[flang][cuda] Emit error when host array is used in CUF kernel (#100693)

Restriction from the standard 2.11.2.

Arrays used or assigned in the loop must have the device, managed or
unifed attribute.

Author: clementval

flang/lib/Semantics/check-cuda.cpp

@@ -307,6 +307,25 @@ template <bool IsCUFKernelDo> class DeviceContextChecker {
       WarnOnIoStmt(source);
     }
   }
+  template <typename A>
+  void ErrorIfHostSymbol(const A &expr, const parser::CharBlock &source) {
+    for (const Symbol &sym : CollectCudaSymbols(expr)) {
+      if (const auto *details =
+              sym.GetUltimate().detailsIf<semantics::ObjectEntityDetails>()) {
+        if (details->IsArray() &&
+            (!details->cudaDataAttr() ||
+                (details->cudaDataAttr() &&
+                    *details->cudaDataAttr() != common::CUDADataAttr::Device &&
+                    *details->cudaDataAttr() != common::CUDADataAttr::Managed &&
+                    *details->cudaDataAttr() !=
+                        common::CUDADataAttr::Unified))) {
+          context_.Say(source,
+              "Host array '%s' cannot be present in CUF kernel"_err_en_US,
+              sym.name());
+        }
+      }
+    }
+  }
   void Check(const parser::ActionStmt &stmt, const parser::CharBlock &source) {
     common::visit(
         common::visitors{
@@ -349,6 +368,19 @@ template <bool IsCUFKernelDo> class DeviceContextChecker {
             [&](const common::Indirection<parser::IfStmt> &x) {
               Check(x.value());
             },
+            [&](const common::Indirection<parser::AssignmentStmt> &x) {
+              if (IsCUFKernelDo) {
+                const evaluate::Assignment *assign{
+                    semantics::GetAssignment(x.value())};
+                if (assign) {
+                  ErrorIfHostSymbol(assign->lhs, source);
+                  ErrorIfHostSymbol(assign->rhs, source);
+                }
+              }
+              if (auto msg{ActionStmtChecker<IsCUFKernelDo>::WhyNotOk(x)}) {
+                context_.Say(source, std::move(*msg));
+              }
+            },
             [&](const auto &x) {
               if (auto msg{ActionStmtChecker<IsCUFKernelDo>::WhyNotOk(x)}) {
                 context_.Say(source, std::move(*msg));

flang/test/Lower/CUDA/cuda-data-transfer.cuf

@@ -133,7 +133,7 @@ subroutine sub4()
   integer, parameter :: n = 10
   real, device :: adev(n)
   real :: ahost(n)
-  real :: b
+  real, managed :: b
   integer :: i
 
   adev = ahost

flang/test/Lower/CUDA/cuda-kernel-loop-directive.cuf

@@ -7,8 +7,8 @@ subroutine sub1()
   integer :: i, j
   integer, parameter :: n = 100
   integer(8) :: istream
-  real :: a(n), b(n)
-  real :: c(n,n), d(n,n)
+  real, device :: a(n), b(n)
+  real, device :: c(n,n), d(n,n)
 
 ! CHECK-LABEL: func.func @_QPsub1()
 ! CHECK: %[[IV:.*]]:2 = hlfir.declare %{{.*}} {uniq_name = "_QFsub1Ei"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)

flang/test/Parser/cuf-sanity-common

@@ -23,7 +23,8 @@ module m
   end subroutine
   subroutine test
     logical isPinned
-    real a(10), x, y, z
+    real, device :: a(10)
+    real :: x, y, z
     !$cuf kernel do(1) <<<*, *, stream = 1>>>
     do j = 1, 10
     end do

flang/test/Semantics/cuf09.cuf

@@ -18,6 +18,8 @@ module m
 end
 
 program main
+  integer, device :: a_d(10 ,10)
+  integer :: b(10, 10)
   !$cuf kernel do <<< *, * >>> ! ok
   do j = 1, 0
   end do
@@ -90,4 +92,12 @@ program main
     else if (ifunc() /= 1) then
     end if
   end do
+
+  !$cuf kernel do (2) <<<*, *>>>
+  do j = 1, 10
+     do i = 1, 10
+        !ERROR: Host array 'b' cannot be present in CUF kernel
+        a_d(i,j) = b(i,j)
+     enddo
+  enddo
 end

flang/test/Semantics/reduce.cuf

@@ -1,9 +1,9 @@
 ! RUN: %python %S/test_errors.py %s %flang_fc1
 subroutine s(n,m,a,l)
   integer, intent(in) :: n
-  integer, intent(in) :: m(n)
-  real, intent(in) :: a(n)
-  logical, intent(in) :: l(n)
+  integer, device, intent(in) :: m(n)
+  real, device, intent(in) :: a(n)
+  logical, device, intent(in) :: l(n)
   integer j, mr
   real ar
   logical lr