpr until C++ 23 (because we cannot have nice things), so I made `yoga::isUndefined()` constexpr, using the same code `std::isnan()` boils down to. I then made `FloatOptional` depend on `Comparison.h` (instead of the other way around), so we can use it.

Note that the use of the `std::floating_point` concept here requires the libc++ bump in the previous diff in the stack.

Reviewed By: yungsters

Differential Revision: D49896837

fbshipit-source-id: 61e2bbbfedecffd007a12d42d998e43d3cf5119c

packages/react-native/ReactCommon/yoga/yoga/algorithm/CalculateLayout.cpp

@@ -563,10 +563,10 @@ static void measureNodeWithMeasureFunc(
   // We want to make sure we don't call measure with negative size
   const float innerWidth = yoga::isUndefined(availableWidth)
       ? availableWidth
-      : yoga::maxOrDefined(0, availableWidth - paddingAndBorderAxisRow);
+      : yoga::maxOrDefined(0.0f, availableWidth - paddingAndBorderAxisRow);
   const float innerHeight = yoga::isUndefined(availableHeight)
       ? availableHeight
-      : yoga::maxOrDefined(0, availableHeight - paddingAndBorderAxisColumn);
+      : yoga::maxOrDefined(0.0f, availableHeight - paddingAndBorderAxisColumn);
 
   if (widthMeasureMode == MeasureMode::Exactly &&
       heightMeasureMode == MeasureMode::Exactly) {
@@ -1223,7 +1223,7 @@ static void justifyMainAxis(
       const float occupiedSpaceByChildNodes =
           availableInnerMainDim - flexLine.layout.remainingFreeSpace;
       flexLine.layout.remainingFreeSpace = yoga::maxOrDefined(
-          0, minAvailableMainDim - occupiedSpaceByChildNodes);
+          0.0f, minAvailableMainDim - occupiedSpaceByChildNodes);
     } else {
       flexLine.layout.remainingFreeSpace = 0;
     }
@@ -1260,7 +1260,7 @@ static void justifyMainAxis(
       case Justify::SpaceBetween:
         if (flexLine.itemsInFlow.size() > 1) {
           betweenMainDim +=
-              yoga::maxOrDefined(flexLine.layout.remainingFreeSpace, 0) /
+              yoga::maxOrDefined(flexLine.layout.remainingFreeSpace, 0.0f) /
               static_cast<float>(flexLine.itemsInFlow.size() - 1);
         }
         break;

packages/react-native/ReactCommon/yoga/yoga/numeric/Comparison.h

@@ -7,63 +7,49 @@
 
 #pragma once
 
+#include <algorithm>
 #include <array>
+#include <cmath>
 
 #include <yoga/Yoga.h>
-#include <yoga/numeric/FloatOptional.h>
 
 namespace facebook::yoga {
 
-template <typename FloatT>
-inline bool isUndefined(FloatT value) {
-  return std::isnan(value);
+constexpr bool isUndefined(auto value) {
+  return value != value;
 }
 
-inline float maxOrDefined(const float a, const float b) {
+constexpr auto maxOrDefined(auto a, auto b) {
   if (!yoga::isUndefined(a) && !yoga::isUndefined(b)) {
-    return fmaxf(a, b);
+    return std::max(a, b);
   }
   return yoga::isUndefined(a) ? b : a;
 }
 
-inline float minOrDefined(const float a, const float b) {
+constexpr auto minOrDefined(auto a, auto b) {
   if (!yoga::isUndefined(a) && !yoga::isUndefined(b)) {
-    return fminf(a, b);
+    return std::min(a, b);
   }
 
   return yoga::isUndefined(a) ? b : a;
 }
 
-inline FloatOptional maxOrDefined(FloatOptional op1, FloatOptional op2) {
-  if (op1 >= op2) {
-    return op1;
-  }
-  if (op2 > op1) {
-    return op2;
-  }
-  return op1.isUndefined() ? op2 : op1;
-}
-
 // Custom equality functions using a hardcoded epsilon of 0.0001f, or returning
 // true if both floats are NaN.
-inline bool inexactEquals(const float a, const float b) {
+inline bool inexactEquals(float a, float b) {
   if (!yoga::isUndefined(a) && !yoga::isUndefined(b)) {
-    return fabs(a - b) < 0.0001f;
+    return std::abs(a - b) < 0.0001f;
   }
   return yoga::isUndefined(a) && yoga::isUndefined(b);
 }
 
