[flang][OpenMP] Ignore target-data operations with no offload targets

When no offload targets are specified flang will ignore "target"
constructs, but not "target data" constructs. This patch makes the
behavior consistent across all offload-related operations.

While ignoring "target" may produce semantically incorrect code, it
may still be a useful debugging tool.

Author: kparzysz

flang/test/Lower/ignore-target-data.f90

@@ -0,0 +1,20 @@
+!RUN: %flang_fc1 -emit-llvm -fopenmp %s -o - | FileCheck %s
+
+!Make sure that there are no calls to the mapper.
+
+!CHECK-NOT: call{{.*}}__tgt_target_data_begin_mapper
+!CHECK-NOT: call{{.*}}__tgt_target_data_end_mapper
+
+program test
+
+call f(1, 2)
+
+contains
+
+subroutine f(x, y)
+  integer :: x, y
+  !$omp target data map(tofrom: x, y)
+  x = x + y
+  !$omp end target data
+end subroutine
+end

mlir/lib/Target/LLVMIR/Dialect/OpenMP/OpenMPToLLVMIRTranslation.cpp

@@ -4378,6 +4378,9 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
   llvm::OpenMPIRBuilder *ompBuilder = moduleTranslation.getOpenMPBuilder();
   llvm::OpenMPIRBuilder::TargetDataInfo info(/*RequiresDevicePointerInfo=*/true,
                                              /*SeparateBeginEndCalls=*/true);
+  bool isTargetDevice = ompBuilder->Config.isTargetDevice();
+  bool isOffloadEntry =
+      isTargetDevice || !ompBuilder->Config.TargetTriples.empty();
 
   LogicalResult result =
       llvm::TypeSwitch<Operation *, LogicalResult>(op)
@@ -4402,6 +4405,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           .Case([&](omp::TargetEnterDataOp enterDataOp) -> LogicalResult {
             if (failed(checkImplementationStatus(*enterDataOp)))
               return failure();
+            if (!isOffloadEntry)
+              return success();
 
             if (auto ifVar = enterDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifVar);
@@ -4422,6 +4427,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           .Case([&](omp::TargetExitDataOp exitDataOp) -> LogicalResult {
             if (failed(checkImplementationStatus(*exitDataOp)))
               return failure();
+            if (!isOffloadEntry)
+              return success();
 
             if (auto ifVar = exitDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifVar);
@@ -4442,6 +4449,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           .Case([&](omp::TargetUpdateOp updateDataOp) -> LogicalResult {
             if (failed(checkImplementationStatus(*updateDataOp)))
               return failure();
+            if (!isOffloadEntry)
+              return success();
 
             if (auto ifVar = updateDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifVar);
@@ -4467,6 +4476,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
 
   if (failed(result))
     return failure();
+  if (!isOffloadEntry)
+    return success();
 
   using InsertPointTy = llvm::OpenMPIRBuilder::InsertPointTy;
   MapInfoData mapData;