+static bool isAlternateVectorMask(SmallVectorImpl<int> &Mask) {
+ bool isAlternate = true;
+ unsigned MaskSize = Mask.size();
+
+ // Example: shufflevector A, B, <0,5,2,7>
+ for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
+ if (Mask[i] < 0)
+ continue;
+ isAlternate = Mask[i] == (int)((i & 1) ? MaskSize + i : i);
+ }
+
+ if (isAlternate)
+ return true;
+
+ isAlternate = true;
+ // Example: shufflevector A, B, <4,1,6,3>
+ for (unsigned i = 0; i < MaskSize && isAlternate; ++i) {
+ if (Mask[i] < 0)
+ continue;
+ isAlternate = Mask[i] == (int)((i & 1) ? i : MaskSize + i);
+ }
+
+ return isAlternate;
+}
+