[MLIR][OpenMP] Fix compiler crash when translating omp.target to LLVM IR

This patch fixes a compiler crash that would happen during translation to LLVM
IR if the optional `map` argument of the `omp.target` operation was not
present. A unit test is added to ensure this has been fixed.

Differential Revision: https://reviews.llvm.org/D158722

Author: skatrak

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

@@ -1884,7 +1884,7 @@ convertOmpTarget(Operation &opInst, llvm::IRBuilderBase &builder,
 
   DataLayout DL = DataLayout(opInst.getParentOfType<ModuleOp>());
   SmallVector<Value> mapOperands = targetOp.getMapOperands();
-  ArrayAttr mapTypes = targetOp.getMapTypes().value();
+  ArrayAttr mapTypes = targetOp.getMapTypes().value_or(nullptr);
 
   llvm::OpenMPIRBuilder::MapInfosTy combinedInfos;
   auto genMapInfoCB = [&](llvm::OpenMPIRBuilder::InsertPointTy codeGenIP)

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

@@ -21,18 +21,36 @@ module attributes {omp.is_target_device = false} {
     }
     llvm.return
   }
+
+  llvm.func @omp_target_no_map() {
+    omp.target {
+      omp.terminator
+    }
+    llvm.return
+  }
 }
 
-// CHECK: call i32 @__tgt_target_kernel(ptr @4, i64 -1, i32 -1, i32 0, ptr @.__omp_offloading_[[DEV:.*]]_[[FIL:.*]]_omp_target_region__l[[LINE:.*]].region_id, ptr %kernel_args)
+// CHECK: define void @omp_target_region_()
+// CHECK: call i32 @__tgt_target_kernel(ptr @4, i64 -1, i32 -1, i32 0, ptr @.__omp_offloading_[[DEV:.*]]_[[FIL:.*]]_omp_target_region__l[[LINE1:.*]].region_id, ptr %kernel_args)
+
+// CHECK: br i1 %{{.*}}, label %omp_offload.failed, label %omp_offload.cont
+// CHECK: omp_offload.failed:
+// CHECK: call void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_region__l[[LINE1]](ptr %{{.*}}, ptr %{{.*}}, ptr %{{.*}})
+// CHECK: omp_offload.cont:
+
+// CHECK: define void @omp_target_no_map()
+// CHECK: call i32 @__tgt_target_kernel(ptr @4, i64 -1, i32 -1, i32 0, ptr @.__omp_offloading_[[DEV:.*]]_[[FIL:.*]]_omp_target_no_map_l[[LINE2:.*]].region_id, ptr %kernel_args)
 
 // CHECK: br i1 %{{.*}}, label %omp_offload.failed, label %omp_offload.cont
 // CHECK: omp_offload.failed:
-// CHECK: call void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_region__l[[LINE]](ptr %{{.*}}, ptr %{{.*}}, ptr %{{.*}})
+// CHECK: call void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_no_map_l[[LINE2]]()
 // CHECK: omp_offload.cont:
 
-// CHECK: define internal void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_region__l[[LINE]](ptr %[[ADDR_A:.*]], ptr %[[ADDR_B:.*]], ptr %[[ADDR_C:.*]])
+// CHECK: define internal void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_region__l[[LINE1]](ptr %[[ADDR_A:.*]], ptr %[[ADDR_B:.*]], ptr %[[ADDR_C:.*]])
 // CHECK: %[[VAL_A:.*]] = load i32, ptr %[[ADDR_A]], align 4
 // CHECK: %[[VAL_B:.*]] = load i32, ptr %[[ADDR_B]], align 4
 // CHECK: %[[SUM:.*]] = add i32 %[[VAL_A]], %[[VAL_B]]
 // CHECK: store i32 %[[SUM]], ptr %[[ADDR_C]], align 4
 
+// CHECK: define internal void @__omp_offloading_[[DEV]]_[[FIL]]_omp_target_no_map_l[[LINE2]]()
+// CHECK: ret void