[mlir][OpenMP] Add copyprivate support to omp.single (#80477)

This adds a new custom CopyPrivateVarList to the single operation.
Each list item is formed by a reference to the variable to be
updated, its type and the function to be used to perform the copy.

It will be translated to LLVM IR using OpenMP builder, that will
use the information in the copyprivate list to call
__kmpc_copyprivate.

This is patch 2 of 4, to add support for COPYPRIVATE in Flang.
Original PR: https://github.com/llvm/llvm-project/pull/73128

flang/lib/Lower/OpenMP.cpp

@@ -2665,6 +2665,7 @@ genSingleOp(Fortran::lower::AbstractConverter &converter,
             const Fortran::parser::OmpClauseList &beginClauseList,
             const Fortran::parser::OmpClauseList &endClauseList) {
   llvm::SmallVector<mlir::Value> allocateOperands, allocatorOperands;
+  llvm::SmallVector<mlir::Value> copyPrivateVars;
   mlir::UnitAttr nowaitAttr;
 
   ClauseProcessor cp(converter, semaCtx, beginClauseList);
@@ -2678,7 +2679,8 @@ genSingleOp(Fortran::lower::AbstractConverter &converter,
       OpWithBodyGenInfo(converter, semaCtx, currentLocation, eval)
           .setGenNested(genNested)
           .setClauses(&beginClauseList),
-      allocateOperands, allocatorOperands, nowaitAttr);
+      allocateOperands, allocatorOperands, copyPrivateVars,
+      /*copyPrivateFuncs=*/nullptr, nowaitAttr);
 }
 
 static mlir::omp::TaskOp

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

@@ -466,10 +466,16 @@ def SingleOp : OpenMP_Op<"single", [AttrSizedOperandSegments]> {
     master thread), in the context of its implicit task. The other threads
     in the team, which do not execute the block, wait at an implicit barrier
     at the end of the single construct unless a nowait clause is specified.
+
+    If copyprivate variables and functions are specified, then each thread
+    variable is updated with the variable value of the thread that executed
+    the single region, using the specified copy functions.
   }];
 
   let arguments = (ins Variadic<AnyType>:$allocate_vars,
                        Variadic<AnyType>:$allocators_vars,
+                       Variadic<OpenMP_PointerLikeType>:$copyprivate_vars,
+                       OptionalAttr<SymbolRefArrayAttr>:$copyprivate_funcs,
                        UnitAttr:$nowait);
 
   let regions = (region AnyRegion:$region);
@@ -481,6 +487,10 @@ def SingleOp : OpenMP_Op<"single", [AttrSizedOperandSegments]> {
                 $allocators_vars, type($allocators_vars)
               ) `)`
           |`nowait` $nowait
+          |`copyprivate` `(`
+              custom<CopyPrivateVarList>(
+                $copyprivate_vars, type($copyprivate_vars), $copyprivate_funcs
+              ) `)`
     ) $region attr-dict
   }];
   let hasVerifier = 1;

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

@@ -573,6 +573,110 @@ static LogicalResult verifyReductionVarList(Operation *op,
   return success();
 }
 
