Use 4 lane swizzles
The alpha lane is already zero, so we don't need to use
a 3 lane swizzle to force zero it.
diff --git a/Source/astcenc_averages_and_directions.cpp b/Source/astcenc_averages_and_directions.cpp
index a674bc7..a56b537 100644
--- a/Source/astcenc_averages_and_directions.cpp
+++ b/Source/astcenc_averages_and_directions.cpp
@@ -598,9 +598,9 @@
vfloat4 c = blk.texel3(iwt);
vfloat4 d = (c - average);
- cov[0] += d.swz<0, 0, 0>() * d; // xx, xy, xz
- cov[1] += d.swz<0, 1, 1>() * d.swz<1, 1, 2>(); // xy, yy, yz
- cov[2] += d * d.swz<2, 2, 2>(); // xz, yz, zz
+ cov[0] += d.swz<0, 0, 0, 3>() * d; // xx, xy, xz
+ cov[1] += d.swz<0, 1, 1, 3>() * d.swz<1, 1, 2, 3>(); // xy, yy, yz
+ cov[2] += d * d.swz<2, 2, 2, 3>(); // xz, yz, zz
minc = min(minc, c);
maxc = max(maxc, c);
