[flang-commits] [flang] [flang][cuda] Perform scalar assignment of c_devptr without runtime (PR #123407)

[via flang-commits]

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>

Because `c_devptr` has a `c_ptr` field, any assignment were done via the Assign runtime function. This leads to stack overflow on the device and taking too much memory. As we know the c_devptr can be directly copied on assignment, make it a special case.


---
Full diff: https://github.com/llvm/llvm-project/pull/123407.diff


3 Files Affected:

- (modified) flang/include/flang/Optimizer/Dialect/FIRType.h (+7) 
- (modified) flang/lib/Optimizer/Builder/FIRBuilder.cpp (+4) 
- (modified) flang/test/Lower/CUDA/cuda-devptr.cuf (+26-4) 


``````````diff
diff --git a/flang/include/flang/Optimizer/Dialect/FIRType.h b/flang/include/flang/Optimizer/Dialect/FIRType.h
index 78257ab7030862..e19fcde8d0e648 100644
--- a/flang/include/flang/Optimizer/Dialect/FIRType.h
+++ b/flang/include/flang/Optimizer/Dialect/FIRType.h
@@ -139,6 +139,13 @@ inline bool isa_builtin_cptr_type(mlir::Type t) {
   return false;
 }
 
+// Is `t` type(c_devptr)?
+inline bool isa_builtin_c_devptr_type(mlir::Type t) {
+  if (auto recTy = mlir::dyn_cast_or_null<fir::RecordType>(t))
+    return recTy.getName().ends_with("T__builtin_c_devptr");
+  return false;
+}
+
 /// Is `t` type(c_devptr)?
 inline bool isa_builtin_cdevptr_type(mlir::Type t) {
   if (auto recTy = mlir::dyn_cast_or_null<fir::RecordType>(t))
diff --git a/flang/lib/Optimizer/Builder/FIRBuilder.cpp b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
index ad1244ef99b416..64c540cfb95ae6 100644
--- a/flang/lib/Optimizer/Builder/FIRBuilder.cpp
+++ b/flang/lib/Optimizer/Builder/FIRBuilder.cpp
@@ -1401,6 +1401,10 @@ static void genComponentByComponentAssignment(fir::FirOpBuilder &builder,
 /// Can the assignment of this record type be implement with a simple memory
 /// copy (it requires no deep copy or user defined assignment of components )?
 static bool recordTypeCanBeMemCopied(fir::RecordType recordType) {
+  // c_devptr type is a special case. It has a nested c_ptr field but we know it
+  // can be copied directly.
+  if (fir::isa_builtin_c_devptr_type(recordType))
+    return true;
   if (fir::hasDynamicSize(recordType))
     return false;
   for (auto [_, fieldType] : recordType.getTypeList()) {
diff --git a/flang/test/Lower/CUDA/cuda-devptr.cuf b/flang/test/Lower/CUDA/cuda-devptr.cuf
index 561d92ecd3e2e7..d61d84d9bc750f 100644
--- a/flang/test/Lower/CUDA/cuda-devptr.cuf
+++ b/flang/test/Lower/CUDA/cuda-devptr.cuf
@@ -1,4 +1,4 @@
-! RUN: bbc -emit-hlfir -fcuda %s -o - | FileCheck %s
+! RUN: bbc -emit-fir -hlfir -fcuda %s -o - | FileCheck %s
 
 ! Test CUDA Fortran specific type
 
@@ -37,12 +37,34 @@ subroutine sub2()
 end
 
 ! CHECK-LABEL: func.func @_QPsub2()
-! CHECK: %[[X:.*]]:2 = hlfir.declare %{{.*}} {data_attr = #cuf.cuda<device>, fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFsub2Ex"} : (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>) -> (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>, !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>)
+! CHECK: %[[X:.*]] = fir.declare %{{.*}} {data_attr = #cuf.cuda<device>, fortran_attrs = #fir.var_attrs<pointer>, uniq_name = "_QFsub2Ex"} : (!fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>) -> !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>
 ! CHECK: %[[CPTR:.*]] = fir.field_index cptr, !fir.type<_QM__fortran_builtinsT__builtin_c_devptr{{[<]?}}{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}{{[>]?}}>
