[NFC] Delete dead ops after cloning (#18669)

This helps increase the readability of IR dumps when looking at `flow.dispatch.region`s because cloneable ops with no consumers were being wrapped in a `flow.dispatch.region` instead of deleted.

Author: IanWood1

compiler/src/iree/compiler/DispatchCreation/BUILD.bazel

@@ -89,6 +89,7 @@ iree_compiler_cc_library(
         "@llvm-project//mlir:Pass",
         "@llvm-project//mlir:SCFDialect",
         "@llvm-project//mlir:SCFTransforms",
+        "@llvm-project//mlir:SideEffectInterfaces",
         "@llvm-project//mlir:Support",
         "@llvm-project//mlir:TensorDialect",
         "@llvm-project//mlir:TensorTransforms",

compiler/src/iree/compiler/DispatchCreation/CMakeLists.txt

@@ -69,6 +69,7 @@ iree_cc_library(
     MLIRPass
     MLIRSCFDialect
     MLIRSCFTransforms
+    MLIRSideEffectInterfaces
     MLIRSupport
     MLIRTensorDialect
     MLIRTensorTransforms

compiler/src/iree/compiler/DispatchCreation/CloneProducersIntoDispatchRegions.cpp

@@ -10,6 +10,7 @@
 #include "mlir/Dialect/Linalg/IR/Linalg.h"
 #include "mlir/IR/PatternMatch.h"
 #include "mlir/Interfaces/FunctionInterfaces.h"
+#include "mlir/Interfaces/SideEffectInterfaces.h"
 
 #define DEBUG_TYPE                                                             \
   "iree-dispatch-creation-clone-producers-into-dispatch-regions"
@@ -34,6 +35,9 @@ struct CloneProducersIntoDispatchRegionsPass final
     });
 
     funcOp->walk([&](Operation *op) {
+      if (isOpTriviallyDead(op)) {
+        return rewriter.eraseOp(op);
+      }
       if (!IREE::Flow::isNonNullAndOutsideDispatch(op) ||
           !isa<linalg::GenericOp>(op)) {
         return;

compiler/src/iree/compiler/DispatchCreation/test/clone_producers_into_dispatch_regions.mlir

@@ -81,7 +81,7 @@ util.func public @complex_create(%real : f32, %imag : f32, %input: tensor<4x2xco
     } -> tensor<4x2xcomplex<f32>>
     flow.return %generic : tensor<4x2xcomplex<f32>>
   }
-  util.return %0 : tensor<4x2xcomplex<f32>>
+  util.return %1 : tensor<4x2xcomplex<f32>>
 }
 
 // CHECK-LABEL: @complex_create
@@ -330,13 +330,13 @@ util.func public @clone_broadcast_dequant_op(
 // -----
 
 // Do no clone index cast operations when they are operands to the dispatch
-util.func public @dont_clone_index_type_op(%arg0 : i64) {
+util.func public @dont_clone_index_type_op(%arg0 : i64) -> tensor<?xf32> {
   %0 = arith.index_cast %arg0 : i64 to index
   %1 = flow.dispatch.region[] -> (tensor<?xf32>{%0}) {
     %2 = tensor.empty(%0) : tensor<?xf32>
     flow.return %2 : tensor<?xf32>
   }
-  util.return
+  util.return %1 : tensor<?xf32>
 }
 // CHECK-LABEL: func public @dont_clone_index_type_op
 //       CHECK:   arith.index_cast
@@ -346,14 +346,14 @@ util.func public @dont_clone_index_type_op(%arg0 : i64) {
 // -----
 // Do no clone index cast operations when they are in-direct operands to the dispatch
 #map = affine_map<()[s0] -> (s0 * 12)>
-util.func public @dont_clone_index_type_op_2(%arg0: i64) {
+util.func public @dont_clone_index_type_op_2(%arg0: i64) -> tensor<?xf32> {
   %0 = arith.index_cast %arg0 : i64 to index
   %1 = affine.apply #map()[%0]
   %2 = flow.dispatch.region -> (tensor<?xf32>{%1}) {
     %3 = tensor.empty(%1) : tensor<?xf32>
     flow.return %3 : tensor<?xf32>
   }
-  util.return
+  util.return %2 : tensor<?xf32>
 }
 // CHECK-LABEL: func public @dont_clone_index_type_op_2
 //       CHECK:   arith.index_cast