OpenMP, NVPTX: memcpy[23]D bias correction

This patch works around behaviour of the 2D and 3D memcpy operations in
the CUDA driver runtime.  Particularly in Fortran, the "base pointer"
of an array (used for either source or destination of a host/device copy)
may lie outside of data that is actually stored on the device.  The fix
is to make sure that we use the first element of data to be transferred
instead, and adjust parameters accordingly.

2023-10-02  Julian Brown  <julian@codesourcery.com>

libgomp/
	* plugin/plugin-nvptx.c (GOMP_OFFLOAD_memcpy2d): Adjust parameters to
	avoid out-of-bounds array checks in CUDA runtime.
	(GOMP_OFFLOAD_memcpy3d): Likewise.
	* testsuite/libgomp.c-c++-common/memcpyxd-bias-1.c: New test.

diff --git a/libgomp/plugin/plugin-nvptx.c b/libgomp/plugin/plugin-nvptx.c
index d4a254ed4f0b950c6d7a66ce15b368137812337e..a31f2592493de7fa0b6f985edfa7062da1a7f867 100644 (file)
--- a/libgomp/plugin/plugin-nvptx.c
+++ b/libgomp/plugin/plugin-nvptx.c
@@ -1907,6 +1907,35 @@ GOMP_OFFLOAD_memcpy2d (int dst_ord, int src_ord, size_t dim1_size,
   data.srcXInBytes = src_offset1_size;
   data.srcY = src_offset0_len;
 
+  if (data.srcXInBytes != 0 || data.srcY != 0)
+    {
+      /* Adjust origin to the actual array data, else the CUDA 2D memory
+        copy API calls below may fail to validate source/dest pointers
+        correctly (especially for Fortran where the "virtual origin" of an
+        array is often outside the stored data).  */
+      if (src_ord == -1)
+       data.srcHost = (const void *) ((const char *) data.srcHost
+                                     + data.srcY * data.srcPitch
+                                     + data.srcXInBytes);
+      else
+       data.srcDevice += data.srcY * data.srcPitch + data.srcXInBytes;
+      data.srcXInBytes = 0;
+      data.srcY = 0;
+    }
+
+  if (data.dstXInBytes != 0 || data.dstY != 0)
+    {
+      /* As above.  */
+      if (dst_ord == -1)
+       data.dstHost = (void *) ((char *) data.dstHost
+                                + data.dstY * data.dstPitch
+                                + data.dstXInBytes);
+      else
+       data.dstDevice += data.dstY * data.dstPitch + data.dstXInBytes;
+      data.dstXInBytes = 0;
+      data.dstY = 0;
+    }
+
   CUresult res = CUDA_CALL_NOCHECK (cuMemcpy2D, &data);
   if (res == CUDA_ERROR_INVALID_VALUE)
     /* If pitch > CU_DEVICE_ATTRIBUTE_MAX_PITCH or for device-to-device
@@ -1975,6 +2004,44 @@ GOMP_OFFLOAD_memcpy3d (int dst_ord, int src_ord, size_t dim2_size,
   data.srcY = src_offset1_len;
   data.srcZ = src_offset0_len;
 
+  if (data.srcXInBytes != 0 || data.srcY != 0 || data.srcZ != 0)
+    {
+      /* Adjust origin to the actual array data, else the CUDA 3D memory
+        copy API call below may fail to validate source/dest pointers
+        correctly (especially for Fortran where the "virtual origin" of an
+        array is often outside the stored data).  */
+      if (src_ord == -1)
+       data.srcHost
+         = (const void *) ((const char *) data.srcHost
+                           + (data.srcZ * data.srcHeight + data.srcY)
+                             * data.srcPitch
+                           + data.srcXInBytes);
+      else
+       data.srcDevice
+         += (data.srcZ * data.srcHeight + data.srcY) * data.srcPitch
+            + data.srcXInBytes;
+      data.srcXInBytes = 0;
+      data.srcY = 0;
+      data.srcZ = 0;
+    }
+
+  if (data.dstXInBytes != 0 || data.dstY != 0 || data.dstZ != 0)
+    {
+      /* As above.  */
+      if (dst_ord == -1)
+       data.dstHost = (void *) ((char *) data.dstHost
+                                + (data.dstZ * data.dstHeight + data.dstY)
+                                  * data.dstPitch
+                                + data.dstXInBytes);
+      else
+       data.dstDevice
+         += (data.dstZ * data.dstHeight + data.dstY) * data.dstPitch
+            + data.dstXInBytes;
+      data.dstXInBytes = 0;
+      data.dstY = 0;
+      data.dstZ = 0;
+    }
+
   CUDA_CALL (cuMemcpy3D, &data);
   return true;
 }

diff --git a/libgomp/testsuite/libgomp.c-c++-common/memcpyxd-bias-1.c b/libgomp/testsuite/libgomp.c-c++-common/memcpyxd-bias-1.c
new file mode 100644 (file)
index 0000000..6aa7b3d
--- /dev/null
+++ b/libgomp/testsuite/libgomp.c-c++-common/memcpyxd-bias-1.c
@@ -0,0 +1,61 @@
+/* { dg-do run } */
+
+#include <stdlib.h>
+#include <stdint.h>
+#include <assert.h>
+#include <omp.h>
+
+/* Say this is N rows and M columns.  */
+#define N 1024
+#define M 2048
+
+#define row_offset 256
+#define row_length 512
+#define col_offset 128
+#define col_length 384
+
+int
+main ()
+{
+  int *arr2d = (int *) calloc (N * M, sizeof (int));
+  uintptr_t dstptr;
+  int hostdev = omp_get_initial_device ();
+  int targdev;
+
+#pragma omp target enter data map(to: arr2d[col_offset*M:col_length*M])
+
+#pragma omp target map(from: targdev, dstptr) \
+                  map(present, tofrom: arr2d[col_offset*M:col_length*M])
+  {
+    for (int j = col_offset; j < col_offset + col_length; j++)
+      for (int i = row_offset; i < row_offset + row_length; i++)
+       arr2d[j * M + i]++;
+    targdev = omp_get_device_num ();
+    dstptr = (uintptr_t) arr2d;
+  }
+
+  /* Copy rectangular block back to the host.  */
+  {
+    size_t volume[2] = { col_length, row_length };
+    size_t offsets[2] = { col_offset, row_offset };
+    size_t dimensions[2] = { N, M };
+    omp_target_memcpy_rect ((void *) arr2d, (const void *) dstptr,
+                           sizeof (int), 2, &volume[0], &offsets[0],
+                           &offsets[0], &dimensions[0], &dimensions[0],
+                           hostdev, targdev);
+  }
+
+#pragma omp target exit data map(release: arr2d[col_offset*M:col_length*M])
+
+  for (int j = 0; j < N; j++)
+    for (int i = 0; i < M; i++)
+      if (i >= row_offset && i < row_offset + row_length
+         && j >= col_offset && j < col_offset + col_length)
+       assert (arr2d[j * M + i] == 1);
+      else
+       assert (arr2d[j * M + i] == 0);
+
+  free (arr2d);
+
+  return 0;
+}