[HLFIR][flang][OpenMP][MLIR] Basic support for delayed privatization code-gen

Similar to llvm#81833 but for `hlfir` since we need different handling for
the `fir` vs. `hlfir` dialect.

Author: ergawy

flang/lib/Lower/Bridge.cpp

@@ -1052,6 +1052,17 @@ class FirConverter : public Fortran::lower::AbstractConverter {
       if (sym.detailsIf<Fortran::semantics::CommonBlockDetails>())
         return symMap->lookupSymbol(sym);
 
+      // For symbols to be privatized in OMP, the symbol is mapped to an
+      // instance of `SymbolBox::Intrinsic` (i.e. a direct mapping to an MLIR
+      // SSA value). This MLIR SSA value is the block argument to the
+      // `omp.private`'s `alloc` block. If this is the case, we return this
+      // `SymbolBox::Intrinsic` value.
+      if (Fortran::lower::SymbolBox v = symMap->lookupSymbol(sym))
+        return v.match(
+            [&](const Fortran::lower::SymbolBox::Intrinsic &)
+                -> Fortran::lower::SymbolBox { return v; },
+            [](const auto &) -> Fortran::lower::SymbolBox { return {}; });
+
       return {};
     }
     if (Fortran::lower::SymbolBox v = symMap->lookupSymbol(sym))

flang/test/Lower/OpenMP/delayed-privatization-firstprivate.f90

@@ -0,0 +1,30 @@
+! Test delayed privatization for the `firstprivate` clause.
+
+! RUN: bbc -emit-hlfir -fopenmp --openmp-enable-delayed-privatization -o - %s 2>&1 | FileCheck %s
+
+subroutine delayed_privatization_firstprivate
+  implicit none
+  integer :: var1
+
+!$OMP PARALLEL FIRSTPRIVATE(var1)
+  var1 = 10
+!$OMP END PARALLEL
+end subroutine
+
+! CHECK-LABEL: omp.private {type = firstprivate}
+! CHECK-SAME: @[[VAR1_PRIVATIZER_SYM:.*]] : !fir.ref<i32> alloc {
+! CHECK-NEXT: ^bb0(%[[PRIV_ARG:.*]]: !fir.ref<i32>):
+! CHECK-NEXT:   %[[PRIV_ALLOC:.*]] = fir.alloca i32 {bindc_name = "var1", pinned, uniq_name = "_QFdelayed_privatization_firstprivateEvar1"}
+! CHECK-NEXT:   %[[PRIV_DECL:.*]]:2 = hlfir.declare %[[PRIV_ALLOC]] {uniq_name = "_QFdelayed_privatization_firstprivateEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK-NEXT:   omp.yield(%[[PRIV_DECL]]#0 : !fir.ref<i32>)
+! CHECK: } copy {
+! CHECK: ^bb0(%[[PRIV_ORIG_ARG:.*]]: !fir.ref<i32>, %[[PRIV_PRIV_ARG:.*]]: !fir.ref<i32>):
+! CHECK:    %[[ORIG_VAL:.*]] = fir.load %[[PRIV_ORIG_ARG]] : !fir.ref<i32>
+! CHECK:    hlfir.assign %[[ORIG_VAL]] to %[[PRIV_PRIV_ARG]] temporary_lhs : i32, !fir.ref<i32>
+! CHECK:    omp.yield(%[[PRIV_PRIV_ARG]] : !fir.ref<i32>)
+! CHECK: }
+
+! CHECK-LABEL: @_QPdelayed_privatization_firstprivate
+! CHECK: omp.parallel private(@[[VAR1_PRIVATIZER_SYM]] %{{.*}} -> %{{.*}} : !fir.ref<i32>) {
+! CHECK: omp.terminator
+

flang/test/Lower/OpenMP/delayed-privatization-private.f90

@@ -0,0 +1,28 @@
+! Test delayed privatization for the `private` clause.
+
+! RUN: bbc -emit-hlfir -fopenmp --openmp-enable-delayed-privatization -o - %s 2>&1 | FileCheck %s
+
+subroutine delayed_privatization_private
+  implicit none
+  integer :: var1
+
+!$OMP PARALLEL PRIVATE(var1)
+  var1 = 10
+!$OMP END PARALLEL
+end subroutine
+
+! CHECK-LABEL: omp.private {type = private}
+! CHECK-SAME: @[[PRIVATIZER_SYM:.*]] : !fir.ref<i32> alloc {
+! CHECK-NEXT: ^bb0(%[[PRIV_ARG:.*]]: !fir.ref<i32>):
+! CHECK-NEXT:   %[[PRIV_ALLOC:.*]] = fir.alloca i32 {bindc_name = "var1", pinned, uniq_name = "_QFdelayed_privatization_privateEvar1"}
+! CHECK-NEXT:   %[[PRIV_DECL:.*]]:2 = hlfir.declare %[[PRIV_ALLOC]] {uniq_name = "_QFdelayed_privatization_privateEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK-NEXT:   omp.yield(%[[PRIV_DECL]]#0 : !fir.ref<i32>)
+! CHECK-NOT: } copy {
+
+! CHECK-LABEL: @_QPdelayed_privatization_private
+! CHECK: %[[ORIG_ALLOC:.*]] = fir.alloca i32 {bindc_name = "var1", uniq_name = "_QFdelayed_privatization_privateEvar1"}
+! CHECK: %[[ORIG_DECL:.*]]:2 = hlfir.declare %[[ORIG_ALLOC]] {uniq_name = "_QFdelayed_privatization_privateEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: omp.parallel private(@[[PRIVATIZER_SYM]] %[[ORIG_DECL]]#0 -> %[[PAR_ARG:.*]] : !fir.ref<i32>) {
+! CHECK: %[[PAR_ARG_DECL:.*]]:2 = hlfir.declare %[[PAR_ARG]] {uniq_name = "_QFdelayed_privatization_privateEvar1"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
+! CHECK: hlfir.assign %{{.*}} to %[[PAR_ARG_DECL]]#0 : i32, !fir.ref<i32>
+! CHECK: omp.terminator