[Flang][OpenMP] Avoid double privatisation of loop variables

[kiranchandramohan]

Summary

Loop variables of a worksharing loop and sequential loops in parallel
region are privatised by default. These variables are marked with
OmpPreDetermined. Skip explicit privatisation of these variables.

Note: This is part of upstreaming from the fir-dev branch of
https://github.com/flang-compiler/f18-llvm-project.

Co-authored-by: Jean Perier <[e-mail]>
Co-authored-by: Mats Petersson <[e-mail]>

[kiranchandramohan]

Rebase and remove whitespace.

flang/lib/Lower/OpenMP.cpp

 //===-- OpenMP.cpp -- Open MP directive lowering --------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
std::visit(
                       getDesignatorNameIfDataRef(designator)) {
                 sym = name->symbol;
               }
             },
             [&](const Fortran::parser::Name &name) { sym = name.symbol; }},
         ompObject.u);
 
     // Privatization for symbols which are pre-determined (like loop index
-    // variables) happen separately, for everything else privatize here
+    // variables) happen separately, for everything else privatize here.
+    if (sym->test(Fortran::semantics::Symbol::Flag::OmpPreDetermined))
+      continue;
     if constexpr (std::is_same_v<T, Fortran::parser::OmpClause::Firstprivate>) {
       converter.copyHostAssociateVar(*sym);
     } else {
       bool success = converter.createHostAssociateVarClone(*sym);
       (void)success;
       assert(success && "Privatization failed due to existing binding");
     }
   }

flang/test/Lower/OpenMP/omp-parallel-private-clause-fixes.f90

+! This test checks a few bug fixes in the PRIVATE clause lowering
+
+! RUN: bbc -fopenmp -emit-fir %s -o - | \
+! RUN:   FileCheck %s 
+
+! CHECK-LABEL: multiple_private_fix
+! CHECK:         %[[VAL_0:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFmultiple_private_fixEi"}
+! CHECK:         %[[VAL_1:.*]] = fir.alloca i32 {bindc_name = "j", uniq_name = "_QFmultiple_private_fixEj"}
+! CHECK:         %[[VAL_2:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFmultiple_private_fixEx"}
+! CHECK:         omp.parallel {
+! CHECK:           %[[PRIV_J:.*]] = fir.alloca i32 {bindc_name = "j", pinned
+! CHECK:           %[[PRIV_X:.*]] = fir.alloca i32 {bindc_name = "x", pinned
+! CHECK:           %[[PRIV_I:.*]] = fir.alloca i32 {{{.*}}, pinned
+! CHECK:           %[[ONE:.*]] = arith.constant 1 : i32
+! CHECK:           %[[VAL_3:.*]] = fir.load %[[VAL_4:.*]] : !fir.ref<i32>
+! CHECK:           %[[VAL_5:.*]] = arith.constant 1 : i32
+! CHECK:           omp.wsloop for (%[[VAL_6:.*]]) : i32 = (%[[ONE]]) to (%[[VAL_3]]) inclusive step (%[[VAL_5]]) {
+! CHECK:             fir.store %[[VAL_6]] to %[[PRIV_I]] : !fir.ref<i32>
+! CHECK:             %[[VAL_7:.*]] = arith.constant 1 : i32
+! CHECK:             %[[VAL_8:.*]] = fir.convert %[[VAL_7]] : (i32) -> index
+! CHECK:             %[[VAL_9:.*]] = fir.load %[[VAL_4]] : !fir.ref<i32>
+! CHECK:             %[[VAL_10:.*]] = fir.convert %[[VAL_9]] : (i32) -> index
+! CHECK:             %[[VAL_11:.*]] = arith.constant 1 : index
+! CHECK:             %[[VAL_12:.*]] = fir.do_loop %[[VAL_13:.*]] = %[[VAL_8]] to %[[VAL_10]] step %[[VAL_11]] -> index {
+! CHECK:               %[[VAL_14:.*]] = fir.convert %[[VAL_13]] : (index) -> i32
+! CHECK:               fir.store %[[VAL_14]] to %[[PRIV_J]] : !fir.ref<i32>
+! CHECK:               %[[LOAD:.*]] = fir.load %[[PRIV_I]] : !fir.ref<i32>
+! CHECK:               %[[VAL_15:.*]] = fir.load %[[PRIV_J]] : !fir.ref<i32>
+! CHECK:               %[[VAL_16:.*]] = arith.addi %[[LOAD]], %[[VAL_15]] : i32
+! CHECK:               fir.store %[[VAL_16]] to %[[PRIV_X]] : !fir.ref<i32>
+! CHECK:               %[[VAL_17:.*]] = arith.addi %[[VAL_13]], %[[VAL_11]] : index
+! CHECK:               fir.result %[[VAL_17]] : index
+! CHECK:             }
+! CHECK:             %[[VAL_18:.*]] = fir.convert %[[VAL_19:.*]] : (index) -> i32
+! CHECK:             fir.store %[[VAL_18]] to %[[PRIV_J]] : !fir.ref<i32>
+! CHECK:             omp.yield
+! CHECK:           }
+! CHECK:           omp.terminator
+! CHECK:         }
+! CHECK:         return
+subroutine multiple_private_fix(gama)
+        integer :: i, j, x, gama
+!$OMP PARALLEL DO PRIVATE(j,x)
+        do i = 1, gama
+          do j = 1, gama
+            x = i + j
+          end do
+        end do
+!$OMP END PARALLEL DO
+end subroutine
+
+! CHECK-LABEL: multiple_private_fix2
+! CHECK:  %[[X1:.*]] = fir.alloca i32 {bindc_name = "x", uniq_name = "_QFmultiple_private_fix2Ex"}
+! CHECK:  omp.parallel  {
+! CHECK:    %[[X2:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFmultiple_private_fix2Ex"}
+! CHECK:    omp.parallel  {
+! CHECK:      %[[X3:.*]] = fir.alloca i32 {bindc_name = "x", pinned, uniq_name = "_QFmultiple_private_fix2Ex"}
+! CHECK:      %[[C3:.*]] = arith.constant 1 : i32
+! CHECK:      fir.store %[[C3]] to %[[X3]] : !fir.ref<i32>
+! CHECK:      omp.terminator
+! CHECK:    }
+! CHECK:      %[[C2:.*]] = arith.constant 1 : i32
+! CHECK:      fir.store %[[C2]] to %[[X2]] : !fir.ref<i32>
+! CHECK:    omp.terminator
+! CHECK:  }
+! CHECK:      %[[C1:.*]] = arith.constant 1 : i32
+! CHECK:      fir.store %[[C1]] to %[[X1]] : !fir.ref<i32>
+! CHECK:  return
+subroutine multiple_private_fix2()
+   integer :: x
+   !$omp parallel private(x)
+   !$omp parallel private(x)
+      x = 1
+   !$omp end parallel
+      x = 1
+   !$omp end parallel
+      x = 1
+end subroutine