[flang][cuda] Add interfaces for double_as_longlong and longlong_as_double (#153719)

Author: clementval

flang/module/cudadevice.f90

@@ -583,6 +583,20 @@ attributes(device) real(8) function sinpi(x) bind(c,name='__nv_sinpi')
     end function
   end interface
 
+  interface double_as_longlong
+    attributes(device) integer(8) function __double_as_longlong(i) bind(c, name='__nv_double_as_longlong')
+      !dir$ ignore_tkr (d) i
+      real(8), value :: i
+    end function
+  end interface
+
+  interface longlong_as_double
+    attributes(device) real(8) function __longlong_as_double(i) bind(c, name='__nv_longlong_as_double')
+      !dir$ ignore_tkr (d) i
+      integer(8), value :: i
+    end function
+  end interface
+
   interface __double2int_rd
     attributes(device) integer function __double2int_rd(r) bind(c, name='__nv_double2int_rd')
       !dir$ ignore_tkr (d) r

flang/test/Lower/CUDA/cuda-libdevice.cuf

@@ -245,6 +245,24 @@ end subroutine
 ! CHECK: %{{.*}} = fir.call @__nv_float2uint_ru(%{{.*}}) proc_attrs<bind_c> fastmath<contract> : (f32) -> i32
 ! CHECK: %{{.*}} = fir.call @__nv_float2uint_rz(%{{.*}}) proc_attrs<bind_c> fastmath<contract> : (f32) -> i32
 
+attributes(global) subroutine test_double_as_longlong()
+  integer(8) :: res
+  real(8) :: r
+  res = double_as_longlong(r)
+end subroutine
+
+! CHECK-LABEL: _QPtest_double_as_longlong
+! CHECK: %{{.*}} = fir.call @__nv_double_as_longlong(%{{.*}}) proc_attrs<bind_c> fastmath<contract> : (f64) -> i64
+
+attributes(global) subroutine test_longlong_as_double()
+  integer(8) :: i
+  real(8) :: res
+  res = longlong_as_double(i)
+end subroutine
+
+! CHECK-LABEL: _QPtest_longlong_as_double
+! CHECK: %{{.*}} = fir.call @__nv_longlong_as_double(%{{.*}}) proc_attrs<bind_c> fastmath<contract> : (i64) -> f64
+
 attributes(global) subroutine test_int_as_float()
   integer :: i
   real :: res