[mlir][flang] Add an interface of OpenACC compute regions for further getAllocaBlock support (llvm#100675)

This PR implements `ComputeRegionOpInterface` to define `getAllocaBlock`
of OpenACC loop and compute constructs (parallel/kernels/serial). The
primary objective here is to accommodate local variables in OpenACC
compute regions. The change in `fir::FirOpBuilder::getAllocaBlock`
allows local variable allocation inside loops and kernels.

Author: khaki3

flang/lib/Optimizer/Builder/FIRBuilder.cpp

@@ -248,6 +248,11 @@ mlir::Value fir::FirOpBuilder::allocateLocal(
 
 /// Get the block for adding Allocas.
 mlir::Block *fir::FirOpBuilder::getAllocaBlock() {
+  if (auto accComputeRegionIface =
+          getRegion().getParentOfType<mlir::acc::ComputeRegionOpInterface>()) {
+    return accComputeRegionIface.getAllocaBlock();
+  }
+
   if (auto ompOutlineableIface =
           getRegion()
               .getParentOfType<mlir::omp::OutlineableOpenMPOpInterface>()) {

flang/test/Lower/OpenACC/acc-loop.f90

@@ -317,10 +317,10 @@ subroutine sub1(i, j, k)
 end subroutine
 
 ! CHECK: func.func @_QPsub1
+! CHECK: acc.parallel
 ! CHECK: %[[DC_K:.*]] = fir.alloca i32 {bindc_name = "k"}
 ! CHECK: %[[DC_J:.*]] = fir.alloca i32 {bindc_name = "j"}
 ! CHECK: %[[DC_I:.*]] = fir.alloca i32 {bindc_name = "i"}
-! CHECK: acc.parallel
 ! CHECK: %[[P_I:.*]] = acc.private varPtr(%[[DC_I]] : !fir.ref<i32>) -> !fir.ref<i32> {implicit = true, name = ""}
 ! CHECK: %[[P_J:.*]] = acc.private varPtr(%[[DC_J]] : !fir.ref<i32>) -> !fir.ref<i32> {implicit = true, name = ""}
 ! CHECK: %[[P_K:.*]] = acc.private varPtr(%[[DC_K]] : !fir.ref<i32>) -> !fir.ref<i32> {implicit = true, name = ""}

mlir/include/mlir/Dialect/OpenACC/CMakeLists.txt

@@ -21,9 +21,10 @@ mlir_tablegen(OpenACCOpsAttributes.cpp.inc -gen-attrdef-defs -attrdefs-dialect=a
 add_public_tablegen_target(MLIROpenACCAttributesIncGen)
 add_dependencies(mlir-headers MLIROpenACCAttributesIncGen)
 
+add_mlir_interface(OpenACCOpsInterfaces)
+
 set(LLVM_TARGET_DEFINITIONS OpenACCTypeInterfaces.td)
 mlir_tablegen(OpenACCTypeInterfaces.h.inc -gen-type-interface-decls)
 mlir_tablegen(OpenACCTypeInterfaces.cpp.inc -gen-type-interface-defs)
 add_public_tablegen_target(MLIROpenACCTypeInterfacesIncGen)
 add_dependencies(mlir-headers MLIROpenACCTypeInterfacesIncGen)
-

mlir/include/mlir/Dialect/OpenACC/OpenACC.h

@@ -22,6 +22,7 @@
 #include "mlir/Bytecode/BytecodeOpInterface.h"
 #include "mlir/Dialect/OpenACC/OpenACCOpsDialect.h.inc"
 #include "mlir/Dialect/OpenACC/OpenACCOpsEnums.h.inc"
+#include "mlir/Dialect/OpenACC/OpenACCOpsInterfaces.h.inc"
 #include "mlir/Dialect/OpenACC/OpenACCTypeInterfaces.h.inc"
 #include "mlir/Dialect/OpenACCMPCommon/Interfaces/AtomicInterfaces.h"
 #include "mlir/Interfaces/ControlFlowInterfaces.h"

mlir/include/mlir/Dialect/OpenACC/OpenACCOps.td

@@ -22,6 +22,7 @@ include "mlir/IR/OpBase.td"
 include "mlir/IR/SymbolInterfaces.td"
 include "mlir/Dialect/OpenACC/OpenACCBase.td"
 include "mlir/Dialect/OpenACC/OpenACCOpsTypes.td"
+include "mlir/Dialect/OpenACC/OpenACCOpsInterfaces.td"
 include "mlir/Dialect/OpenACC/OpenACCTypeInterfaces.td"
 include "mlir/Dialect/OpenACCMPCommon/Interfaces/AtomicInterfaces.td"
 include "mlir/Dialect/OpenACCMPCommon/Interfaces/OpenACCMPOpsInterfaces.td"
@@ -1067,7 +1068,9 @@ def OpenACC_ReductionRecipeOp : OpenACC_Op<"reduction.recipe",
 //===----------------------------------------------------------------------===//
 
