Add custom op examples and documentation (#638)

Added step by step instructions for adding custom op in Qeff

---------

Signed-off-by: Rishin Raj <rishinr@qti.qualcomm.com>
Co-authored-by: Hem Agnihotri <hemagnih@qti.qualcomm.com>

Author: quic-rishinr

examples/onboarding_guide/customop/CustomGELU/src/customgelu_aic.cpp

@@ -0,0 +1,23 @@
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+// SPDX-License-Identifier: BSD-3-Clause
+//
+//-----------------------------------------------------------------------------
+
+#include "CustomOpAICInterface.h"
+#include "stddef.h"
+
+extern "C" {
+
+/* The AIC compilation target supports an API similar to the Interpreter API.
+Additionally, threadId, which is the AIC thread ID, is passed.
+Kernel is invoked by four AIC threads with threadId equal to 0, 1, 2, and 3. */
+
+void CustomGELUAIC(
+	const CustomOpContext *ctx, 
+	const int32_t threadId)
+{
+}
+
+}

examples/onboarding_guide/customop/CustomGELU/src/customgelu_functions.cpp

@@ -0,0 +1,74 @@
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+// SPDX-License-Identifier: BSD-3-Clause
+//
+//-----------------------------------------------------------------------------
+
+#include "CustomOpFunctions.h"
+#include "CustomOpInterpreterInterface.h"
+#include "CustomOpTileConfigHelpers.h"
+#include "CustomOpTypes.h"
+
+#include <string.h>
+
+extern "C" {
+bool customOpVerify(
+	const CustomOpPropertiesHandle *const opProp)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	return true;
+}
+
+const char * customOpSelectImpl(
+	const CustomOpPropertiesHandle *const opProp, 
+	const CustomOpKernelInfo *const kernelInfos, 
+	const int32_t numKernels, 
+	const char *backend)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	/* For AIC pick '<OpName>AIC', for Interpreter pick '<OpName>Interpreter' */
+	if (strcmp(backend, "AIC") == 0)
+	{
+		return "";
+	}
+	else if (strcmp(backend, "Interpreter") == 0)
+	{
+		return "";
+	}
+	return nullptr;
+}
+
+bool customOpInferShape(
+	CustomOpPropertiesHandle *const opProp)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	return false;
+}
+
+bool customOpSetProperties(
+	CustomOpPropertiesHandle *opProp)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	return false;
+}
+
+bool customOpMapTiles(
+	CustomOpPropertiesHandle *opProp)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	return false;
+}
+void customOpDeallocateMemory(
+	CustomOpPropertiesHandle *opProp)
+{
+	/* Refer to function declaration at CustomOpFunctions.h for usage. */
+	
+	CustomOpTileConfigHelpers::destroyTileConfigsAndMergeConfigs(opProp);
+}
+}

examples/onboarding_guide/customop/CustomGELU/src/customgelu_interpreter.cpp

@@ -0,0 +1,33 @@
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries.
+// SPDX-License-Identifier: BSD-3-Clause
+//
+//-----------------------------------------------------------------------------
+
+/*
+* This file can be compiled separately and can be loaded using dlopen
+* Compilation command: (tried with gcc 5.5)
+* g++ -shared -std=c++11 -fPIC -o <opName>_lib.so <opName_functions>.cpp <opName_interpreter>.cpp -I/opt/qti-aic/dev/inc
+* for example: g++ -shared -std=c++11 -fPIC -o reluop_lib.so reluop_functions.cpp reluop_interpreter.cpp -I/opt/qti-aic/dev/inc
+*/
+
+#include "CustomOpInterpreterInterface.h"
+
+extern "C" {
+void CustomGELUInterpreter(
+	CustomOpContext *ctx)
+{
+	/* The interpreter implementation is provided to the compiler as a shared library
+	(or collection of shared libraries). Each shared library can contain multiple
+	versions (flavors) of implementations of the operation, refered onwards as kernels.
+	A kernel is selected at model compilation time by the selection function. The
+	developer is responsible for compilation of these shared libraries. As the interface
+	is C, the shared libraries can be compiled by various compilers (GCC, CLANG, etc).
+	In addition, as these shared libraries are running on the Host CPU, the developer
+	can open files, dump results, use stdout/stderr for printing debug messages, etc.
+	This makes the Interpreter implementation a very effective way for debugging the
+	operation functionality as part of model execution. The signature of the
+	kernel (implementation) is generic, and fits any custom operation. */
+}
+}