Change NaN with large number

Summary:
Changed NaN with large number to support `-ffast-math` compiler flag.For  `-ffast-math` to work, all floating point numbers should be finite. Reason for not going with `FLT_MAX`, is that, it may cause number overflow during math operations. So thats why I opted for big number smaller than `FLT_MAX`.  Earlier we used NaN, while NaN is involved in comparision the comparision operator behaves differently, it always returns false. Also operators like, fmaxf,fminf etc. have wierd beahviours. This diff takes care of those things as far as possible, and all tests are passing.

Running ./instrumentation_tests/run instrumentation_tests/com/facebook/feed/ctacoalescing:ctacoalescing --class AttachmentCallToActionSelectorBenchmarkTest --benchmark --extra-arg iterations=100 shows the perf gain of 13-15%

Reviewed By: emilsjolander

Differential Revision: D6969537

fbshipit-source-id: bdc09eaf703e0d313ca65c25a4fb44c99203d9bf

java/com/facebook/yoga/YogaConstants.java

@@ -9,12 +9,29 @@ package com.facebook.yoga;
 
 public class YogaConstants {
 
-  public static final float UNDEFINED = Float.NaN;
+  /**
+   * Large positive number signifies that the property(float) is undefined. Earlier we used to have
+   * YGundefined as NAN, but the downside of this is that we can't use -ffast-math compiler flag as
+   * it assumes all floating-point calculation involve and result into finite numbers. For more
+   * information regarding -ffast-math compiler flag in clang, have a look at
+   * https://clang.llvm.org/docs/UsersManual.html#cmdoption-ffast-math
+   */
+  public static final float UNDEFINED = (float) (10E20);
 
   public static boolean shouldUseFastMath = false;
 
   public static boolean isUndefined(float value) {
-    return Float.compare(value, UNDEFINED) == 0;
+    // Value of a float in the case of it being not defined is 10.1E20. Earlier it used to be NAN,
+    // the benefit of which
+    // was that if NAN is involved in any mathematical expression the result was NAN. But since we
+    // want to have `-ffast-math`
+    // flag being used by compiler which assumes that the floating point values are not NAN and Inf,
+    // we represent YGUndefined as 10.1E20.
+    // But now if YGUndefined is involved in any mathematical operations this value(10.1E20) would
+    // change.
+    // So the following check makes sure that if the value is outside a range (-10E8, 10E8) then it
+    // is undefined.
+    return (Float.compare(value, (float) 10E8) >= 0 || Float.compare(value, (float) -10E8) <= 0);
   }
 
   public static boolean isUndefined(YogaValue value) {

java/com/facebook/yoga/YogaNode.java

@@ -652,11 +652,11 @@ public class YogaNode implements Cloneable {
     }
 
     return mMeasureFunction.measure(
-          this,
-          width,
-          YogaMeasureMode.fromInt(widthMode),
-          height,
-          YogaMeasureMode.fromInt(heightMode));
+        this,
+        width,
+        YogaMeasureMode.fromInt(widthMode),
+        height,
+        YogaMeasureMode.fromInt(heightMode));
   }
 
   private native void jni_YGNodeSetHasBaselineFunc(long nativePointer, boolean hasMeasureFunc);