Fix oclgrind error on CLGEMMLowp reshaped only RHS quantized per channel

Fix corner case in which the quantization is per channel and OFM == 1
The function can safely set the per_channel quantization flag to false since there is only one output channel
This way, the kernel will avoid adding useless padding to the output multipliers and shifts

Resolve COMPMID-4384

Change-Id: Ic03452bfaf52d1be536cd371721adedd2e580a08
Signed-off-by: Giorgio Arena <giorgio.arena@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/5648
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Georgios Pinitas <georgios.pinitas@arm.com>

2 files changed, 7 insertions, 1 deletions

diff --git a/src/core/CL/kernels/CLGEMMLowpMatrixMultiplyReshapedOnlyRHSKernel.cpp b/src/core/CL/kernels/CLGEMMLowpMatrixMultiplyReshapedOnlyRHSKernel.cpp
index d39900a561..37c11000db 100644
--- a/src/core/CL/kernels/CLGEMMLowpMatrixMultiplyReshapedOnlyRHSKernel.cpp
+++ b/src/core/CL/kernels/CLGEMMLowpMatrixMultiplyReshapedOnlyRHSKernel.cpp
@@ -256,7 +256,7 @@ std::pair<Status, Window> validate_and_configure_window(ITensorInfo *input0, ITe
             window_changed = window_changed || update_window_and_padding(win_out, bias_access);
         }
 
-        if(output_multipliers != nullptr && output_multipliers->dimension(0) > 1)
+        if(output_multipliers != nullptr && output_stage.is_quantized_per_channel)
         {
             AccessWindowHorizontal output_multipliers_access(output_multipliers, 0, num_elems_processed_per_iteration_x);
             AccessWindowHorizontal output_shifts_access(output_shifts, 0, num_elems_processed_per_iteration_x);
diff --git a/src/runtime/CL/functions/CLGEMMLowpMatrixMultiplyCore.cpp b/src/runtime/CL/functions/CLGEMMLowpMatrixMultiplyCore.cpp
index b189955c04..5a9ff7990f 100644
--- a/src/runtime/CL/functions/CLGEMMLowpMatrixMultiplyCore.cpp
+++ b/src/runtime/CL/functions/CLGEMMLowpMatrixMultiplyCore.cpp
@@ -344,6 +344,12 @@ void CLGEMMLowpMatrixMultiplyCore::configure(const CLCompileContext &compile_con
 
         GEMMLowpOutputStageInfo gemmlowp_output_stage = gemm_info.gemmlowp_output_stage();
         gemmlowp_output_stage.output_data_type        = _matrix_a->info()->data_type();
+        if(num_filters == 1)
+        {
+            // Per-channel quantization with OFM == 1 is equivalent to uniform quantization.
+            // Setting this flag to false prevents the kernel from adding useless padding to the output multipliers and shifts
+            gemmlowp_output_stage.is_quantized_per_channel = false;
+        }
 
         gemm_kernel_info.output_stage = gemmlowp_output_stage;