[llvm] [LV][AArch64]: Utilise SVE ld4/st4 instructions via auto-vectorisation (PR #89018)

[Mel Chen via llvm-commits]

================
@@ -2572,23 +2586,40 @@ void InnerLoopVectorizer::vectorizeInterleaveGroup(
     }
 
     if (VecTy->isScalableTy()) {
-      assert(InterleaveFactor == 2 &&
-             "Unsupported deinterleave factor for scalable vectors");
-
+      assert(isPowerOf2_32(InterleaveFactor)  &&
+            "Unsupported deinterleave factor for scalable vectors");
       for (unsigned Part = 0; Part < UF; ++Part) {
         // Scalable vectors cannot use arbitrary shufflevectors (only splats),
         // so must use intrinsics to deinterleave.
-        Value *DI = Builder.CreateIntrinsic(
-            Intrinsic::experimental_vector_deinterleave2, VecTy, NewLoads[Part],
-            /*FMFSource=*/nullptr, "strided.vec");
+        
+        std::queue<Value *>Queue;
+        Queue.push(NewLoads[Part]);
+        // NonLeaf represents how many times we will do deinterleaving,
+        // think of it as a tree, each node will be deinterleaved, untill we reach to
+        // the leaf nodes which will be the final results of deinterleaving.
+        unsigned NonLeaf = InterleaveFactor - 1;
+        for (unsigned i = 0; i < NonLeaf; i ++) {
+          auto Node = Queue.front();
+          Queue.pop();
+          auto DeinterleaveType = Node->getType();
+          Value *DI = Builder.CreateIntrinsic(
+            Intrinsic::experimental_vector_deinterleave2, DeinterleaveType, Node,
+            /*FMFSource=*/nullptr, "root.strided.vec");
+          Value *StridedVec1 = Builder.CreateExtractValue(DI, 0);
+          Value *StridedVec2 = Builder.CreateExtractValue(DI, 1);
+          Queue.push(StridedVec1);
+          Queue.push(StridedVec2);
+        }
+
         unsigned J = 0;
-        for (unsigned I = 0; I < InterleaveFactor; ++I) {
+        for (unsigned I = 0; I < InterleaveFactor && !Queue.empty(); ++I) {
           Instruction *Member = Group->getMember(I);
 
           if (!Member)
             continue;
 
-          Value *StridedVec = Builder.CreateExtractValue(DI, I);
+          auto StridedVec = Queue.front();
+          Queue.pop();
----------------
Mel-Chen wrote:

Here is a example:
A vector 0 1 2 3 4 5 6 7
If we do deinterleave 4 on the vector, we should get:
member 0: 0 4
member 1: 1 5
member 2: 2 6
member 3: 3 7
But the Queue in your change may like:  0 4, 2 6, 1 5, 3 7.
Please confirm the Queue is sorted by a correct rank.

https://github.com/llvm/llvm-project/pull/89018