[flang-commits] [flang] [flang][cuda] Do not lower device variables in main program as globals (PR #102512)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

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

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

<details>
<summary>Changes</summary>

Flang considers arrays in main program larger than 32 bytes having the SAVE attribute and lowers them as globals. In CUDA Fortran, device variables are not allowed to have the SAVE attribute and should be allocated dynamically in the main program scope.
This patch updates lowering so CUDA Fortran device variables are not considered with the SAVE attribute. 

---
Full diff: https://github.com/llvm/llvm-project/pull/102512.diff


2 Files Affected:

- (modified) flang/lib/Evaluate/tools.cpp (+2-1) 
- (modified) flang/test/Lower/CUDA/cuda-program-global.cuf (+4-3) 


``````````diff
diff --git a/flang/lib/Evaluate/tools.cpp b/flang/lib/Evaluate/tools.cpp
index 34faba39ffd46f..e042d4d5a09d5d 100644
--- a/flang/lib/Evaluate/tools.cpp
+++ b/flang/lib/Evaluate/tools.cpp
@@ -1696,7 +1696,8 @@ bool IsSaved(const Symbol &original) {
       (features.IsEnabled(common::LanguageFeature::SaveMainProgram) ||
           (features.IsEnabled(
                common::LanguageFeature::SaveBigMainProgramVariables) &&
-              symbol.size() > 32))) {
+              symbol.size() > 32)) &&
+      !Fortran::evaluate::IsCUDADeviceSymbol(symbol)) {
     // With SaveBigMainProgramVariables, keeping all unsaved main program
     // variables of 32 bytes or less on the stack allows keeping numerical and
     // logical scalars, small scalar characters or derived, small arrays, and
diff --git a/flang/test/Lower/CUDA/cuda-program-global.cuf b/flang/test/Lower/CUDA/cuda-program-global.cuf
index 97b9927b3082fd..498725cd44905f 100644
--- a/flang/test/Lower/CUDA/cuda-program-global.cuf
+++ b/flang/test/Lower/CUDA/cuda-program-global.cuf
@@ -1,6 +1,7 @@
 ! RUN: bbc -emit-hlfir -fcuda %s -o - | FileCheck %s
 
-! Test lowering of program local variable that are global
+! Test lowering of program local variables. Make sure CUDA device variables are
+! not lowered as global.
 
 program test
   integer, device :: a(10)
@@ -10,10 +11,10 @@ program test
 end
 
 ! CHECK-LABEL: func.func @_QQmain()
-! CHECK: fir.address_of(@_QFEa) : !fir.ref<!fir.array<10xi32>>
+! CHECK: cuf.alloc !fir.array<10xi32> {bindc_name = "a", data_attr = #cuf.cuda<device>, uniq_name = "_QFEa"} -> !fir.ref<!fir.array<10xi32>>
 ! CHECK: fir.address_of(@_QFEb) : !fir.ref<!fir.array<10xi32>>
 ! CHECK: %[[ALLOCA:.*]] = fir.alloca i32 {bindc_name = "i", uniq_name = "_QFEi"}
 ! CHECK: hlfir.declare %[[ALLOCA]] {uniq_name = "_QFEi"} : (!fir.ref<i32>) -> (!fir.ref<i32>, !fir.ref<i32>)
 
-! CHECK: fir.global internal @_QFEa {data_attr = #cuf.cuda<device>} : !fir.array<10xi32> {{{$}}
+! CHECK-NOT: fir.global internal @_QFEa {data_attr = #cuf.cuda<device>} : !fir.array<10xi32> {{{$}}
 ! CHECK: fir.global internal @_QFEb : !fir.array<10xi32> {{{$}}

``````````

</details>


https://github.com/llvm/llvm-project/pull/102512