Optimize CpuGemmConv2d start-up time

When weight has no holes, we can replace CpuWeightsReshapeKernel with:
 - Collapse by reinterpreting weight's 3 spatial dimensions
 - Perform CpuTranspose

For more details see the documentation in
src/cpu/operators/CpuGemmConv2d.cpp

This is one optimization since the CpuTranspose is better performing
than CpuWeightsReshapeKernel

A second optimization is to fuse this transpose with other weight
transformations (e.g. pretranspose_B_array in CpuGemmAssemblyDispatch)

However this second optimization depends on how the underlying gemm
methods (the fall back path: CpuGemmMatrixMultiplyKernel or the assembly
path: CpuGemmAssemblyDispatch) chooses to fuse the transpose.

Therefore, this patch moves the transpose down from CpuGemmConv2d, to
the individual gemm operators where the fusion decision needs to be
made, by passing an extra "transpose_b" flag to CpuGemm

New transpose_b flag in different scopes (they are all the same, but
with different names because pretranspose_b has a different meaning in
GemmAssemblyDispatch):
GEMMInfo::pretranspose_B -> AsmGemmInfo::transpose_b

New auxilliary tensors holding the transposed b result:
- CpuGemm optimized path: CpuGemmAssemblyDispatch::PrePretransposedB
- CpuGemm fallback path:  CpuGemm::PreTransposedRHS

Note that this patch does not yet have the second optimization
(COMPMID-6595), but it prepares for it.

Relates to COMPMID-6595
Resolves COMPMID-6499

Change-Id: I999a2da9da4b2b15369a3cc06d7872c86e0190ea
Signed-off-by: SiCong Li <sicong.li@arm.com>
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/10526
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Anitha Raj <Anitha.Raj@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/arm_compute/function_info/GEMMInfo.h b/arm_compute/function_info/GEMMInfo.h
index c24762c0aa..a827c79fda 100644
--- a/arm_compute/function_info/GEMMInfo.h
+++ b/arm_compute/function_info/GEMMInfo.h
@@ -105,6 +105,7 @@ public:
      * @param[in] activation_info             (Optional) Activation to apply after the matrix multiplication
      * @param[in] fixed_format                (Optional) Specify the selection of fixed format kernels for variable weights support in GEMM. These kernels expect the weights tensor to be in amemory format that is fixed by the kernel itself. For more information, see arm_compute::WeightFormat.
      * @param[in] weight_format               (Optional) arm_gemm:WeightFormat enumeration requested by the user. Default is arm_compute::WeightFormat::UNSPECIFIED.
+     * @param[in] pretranspose_B              (Optional) Pretranspose matrix B (transposition of its lowest 2 dimensions), in addition to and before, any further transformations of B
      */
     GEMMInfo(bool                       is_a_reshaped,
              bool                       is_b_reshaped,
@@ -118,7 +119,8 @@ public:
              bool                       broadcast_bias          = false,
              const ActivationLayerInfo &activation_info         = ActivationLayerInfo(),
              bool                       fixed_format            = false,
-             arm_compute::WeightFormat  weight_format           = arm_compute::WeightFormat::UNSPECIFIED) noexcept
+             arm_compute::WeightFormat  weight_format           = arm_compute::WeightFormat::UNSPECIFIED,
+             bool                       pretranspose_B          = false) noexcept
         : _is_a_reshaped(is_a_reshaped),
           _is_b_reshaped(is_b_reshaped),
           _reshape_b_only_on_first_run(reshape_b_only_on_first_run),
@@ -130,7 +132,7 @@ public:
           _fp_mixed_precision(fp_mixed_precision),
           _broadcast_bias(broadcast_bias),
           _pretranspose_A(false),
-          _pretranspose_B(false),
+          _pretranspose_B(pretranspose_B),
           _activation_info(activation_info),
           _fixed_format(fixed_format),
           _weight_format(weight_format)
@@ -251,6 +253,8 @@ public:
         _pretranspose_A = flag;
     }
     /** Flag which specifies whether b should be pre-transposed if supported.
+     * More concretely, the "pre-transpose" is the transposition of the b tensor's lowest 2 dimensions
+     * If specified true, this pre-transpose will occur in addition to and before, any further transformations of the b matrix
      *
      * @return True if b should be pre-transposed else false.
      */