[flang][OpenMP] Add hostIsSource paramemter to copyHostAssociateVar (#123162)

This fixes a bug when the same variable is used in `firstprivate` and
`lastprivate` clauses on the same construct. The issue boils down to the
fact that `copyHostAssociateVar` was deciding the direction of the copy
assignment (i.e. the `lhs` and `rhs`) based on whether the
`copyAssignIP`
parameter is set. This is not the best way to do it since it is not
related to whether we doing a copy from host to localized copy or the
other way around. When we set the insertion for `firstprivate` in
delayed privatization, this resulted in switching the direction of the
copy assignment. Instead, this PR adds a new paramter to explicitely
tell
the function the direction of the assignment.

This is a follow up PR for
#122471, only the latest commit
is relevant.

Author: ergawy

flang/include/flang/Lower/AbstractConverter.h

@@ -130,9 +130,18 @@ class AbstractConverter {
   virtual void
   createHostAssociateVarCloneDealloc(const Fortran::semantics::Symbol &sym) = 0;
 
-  virtual void copyHostAssociateVar(
-      const Fortran::semantics::Symbol &sym,
-      mlir::OpBuilder::InsertPoint *copyAssignIP = nullptr) = 0;
+  /// For a host-associated symbol (a symbol associated with another symbol from
+  /// an enclosing scope), either:
+  ///
+  /// * if \p hostIsSource == true: copy \p sym's value *from* its corresponding
+  /// host symbol,
+  ///
+  /// * if \p hostIsSource == false: copy \p sym's value *to* its corresponding
+  /// host symbol.
+  virtual void
+  copyHostAssociateVar(const Fortran::semantics::Symbol &sym,
+                       mlir::OpBuilder::InsertPoint *copyAssignIP = nullptr,
+                       bool hostIsSource = true) = 0;
 
   virtual void copyVar(mlir::Location loc, mlir::Value dst, mlir::Value src,
                        fir::FortranVariableFlagsEnum attrs) = 0;

flang/lib/Lower/Bridge.cpp

@@ -891,9 +891,10 @@ class FirConverter : public Fortran::lower::AbstractConverter {
                  isPointer, Fortran::semantics::Symbol::Flags());
   }
 
-  void copyHostAssociateVar(
-      const Fortran::semantics::Symbol &sym,
-      mlir::OpBuilder::InsertPoint *copyAssignIP = nullptr) override final {
+  void
+  copyHostAssociateVar(const Fortran::semantics::Symbol &sym,
+                       mlir::OpBuilder::InsertPoint *copyAssignIP = nullptr,
+                       bool hostIsSource = true) override final {
     // 1) Fetch the original copy of the variable.
     assert(sym.has<Fortran::semantics::HostAssocDetails>() &&
            "No host-association found");
@@ -908,16 +909,14 @@ class FirConverter : public Fortran::lower::AbstractConverter {
            "Host and associated symbol boxes are the same");
 
     // 3) Perform the assignment.
-    mlir::OpBuilder::InsertPoint insPt = builder->saveInsertionPoint();
+    mlir::OpBuilder::InsertionGuard guard(*builder);
     if (copyAssignIP && copyAssignIP->isSet())
       builder->restoreInsertionPoint(*copyAssignIP);
     else
       builder->setInsertionPointAfter(sb.getAddr().getDefiningOp());
 
