Replace FP division with fixed-point shift in atan2

jserv · jserv · commit 46e6bb5fe201 · 2025-07-30T15:58:17.000+08:00
The double-precision division was replaced with bit shift operation in
twin_atan2_first_quadrant(), using right shift by 15 bits equivalent to
division by 32768.
diff --git a/src/trig.c b/src/trig.c
@@ -148,7 +148,8 @@ static twin_angle_t twin_atan2_first_quadrant(twin_fixed_t y, twin_fixed_t x)
         }
     }
 
-    return (twin_angle_t) (double) angle / (32768.0) * TWIN_ANGLE_360;
+    /* Fixed-point conversion: angle * TWIN_ANGLE_360 / 32768 */
+    return (twin_angle_t) ((angle * TWIN_ANGLE_360) >> 15);
 }
 
 twin_angle_t twin_atan2(twin_fixed_t y, twin_fixed_t x)

Original file line number	Diff line number	Diff line change
`@@ -148,7 +148,8 @@ static twin_angle_t twin_atan2_first_quadrant(twin_fixed_t y, twin_fixed_t x)`
`148`	`148`	`}`
`149`	`149`	`}`
`150`	`150`
`151`		`- return (twin_angle_t) (double) angle / (32768.0) * TWIN_ANGLE_360;`
	`151`	`+ /* Fixed-point conversion: angle * TWIN_ANGLE_360 / 32768 */`
	`152`	`+ return (twin_angle_t) ((angle * TWIN_ANGLE_360) >> 15);`
`152`	`153`	`}`
`153`	`154`
`154`	`155`	`twin_angle_t twin_atan2(twin_fixed_t y, twin_fixed_t x)`