[flang] Consider bind(c) when lowering calls to intrinsic module procedures

flang/lib/Lower/ConvertCall.cpp

@@ -2122,7 +2122,12 @@ genProcedureRef(CallContext &callContext) {
   mlir::Location loc = callContext.loc;
   if (auto *intrinsic = callContext.procRef.proc().GetSpecificIntrinsic())
     return genIntrinsicRef(intrinsic, callContext);
-  if (Fortran::lower::isIntrinsicModuleProcRef(callContext.procRef))
+  // If it is an intrinsic module procedure reference - then treat as
+  // intrinsic unless it is bind(c) (since implementation is external from
+  // module).
+  if (Fortran::lower::isIntrinsicModuleProcRef(callContext.procRef) &&
+      !Fortran::semantics::IsBindCProcedure(
+          *callContext.procRef.proc().GetSymbol()))
     return genIntrinsicRef(nullptr, callContext);
 
   if (callContext.isStatementFunctionCall())
@@ -2227,8 +2232,7 @@ bool Fortran::lower::isIntrinsicModuleProcRef(
     return false;
   const Fortran::semantics::Symbol *module =
       symbol->GetUltimate().owner().GetSymbol();
-  return module && module->attrs().test(Fortran::semantics::Attr::INTRINSIC) &&
-         module->name().ToString().find("omp_lib") == std::string::npos;
+  return module && module->attrs().test(Fortran::semantics::Attr::INTRINSIC);
 }
 
 std::optional<hlfir::EntityWithAttributes> Fortran::lower::convertCallToHLFIR(

flang/module/omp_lib.h

@@ -90,7 +90,7 @@
     omp_atv_blocked = 17, &
     omp_atv_interleaved = 18
 
-  type :: omp_alloctrait
+  type, bind(c) :: omp_alloctrait
     integer(kind=omp_alloctrait_key_kind) :: key, value
   end type omp_alloctrait
 
@@ -264,23 +264,23 @@
       integer(kind=omp_integer_kind), intent(out) :: place_nums(*)
     end subroutine omp_get_partition_place_nums
 
-    subroutine omp_set_affinity_format(format)
+    subroutine omp_set_affinity_format(format) bind(c)
       import
       character(len=*), intent(in) :: format
     end subroutine omp_set_affinity_format
 
-    function omp_get_affinity_format(buffer)
+    function omp_get_affinity_format(buffer) bind(c)
       import
       character(len=*), intent(out) :: buffer
       integer(kind=omp_integer_kind) :: omp_get_affinity_format
     end function omp_get_affinity_format
 
-    subroutine omp_display_affinity(format)
+    subroutine omp_display_affinity(format) bind(c)
       import
       character(len=*), intent(in) :: format
     end subroutine omp_display_affinity
 
-    function omp_capture_affinity(buffer, format)
+    function omp_capture_affinity(buffer, format) bind(c)
       import
       character(len=*), intent(out) :: buffer
       character(len=*), intent(in) :: format
@@ -339,7 +339,7 @@
       integer(kind=omp_integer_kind) :: omp_pause_resource
     end function omp_pause_resource
 
-    function omp_pause_resource_all(kind)
+    function omp_pause_resource_all(kind) bind(c)
       import
       integer(kind=omp_pause_resource_kind), value :: kind
       integer(kind=omp_integer_kind) :: omp_pause_resource_all
@@ -428,7 +428,7 @@
 ! Device Memory Routines
 
 ! Memory Management Routines
-    function omp_init_allocator(memspace, ntraits, traits)
+    function omp_init_allocator(memspace, ntraits, traits) bind(c)
       import
       integer(kind=omp_memspace_handle_kind), value :: memspace
       integer, value :: ntraits
@@ -446,7 +446,7 @@
       integer(kind=omp_allocator_handle_kind), value :: allocator
     end subroutine omp_set_default_allocator
 
-    function omp_get_default_allocator()
+    function omp_get_default_allocator() bind(c)
       import
       integer(kind=omp_allocator_handle_kind) :: omp_get_default_allocator
     end function omp_get_default_allocator

flang/test/Lower/OpenMP/omp-lib-num-threads.f90

@@ -0,0 +1,21 @@
+! RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - 2>&1 | FileCheck %s
+! RUN: bbc -fopenmp -emit-hlfir -o - %s 2>&1 | FileCheck %s
+!
+! Test that the calls to omp_lib's omp_get_num_threads and omp_set_num_threads
+! get lowered even though their implementation is not in the omp_lib module
+! (and this matters because this is an intrinsic module - and calls to
+! intrinsics are specially resolved).
+
+program main
+  use omp_lib
+  integer(omp_integer_kind) :: num_threads
+  integer(omp_integer_kind), parameter :: requested_num_threads = 4
+  call omp_set_num_threads(requested_num_threads)
+  num_threads = omp_get_num_threads()
+  print *, num_threads
+end program
+
+!CHECK-NOT: not yet implemented: intrinsic: omp_set_num_threads
+!CHECK-NOT: not yet implemented: intrinsic: omp_get_num_threads
+!CHECK: fir.call @omp_set_num_threads
+!CHECK: fir.call @omp_get_num_threads