[flang][cuda][openacc] Don't apply CUDA Fortran COMMON/EQUIVALENCE rule to internal UseDevice marker (#197036)

wangzpgi · web-flow · commit 7be448e6e090 · 2026-05-11T21:32:27.000Z
`CUDADataAttr::UseDevice` is not user-spellable; the symbol that
actually lives in COMMON/EQUIVALENCE carries no CUDA attribute. The CUDA
Fortran restriction (CUDA Fortran Programming Guide §3.2) does not apply
to it.

Exclude `UseDevice` from the COMMON/EQUIVALENCE check alongside the
existing `Pinned` exclusion, and add a Semantics regression test.
diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
@@ -1243,7 +1243,14 @@ void CheckHelper::CheckObjectEntity(
     case common::CUDADataAttr::UseDevice:
       break;
     }
-    if (attr != common::CUDADataAttr::Pinned) {
+    // CUDADataAttr::UseDevice is not user-spellable; it is set internally on
+    // construct-scoped symbol copies created for OpenACC `host_data
+    // use_device(...)` operands so that later passes can resolve them to the
+    // device address. The original symbol that actually lives in COMMON or an
+    // equivalence group carries no CUDA attribute, so the CUDA Fortran
+    // restrictions on user-written ATTRIBUTES(...) do not apply to it.
+    if (attr != common::CUDADataAttr::Pinned &&
+        attr != common::CUDADataAttr::UseDevice) {
       if (details.commonBlock()) {
         messages_.Say(
             "Object '%s' with ATTRIBUTES(%s) may not be in COMMON"_err_en_US,
diff --git a/flang/test/Semantics/OpenACC/acc-host-data-common.f90 b/flang/test/Semantics/OpenACC/acc-host-data-common.f90
@@ -0,0 +1,36 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenacc
+
+! Regression test: a variable that lives in a COMMON block must not be
+! rejected when it appears in an OpenACC `host_data use_device(...)`
+! clause. The CUDA Fortran restriction "object with ATTRIBUTES(USEDEVICE)
+! may not be in COMMON" applies only to user-spelled
+! `attributes(usedevice)` dummy arguments, not to the internal
+! CUDADataAttr::UseDevice marker that name resolution attaches to
+! construct-scoped copies of `use_device` operands.
+
+subroutine vadd(a, b, c, n)
+  real(8) :: a(*), b(*), c(*)
+  integer :: n, i
+  do i = 1, n - 1
+    c(i) = a(i) + b(i)
+  end do
+end subroutine
+
+program acc_host_data_common
+  integer, parameter :: N = 100
+  real(8) :: a(2:N), b(2:N), c0(2:N), c1(2:N)
+  common /arrays/ a, b, c0, c1
+  integer :: i
+
+  !$acc data copy(a, b, c0)
+  !$acc parallel loop
+  do i = 2, N
+    a(i) = i
+    b(i) = 2.0_8 * i
+  end do
+
+  !$acc host_data use_device(a, b, c0)
+  call vadd(a, b, c0, N)
+  !$acc end host_data
+  !$acc end data
+end program
