[llvm] [OpenMP] Adds omp_target_is_accessible routine (PR #138294)
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Fri May 2 08:26:46 PDT 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-offload
Author: None (nicebert)
<details>
<summary>Changes</summary>
Adds omp_target_is_accessible routine.
Refactors common code from omp_target_is_present to work for both routines.
---
Full diff: https://github.com/llvm/llvm-project/pull/138294.diff
5 Files Affected:
- (modified) offload/include/omptarget.h (+1)
- (modified) offload/libomptarget/OpenMP/API.cpp (+15-21)
- (modified) offload/libomptarget/exports (+1)
- (modified) offload/libomptarget/omptarget.cpp (+25)
- (added) offload/test/mapping/is_accessible.cpp (+43)
``````````diff
diff --git a/offload/include/omptarget.h b/offload/include/omptarget.h
index 6971780c7bdb5..8af8c4f659b35 100644
--- a/offload/include/omptarget.h
+++ b/offload/include/omptarget.h
@@ -280,6 +280,7 @@ int omp_get_initial_device(void);
void *omp_target_alloc(size_t Size, int DeviceNum);
void omp_target_free(void *DevicePtr, int DeviceNum);
int omp_target_is_present(const void *Ptr, int DeviceNum);
+int omp_target_is_accessible(const void *Ptr, size_t Size, int DeviceNum);
int omp_target_memcpy(void *Dst, const void *Src, size_t Length,
size_t DstOffset, size_t SrcOffset, int DstDevice,
int SrcDevice);
diff --git a/offload/libomptarget/OpenMP/API.cpp b/offload/libomptarget/OpenMP/API.cpp
index 4576f9bd06121..a0a126004d3f9 100644
--- a/offload/libomptarget/OpenMP/API.cpp
+++ b/offload/libomptarget/OpenMP/API.cpp
@@ -39,6 +39,8 @@ EXTERN void ompx_dump_mapping_tables() {
using namespace llvm::omp::target::ompt;
#endif
+int checkTargetAddressMapping(const void *Ptr, size_t Size, int DeviceNum, const char *Name);
+
void *targetAllocExplicit(size_t Size, int DeviceNum, int Kind,
const char *Name);
void targetFreeExplicit(void *DevicePtr, int DeviceNum, int Kind,
@@ -168,33 +170,25 @@ EXTERN int omp_target_is_present(const void *Ptr, int DeviceNum) {
DP("Call to omp_target_is_present for device %d and address " DPxMOD "\n",
DeviceNum, DPxPTR(Ptr));
- if (!Ptr) {
- DP("Call to omp_target_is_present with NULL ptr, returning false\n");
- return false;
- }
-
- if (DeviceNum == omp_get_initial_device()) {
- DP("Call to omp_target_is_present on host, returning true\n");
- return true;
- }
-
- auto DeviceOrErr = PM->getDevice(DeviceNum);
- if (!DeviceOrErr)
- FATAL_MESSAGE(DeviceNum, "%s", toString(DeviceOrErr.takeError()).c_str());
-
// omp_target_is_present tests whether a host pointer refers to storage that
// is mapped to a given device. However, due to the lack of the storage size,
// only check 1 byte. Cannot set size 0 which checks whether the pointer (zero
// length array) is mapped instead of the referred storage.
- TargetPointerResultTy TPR =
- DeviceOrErr->getMappingInfo().getTgtPtrBegin(const_cast<void *>(Ptr), 1,
- /*UpdateRefCount=*/false,
- /*UseHoldRefCount=*/false);
- int Rc = TPR.isPresent();
- DP("Call to omp_target_is_present returns %d\n", Rc);
- return Rc;
+ return checkTargetAddressMapping(Ptr, 1, DeviceNum, "omp_target_is_present");
}
+EXTERN int omp_target_is_accessible(const void *Ptr, size_t Size, int DeviceNum) {
+ OMPT_IF_BUILT(ReturnAddressSetterRAII RA(__builtin_return_address(0)));
+ DP("Call to omp_target_is_accessible for device %d and address " DPxMOD
+ " with size %zu\n",
+ DeviceNum, DPxPTR(Ptr), Size);
+
+ // omp_target_is_accessible tests whether a host pointer refers to storage
+ // that is mapped to a given device and is accessible from the device. The
+ // storage size is provided.
