Add custom implementation of half float

2025-03-06 15:35:12 +01:00
parent 7b70b6cce5
commit 05b0aa9a2f
3 changed files with 90 additions and 8 deletions
@@ -0,0 +1,61 @@
+#ifndef TFLOAT16_H
+#define TFLOAT16_H
+
+// crude implementation of float16 for platforms that do not support _Float16
+
+#include <stdint.h>
+
+class TFloat16
+{
+    uint16_t b16;
+public:
+    TFloat16(){ b16 = 0; }
+    explicit inline TFloat16(float f)
+    {
+        uint32_t i = *reinterpret_cast<uint32_t*>(&f);
+        uint32_t sign = (i >> 16) & 0x8000;
+        uint32_t exp = (i >> 23) & 0xff;
+        uint32_t mantisa = (i & 0x7fffff) >> 13;
+
+        b16 = 0;
+        if(exp < 111)
+        {
+            // do nothing it map to 0
+        }
+        else if(exp == 111)
+        {
+            b16 |= sign;
+            b16 |= mantisa;
+        }
+        else if(exp > 142)
+        {
+            b16 = 0x7c00;// inf
+            b16 |= sign;
+        }
+        else
+        {
+            b16 |= sign;
+            b16 |= (exp - 112) << 10;
+            b16 |= mantisa;
+        }
+    }
+    friend TFloat16 operator*(TFloat16 a, TFloat16 b)
+    {
+        return TFloat16(static_cast<float>(a) * static_cast<float>(b));
+    }
+    operator float() const
+    {
+        uint32_t i = 0;
+        uint32_t sign = b16 & 0x8000;
+        uint32_t exp = (b16 & 0x7c00) >> 10;
+        if(b16)
+        {
+            i |= sign << 16;
+            i |= (exp + 112) << 23;
+            i |= (b16 & 0x3ff) << 13;
+        }
+        return *reinterpret_cast<float*>(&i);
+    }
+};
+
+#endif // TFLOAT16_H