[llvm] [mlir] [Flang] [OpenMP] Add LLVM lowering support for PRIORITY in TASK (PR #120710)

[Thirumalai Shaktivel via llvm-commits]

================
@@ -1958,6 +1963,30 @@ OpenMPIRBuilder::InsertPointOrErrorTy OpenMPIRBuilder::createTask(
                            SharedsSize);
     }
 
+    if (Priority) {
+      //
+      // The return type of "__kmpc_omp_task_alloc" is "kmp_task_t *",
+      // we populate the priority information into the "kmp_task_t" here
+      //
+      // The struct "kmp_task_t" definition is available in kmp.h
+      // kmp_task_t = { shareds, routine, part_id, data1, data2 }
+      // data2 is used for priority
+      //
+      Type *Int32Ty = Builder.getInt32Ty();
+      // kmp_task_t* => { ptr }
+      Type *taskPtr = StructType::get(VoidPtr);
+      Value *taskGEP = Builder.CreateInBoundsGEP(
+          taskPtr, TaskData,
+          {ConstantInt::get(Int32Ty, 0), ConstantInt::get(Int32Ty, 0)});
+      // kmp_task_t => { ptr, ptr, i32, ptr, ptr }
+      Type *taskStructType = StructType::get(
+          VoidPtr, VoidPtr, Builder.getInt32Ty(), VoidPtr, VoidPtr);
+      Value *priorityData = Builder.CreateInBoundsGEP(
+          taskStructType, taskGEP,
+          {ConstantInt::get(Int32Ty, 0), ConstantInt::get(Int32Ty, 4)});
+      Builder.CreateStore(Priority, priorityData);
----------------
Thirumalai-Shaktivel wrote:

> Is this sufficient because priority is the first field of kmp_cmplrdata

Yes, because I checked whether the priority value is passed to runtime by printing the value inside the `__kmpc_omp_task`, and it prints the correct value.

But, after thinking about this, we should indeed index through kmp_cmplrdata_t (which might fix some bugs in the future.)

https://github.com/llvm/llvm-project/pull/120710