[mlir][OpenMP] Add omp.taskgroup operation

[shraiysh]

Summary

This patch adds omp.taskgroup operation according to OpenMP 5.0 2.17.6.

Also added tests for the same.

[shraiysh]

Ping for review!

[kiranchandramohan]

LGTM.

[peixin]

mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td

573

Nit: Usually we say parameter meaning one constant expression In OpenMP standard?

[shraiysh]

mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td

573

I remember addressing this comment but it somehow did not get added when landing. Pushing as an NFC.

[shraiysh]

mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td

573

Added in https://reviews.llvm.org/rG66e24da02728

mlir/include/mlir/Dialect/OpenMP/OpenMPOps.td

let description = [{
     The `priority` clause is a hint for the priority of the generated task.
     The `priority` is a non-negative integer expression that provides a hint for
     task execution order. Among all tasks ready to be executed, higher priority
     tasks (those with a higher numerical value in the priority clause
     expression) are recommended to execute before lower priority ones. The
     default priority-value when no priority clause is specified should be
     assumed to be zero (the lowest priority).
 
-    The `allocators_vars` and `allocate_vars` parameters are a variadic list of
+    The `allocators_vars` and `allocate_vars` arguments are a variadic list of
     values that specify the memory allocator to be used to obtain storage for
     private values.
 
   }];
 
   // TODO: depend, affinity and detach clauses
   let arguments = (ins Optional<I1>:$if_expr,
                        Optional<I1>:$final_expr,
def TaskOp : OpenMP_Op<"task", [AttrSizedOperandSegments,
   }];
   let extraClassDeclaration = [{
     /// Returns the reduction variables
     operand_range getReductionVars() { return in_reduction_vars(); }
   }];
   let hasVerifier = 1;
 }
 
+def TaskGroupOp : OpenMP_Op<"taskgroup", [AttrSizedOperandSegments,
+                            ReductionClauseInterface,
+                            AutomaticAllocationScope]> {
+  let summary = "taskgroup construct";
+  let description = [{
+    The taskgroup construct specifies a wait on completion of child tasks of the
+    current task and their descendent tasks.
+
+    When a thread encounters a taskgroup construct, it starts executing the
+    region. All child tasks generated in the taskgroup region and all of their
+    descendants that bind to the same parallel region as the taskgroup region
+    are part of the taskgroup set associated with the taskgroup region. There is
+    an implicit task scheduling point at the end of the taskgroup region. The
+    current task is suspended at the task scheduling point until all tasks in
+    the taskgroup set complete execution.
+
+    The `task_reduction` clause specifies a reduction among tasks. For each list
+    item, the number of copies is unspecified. Any copies associated with the
+    reduction are initialized before they are accessed by the tasks
+    participating in the reduction. After the end of the region, the original
+    list item contains the result of the reduction.
+
+    The `allocators_vars` and `allocate_vars` parameters are a variadic list of
+    values that specify the memory allocator to be used to obtain storage for
+    private values.
+  }];
+
+  let arguments = (ins Variadic<OpenMP_PointerLikeType>:$task_reduction_vars,
+                       OptionalAttr<SymbolRefArrayAttr>:$task_reductions,
+                       Variadic<AnyType>:$allocate_vars,
+                       Variadic<AnyType>:$allocators_vars);
+
+  let regions = (region AnyRegion:$region);
+
+  let assemblyFormat = [{
+    oilist(`task_reduction` `(`
+              custom<ReductionVarList>(
+                $task_reduction_vars, type($task_reduction_vars), $task_reductions
+              ) `)`
+          |`allocate` `(`
+              custom<AllocateAndAllocator>(
+                $allocate_vars, type($allocate_vars),
+                $allocators_vars, type($allocators_vars)
+              ) `)`
+    ) $region attr-dict
+  }];
+
+  let extraClassDeclaration = [{
+    /// Returns the reduction variables
+    operand_range getReductionVars() { return task_reduction_vars(); }
+  }];
+
+  let hasVerifier = 1;
+
+}
+
 //===----------------------------------------------------------------------===//
 // 2.10.4 taskyield Construct
 //===----------------------------------------------------------------------===//
 
 def TaskyieldOp : OpenMP_Op<"taskyield"> {
   let summary = "taskyield construct";
   let description = [{
     The taskyield construct specifies that the current task can be suspended

mlir/lib/Dialect/OpenMP/IR/OpenMPDialect.cpp

 //===----------------------------------------------------------------------===//
 // TaskOp
 //===----------------------------------------------------------------------===//
 LogicalResult TaskOp::verify() {
   return verifyReductionVarList(*this, in_reductions(), in_reduction_vars());
 }
 
 //===----------------------------------------------------------------------===//
+// TaskGroupOp
+//===----------------------------------------------------------------------===//
+LogicalResult TaskGroupOp::verify() {
+  return verifyReductionVarList(*this, task_reductions(),
+                                task_reduction_vars());
+}
+
+//===----------------------------------------------------------------------===//
 // WsLoopOp
 //===----------------------------------------------------------------------===//
 
 void WsLoopOp::build(OpBuilder &builder, OperationState &state,
                      ValueRange lowerBound, ValueRange upperBound,
                      ValueRange step, ArrayRef<NamedAttribute> attributes) {
   build(builder, state, lowerBound, upperBound, step,
         /*linear_vars=*/ValueRange(),

mlir/test/Dialect/OpenMP/ops.mlir

omp.section {
       omp.cancel cancellation_construct_type(sections)
       omp.terminator
     }
     // CHECK: omp.terminator
     omp.terminator
   }
   return
 }
+
+// CHECK-LABEL: @omp_taskgroup_no_tasks
+func.func @omp_taskgroup_no_tasks() -> () {
+
+  // CHECK: omp.taskgroup
+  omp.taskgroup {
+    // CHECK: "test.foo"() : () -> ()
+    "test.foo"() : () -> ()
+    // CHECK: omp.terminator
+    omp.terminator
+  }
+  return
+}
+
+// CHECK-LABEL: @omp_taskgroup_multiple_tasks
+func.func @omp_taskgroup_multiple_tasks() -> () {
+  // CHECK: omp.taskgroup
+  omp.taskgroup {
+    // CHECK: omp.task
+    omp.task {
+      "test.foo"() : () -> ()
+      // CHECK: omp.terminator
+      omp.terminator
+    }
+    // CHECK: omp.task
+    omp.task {
+      "test.foo"() : () -> ()
+      // CHECK: omp.terminator
+      omp.terminator
+    }
+    // CHECK: omp.terminator
+    omp.terminator
+  }
+  return
+}