-inline bool inexactEquals(const double a, const double b) {
+inline bool inexactEquals(double a, double b) {
   if (!yoga::isUndefined(a) && !yoga::isUndefined(b)) {
-    return fabs(a - b) < 0.0001;
+    return std::abs(a - b) < 0.0001;
   }
   return yoga::isUndefined(a) && yoga::isUndefined(b);
 }
 
-inline bool inexactEquals(const FloatOptional a, const FloatOptional b) {
-  return inexactEquals(a.unwrap(), b.unwrap());
-}
-
 inline bool inexactEquals(const YGValue& a, const YGValue& b) {
   if (a.unit != b.unit) {
     return false;

packages/react-native/ReactCommon/yoga/yoga/numeric/FloatOptional.h

@@ -7,7 +7,7 @@
 
 #pragma once
 
-#include <cmath>
+#include <yoga/numeric/Comparison.h>
 #include <limits>
 
 namespace facebook::yoga {
@@ -29,53 +29,61 @@ struct FloatOptional {
     return isUndefined() ? defaultValue : value_;
   }
 
-  bool isUndefined() const {
-    return std::isnan(value_);
+  constexpr bool isUndefined() const {
+    return yoga::isUndefined(value_);
   }
 };
 
 // operators take FloatOptional by value, as it is a 32bit value
 
-inline bool operator==(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator==(FloatOptional lhs, FloatOptional rhs) {
   return lhs.unwrap() == rhs.unwrap() ||
       (lhs.isUndefined() && rhs.isUndefined());
 }
-inline bool operator!=(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator!=(FloatOptional lhs, FloatOptional rhs) {
   return !(lhs == rhs);
 }
 
-inline bool operator==(FloatOptional lhs, float rhs) {
+constexpr bool operator==(FloatOptional lhs, float rhs) {
   return lhs == FloatOptional{rhs};
 }
-inline bool operator!=(FloatOptional lhs, float rhs) {
+constexpr bool operator!=(FloatOptional lhs, float rhs) {
   return !(lhs == rhs);
 }
 
-inline bool operator==(float lhs, FloatOptional rhs) {
+constexpr bool operator==(float lhs, FloatOptional rhs) {
   return rhs == lhs;
 }
-inline bool operator!=(float lhs, FloatOptional rhs) {
+constexpr bool operator!=(float lhs, FloatOptional rhs) {
   return !(lhs == rhs);
 }
 
-inline FloatOptional operator+(FloatOptional lhs, FloatOptional rhs) {
+constexpr FloatOptional operator+(FloatOptional lhs, FloatOptional rhs) {
   return FloatOptional{lhs.unwrap() + rhs.unwrap()};
 }
 
-inline bool operator>(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator>(FloatOptional lhs, FloatOptional rhs) {
   return lhs.unwrap() > rhs.unwrap();
 }
 
-inline bool operator<(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator<(FloatOptional lhs, FloatOptional rhs) {
   return lhs.unwrap() < rhs.unwrap();
 }
 
-inline bool operator>=(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator>=(FloatOptional lhs, FloatOptional rhs) {
   return lhs > rhs || lhs == rhs;
 }
 
-inline bool operator<=(FloatOptional lhs, FloatOptional rhs) {
+constexpr bool operator<=(FloatOptional lhs, FloatOptional rhs) {
   return lhs < rhs || lhs == rhs;
 }
 
+constexpr FloatOptional maxOrDefined(FloatOptional lhs, FloatOptional rhs) {
+  return FloatOptional{yoga::maxOrDefined(lhs.unwrap(), rhs.unwrap())};
+}
+
+inline bool inexactEquals(FloatOptional lhs, FloatOptional rhs) {
+  return yoga::inexactEquals(lhs.unwrap(), rhs.unwrap());
+}
+
 } // namespace facebook::yoga