Allow CPUBuffers for CPUDevices to share copied host pointer data

Device data allocated for Buffer objects allocated via clCreateBuffer()
using the CL_MEM_COPY_HOST_PTR flag for CPUDevices should be allocated
only once in global device memory, and shared between the CPUDevices.

Previously, shamrock was creating a brand new allocation for each
device buffer, for the same MemObject.  This was causing the
test_device_partition Khronos test to fail (for device fission).

This is now fixed, by enabling sharing of device data.

Signed-off-by: Gil Pitney <gil.pitney@linaro.org>

3 files changed, 39 insertions, 18 deletions

diff --git a/src/core/cpu/buffer.cpp b/src/core/cpu/buffer.cpp
index 00d9279..97c61d9 100644
--- a/src/core/cpu/buffer.cpp
+++ b/src/core/cpu/buffer.cpp
@@ -90,25 +90,35 @@ bool CPUBuffer::allocate()
 {
     size_t buf_size = p_buffer->size();
     int    retval;
+    void   *shared_ptr = p_buffer->shared_ptr();
 
     if (buf_size == 0)
         // Something went wrong...
         return false;
 
-    if (!p_data)
-    {
-        // We don't use a host ptr, we need to allocate a buffer
-        retval = posix_memalign(&p_data, 128, buf_size);  // align for type double16 size.
-        if (retval)
-            return false;
-
-        p_data_malloced = true;
+    if (!shared_ptr) {
+        if (!p_data)
+        {
+            // We don't use a host ptr, we need to allocate a buffer
+            retval = posix_memalign(&p_data, 128, buf_size);  // align for type double16 size.
+            if (retval)
+                return false;
+
+            p_data_malloced = true;
+
+            // Now set the shared data pointer, so we need not allocate again for this MemObject:
+            p_buffer->setSharedPtr(p_data);
+        }
+
+        if (p_buffer->type() != MemObject::SubBuffer &&
+            p_buffer->flags() & CL_MEM_COPY_HOST_PTR)
+        {
+            std::memcpy(p_data, p_buffer->host_ptr(), buf_size);
+        }
     }
-
-    if (p_buffer->type() != MemObject::SubBuffer &&
-        p_buffer->flags() & CL_MEM_COPY_HOST_PTR)
-    {
-        std::memcpy(p_data, p_buffer->host_ptr(), buf_size);
+    else {
+        // If the CPUBuffer data has already been allocated by the first device, use it:
+        if (!p_data) p_data = shared_ptr;
     }
 
     // Say to the memobject that we are allocated
diff --git a/src/core/memobject.cpp b/src/core/memobject.cpp
index 3912740..bd8736f 100644
--- a/src/core/memobject.cpp
+++ b/src/core/memobject.cpp
@@ -51,7 +51,7 @@ using namespace Coal;
 MemObject::MemObject(Context *ctx, cl_mem_flags flags, void *host_ptr,
                      cl_int *errcode_ret)
 : Object(Object::T_MemObject, ctx), p_num_devices(0), p_flags(flags),
-  p_host_ptr(host_ptr), p_devicebuffers(0), p_dtor_callback_stack()
+  p_host_ptr(host_ptr), p_devicebuffers(0), p_dtor_callback_stack(), p_shared_ptr(NULL)
 {
     // Check the flags value
     const cl_mem_flags all_flags = CL_MEM_READ_WRITE | CL_MEM_WRITE_ONLY |
@@ -168,8 +168,7 @@ cl_int MemObject::init()
 
     // If we have more than one device, the allocation on the devices is
     // defered to first use, so host_ptr can become invalid. So, copy it in
-    // a RAM location and keep it. Also, set a flag telling CPU devices that
-    // they don't need to reallocate and re-copy host_ptr
+    // a RAM location and keep it.
     // SubBuffer should simply reuse Buffer data
     if (p_num_devices > 1 && (p_flags & CL_MEM_COPY_HOST_PTR)
                           && type() != SubBuffer)
@@ -215,7 +214,7 @@ cl_int MemObject::init()
     std::free((void *)devices);
     devices = 0;
 
-    // If we have only one device, already allocate the buffer
+    // If we have only one device, pre-allocate the buffer
     if (p_num_devices == 1)
     {
         if (!p_devicebuffers[0]->allocate())
@@ -259,6 +258,16 @@ void *MemObject::host_ptr() const
     }
 }
 
+void *MemObject::shared_ptr() const
+{
+    return p_shared_ptr;
+}
+
+void MemObject::setSharedPtr(void *ptr)
+{
+    p_shared_ptr = ptr;
+}
+
 DeviceBuffer *MemObject::deviceBuffer(DeviceInterface *device) const
 {
     for (unsigned int i=0; i<p_num_devices; ++i)
diff --git a/src/core/memobject.h b/src/core/memobject.h
index 82cbfab..ede6050 100644
--- a/src/core/memobject.h
+++ b/src/core/memobject.h
@@ -98,6 +98,8 @@ class MemObject : public Object
 
         cl_mem_flags flags() const;                     /*!< \brief Flags */
         void *host_ptr() const;                         /*!< \brief Host pointer */
+        void *shared_ptr() const;                       /*!< \brief Shared data pointer */
+        void setSharedPtr(void *ptr);                   /*!< \brief Set the shared data pointer */
         DeviceBuffer *deviceBuffer(DeviceInterface *device) const; /*!< \brief \c Coal::DeviceBuffer for the given \p device */
 
         void deviceAllocated(DeviceBuffer *buffer);     /*!< \brief Is the \c Coal::DeviceBuffer for \p buffer allocated ? */
@@ -138,7 +140,7 @@ class MemObject : public Object
         unsigned int   p_num_devices, p_devices_to_allocate;
         void          *p_host_ptr;
         DeviceBuffer **p_devicebuffers;
-
+        void          *p_shared_ptr;  // Copied host data shared between CPUBuffers.
         typedef std::pair<void (CL_CALLBACK *)(cl_mem memobj, void *user_data), void*> dtor_callback_t;
         concurrent_stack<dtor_callback_t> p_dtor_callback_stack;