+ return checkTargetAddressMapping(Ptr, Size, DeviceNum, "omp_target_is_accessible");
+}
+
EXTERN int omp_target_memcpy(void *Dst, const void *Src, size_t Length,
size_t DstOffset, size_t SrcOffset, int DstDevice,
int SrcDevice) {
diff --git a/offload/libomptarget/exports b/offload/libomptarget/exports
index 2406776c1fb5f..0b770a2f1980a 100644
--- a/offload/libomptarget/exports
+++ b/offload/libomptarget/exports
@@ -37,6 +37,7 @@ VERS1.0 {
__kmpc_push_target_tripcount_mapper;
ompx_dump_mapping_tables;
omp_get_mapped_ptr;
+ omp_target_is_accessible;
omp_get_num_devices;
omp_get_device_num;
omp_get_initial_device;
diff --git a/offload/libomptarget/omptarget.cpp b/offload/libomptarget/omptarget.cpp
index 5b25d955dd320..8716b33ce068a 100644
--- a/offload/libomptarget/omptarget.cpp
+++ b/offload/libomptarget/omptarget.cpp
@@ -198,6 +198,31 @@ static int32_t getParentIndex(int64_t Type) {
return ((Type & OMP_TGT_MAPTYPE_MEMBER_OF) >> 48) - 1;
}
+int checkTargetAddressMapping(const void *Ptr, size_t Size, int DeviceNum, const char *Name) {
+ if (!Ptr) {
+ DP("Call to %s with NULL ptr, returning false\n", Name);
+ return false;
+ }
+
+ if (DeviceNum == omp_get_initial_device()) {
+ DP("Call to %s on host, returning true\n", Name);
+ return true;
+ }
+
+ auto DeviceOrErr = PM->getDevice(DeviceNum);
+ if (!DeviceOrErr)
+ FATAL_MESSAGE(DeviceNum, "%s", toString(DeviceOrErr.takeError()).c_str());
+
+ TargetPointerResultTy TPR =
+ DeviceOrErr->getMappingInfo().getTgtPtrBegin(const_cast<void *>(Ptr), Size,
+ false,
+ false);
+
+ int Rc = TPR.isPresent();
+ DP("Call to %s returns %d\n", Name, Rc);
+ return Rc;
+}
+
void *targetAllocExplicit(size_t Size, int DeviceNum, int Kind,
const char *Name) {
DP("Call to %s for device %d requesting %zu bytes\n", Name, DeviceNum, Size);
diff --git a/offload/test/mapping/is_accessible.cpp b/offload/test/mapping/is_accessible.cpp
new file mode 100644
index 0000000000000..daf38e7afaf76
--- /dev/null
+++ b/offload/test/mapping/is_accessible.cpp
@@ -0,0 +1,43 @@
+// RUN: %libomptarget-compilexx-generic
+// RUN: %libomptarget-run-generic 2>&1 \
+// RUN: | %fcheck-generic
+
+// REQUIRES: unified_shared_memory
+
+#include <stdio.h>
+#include <iostream>
+#include <omp.h>
+#include <assert.h>
+
+// The runtime considers unified shared memory to be always present.
+#pragma omp requires unified_shared_memory
+
+int main() {
+ int size = 10;
+ int *x = (int *)malloc(size * sizeof(int));
+ const int dev_num = omp_get_default_device();
+
+ int is_accessible = omp_target_is_accessible(x, size * sizeof(int), dev_num);
+ int errors = 0;
+ int uses_shared_memory = 0;
+
+ #pragma omp target map(to: uses_shared_memory)
+ uses_shared_memory = 1;
+
+ assert(uses_shared_memory != is_accessible);
+
+ if (is_accessible) {
+ #pragma omp target firstprivate(x)
+ for (int i = 0; i < size; i++)
+ x[i] = i * 3;
+
+ for (int i = 0; i < size; i++)
+ errors += (x[i] == (i * 3) ? 1 : 0);
+ }
+
+ free(x);
+ // CHECK: x overwritten 0 times
+ printf("x overwritten %d times\n", errors);
+
+ return errors;
+}
``````````
</details>
https://github.com/llvm/llvm-project/pull/138294
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