Code review and speedup for Amaze Demosaic

rtengine/sleefsseavx.c

@@ -1316,7 +1316,9 @@ return vmaxf( b, vminf(a,c));
 }
 
 static INLINE vfloat ULIMV( vfloat a, vfloat b, vfloat c  ){
-	return vself( vmaskf_lt(b,c), LIMV(a,b,c), LIMV(a,c,b));
+    // made to clamp a in range [b,c] but in fact it's also the median of a,b,c, which means that the result is independent on order of arguments
+    // ULIMV(a,b,c) = ULIMV(a,c,b) = ULIMV(b,a,c) = ULIMV(b,c,a) = ULIMV(c,a,b) = ULIMV(c,b,a)
+	return vmaxf(vminf(a,b), vminf(vmaxf(a,b),c));
 }
 
 static INLINE vfloat SQRV(vfloat a){
@@ -1324,17 +1326,45 @@ static INLINE vfloat SQRV(vfloat a){
 }
 
 static inline void vswap( vmask condition, vfloat &a, vfloat &b) {
+    // conditional swap the elements of two vfloats
     vfloat temp = vself(condition, a, b); // the values which fit to condition
     condition = vnotm(condition); // invert the condition
     a = vself(condition, a, b); // the values which fit to inverted condition
     b = temp;
 }
 
-static inline float vhadd( vfloat a )
-{
+static inline float vhadd( vfloat a ) {
+    // returns a[0] + a[1] + a[2] + a[3]
     a += _mm_movehl_ps(a, a);
     return _mm_cvtss_f32(_mm_add_ss(a, _mm_shuffle_ps(a, a, 1)));
 }
 
+static INLINE vfloat vmul2f(vfloat a){
+    // fastest way to multiply by 2
+	return a + a;
+}
+
+static INLINE vfloat vintpf(vfloat a, vfloat b, vfloat c) {
+    // calculate a * b + (1 - a) * c (interpolate two values)
+    // following is valid:
+    // vintpf(a, b+x, c+x) = vintpf(a, b, c) + x
+    // vintpf(a, b*x, c*x) = vintpf(a, b, c) * x
+    return a * (b-c) + c;
+}
+
+static INLINE vfloat vdup(vfloat a){
+    // returns { a[0],a[0],a[1],a[1] }
+    return _mm_unpacklo_ps( a, a );
+}
+
+static INLINE vfloat vaddc2vfu(float &a)
+{
+    // loads a[0]..a[7] and returns { a[0]+a[1], a[2]+a[3], a[4]+a[5], a[6]+a[7] }
+    vfloat a1 = _mm_loadu_ps( &a );
+    vfloat a2 = _mm_loadu_ps( (&a) + 4 );
+    return  _mm_shuffle_ps(a1,a2,_MM_SHUFFLE( 2,0,2,0 )) + _mm_shuffle_ps(a1,a2,_MM_SHUFFLE( 3,1,3,1 ));
+}
+
+
 #endif // __SSE2__
 #endif // SLEEFSSEAVX