COMPUTE-8024 Fixed the maximum OpenCL workgroup size

The maximum workgroup size depends on the kernel and the device, rather
than being a property of the device. The present patch fixes the case
when a kernel is queued with no workgroup size and the default workgroup
size is used instead.

A previous patch introduced a maximum workgroup size that depended on
the device but ignored the kernel. In OpenCL the maximum workgroup size
we query from the device is an upper bound of the actual maximum that
we can query for a given kernel running on the same device. For some
kernels the values will match, but for others we will get a lower value
when querying for an specific kernel (i.e. if the kernel uses a high
number of registers).

Change-Id: I3bed6bde80ddc4f0ddb8f82c80903774aa1999b6
Reviewed-on: http://mpd-gerrit.cambridge.arm.com/89471
Tested-by: Kaizen <jeremy.johnson+kaizengerrit@arm.com>
Reviewed-by: Anthony Barbier <anthony.barbier@arm.com>

1 files changed, 22 insertions, 3 deletions

diff --git a/src/core/CL/ICLKernel.cpp b/src/core/CL/ICLKernel.cpp
index 1e04f00343..17b58b727f 100644
--- a/src/core/CL/ICLKernel.cpp
+++ b/src/core/CL/ICLKernel.cpp
@@ -52,18 +52,28 @@ void arm_compute::enqueue(cl::CommandQueue &queue, ICLKernel &kernel, const Wind
                     (window.y().end() - window.y().start()) / window.y().step(),
                     (window.z().end() - window.z().start()) / window.z().step());
 
+    cl::NDRange valid_lws;
+    if(lws_hint[0] * lws_hint[1] * lws_hint[2] > kernel.get_max_workgroup_size())
+    {
+        valid_lws = cl::NullRange;
+    }
+    else
+    {
+        valid_lws = lws_hint;
+    }
+
     cl::NDRange lws = cl::NullRange;
 
-    if((lws_hint[0] <= gws[0]) && (lws_hint[1] <= gws[1]) && (lws_hint[2] <= gws[2]))
+    if((valid_lws[0] <= gws[0]) && (valid_lws[1] <= gws[1]) && (valid_lws[2] <= gws[2]))
     {
-        lws = lws_hint;
+        lws = valid_lws;
     }
 
     queue.enqueueNDRangeKernel(kernel.kernel(), cl::NullRange, gws, lws);
 }
 
 ICLKernel::ICLKernel()
-    : _kernel(nullptr), _lws_hint(CLKernelLibrary::get().default_ndrange()), _target(GPUTarget::MIDGARD), _config_id(arm_compute::default_config_id)
+    : _kernel(nullptr), _lws_hint(CLKernelLibrary::get().default_ndrange()), _target(GPUTarget::MIDGARD), _config_id(arm_compute::default_config_id), _max_workgroup_size(0)
 {
 }
 
@@ -163,3 +173,12 @@ GPUTarget ICLKernel::get_target() const
 {
     return _target;
 }
+
+size_t ICLKernel::get_max_workgroup_size()
+{
+    if(_max_workgroup_size == 0)
+    {
+        _max_workgroup_size = CLKernelLibrary::get().max_local_workgroup_size(_kernel);
+    }
+    return _max_workgroup_size;
+}