[MLIR][MemRef] Add alloca support for erase_dead_alloc_and_stores (#142131)

Previously, `erase_dead_alloc_and_stores` didn't support
`memref.alloca`. This patch introduces support for it.

---------

Signed-off-by: Vitalii Shutov <[email protected]>

Author: Lallapallooza

mlir/include/mlir/Dialect/MemRef/TransformOps/MemRefTransformOps.td

@@ -245,7 +245,7 @@ def MemRefEraseDeadAllocAndStoresOp
     ]> {
   let description = [{
     This applies memory optimization on memref. In particular it does store to
-    load forwarding, dead store elimination and dead alloc elimination.
+    load forwarding, dead store elimination and dead alloc/alloca elimination.
 
     #### Return modes
 

mlir/lib/Dialect/MemRef/Utils/MemRefUtils.cpp

@@ -156,13 +156,15 @@ static bool resultIsNotRead(Operation *op, std::vector<Operation *> &uses) {
 
 void eraseDeadAllocAndStores(RewriterBase &rewriter, Operation *parentOp) {
   std::vector<Operation *> opToErase;
-  parentOp->walk([&](memref::AllocOp op) {
+  parentOp->walk([&](Operation *op) {
     std::vector<Operation *> candidates;
-    if (resultIsNotRead(op, candidates)) {
+    if (isa<memref::AllocOp, memref::AllocaOp>(op) &&
+        resultIsNotRead(op, candidates)) {
       llvm::append_range(opToErase, candidates);
-      opToErase.push_back(op.getOperation());
+      opToErase.push_back(op);
     }
   });
+
   for (Operation *op : opToErase)
     rewriter.eraseOp(op);
 }

mlir/test/Dialect/MemRef/transform-ops.mlir

@@ -327,6 +327,30 @@ module attributes {transform.with_named_sequence} {
   }
 }
 
+// -----
+
+// CHECK-LABEL: func.func @dead_alloca
+func.func @dead_alloca() {
+  // CHECK-NOT: %{{.+}} = memref.alloca
+  %0 = memref.alloca() : memref<8x64xf32, 3>
+  %1 = memref.subview %0[0, 0] [8, 4] [1, 1] : memref<8x64xf32, 3> to
+    memref<8x4xf32, affine_map<(d0, d1) -> (d0 * 64 + d1)>, 3>
+  %c0 = arith.constant 0 : index
+  %cst_0 = arith.constant dense<0.000000e+00> : vector<1x4xf32>
+  vector.transfer_write %cst_0, %1[%c0, %c0] {in_bounds = [true, true]} :
+    vector<1x4xf32>, memref<8x4xf32, affine_map<(d0, d1) -> (d0 * 64 + d1)>, 3>
+  return
+}
+
+module attributes {transform.with_named_sequence} {
+  transform.named_sequence @__transform_main(%arg1: !transform.any_op {transform.readonly}) {
+    %0 = transform.structured.match ops{["func.func"]} in %arg1 : (!transform.any_op) -> !transform.any_op
+    transform.memref.erase_dead_alloc_and_stores %0 : (!transform.any_op) -> ()
+    transform.yield
+  }
+}
+
+
 // -----
 
 // CHECK-LABEL: @store_to_load