     Fortran::lower::SymbolBox *lhs_sb, *rhs_sb;
-    if (copyAssignIP && copyAssignIP->isSet() &&
-        sym.test(Fortran::semantics::Symbol::Flag::OmpLastPrivate)) {
-      // lastprivate case
+    if (!hostIsSource) {
       lhs_sb = &hsb;
       rhs_sb = &sb;
     } else {
@@ -926,11 +925,6 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     }
 
     copyVar(sym, *lhs_sb, *rhs_sb, sym.flags());
-
-    if (copyAssignIP && copyAssignIP->isSet() &&
-        sym.test(Fortran::semantics::Symbol::Flag::OmpLastPrivate)) {
-      builder->restoreInsertionPoint(insPt);
-    }
   }
 
   void genEval(Fortran::lower::pft::Evaluation &eval,

flang/lib/Lower/OpenMP/DataSharingProcessor.cpp

@@ -145,7 +145,7 @@ void DataSharingProcessor::copyFirstPrivateSymbol(
 void DataSharingProcessor::copyLastPrivateSymbol(
     const semantics::Symbol *sym, mlir::OpBuilder::InsertPoint *lastPrivIP) {
   if (sym->test(semantics::Symbol::Flag::OmpLastPrivate))
-    converter.copyHostAssociateVar(*sym, lastPrivIP);
+    converter.copyHostAssociateVar(*sym, lastPrivIP, /*hostIsSource=*/false);
 }
 
 void DataSharingProcessor::collectOmpObjectListSymbol(

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -2082,7 +2082,7 @@ genSectionsOp(lower::AbstractConverter &converter, lower::SymMap &symTable,
       const auto &objList = std::get<ObjectList>(lastp->t);
       for (const Object &object : objList) {
         semantics::Symbol *sym = object.sym();
-        converter.copyHostAssociateVar(*sym, &insp);
+        converter.copyHostAssociateVar(*sym, &insp, /*hostIsSource=*/false);
       }
     }
   }

flang/test/Lower/OpenMP/same_var_first_lastprivate.f90

@@ -0,0 +1,39 @@
+! RUN: %flang_fc1 -fopenmp -emit-hlfir %s -o - | FileCheck %s
+
+subroutine first_and_lastprivate
+  integer i
+  integer :: var = 1
+
+  !$omp parallel do firstprivate(var) lastprivate(var)
+  do i=1,1
+  end do
+  !$omp end parallel do
+end subroutine
+
+! CHECK:  omp.private {type = firstprivate} @{{.*}}Evar_firstprivate_ref_i32 : {{.*}} alloc {
+! CHECK:    %[[ALLOC:.*]] = fir.alloca i32 {{.*}}
+! CHECK:    %[[ALLOC_DECL:.*]]:2 = hlfir.declare %[[ALLOC]]
+! CHECK:    omp.yield(%[[ALLOC_DECL]]#0 : !fir.ref<i32>)
+! CHECK:  } copy {
+! CHECK: ^{{.*}}(%[[ORIG_REF:.*]]: {{.*}}, %[[PRIV_REF:.*]]: {{.*}}):
+! CHECK:    %[[ORIG_VAL:.*]] = fir.load %[[ORIG_REF]]
+! CHECK:    hlfir.assign %[[ORIG_VAL]] to %[[PRIV_REF]]
+! CHECK:    omp.yield(%[[PRIV_REF]] : !fir.ref<i32>)
+! CHECK:  }
+
+! CHECK:  func.func @{{.*}}first_and_lastprivate()
+! CHECK:    %[[ORIG_VAR_DECL:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "{{.*}}Evar"}
+! CHECK:    omp.parallel {
+! CHECK:      omp.barrier
+! CHECK:      omp.wsloop private(@{{.*}}var_firstprivate_ref_i32 {{.*}}) {
+! CHECK:        omp.loop_nest {{.*}} {
+! CHECK:          %[[PRIV_VAR_DECL:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "{{.*}}Evar"}
+! CHECK:          fir.if %{{.*}} {
+! CHECK:            %[[PRIV_VAR_VAL:.*]] = fir.load %[[PRIV_VAR_DECL]]#0 : !fir.ref<i32>
+! CHECK:            hlfir.assign %[[PRIV_VAR_VAL]] to %[[ORIG_VAR_DECL]]#0
+! CHECK:          }
+! CHECK:          omp.yield
+! CHECK:        }
+! CHECK:      }
+! CHECK:      omp.terminator
+! CHECK:    }