-! CHECK: %[[CPTR_COORD:.*]] = fir.coordinate_of %{{.*}}#1, %[[CPTR]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{{[<]?}}{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}{{[>]?}}>>, !fir.field) -> !fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>
+! CHECK: %[[CPTR_COORD:.*]] = fir.coordinate_of %{{.*}}, %[[CPTR]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{{[<]?}}{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}{{[>]?}}>>, !fir.field) -> !fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>
 ! CHECK: %[[ADDRESS:.*]] = fir.field_index __address, !fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>
 ! CHECK: %[[ADDRESS_COORD:.*]] = fir.coordinate_of %[[CPTR_COORD]], %[[ADDRESS]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>, !fir.field) -> !fir.ref<i64>
 ! CHECK: %[[ADDRESS_LOADED:.*]] = fir.load %[[ADDRESS_COORD]] : !fir.ref<i64>
 ! CHECK: %[[ADDRESS_IDX:.*]] = fir.convert %[[ADDRESS_LOADED]] : (i64) -> !fir.ptr<!fir.array<?xf32>>
 ! CHECK: %[[EMBOX:.*]] = fir.embox %[[ADDRESS_IDX]](%{{.*}}) : (!fir.ptr<!fir.array<?xf32>>, !fir.shape<1>) -> !fir.box<!fir.ptr<!fir.array<?xf32>>>
-! CHECK: fir.store %[[EMBOX]] to %[[X]]#1 : !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>
+! CHECK: fir.store %[[EMBOX]] to %[[X]] : !fir.ref<!fir.box<!fir.ptr<!fir.array<?xf32>>>>
+
+attributes(global) subroutine assign_c_devptr(p, a)
+  use __fortran_builtins, only: c_devloc => __builtin_c_devloc
+  use __fortran_builtins, only: c_devptr => __builtin_c_devptr
+  type (c_devptr), device :: p
+  complex :: a(10)
+  p = c_devloc(a(1))
+end subroutine
+
+! CHECK-LABEL: func.func @_QPassign_c_devptr
+! CHECK: %[[P:.*]] = fir.declare %arg0 dummy_scope %{{.*}} {data_attr = #cuf.cuda<device>, uniq_name = "_QFassign_c_devptrEp"}
+! CHECK: %[[C_DEVLOC_RES:.*]] = fir.declare %15 {uniq_name = ".tmp.intrinsic_result"} : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>>) -> !fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>>
+! CHECK: %[[CPTR_FIELD:.*]] = fir.field_index cptr, !fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>
+! CHECK: %[[RES_CPTR_COORD:.*]] = fir.coordinate_of %[[C_DEVLOC_RES]], %[[CPTR_FIELD]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>>, !fir.field) -> !fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>
+! CHECK: %[[CPTR_FIELD:.*]] = fir.field_index cptr, !fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>
+! CHECK: %[[P_CPTR_COORD:.*]] = fir.coordinate_of %[[P]], %[[CPTR_FIELD]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_devptr{cptr:!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>}>>, !fir.field) -> !fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>
+! CHECK: %[[ADDRESS_FIELD:.*]] = fir.field_index __address, !fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>
+! CHECK: %[[RES_ADDR_COORD:.*]] = fir.coordinate_of %[[RES_CPTR_COORD]], %[[ADDRESS_FIELD]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>, !fir.field) -> !fir.ref<i64>
+! CHECK: %[[ADDRESS_FIELD:.*]] = fir.field_index __address, !fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>
+! CHECK: %[[P_ADDR_COORD:.*]] = fir.coordinate_of %[[P_CPTR_COORD]], %[[ADDRESS_FIELD]] : (!fir.ref<!fir.type<_QM__fortran_builtinsT__builtin_c_ptr{__address:i64}>>, !fir.field) -> !fir.ref<i64>
+! CHECK: %[[ADDR:.*]] = fir.load %[[RES_ADDR_COORD]] : !fir.ref<i64>
+! CHECK: fir.store %[[ADDR]] to %[[P_ADDR_COORD]] : !fir.ref<i64>

``````````

</details>


https://github.com/llvm/llvm-project/pull/123407