[mlir][affine] Skip point-wise copy for scalar memref

Point wise copy does not consider scalar typed memref and it does not
generate any affine.for on top. It causes segmentation fault. We can
skip the point-wise copy in case of scalar memref.

Fixes #61167

Author: Lewuathe

mlir/lib/Dialect/Affine/Utils/LoopUtils.cpp

@@ -2131,6 +2131,9 @@ static LogicalResult generateCopy(
 
   if (!copyOptions.generateDma) {
     // Point-wise copy generation.
+    // Unable to copy generation for scala memref due to lack of access point.
+    if (rank == 0)
+      return failure();
     auto copyNest =
         generatePointWiseCopy(loc, memref, fastMemRef, lbMaps,
                               /*lbOperands=*/regionSymbols, ubMaps,

mlir/test/Dialect/Affine/affine-data-copy.mlir

@@ -354,3 +354,52 @@ func.func @arbitrary_memory_space() {
   }
   return
 }
+
+
+// CHECK-LABEL: func @scalar_memref_copy_without_dma
+func.func @scalar_memref_copy_without_dma() {
+    %false = arith.constant false
+    %4 = memref.alloc() {alignment = 128 : i64} : memref<i1>
+    affine.store %false, %4[] : memref<i1>
+
+    // CHECK: %[[FALSE:.*]] = arith.constant false
+    // CHECK: %[[MEMREF:.*]] = memref.alloc() {alignment = 128 : i64} : memref<i1>
+    // CHECK: affine.store %[[FALSE]], %[[MEMREF]][] : memref<i1>
+    return
+}
+
+// CHECK-LABEL: func @scalar_memref_copy_in_loop
+func.func @scalar_memref_copy_in_loop(%3:memref<480xi1>) {
+  %false = arith.constant false
+  %4 = memref.alloc() {alignment = 128 : i64} : memref<i1>
+  affine.store %false, %4[] : memref<i1>
+  %5 = memref.alloc() {alignment = 128 : i64} : memref<i1>
+  memref.copy %4, %5 : memref<i1> to memref<i1>
+  affine.for %arg0 = 0 to 480 {
+    %11 = affine.load %3[%arg0] : memref<480xi1>
+    %12 = affine.load %5[] : memref<i1>
+    %13 = arith.cmpi slt, %11, %12 : i1
+    %14 = arith.select %13, %11, %12 : i1
+    affine.store %14, %5[] : memref<i1>
+  }
+
+  // CHECK: %[[FALSE:.*]] = arith.constant false
+  // CHECK: %[[MEMREF:.*]] = memref.alloc() {alignment = 128 : i64} : memref<i1>
+  // CHECK: affine.store %[[FALSE]], %[[MEMREF]][] : memref<i1>
+  // CHECK: %[[TARGET:.*]] = memref.alloc() {alignment = 128 : i64} : memref<i1>
+  // CHECK: memref.copy %alloc, %[[TARGET]] : memref<i1> to memref<i1>
+  // CHECK: %[[FAST_MEMREF:.*]] = memref.alloc() : memref<480xi1>
+  // CHECK: affine.for %{{.*}} = 0 to 480 {
+  // CHECK:   %{{.*}} = affine.load %arg0[%{{.*}}] : memref<480xi1>
+  // CHECK:   affine.store %{{.*}}, %[[FAST_MEMREF]][%{{.*}}] : memref<480xi1>
+  // CHECK: }
+  // CHECK: affine.for %arg1 = 0 to 480 {
+  // CHECK:   %[[L0:.*]] = affine.load %[[FAST_MEMREF]][%arg1] : memref<480xi1>
+  // CHECK:   %[[L1:.*]] = affine.load %[[TARGET]][] : memref<i1>
+  // CHECK:   %[[CMPI:.*]] = arith.cmpi slt, %[[L0]], %[[L1]] : i1
+  // CHECK:   %[[SELECT:.*]] = arith.select %[[CMPI]], %[[L0]], %[[L1]] : i1
+  // CHECK:   affine.store %[[SELECT]], %[[TARGET]][] : memref<i1>
+  // CHECK: }
+  // CHECK: memref.dealloc %[[FAST_MEMREF]] : memref<480xi1>
+  return
+}