+//===----------------------------------------------------------------------===//
+// Parser, printer and verifier for CopyPrivateVarList
+//===----------------------------------------------------------------------===//
+
+/// copyprivate-entry-list ::= copyprivate-entry
+///                          | copyprivate-entry-list `,` copyprivate-entry
+/// copyprivate-entry ::= ssa-id `->` symbol-ref `:` type
+static ParseResult parseCopyPrivateVarList(
+    OpAsmParser &parser,
+    SmallVectorImpl<OpAsmParser::UnresolvedOperand> &operands,
+    SmallVectorImpl<Type> &types, ArrayAttr &copyPrivateSymbols) {
+  SmallVector<SymbolRefAttr> copyPrivateFuncsVec;
+  if (failed(parser.parseCommaSeparatedList([&]() {
+        if (parser.parseOperand(operands.emplace_back()) ||
+            parser.parseArrow() ||
+            parser.parseAttribute(copyPrivateFuncsVec.emplace_back()) ||
+            parser.parseColonType(types.emplace_back()))
+          return failure();
+        return success();
+      })))
+    return failure();
+  SmallVector<Attribute> copyPrivateFuncs(copyPrivateFuncsVec.begin(),
+                                          copyPrivateFuncsVec.end());
+  copyPrivateSymbols = ArrayAttr::get(parser.getContext(), copyPrivateFuncs);
+  return success();
+}
+
+/// Print CopyPrivate clause
+static void printCopyPrivateVarList(OpAsmPrinter &p, Operation *op,
+                                    OperandRange copyPrivateVars,
+                                    TypeRange copyPrivateTypes,
+                                    std::optional<ArrayAttr> copyPrivateFuncs) {
+  if (!copyPrivateFuncs.has_value())
+    return;
+  llvm::interleaveComma(
+      llvm::zip(copyPrivateVars, *copyPrivateFuncs, copyPrivateTypes), p,
+      [&](const auto &args) {
+        p << std::get<0>(args) << " -> " << std::get<1>(args) << " : "
+          << std::get<2>(args);
+      });
+}
+
+/// Verifies CopyPrivate Clause
+static LogicalResult
+verifyCopyPrivateVarList(Operation *op, OperandRange copyPrivateVars,
+                         std::optional<ArrayAttr> copyPrivateFuncs) {
+  size_t copyPrivateFuncsSize =
+      copyPrivateFuncs.has_value() ? copyPrivateFuncs->size() : 0;
+  if (copyPrivateFuncsSize != copyPrivateVars.size())
+    return op->emitOpError() << "inconsistent number of copyPrivate vars (= "
+                             << copyPrivateVars.size()
+                             << ") and functions (= " << copyPrivateFuncsSize
+                             << "), both must be equal";
+  if (!copyPrivateFuncs.has_value())
+    return success();
+
+  for (auto copyPrivateVarAndFunc :
+       llvm::zip(copyPrivateVars, *copyPrivateFuncs)) {
+    auto symbolRef =
+        llvm::cast<SymbolRefAttr>(std::get<1>(copyPrivateVarAndFunc));
+    std::optional<std::variant<mlir::func::FuncOp, mlir::LLVM::LLVMFuncOp>>
+        funcOp;
+    if (mlir::func::FuncOp mlirFuncOp =
+            SymbolTable::lookupNearestSymbolFrom<mlir::func::FuncOp>(op,
+                                                                     symbolRef))
+      funcOp = mlirFuncOp;
+    else if (mlir::LLVM::LLVMFuncOp llvmFuncOp =
+                 SymbolTable::lookupNearestSymbolFrom<mlir::LLVM::LLVMFuncOp>(
+                     op, symbolRef))
+      funcOp = llvmFuncOp;
+
+    auto getNumArguments = [&] {
+      return std::visit([](auto &f) { return f.getNumArguments(); }, *funcOp);
+    };
+
+    auto getArgumentType = [&](unsigned i) {
+      return std::visit([i](auto &f) { return f.getArgumentTypes()[i]; },
+                        *funcOp);
+    };
+
+    if (!funcOp)
+      return op->emitOpError() << "expected symbol reference " << symbolRef
+                               << " to point to a copy function";
+
+    if (getNumArguments() != 2)
+      return op->emitOpError()
+             << "expected copy function " << symbolRef << " to have 2 operands";
+
+    Type argTy = getArgumentType(0);
+    if (argTy != getArgumentType(1))
+      return op->emitOpError() << "expected copy function " << symbolRef
+                               << " arguments to have the same type";
+
+    Type varType = std::get<0>(copyPrivateVarAndFunc).getType();
+    if (argTy != varType)
+      return op->emitOpError()
+             << "expected copy function arguments' type (" << argTy
+             << ") to be the same as copyprivate variable's type (" << varType
+             << ")";
+  }
+
+  return success();
+}
+
 //===----------------------------------------------------------------------===//
 // Parser, printer and verifier for DependVarList
 //===----------------------------------------------------------------------===//
@@ -1152,7 +1256,8 @@ LogicalResult SingleOp::verify() {
     return emitError(
         "expected equal sizes for allocate and allocator variables");
 
