[flang] Check for BIND(C) through use association.

If the interface specifies BIND(C), then the declarations using
this interface inherit BIND(C), and if they are referenced via use
association they must be classified as BIND(C) subprograms.

Differential Revision: https://reviews.llvm.org/D145084

flang/lib/Semantics/tools.cpp

@@ -278,7 +278,8 @@ bool IsPointerDummy(const Symbol &symbol) {
   return IsPointer(symbol) && IsDummy(symbol);
 }
 
-bool IsBindCProcedure(const Symbol &symbol) {
+bool IsBindCProcedure(const Symbol &original) {
+  const Symbol &symbol{original.GetUltimate()};
   if (const auto *procDetails{symbol.detailsIf<ProcEntityDetails>()}) {
     if (procDetails->procInterface()) {
       // procedure component with a BIND(C) interface

flang/test/Lower/bindc_procs.f90

@@ -0,0 +1,56 @@
+! RUN: bbc -emit-fir %s -o - | FileCheck %s
+
+! CHECK-DAG: func.func private @proc1() attributes {fir.bindc_name = "proc1"}
+module decl1
+  interface
+     subroutine proc_iface() bind(C)
+     end subroutine proc_iface
+  end interface
+  procedure (proc_iface) PrOc1
+end module decl1
+subroutine test1(x)
+  use decl1
+  call PrOc1
+end subroutine test1
+
+! CHECK-DAG: func.func private @proc2() attributes {fir.bindc_name = "proc2"}
+module decl2
+  interface
+     subroutine proc_iface() bind(C)
+     end subroutine proc_iface
+  end interface
+end module decl2
+subroutine test2(x)
+  use decl2
+  procedure (proc_iface) PrOc2
+  call PrOc2
+end subroutine test2
+
+! CHECK-DAG: func.func private @func3() -> f32 attributes {fir.bindc_name = "func3"}
+module decl3
+  interface
+     real function func_iface() bind(C)
+     end function func_iface
+  end interface
+  procedure (func_iface) FuNc3
+end module decl3
+subroutine test3(x)
+  use decl3
+  real :: x
+  x = FuNc3()
+end subroutine test3
+
+! CHECK-DAG: func.func private @func4() -> f32 attributes {fir.bindc_name = "func4"}
+module decl4
+  interface
+     real function func_iface() bind(C)
+     end function func_iface
+  end interface
+end module decl4
+subroutine test4(x)
+  use decl4
+  procedure (func_iface) FuNc4
+  real :: x
+  x = FuNc4()
+end subroutine test4
+