[MLIR][OpenMP] Better error reporting for unsupported nowait (#78551)

Provides some context for failing to generate LLVM IR for `target
enter|exit|update` directives when `nowait` is provided. This is
directly helpful for flang users since they would get this error message
if they tried to use `nowait`. Before that we had a very generic
message.

This is a follow-up to #78269,
please only review the latest commit (the one with the same commit
message as the PR title).

Author: ergawy

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

@@ -1884,7 +1884,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           })
           .Case([&](omp::EnterDataOp enterDataOp) {
             if (enterDataOp.getNowait())
-              return failure();
+              return (LogicalResult)(enterDataOp.emitError(
+                  "`nowait` is not supported yet"));
 
             if (auto ifExprVar = enterDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifExprVar);
@@ -1900,7 +1901,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           })
           .Case([&](omp::ExitDataOp exitDataOp) {
             if (exitDataOp.getNowait())
-              return failure();
+              return (LogicalResult)(exitDataOp.emitError(
+                  "`nowait` is not supported yet"));
 
             if (auto ifExprVar = exitDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifExprVar);
@@ -1917,7 +1919,8 @@ convertOmpTargetData(Operation *op, llvm::IRBuilderBase &builder,
           })
           .Case([&](omp::UpdateDataOp updateDataOp) {
             if (updateDataOp.getNowait())
-              return failure();
+              return (LogicalResult)(updateDataOp.emitError(
+                  "`nowait` is not supported yet"));
 
             if (auto ifExprVar = updateDataOp.getIfExpr())
               ifCond = moduleTranslation.lookupValue(ifExprVar);

mlir/test/Target/LLVMIR/omptarget-nowait-llvm.mlir

@@ -0,0 +1,39 @@
+// RUN: not mlir-translate -mlir-to-llvmir -split-input-file %s 2>&1 | FileCheck %s
+
+llvm.func @_QPopenmp_target_data_update() {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "i", in_type = i32, operand_segment_sizes = array<i32: 0, 0>, uniq_name = "_QFopenmp_target_dataEi"} : (i64) -> !llvm.ptr
+  %2 = omp.map_info var_ptr(%1 : !llvm.ptr, i32)   map_clauses(to) capture(ByRef) -> !llvm.ptr {name = ""}
+
+  // CHECK: error: `nowait` is not supported yet
+  omp.target_update_data motion_entries(%2 : !llvm.ptr) nowait
+
+  llvm.return
+}
+
+// -----
+
+llvm.func @_QPopenmp_target_data_enter() {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "i", in_type = i32, operand_segment_sizes = array<i32: 0, 0>, uniq_name = "_QFopenmp_target_dataEi"} : (i64) -> !llvm.ptr
+  %2 = omp.map_info var_ptr(%1 : !llvm.ptr, i32)   map_clauses(to) capture(ByRef) -> !llvm.ptr {name = ""}
+
+  // CHECK: error: `nowait` is not supported yet
+  omp.target_enter_data map_entries(%2 : !llvm.ptr) nowait
+
+  llvm.return
+}
+
+
+// -----
+
+llvm.func @_QPopenmp_target_data_exit() {
+  %0 = llvm.mlir.constant(1 : i64) : i64
+  %1 = llvm.alloca %0 x i32 {bindc_name = "i", in_type = i32, operand_segment_sizes = array<i32: 0, 0>, uniq_name = "_QFopenmp_target_dataEi"} : (i64) -> !llvm.ptr
+  %2 = omp.map_info var_ptr(%1 : !llvm.ptr, i32)   map_clauses(from) capture(ByRef) -> !llvm.ptr {name = ""}
+
+  // CHECK: error: `nowait` is not supported yet
+  omp.target_exit_data map_entries(%2 : !llvm.ptr) nowait
+
+  llvm.return
+}