sharding propagation: add only one shardop for each result

Author: fschlimb

mlir/include/mlir/Dialect/Mesh/IR/MeshOps.h

@@ -201,10 +201,13 @@ ShapedType shardShapedType(ShapedType shape, MeshOp mesh,
 Type shardType(Type type, MeshOp mesh, MeshSharding sharding);
 
 // Insert shard op if there is not one that already has the same sharding.
+// Use newShardOp if it is not null. Otherwise create a new one.
 // May insert resharding if required.
-void maybeInsertTargetShardingAnnotation(MeshSharding sharding,
-                                         OpOperand &operand,
-                                         OpBuilder &builder);
+// Return the target ShardOP (new or existing).
+ShardOp maybeInsertTargetShardingAnnotation(MeshSharding sharding,
+                                            OpOperand &operand,
+                                            OpBuilder &builder,
+                                            ShardOp newShardOp);
 void maybeInsertTargetShardingAnnotation(MeshSharding sharding, OpResult result,
                                          OpBuilder &builder);
 void maybeInsertSourceShardingAnnotation(MeshSharding sharding,

mlir/lib/Dialect/Mesh/IR/MeshOps.cpp

@@ -275,9 +275,10 @@ Type mesh::shardType(Type type, MeshOp mesh, MeshSharding sharding) {
   return type;
 }
 
-void mlir::mesh::maybeInsertTargetShardingAnnotation(MeshSharding sharding,
-                                                     OpOperand &operand,
-                                                     OpBuilder &builder) {
+ShardOp mlir::mesh::maybeInsertTargetShardingAnnotation(MeshSharding sharding,
+                                                        OpOperand &operand,
+                                                        OpBuilder &builder,
+                                                        ShardOp newShardOp) {
   OpBuilder::InsertionGuard insertionGuard(builder);
   Value operandValue = operand.get();
   Operation *operandOp = operand.getOwner();
@@ -286,34 +287,40 @@ void mlir::mesh::maybeInsertTargetShardingAnnotation(MeshSharding sharding,
   if (shardOp && sharding == shardOp.getSharding() &&
       !shardOp.getAnnotateForUsers()) {
     // No need for anything the correct sharding is already set.
-    return;
+    return newShardOp ? newShardOp : shardOp;
   }
 
-  auto shardingOp = builder.create<ShardingOp>(operandValue.getLoc(), sharding);
-  auto newShardOp =
-      builder.create<ShardOp>(operandValue.getLoc(), operandValue, shardingOp,
-                              /*annotate_for_users*/ false);
+  if (!newShardOp) {
+    auto shardingOp =
+        builder.create<ShardingOp>(operandValue.getLoc(), sharding);
+    newShardOp =
+        builder.create<ShardOp>(operandValue.getLoc(), operandValue, shardingOp,
+                                /*annotate_for_users*/ false);
+  }
   IRRewriter rewriter(builder);
   rewriter.replaceUsesWithIf(
       operandValue, newShardOp, [operandOp, operandValue](OpOperand &use) {
         return use.getOwner() == operandOp && use.get() == operandValue;
       });
 
   if (!shardOp || shardOp.getAnnotateForUsers()) {
-    return;
+    return newShardOp;
   }
 
-  auto newShardOp2 =
-      builder.create<ShardOp>(operandValue.getLoc(), newShardOp, shardingOp,
-                              /*annotate_for_users*/ true);
+  auto newShardOp2 = builder.create<ShardOp>(operandValue.getLoc(), newShardOp,
+                                             newShardOp.getSharding(),
+                                             /*annotate_for_users*/ true);
   rewriter.replaceAllUsesExcept(newShardOp, newShardOp2, newShardOp2);
+  return newShardOp;
 }
 
 void mlir::mesh::maybeInsertTargetShardingAnnotation(MeshSharding sharding,
                                                      OpResult result,
                                                      OpBuilder &builder) {
+  ShardOp newShardOp;
   for (auto &use : llvm::make_early_inc_range(result.getUses())) {
-    maybeInsertTargetShardingAnnotation(sharding, use, builder);
+    newShardOp =
+        maybeInsertTargetShardingAnnotation(sharding, use, builder, newShardOp);
   }
 }