Add additional criteria for hoisting vector.transfer_reads

[harsh]

Summary

Non-subview uses of an alloc outside the current loop
can be safely ignored when considering hoisting vector
transfer_reads. This patch adds a condition to check for that
case and updates the unit test accordingly.

mlir/lib/Dialect/Linalg/Transforms/Hoisting.cpp

while (!users.empty()) {
     if (!processed.insert(user).second)
       continue;
     if (auto subView = dyn_cast<memref::SubViewOp>(user)) {
       users.append(subView->getUsers().begin(), subView->getUsers().end());
       continue;
     }
     if (isMemoryEffectFree(user) || isa<vector::TransferReadOp>(user))
       continue;
+    if (!loop->isAncestor(user))
+      continue;
     return false;
   }
   return true;
 }
 
 void mlir::linalg::hoistRedundantVectorTransfers(func::FuncOp func) {
   bool changed = true;
   while (changed) {

mlir/test/Dialect/Linalg/hoisting.mlir

 // CHECK:          %[[D0:.+]] = vector.transfer_read %[[ALLOC]][%[[C0]], %[[C0]]], %[[CST]] {in_bounds = [true, true]} :
 // CHECK-SAME:       memref<32x64xf32>, vector<32x64xf32>
 // CHECK:          scf.for %[[ARG0:.+]] = %[[C0]] to %[[C1024]] step %[[C128]] {
 // CHECK:            %[[D1:.+]] = vector.transfer_read %[[ALLOC_0]][%[[C0]], %[[C0]]], %[[CST]] {in_bounds = [true, true]}
 // CHECK-SAME:         : memref<32x128xf32>, vector<32x128xf32>
 // CHECK:            "some_use"(%[[D0]], %[[D1]], %[[CAST]]) : (vector<32x64xf32>, vector<32x128xf32>, memref<32x128xf32,
 // CHECK-SAME:         strided<[128, 1], offset: ?>>) -> ()
 // CHECK:          }
+// CHECK:          memref.dealloc %[[ALLOC]] : memref<32x64xf32>
 // CHECK:          return
 func.func @hoist_vector_transfer_read() {
   %c0 = arith.constant 0 : index
   %c128 = arith.constant 128 : index
   %c1024 = arith.constant 1024 : index
   %cst_2 = arith.constant 0.000000e+00 : f32
   %memref0 = memref.alloc() : memref<32x64xf32>
   %memref2 = memref.alloc() : memref<32x128xf32>
   %subview2 = memref.subview %memref2[%c0, %c0] [32, 128] [1, 1]: memref<32x128xf32> to memref<32x128xf32, strided<[128, 1], offset: ?>>
   scf.for %arg0 = %c0 to %c1024 step %c128 {
     %2 = vector.transfer_read %memref2[%c0, %c0], %cst_2 {in_bounds = [true, true]} : memref<32x128xf32>, vector<32x128xf32>
     %3 = vector.transfer_read %memref0[%c0, %c0], %cst_2 {in_bounds = [true, true]} : memref<32x64xf32>, vector<32x64xf32>
     "some_use"(%3, %2, %subview2) : (vector<32x64xf32>, vector<32x128xf32>, memref<32x128xf32, strided<[128, 1], offset: ?>>) -> ()
   }
+  memref.dealloc %memref0 : memref<32x64xf32>
   return
 }
 
 transform.sequence failures(propagate) {
 ^bb1(%arg1: !pdl.operation):
   %0 = transform.structured.match ops{["func.func"]} in %arg1
     : (!pdl.operation) -> !pdl.operation
   transform.structured.hoist_redundant_vector_transfers %0
     : (!pdl.operation) -> !pdl.operation
 }