[util] Implement fclamp for fp special cases

src/util/util_math.h

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <cmath>
+
 namespace dxvk {
   
   constexpr size_t CACHE_LINE_SIZE = 64;
@@ -16,4 +18,12 @@ namespace dxvk {
     return (what + to - 1) & ~(to - 1);
   }
 
+  // Equivalent of std::clamp for use with floating point numbers
+  // Handles (-){INFINITY,NAN} cases.
+  // Will return min in cases of NAN, etc.
+  inline float fclamp(float value, float min, float max) {
+    return std::fmin(
+      std::fmax(value, min), max);
+  }
+  
 }