Fused GEMM+GEMM (#351)

* initial stub for gemm_gemm_xdl_cshuffle

* set up example code

* compiles

* prevent integer overflow

* harmonize interface between ref_gemm and ref_batched_gemm

* batched_gemm_gemm

* fix example

* host tensor gen: diagonal pattern in lowest two-dimensions only

* make c descriptors containing only integral constants

* clean up

* add BlockwiseGemmXdlops_v2 while exploring an unified approach

* implement proper interface

* tidy up example

* fix compilation warnings

* coarsely controlled 2nd gemm padding

* remove rocm-cmake's hard requirement for certain revision

* clang-format

* resolve merge conflict

* fix compilation error on gfx10

* adds acc0 elementwise op to interface

* add gemm_gemm instances and tests

* avoid LDS data hazard

* fix build

Co-authored-by: Chao Liu <chao.liu2@amd.com>

[ROCm/composable_kernel commit: c20a75b07d]

include/ck/utility/static_buffer.hpp

@@ -1,8 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright (c) 2018-2022, Advanced Micro Devices, Inc. All rights reserved.
 
-#ifndef CK_STATIC_BUFFER_HPP
-#define CK_STATIC_BUFFER_HPP
+#pragma once
 
 #include "statically_indexed_array.hpp"
 
@@ -20,13 +19,6 @@ struct StaticBuffer : public StaticallyIndexedArray<T, N>
 
     __host__ __device__ constexpr StaticBuffer() : base{} {}
 
-    __host__ __device__ constexpr StaticBuffer& operator=(StaticBuffer& y)
-    {
-        StaticBuffer& x = *this;
-        static_for<0, base::Size(), 1>{}([&](auto i) { x(i) = y[i]; });
-        return x;
-    }
-
     template <typename... Ys>
     __host__ __device__ constexpr StaticBuffer& operator=(const Tuple<Ys...>& y)
     {
@@ -201,4 +193,3 @@ __host__ __device__ constexpr auto make_static_buffer(LongNumber<N>)
 }
 
 } // namespace ck
-#endif