[llvm] 333f636 - [OpenMPOpt] Make parallel regions reachable from new DeviceRTL loop functions (#150927)
via llvm-commits
llvm-commits at lists.llvm.org
Mon Apr 27 05:11:22 PDT 2026
Author: Sergio Afonso
Date: 2026-04-27T13:11:17+01:00
New Revision: 333f636c9af90fd77bc6669a74f8bd9e2832640b
URL: https://github.com/llvm/llvm-project/commit/333f636c9af90fd77bc6669a74f8bd9e2832640b
DIFF: https://github.com/llvm/llvm-project/commit/333f636c9af90fd77bc6669a74f8bd9e2832640b.diff
LOG: [OpenMPOpt] Make parallel regions reachable from new DeviceRTL loop functions (#150927)
This patch updates the OpenMP optimization pass to know about the new
DeviceRTL functions for loop constructs.
This change marks these functions as potentially containing parallel
regions, which fixes a current bug with the state machine rewrite
optimization. It previously failed to identify parallel regions located
inside of the callbacks passed to these new DeviceRTL functions, causing
the resulting code to skip executing these parallel regions.
As a result, Generic kernels produced by Flang that contain parallel
regions now work properly.
One known related issue not fixed by this patch is that the presence of
calls to these functions will prevent the SPMD-ization of Generic
kernels by OpenMPOpt. Previously, this was due to assuming there was no
parallel region. This is changed by this patch, but instead we now mark
it temporarily as unsupported in an SPMD context. The reason is that,
without additional changes, code intended for the main thread of the
team located outside of the parallel region would not be guarded
properly, resulting in race conditions and generally invalid behavior.
Added:
offload/test/offloading/fortran/target-generic-loops.f90
offload/test/offloading/fortran/target-spmd-loops.f90
Modified:
llvm/lib/Transforms/IPO/OpenMPOpt.cpp
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
index 5266103d1ac24..7da65ff4dbd51 100644
--- a/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
+++ b/llvm/lib/Transforms/IPO/OpenMPOpt.cpp
@@ -5021,6 +5021,29 @@ struct AAKernelInfoCallSite : AAKernelInfo {
case OMPRTL___kmpc_free_shared:
// Return without setting a fixpoint, to be resolved in updateImpl.
return;
+ case OMPRTL___kmpc_distribute_static_loop_4:
+ case OMPRTL___kmpc_distribute_static_loop_4u:
+ case OMPRTL___kmpc_distribute_static_loop_8:
+ case OMPRTL___kmpc_distribute_static_loop_8u:
+ case OMPRTL___kmpc_distribute_for_static_loop_4:
+ case OMPRTL___kmpc_distribute_for_static_loop_4u:
+ case OMPRTL___kmpc_distribute_for_static_loop_8:
+ case OMPRTL___kmpc_distribute_for_static_loop_8u:
+ case OMPRTL___kmpc_for_static_loop_4:
+ case OMPRTL___kmpc_for_static_loop_4u:
+ case OMPRTL___kmpc_for_static_loop_8:
+ case OMPRTL___kmpc_for_static_loop_8u:
+ // Parallel regions might be reached by these calls, as they take a
+ // callback argument potentially containing arbitrary user-provided
+ // code.
+ ReachedUnknownParallelRegions.insert(&CB);
+ // TODO: The presence of these calls on their own does not prevent a
+ // kernel from being SPMD-izable. We mark it as such because we need
+ // further changes in order to also consider the contents of the
+ // callbacks passed to them.
+ SPMDCompatibilityTracker.indicatePessimisticFixpoint();
+ SPMDCompatibilityTracker.insert(&CB);
+ break;
default:
// Unknown OpenMP runtime calls cannot be executed in SPMD-mode,
// generally. However, they do not hide parallel regions.
diff --git a/offload/test/offloading/fortran/target-generic-loops.f90 b/offload/test/offloading/fortran/target-generic-loops.f90
new file mode 100644
index 0000000000000..07bcbfd2c8752
--- /dev/null
+++ b/offload/test/offloading/fortran/target-generic-loops.f90
@@ -0,0 +1,130 @@
+! Offloading test for generic target regions containing
diff erent kinds of
+! loop constructs inside.
+! REQUIRES: flang, amdgpu
+
+! RUN: %libomptarget-compile-fortran-run-and-check-generic
+program main
+ integer :: i1, i2, n1, n2, counter
+
+ n1 = 100
+ n2 = 50
+
+ counter = 0
+ !$omp target map(tofrom:counter)
+ !$omp teams distribute reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ !$omp end target
+
+ ! CHECK: 1 100
+ print '(I2" "I0)', 1, counter
+
+ counter = 0
+ !$omp target map(tofrom:counter)
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ !$omp end target
+
+ ! CHECK: 2 200
+ print '(I2" "I0)', 2, counter
+
+ counter = 0
+ !$omp target map(tofrom:counter)
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ !$omp end target
+
+ ! CHECK: 3 203
+ print '(I2" "I0)', 3, counter
+
+ counter = 0
+ !$omp target map(tofrom: counter)
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ !$omp end target
+
+ ! CHECK: 4 102
+ print '(I2" "I0)', 4, counter
+
+
+ counter = 0
+ !$omp target teams distribute reduction(+:counter)
+ do i1=1, n1
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ end do
+
+ ! CHECK: 5 5000
+ print '(I2" "I0)', 5, counter
+
+ counter = 0
+ !$omp target teams distribute reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ end do
+
+ ! CHECK: 6 5200
+ print '(I2" "I0)', 6, counter
+
+ counter = 0
+ !$omp target teams distribute reduction(+:counter)
+ do i1=1, n1
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ end do
+
+ ! CHECK: 7 10000
+ print '(I2" "I0)', 7, counter
+
+ counter = 0
+ !$omp target teams distribute reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ !$omp parallel do reduction(+:counter)
+ do i2=1, n2
+ counter = counter + 1
+ end do
+ counter = counter + 1
+ end do
+
+ ! CHECK: 8 10300
+ print '(I2" "I0)', 8, counter
+end program
diff --git a/offload/test/offloading/fortran/target-spmd-loops.f90 b/offload/test/offloading/fortran/target-spmd-loops.f90
new file mode 100644
index 0000000000000..7407f0c0768cb
--- /dev/null
+++ b/offload/test/offloading/fortran/target-spmd-loops.f90
@@ -0,0 +1,39 @@
+! Offloading test for generic target regions containing
diff erent kinds of
+! loop constructs inside.
+! REQUIRES: flang, amdgpu
+
+! RUN: %libomptarget-compile-fortran-run-and-check-generic
+program main
+ integer :: i1, n1, counter
+
+ n1 = 100
+
+ counter = 0
+ !$omp target parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+
+ ! CHECK: 1 100
+ print '(I2" "I0)', 1, counter
+
+ counter = 0
+ !$omp target map(tofrom:counter)
+ !$omp parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+ !$omp end target
+
+ ! CHECK: 2 100
+ print '(I2" "I0)', 2, counter
+
+ counter = 0
+ !$omp target teams distribute parallel do reduction(+:counter)
+ do i1=1, n1
+ counter = counter + 1
+ end do
+
+ ! CHECK: 3 100
+ print '(I2" "I0)', 3, counter
+end program
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