///
/// \returns N above, or the number of times even elements must be dropped if
/// there is such a number. Otherwise returns zero.
-static int canLowerByDroppingEvenElements(ArrayRef<int> Mask) {
- // Figure out whether we're looping over two inputs or just one.
- bool IsSingleInput = isSingleInputShuffleMask(Mask);
-
+static int canLowerByDroppingEvenElements(ArrayRef<int> Mask,
+ bool IsSingleInput) {
// The modulus for the shuffle vector entries is based on whether this is
// a single input or not.
int ShuffleModulus = Mask.size() * (IsSingleInput ? 1 : 2);
// We special case these as they can be particularly efficiently handled with
// the PACKUSB instruction on x86 and they show up in common patterns of
// rearranging bytes to truncate wide elements.
- if (int NumEvenDrops = canLowerByDroppingEvenElements(Mask)) {
+ bool IsSingleInput = isSingleInputShuffleMask(Mask);
+ if (int NumEvenDrops = canLowerByDroppingEvenElements(Mask, IsSingleInput)) {
// NumEvenDrops is the power of two stride of the elements. Another way of
// thinking about it is that we need to drop the even elements this many
// times to get the original input.
- bool IsSingleInput = isSingleInputShuffleMask(Mask);
// First we need to zero all the dropped bytes.
assert(NumEvenDrops <= 3 &&