[Flang][OpenMP] Add Lowering support for Collapse with Taskloop

Supprot for lowering collapse already exists within
`genLoopNestClauses`, which is called when lowering taskloop. However,
the TODO message still included the Collapse clause, so it was not
activated. By removing this, it enables lowering of the Collapse
clause in taskloop.

Author: Stylie777

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -1773,7 +1773,7 @@ static void genTaskloopClauses(lower::AbstractConverter &converter,
   cp.processGrainsize(stmtCtx, clauseOps);
   cp.processNumTasks(stmtCtx, clauseOps);
 
-  cp.processTODO<clause::Allocate, clause::Collapse, clause::Default,
+  cp.processTODO<clause::Allocate, clause::Default,
                  clause::Final, clause::If, clause::InReduction,
                  clause::Lastprivate, clause::Mergeable, clause::Nogroup,
                  clause::Priority, clause::Reduction, clause::Shared,

flang/test/Lower/OpenMP/taskloop-collapse.f90

@@ -0,0 +1,34 @@
+! Test the collapse clause when being used with the taskloop construct
+! RUN: bbc -emit-hlfir -fopenmp -fopenmp-version=45 %s -o - 2>&1 | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=45 %s -o - 2>&1 | FileCheck %s
+
+! CHECK-LABEL: omp.private
+! CHECK-SAME: {type = private} @[[J_PRIVATE:.*]] : i32
+! CHECK-LABEL: omp.private
+! CHECK-SAME: {type = private} @[[I_PRIVATE:.*]] : i32
+! CHECK-LABEL: omp.private
+! CHECK-SAME: {type = firstprivate} @[[SUM_FIRSTPRIVATE:.*]] : i32 copy
+
+! CHECK-LABEL: func.func @_QPtest()
+! CHECK: %[[ALLOCA_I:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFtestEi"}
+! CHECK: %[[DECLARE_I:.*]]:2 = hlfir.declare %1 {uniq_name = "_QFtestEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[ALLOCA_J:.*]] = fir.alloca i32 {bindc_name = "j", uniq_name = "_QFtestEj"}
+! CHECK: %[[DECLARE_J:.*]]:2 = hlfir.declare %3 {uniq_name = "_QFtestEj"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: %[[ALLOCA_SUM:.*]] = fir.alloca i32 {bindc_name = "sum", uniq_name = "_QFtestEsum"}
+! CHECK: %[[DECLARE_SUM:.*]]:2 = hlfir.declare %5 {uniq_name = "_QFtestEsum"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+
+subroutine test()
+    integer :: i, j, sum
+
+    !$omp taskloop collapse(2)
+    ! CHECK-LABEL: omp.taskloop
+    ! CHECK-SAME: private(@_QFtestEsum_firstprivate_i32 %[[DECLARE_SUM]]#0 -> %arg0, @_QFtestEi_private_i32 %[[DECLARE_I]]#0 -> %arg1, @_QFtestEj_private_i32 %[[DECLARE_J]]#0 -> %arg2 : !fir.ref<i32>, !fir.ref<i32>, !fir.ref<i32>)
+    ! CHECK-LABEL: omp.loop_nest
+    ! CHECK-SAME: (%arg3, %arg4) : i32 = (%c1_i32, %c1_i32_1) to (%c10_i32, %c5_i32) inclusive step (%c1_i32_0, %c1_i32_2) collapse(2)
+    do i = 1, 10
+        do j = 1, 5
+            sum = sum + i + j
+        end do
+    end do
+    !$omp end taskloop
+end subroutine