 def OpenACC_ParallelOp : OpenACC_Op<"parallel",
-    [AttrSizedOperandSegments, RecursiveMemoryEffects,
+    [AttrSizedOperandSegments, AutomaticAllocationScope,
+     RecursiveMemoryEffects,
+     DeclareOpInterfaceMethods<ComputeRegionOpInterface>,
      MemoryEffects<[MemWrite<OpenACC_ConstructResource>,
                     MemRead<OpenACC_CurrentDeviceIdResource>]>]> {
   let summary = "parallel construct";
@@ -1231,7 +1234,9 @@ def OpenACC_ParallelOp : OpenACC_Op<"parallel",
 //===----------------------------------------------------------------------===//
 
 def OpenACC_SerialOp : OpenACC_Op<"serial",
-    [AttrSizedOperandSegments, RecursiveMemoryEffects,
+    [AttrSizedOperandSegments, AutomaticAllocationScope,
+     RecursiveMemoryEffects,
+     DeclareOpInterfaceMethods<ComputeRegionOpInterface>,
      MemoryEffects<[MemWrite<OpenACC_ConstructResource>,
                     MemRead<OpenACC_CurrentDeviceIdResource>]>]> {
   let summary = "serial construct";
@@ -1347,7 +1352,9 @@ def OpenACC_SerialOp : OpenACC_Op<"serial",
 //===----------------------------------------------------------------------===//
 
 def OpenACC_KernelsOp : OpenACC_Op<"kernels",
-    [AttrSizedOperandSegments, RecursiveMemoryEffects,
+    [AttrSizedOperandSegments, AutomaticAllocationScope,
+     RecursiveMemoryEffects,
+     DeclareOpInterfaceMethods<ComputeRegionOpInterface>,
      MemoryEffects<[MemWrite<OpenACC_ConstructResource>,
                     MemRead<OpenACC_CurrentDeviceIdResource>]>]> {
   let summary = "kernels construct";
@@ -1737,9 +1744,11 @@ def OpenACC_HostDataOp : OpenACC_Op<"host_data",
 //===----------------------------------------------------------------------===//
 
 def OpenACC_LoopOp : OpenACC_Op<"loop",
-    [AttrSizedOperandSegments, RecursiveMemoryEffects,
-     MemoryEffects<[MemWrite<OpenACC_ConstructResource>]>,
-     DeclareOpInterfaceMethods<LoopLikeOpInterface>]> {
+    [AttrSizedOperandSegments, AutomaticAllocationScope,
+     RecursiveMemoryEffects,
+     DeclareOpInterfaceMethods<ComputeRegionOpInterface>,
+     DeclareOpInterfaceMethods<LoopLikeOpInterface>,
+     MemoryEffects<[MemWrite<OpenACC_ConstructResource>]>]> {
   let summary = "loop construct";
 
   let description = [{

mlir/include/mlir/Dialect/OpenACC/OpenACCOpsInterfaces.td

@@ -0,0 +1,29 @@
+//===-- OpenACCOpsInterfaces.td - OpenACC type interfaces ---*- tablegen -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef OPENACC_OPS_INTERFACES
+#define OPENACC_OPS_INTERFACES
+
+include "mlir/IR/OpBase.td"
+
+def ComputeRegionOpInterface : OpInterface<"ComputeRegionOpInterface"> {
+  let cppNamespace = "::mlir::acc";
+
+  let description = [{
+    An interface for compute and loop construct operations.
+  }];
+
+  let methods = [
+    InterfaceMethod<"Get alloca block", "::mlir::Block*", "getAllocaBlock",
+      (ins), [{
+        return &$_op.getRegion().front();
+      }]>,
+  ];
+}
+
+#endif // OPENACC_OPS_INTERFACES

mlir/lib/Dialect/OpenACC/IR/CMakeLists.txt

@@ -9,6 +9,7 @@ add_mlir_dialect_library(MLIROpenACCDialect
   MLIROpenACCEnumsIncGen
   MLIROpenACCAttributesIncGen
   MLIROpenACCMPOpsInterfacesIncGen
+  MLIROpenACCOpsInterfacesIncGen
   MLIROpenACCTypeInterfacesIncGen
 
   LINK_LIBS PUBLIC

mlir/lib/Dialect/OpenACC/IR/OpenACC.cpp

@@ -24,6 +24,7 @@ using namespace acc;
 
 #include "mlir/Dialect/OpenACC/OpenACCOpsDialect.cpp.inc"
 #include "mlir/Dialect/OpenACC/OpenACCOpsEnums.cpp.inc"
+#include "mlir/Dialect/OpenACC/OpenACCOpsInterfaces.cpp.inc"
 #include "mlir/Dialect/OpenACC/OpenACCTypeInterfaces.cpp.inc"
 #include "mlir/Dialect/OpenACCMPCommon/Interfaces/OpenACCMPOpsInterfaces.cpp.inc"
 

mlir/lib/Dialect/OpenACC/Transforms/CMakeLists.txt

@@ -10,6 +10,7 @@ add_mlir_dialect_library(MLIROpenACCTransforms
   MLIROpenACCEnumsIncGen
   MLIROpenACCAttributesIncGen
   MLIROpenACCMPOpsInterfacesIncGen
+  MLIROpenACCOpsInterfacesIncGen
   MLIROpenACCTypeInterfacesIncGen
 
   LINK_LIBS PUBLIC