dsp/staurating_scale: fix math
@@ -91,16 +91,12 @@ pub fn macc_i32(y0: i32, x: &[i32], a: &[i32], shift: u32) -> i32 {
/// Combine high and low i32 into a single downscaled i32, saturating the type.
pub fn saturating_scale(lo: i32, hi: i32, shift: u32) -> i32 {
debug_assert!(shift & 31 == shift);
-
- let shift_hi = 31 - shift;
- debug_assert!(shift_hi & 31 == shift_hi);
-
- let over = hi >> shift;
- if over < -1 {
- i32::MIN
- } else if over > 0 {
+ let scale = -1 << shift;
+ if hi <= scale {
+ -i32::MAX
+ } else if -hi <= scale {
i32::MAX
} else {
- (lo >> shift) + (hi << shift_hi)
+ (lo >> shift) + (hi << (31 - shift))
}
}
