Pica: Add float24 structure.

24-bit floating points are used internally for calculations on the GPU, however the current code will still emulate that with 32-bit floating points.
In the future we might want to accurately perform the calculations with correct bitness in the future, but for now we just wrap the calculations around this class.

src/video_core/pica.h

@@ -161,6 +161,81 @@ ASSERT_REG_POSITION(vertex_descriptor, 0x200);
 // The total number of registers is chosen arbitrarily, but let's make sure it's not some odd value anyway.
 static_assert(sizeof(Regs) == 0x300 * sizeof(u32), "Invalid total size of register set");
 
+
+struct float24 {
+    static float24 FromFloat32(float val) {
+        float24 ret;
+        ret.value = val;
+        return ret;
+    }
+
+    // 16 bit mantissa, 7 bit exponent, 1 bit sign
+    // TODO: No idea if this works as intended
+    static float24 FromRawFloat24(u32 hex) {
+        float24 ret;
+        if ((hex & 0xFFFFFF) == 0) {
+            ret.value = 0;
+        } else {
+            u32 mantissa = hex & 0xFFFF;
+            u32 exponent = (hex >> 16) & 0x7F;
+            u32 sign = hex >> 23;
+            ret.value = powf(2.0f, (float)exponent-63.0f) * (1.0f + mantissa * powf(2.0f, -16.f));
+            if (sign)
+                ret.value = -ret.value;
+        }
+        return ret;
+    }
+
+    // Not recommended for anything but logging
+    float ToFloat32() const {
+        return value;
+    }
+
+    float24 operator * (const float24& flt) const {
+        return float24::FromFloat32(ToFloat32() * flt.ToFloat32());
+    }
+
+    float24 operator / (const float24& flt) const {
+        return float24::FromFloat32(ToFloat32() / flt.ToFloat32());
+    }
+
+    float24 operator + (const float24& flt) const {
+        return float24::FromFloat32(ToFloat32() + flt.ToFloat32());
+    }
+
+    float24 operator - (const float24& flt) const {
+        return float24::FromFloat32(ToFloat32() - flt.ToFloat32());
+    }
+
+    float24 operator - () const {
+        return float24::FromFloat32(-ToFloat32());
+    }
+
+    bool operator < (const float24& flt) const {
+        return ToFloat32() < flt.ToFloat32();
+    }
+
+    bool operator > (const float24& flt) const {
+        return ToFloat32() > flt.ToFloat32();
+    }
+
+    bool operator >= (const float24& flt) const {
+        return ToFloat32() >= flt.ToFloat32();
+    }
+
+    bool operator <= (const float24& flt) const {
+        return ToFloat32() <= flt.ToFloat32();
+    }
+
+private:
+    float24() = default;
+
+    // Stored as a regular float, merely for convenience
+    // TODO: Perform proper arithmetic on this!
+    float value;
+};
+
+
 union CommandHeader {
     CommandHeader(u32 h) : hex(h) {}