Avoid loop tail (#521)

Author: solidpixel

Source/astcenc_weight_align.cpp

@@ -175,24 +175,16 @@ static void compute_lowest_and_highest_weight(
 	// unrounded weights in a straightforward way.
 	vfloat min_weight(FLT_MAX);
 	vfloat max_weight(-FLT_MAX);
-	unsigned int partial_weight_start = round_down_to_simd_multiple_vla(weight_count);
-	for (unsigned int i = 0; i < partial_weight_start; i += ASTCENC_SIMD_WIDTH)
-	{
-		vfloat weights = loada(dec_weight_ideal_value + i);
-		min_weight = min(min_weight, weights);
-		max_weight = max(max_weight, weights);
-	}
 
-	if (partial_weight_start != weight_count)
+	vint lane_id = vint::lane_id();
+	for (unsigned int i = 0; i < weight_count; i += ASTCENC_SIMD_WIDTH)
 	{
-		vfloat partial_weights = loada(dec_weight_ideal_value + partial_weight_start);
-		vmask active = vint::lane_id() < vint(weight_count - partial_weight_start);
-
-		vmask smaller = active & (partial_weights < min_weight);
-		min_weight = select(min_weight, partial_weights, smaller);
+		vmask active = lane_id < vint(weight_count);
+		lane_id += vint(ASTCENC_SIMD_WIDTH);
 
-		vmask larger = active & (partial_weights > max_weight);
-		max_weight = select(max_weight, partial_weights, larger);
+		vfloat weights = loada(dec_weight_ideal_value + i);
+		min_weight = min(min_weight, select(min_weight, weights, active));
+		max_weight = max(max_weight, select(max_weight, weights, active));
 	}
 
 	min_weight = hmin(min_weight);