Add kernel and kernel writer skeletons

* Add the skeleton for kernel, kernel writer and their respective
  OpenCL implementation.
* Add method to write code comment and its test.

Resolves: COMPMID-6343
Signed-off-by: Viet-Hoa Do <viet-hoa.do@arm.com>
Change-Id: Ib986228154f7a00da7a5fd3b7105941325fe13b1
Reviewed-on: https://review.mlplatform.org/c/ml/ComputeLibrary/+/9889
Tested-by: Arm Jenkins <bsgcomp@arm.com>
Reviewed-by: Gunes Bayir <gunes.bayir@arm.com>
Comments-Addressed: Arm Jenkins <bsgcomp@arm.com>
Benchmark: Arm Jenkins <bsgcomp@arm.com>
diff --git a/compute_kernel_writer/src/Kernel.cpp b/compute_kernel_writer/src/Kernel.cpp
new file mode 100644
index 0000000..ccc68ec
--- /dev/null
+++ b/compute_kernel_writer/src/Kernel.cpp
@@ -0,0 +1,45 @@
+/*
+ * Copyright (c) 2023 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "ckw/Kernel.h"
+
+namespace ckw
+{
+
+Kernel::Kernel(TargetLanguage language, const std::string &source_code)
+    : _language(language), _source_code(source_code)
+{
+}
+
+TargetLanguage Kernel::target_language() const
+{
+    return _language;
+}
+
+const std::string &Kernel::source_code() const
+{
+    return _source_code;
+}
+
+} // namespace ckw
diff --git a/compute_kernel_writer/src/KernelWriter.cpp b/compute_kernel_writer/src/KernelWriter.cpp
new file mode 100644
index 0000000..eb8399a
--- /dev/null
+++ b/compute_kernel_writer/src/KernelWriter.cpp
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2023 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "ckw/KernelWriter.h"
+#include "ckw/Error.h"
+#include "src/cl/CLKernelWriter.h"
+
+namespace ckw
+{
+
+std::unique_ptr<KernelWriter> KernelWriter::create_instance(TargetArchitecture architecture, TargetLanguage language)
+{
+    switch(language)
+    {
+        case TargetLanguage::OpenCL:
+            // Currently this is the oldest and the only supported GPU architecture.
+            CKW_ASSERT(architecture == TargetArchitecture::GpuArmMaliValhall);
+            return std::make_unique<CLKernelWriter>();
+
+        default:
+            CKW_THROW_MSG("Language not supported!");
+    }
+}
+
+KernelWriter::~KernelWriter() = default;
+
+} // namespace ckw
diff --git a/compute_kernel_writer/src/cl/CLKernelWriter.cpp b/compute_kernel_writer/src/cl/CLKernelWriter.cpp
new file mode 100644
index 0000000..231d321
--- /dev/null
+++ b/compute_kernel_writer/src/cl/CLKernelWriter.cpp
@@ -0,0 +1,64 @@
+/*
+ * Copyright (c) 2023 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "src/cl/CLKernelWriter.h"
+#include "ckw/Error.h"
+
+namespace ckw
+{
+
+CLKernelWriter::CLKernelWriter()
+{
+}
+
+CLKernelWriter::~CLKernelWriter() = default;
+
+std::unique_ptr<Kernel> CLKernelWriter::emit_kernel(const std::string &name)
+{
+    CKW_UNUSED(name);
+    CKW_THROW_MSG("Not implemented!");
+}
+
+void CLKernelWriter::comment(const std::string &text)
+{
+#ifdef COMPUTE_KERNEL_WRITER_DEBUG_ENABLED
+
+    CKW_ASSERT(text.find("\n") == text.npos);
+    CKW_ASSERT(text.find("\r") == text.npos);
+
+    append_code("// ", text, "\n");
+
+#else // COMPUTE_KERNEL_WRITER_DEBUG_ENABLED
+
+    CKW_UNUSED(text);
+
+#endif // COMPUTE_KERNEL_WRITER_DEBUG_ENABLED
+}
+
+const std::string &CLKernelWriter::body_source_code() const
+{
+    return _body_source_code;
+}
+
+} // namespace ckw
diff --git a/compute_kernel_writer/src/cl/CLKernelWriter.h b/compute_kernel_writer/src/cl/CLKernelWriter.h
new file mode 100644
index 0000000..e6f0641
--- /dev/null
+++ b/compute_kernel_writer/src/cl/CLKernelWriter.h
@@ -0,0 +1,91 @@
+/*
+ * Copyright (c) 2023 Arm Limited.
+ *
+ * SPDX-License-Identifier: MIT
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef CKW_SRC_CL_CLKERNELWRITER_H
+#define CKW_SRC_CL_CLKERNELWRITER_H
+
+#include "ckw/KernelWriter.h"
+#include <utility>
+
+namespace ckw
+{
+
+/** OpenCL kernel writer. */
+class CLKernelWriter : public KernelWriter
+{
+public:
+    // =============================================================================================
+    // Construtors and destructor
+    // =============================================================================================
+
+    /** Initialize a new instance of @ref CLKernelWriter class. */
+    CLKernelWriter();
+
+    /** Destructor */
+    ~CLKernelWriter();
+
+    // =============================================================================================
+    // Misc
+    // =============================================================================================
+
+    void comment(const std::string &text) override;
+
+    // =============================================================================================
+    // Code generation
+    // =============================================================================================
+
+    std::unique_ptr<Kernel> emit_kernel(const std::string &name) override;
+
+protected:
+    /** Append the specified code to the kernel body source code. */
+    template <typename T, typename... TArgs>
+    void append_code(T &&code, TArgs &&...args)
+    {
+        append_code(std::forward<T>(code));
+        append_code(std::forward<TArgs>(args)...);
+    }
+
+    /** Append the specified code to the kernel body source code. */
+    template <typename T>
+    void append_code(T &&code)
+    {
+        _body_source_code += std::forward<T>(code);
+    }
+
+    /** Get the current kernel body source code. */
+    const std::string &body_source_code() const;
+
+private:
+    /** This string contains the kernel body source code, not the full CL source code.
+     * The full source code will only be generated when the user calls @ref KernelWriter::emit_kernel.
+     *
+     * In order to add code to this, use @ref CLKernelWriter::append_code.
+     * Do not attempt to concatenate and alter this string directly.
+     */
+    std::string _body_source_code{};
+};
+
+} // namespace ckw
+
+#endif // CKW_SRC_CL_CLKERNELWRITER_H