[flang][cuda] Fix semantic for the CONSTANT attribute

[clementval]

Object with the CONSTANT attribute cannot be declared in the host subprogram.

It can be declared in a module or a device subprogram.

Adapt the semantic check to trigger the error in host subprogram.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

@llvm/pr-subscribers-flang-fir-hlfir

Author: Valentin Clement (バレンタイン クレメン) (clementval)

Changes

Object with the CONSTANT attribute cannot be declared in the host subprogram.

It can be declared in a module or a device subprogram.

Adapt the semantic check to trigger the error in host subprogram.

---

Full diff: https://github.com/llvm/llvm-project/pull/82821.diff

3 Files Affected:

• (modified) flang/lib/Semantics/check-declarations.cpp (+6-1)
• (modified) flang/test/Lower/CUDA/cuda-data-attribute.cuf (-10)
• (modified) flang/test/Semantics/cuf03.cuf (+6)

diff --git a/flang/lib/Semantics/check-declarations.cpp b/flang/lib/Semantics/check-declarations.cpp
index 2db3f9a27d8f4a..e9adc086402d63 100644
--- a/flang/lib/Semantics/check-declarations.cpp
+++ b/flang/lib/Semantics/check-declarations.cpp
@@ -920,7 +920,12 @@ void CheckHelper::CheckObjectEntity(
     auto attr{*details.cudaDataAttr()};
     switch (attr) {
     case common::CUDADataAttr::Constant:
-      if (IsAllocatableOrPointer(symbol) || symbol.attrs().test(Attr::TARGET)) {
+      if (subpDetails && !inDeviceSubprogram) {
+        messages_.Say(
+            "Object '%s' with ATTRIBUTES(CONSTANT) may not be declared in a host subprogram"_err_en_US,
+            symbol.name());
+      } else if (IsAllocatableOrPointer(symbol) ||
+          symbol.attrs().test(Attr::TARGET)) {
         messages_.Say(
             "Object '%s' with ATTRIBUTES(CONSTANT) may not be allocatable, pointer, or target"_err_en_US,
             symbol.name());
diff --git a/flang/test/Lower/CUDA/cuda-data-attribute.cuf b/flang/test/Lower/CUDA/cuda-data-attribute.cuf
index 7596c6b21efb0d..94aa62352c2a0b 100644
--- a/flang/test/Lower/CUDA/cuda-data-attribute.cuf
+++ b/flang/test/Lower/CUDA/cuda-data-attribute.cuf
@@ -16,30 +16,20 @@ module cuda_var
 contains
 
 subroutine local_var_attrs
-  real, constant :: rc
   real, device :: rd
   real, allocatable, managed :: rm
   real, allocatable, pinned :: rp
 end subroutine
 
 ! CHECK-LABEL: func.func @_QMcuda_varPlocal_var_attrs()
-! CHECK: %{{.*}}:2 = hlfir.declare %{{.*}} {cuda_attr = #fir.cuda<constant>, uniq_name = "_QMcuda_varFlocal_var_attrsErc"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
 ! CHECK: %{{.*}}:2 = hlfir.declare %{{.*}} {cuda_attr = #fir.cuda<device>, uniq_name = "_QMcuda_varFlocal_var_attrsErd"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
 ! CHECK: %{{.*}}:2 = hlfir.declare %{{.*}} {cuda_attr = #fir.cuda<managed>, fortran_attrs = #fir.var_attrs<allocatable>, uniq_name = "_QMcuda_varFlocal_var_attrsErm"} : (!fir.ref<!fir.box<!fir.heap<f32>>>) -> (!fir.ref<!fir.box<!fir.heap<f32>>>, !fir.ref<!fir.box<!fir.heap<f32>>>)
 ! CHECK: %{{.*}}:2 = hlfir.declare %{{.*}} {cuda_attr = #fir.cuda<pinned>, fortran_attrs = #fir.var_attrs<allocatable>, uniq_name = "_QMcuda_varFlocal_var_attrsErp"} : (!fir.ref<!fir.box<!fir.heap<f32>>>) -> (!fir.ref<!fir.box<!fir.heap<f32>>>, !fir.ref<!fir.box<!fir.heap<f32>>>)
 
-! FIR: %{{.*}} = fir.declare %{{.*}} {cuda_attr = #fir.cuda<constant>, uniq_name = "_QMcuda_varFlocal_var_attrsErc"} : (!fir.ref<f32>) -> !fir.ref<f32>
 ! FIR: %{{.*}} = fir.declare %{{.*}} {cuda_attr = #fir.cuda<device>, uniq_name = "_QMcuda_varFlocal_var_attrsErd"} : (!fir.ref<f32>) -> !fir.ref<f32>
 ! FIR: %{{.*}} = fir.declare %{{.*}} {cuda_attr = #fir.cuda<managed>, fortran_attrs = #fir.var_attrs<allocatable>, uniq_name = "_QMcuda_varFlocal_var_attrsErm"} : (!fir.ref<!fir.box<!fir.heap<f32>>>) -> !fir.ref<!fir.box<!fir.heap<f32>>>
 ! FIR: %{{.*}} = fir.declare %{{.*}} {cuda_attr = #fir.cuda<pinned>, fortran_attrs = #fir.var_attrs<allocatable>, uniq_name = "_QMcuda_varFlocal_var_attrsErp"} : (!fir.ref<!fir.box<!fir.heap<f32>>>) -> !fir.ref<!fir.box<!fir.heap<f32>>>
 
-subroutine dummy_arg_constant(dc)
-  real, constant :: dc
-end subroutine
-! CHECK-LABEL: func.func @_QMcuda_varPdummy_arg_constant(
-! CHECK-SAME: %[[ARG0:.*]]: !fir.ref<f32> {fir.bindc_name = "dc", fir.cuda_attr = #fir.cuda<constant>}
-! CHECK: %{{.*}}:2 = hlfir.declare %[[ARG0]] {cuda_attr = #fir.cuda<constant>, uniq_name = "_QMcuda_varFdummy_arg_constantEdc"} : (!fir.ref<f32>) -> (!fir.ref<f32>, !fir.ref<f32>)
-
 subroutine dummy_arg_device(dd)
   real, device :: dd
 end subroutine
diff --git a/flang/test/Semantics/cuf03.cuf b/flang/test/Semantics/cuf03.cuf
index bebfdadbdbb16b..4260d7edd626f9 100644
--- a/flang/test/Semantics/cuf03.cuf
+++ b/flang/test/Semantics/cuf03.cuf
@@ -55,5 +55,11 @@ module m
     real, managed :: ma(n) ! ok
     !WARNING: Pointer 'dp' may not be associated in a device subprogram
     real, device, pointer :: dp
+    real, constant :: rc ! ok
+  end subroutine
+
+  subroutine host()
+    !ERROR: Object 'rc' with ATTRIBUTES(CONSTANT) may not be declared in a host subprogram
+    real, constant :: rc
   end subroutine
 end module