-  return success();
+  return verifyCopyPrivateVarList(*this, getCopyprivateVars(),
+                                  getCopyprivateFuncs());
 }
 
 //===----------------------------------------------------------------------===//

mlir/test/Dialect/OpenMP/invalid.mlir

@@ -1255,7 +1255,63 @@ func.func @omp_single(%data_var : memref<i32>) -> () {
   // expected-error @below {{expected equal sizes for allocate and allocator variables}}
   "omp.single" (%data_var) ({
     omp.barrier
-  }) {operandSegmentSizes = array<i32: 1,0>} : (memref<i32>) -> ()
+  }) {operandSegmentSizes = array<i32: 1,0,0>} : (memref<i32>) -> ()
+  return
+}
+
+// -----
+
+func.func @omp_single_copyprivate(%data_var : memref<i32>) -> () {
+  // expected-error @below {{inconsistent number of copyPrivate vars (= 1) and functions (= 0), both must be equal}}
+  "omp.single" (%data_var) ({
+    omp.barrier
+  }) {operandSegmentSizes = array<i32: 0,0,1>} : (memref<i32>) -> ()
+  return
+}
+
+// -----
+
+func.func @omp_single_copyprivate(%data_var : memref<i32>) -> () {
+  // expected-error @below {{expected symbol reference @copy_func to point to a copy function}}
+  omp.single copyprivate(%data_var -> @copy_func : memref<i32>) {
+    omp.barrier
+  }
+  return
+}
+
+// -----
+
+func.func private @copy_func(memref<i32>)
+
+func.func @omp_single_copyprivate(%data_var : memref<i32>) -> () {
+  // expected-error @below {{expected copy function @copy_func to have 2 operands}}
+  omp.single copyprivate(%data_var -> @copy_func : memref<i32>) {
+    omp.barrier
+  }
+  return
+}
+
+// -----
+
+func.func private @copy_func(memref<i32>, memref<f32>)
+
+func.func @omp_single_copyprivate(%data_var : memref<i32>) -> () {
+  // expected-error @below {{expected copy function @copy_func arguments to have the same type}}
+  omp.single copyprivate(%data_var -> @copy_func : memref<i32>) {
+    omp.barrier
+  }
+  return
+}
+
+// -----
+
+func.func private @copy_func(memref<f32>, memref<f32>)
+
+func.func @omp_single_copyprivate(%data_var : memref<i32>) -> () {
+  // expected-error @below {{expected copy function arguments' type ('memref<f32>') to be the same as copyprivate variable's type ('memref<i32>')}}
+  omp.single copyprivate(%data_var -> @copy_func : memref<i32>) {
+    omp.barrier
+  }
   return
 }
 

mlir/test/Dialect/OpenMP/ops.mlir

@@ -1622,6 +1622,23 @@ func.func @omp_single_multiple_blocks() {
   return
 }
 
+func.func private @copy_i32(memref<i32>, memref<i32>)
+
+// CHECK-LABEL: func @omp_single_copyprivate
+func.func @omp_single_copyprivate(%data_var: memref<i32>) {
+  omp.parallel {
+    // CHECK: omp.single copyprivate(%{{.*}} -> @copy_i32 : memref<i32>) {
+    omp.single copyprivate(%data_var -> @copy_i32 : memref<i32>) {
+      "test.payload"() : () -> ()
+      // CHECK: omp.terminator
+      omp.terminator
+    }
+    // CHECK: omp.terminator
+    omp.terminator
+  }
+  return
+}
+
 // CHECK-LABEL: @omp_task
 // CHECK-SAME: (%[[bool_var:.*]]: i1, %[[i64_var:.*]]: i64, %[[i32_var:.*]]: i32, %[[data_var:.*]]: memref<i32>)
 func.func @omp_task(%bool_var: i1, %i64_var: i64, %i32_var: i32, %data_var: memref<i32>) {