[flang][cuda] Allow constant actual argument for device dummy (#121845)

The reference compiler allows this use case. Note that writing to this
variable would result in CUDA error.

Author: clementval

flang/lib/Common/Fortran.cpp

@@ -136,7 +136,8 @@ bool AreCompatibleCUDADataAttrs(std::optional<CUDADataAttr> x,
       if (*x == CUDADataAttr::Device) {
         if ((y &&
                 (*y == CUDADataAttr::Managed || *y == CUDADataAttr::Unified ||
-                    *y == CUDADataAttr::Shared)) ||
+                    *y == CUDADataAttr::Shared ||
+                    *y == CUDADataAttr::Constant)) ||
             (!y && (isCudaUnified || isCudaManaged))) {
           if (y && *y == CUDADataAttr::Shared && warning) {
             *warning = "SHARED attribute ignored"s;

flang/test/Semantics/cuf10.cuf

@@ -2,6 +2,7 @@
 module m
   real, device :: a(4,8)
   real, managed, allocatable :: b(:,:)
+  integer, constant :: x = 1
  contains
   attributes(global) subroutine kernel(a,b,c,n,m)
     integer, value :: n
@@ -23,4 +24,10 @@ module m
       call devsub(c,4) ! not checked in OpenACC construct
     end do
   end
+  attributes(global) subroutine sub1(x)
+    integer :: x
+  end
+  subroutine sub2()
+    call sub1<<<1,1>>>(x) ! actual constant to device dummy
+  end
 end