ray: simplify nan checking by creating a macro.

Avoids the #ifdef forest and code duplication resulting from it.
There was mismatch in the two code paths, see [1] and [2], and this
commit avoids repeating the same mistake.

While there, use isnan() instead of fpclassify() == FP_NAN for the case
where isnanf() isn't available.

We use isnanf() (if available) instead of isnan() due to [3]:

    I initially used isinf() and isnan(), but those ended up breaking
    when using GCC because it tried to promote floats to doubles, and
    the results wouldn't match any more—especially when using GCC
    vectorisation.
    It could very well be a bug in GCC.

[1] #223
[2] https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3976
[3] #174 (comment)

Author: ericonr

src/graphene-private.h

@@ -105,6 +105,14 @@
 
 #endif /* __GNUC__ */
 
+#if defined(_M_X64) && ! defined(isnanf)
+# define graphene_isnan(x) _isnanf(x)
+#elif defined(HAVE_ISNANF)
+# define graphene_isnan(x) isnanf(x)
+#else
+# define graphene_isnan(x) isnan(x)
+#endif
+
 static inline bool
 graphene_approx_val (float a, float b)
 {

src/graphene-ray.c

@@ -52,11 +52,6 @@
 #include <math.h>
 #include <float.h>
 
-#if defined(_M_X64) && ! defined(isnanf)
-# define isnanf(x) _isnanf(x)
-# define HAVE_ISNANF
-#endif
-
 /**
  * graphene_ray_alloc: (constructor)
  *
@@ -555,17 +550,10 @@ graphene_ray_intersect_box (const graphene_ray_t *r,
   /* These lines also handle the case where tx_min or tx_max is NaN
    * (result of 0 * INFINITY): NaN != NaN
    */
-#ifdef HAVE_ISNANF
-  if (ty_min > tx_min || isnanf (tx_min))
-    tx_min = ty_min;
-  if (ty_max < tx_max || isnanf (tx_max))
-    tx_max = ty_max;
-#else
-  if (ty_min > tx_min || fpclassify (tx_min) == FP_NAN)
+  if (ty_min > tx_min || graphene_isnan (tx_min))
     tx_min = ty_min;
-  if (ty_max > tx_max || fpclassify (tx_max) == FP_NAN)
+  if (ty_max < tx_max || graphene_isnan (tx_max))
     tx_max = ty_max;
-#endif
 
   float tz_min, tz_max;
   if (graphene_vec3_get_z (&inv_dir) >= 0.f)
@@ -582,17 +570,10 @@ graphene_ray_intersect_box (const graphene_ray_t *r,
   if ((tx_min > tz_max) || (tz_min > tx_max))
     return GRAPHENE_RAY_INTERSECTION_KIND_NONE;
 
-#ifdef HAVE_ISNANF
-  if (tz_min > tx_min || isnanf (tx_min))
-    tx_min = tz_min;
-  if (tz_max < tx_max || isnanf (tx_max))
-    tx_max = tz_max;
-#else
-  if (tz_min > tx_min || fpclassify (tx_min) == FP_NAN)
+  if (tz_min > tx_min || graphene_isnan (tx_min))
     tx_min = tz_min;
-  if (tz_max < tx_max || fpclassify (tx_max) == FP_NAN)
+  if (tz_max < tx_max || graphene_isnan (tx_max))
     tx_max = tz_max;
-#endif
 
   /* return the point closest to the ray (positive side) */
   if (tx_max < 0)