Add OpenCL trace support

- Adds the file TracyOpenCL.hpp which contains the API to annotate OpenCL applications
- It works in a similar fashion to the Vulkan annotations
- Adds an example OpenCL application in examples/OpenCLVectorAdd
- Adds "OpenCL Context" to the UI
- Manual entry for annotating OpenCL zones

manual/tracy.tex

@@ -1197,6 +1197,16 @@ To mark a GPU zone use the \texttt{TracyVkZone(ctx, cmdbuf, name)} macro, where
 
 You also need to periodically collect the GPU events using the \texttt{TracyVkCollect(ctx, cmdbuf)} macro\footnote{It is considerably faster than the OpenGL's \texttt{TracyGpuCollect}.}. The provided command buffer must be in the recording state and outside of a render pass instance.
 
+\subsubsection{OpenCL}
+
+OpenCL support is achieved by including the \texttt{tracy/TracyOpenCL.hpp} header file. Tracing OpenCL requires the creation of a Tracy OpenCL context using the macro \texttt{TracyCLContext(context, device)}, which will return an instance of \texttt{TracyCLCtx} object that must be used when creating zones. The specified \texttt{device} must be part of the \texttt{context}. Cleanup is performed using the \texttt{TracyCLDestroy(ctx)} macro. Although not common, it is possible to create multiple OpenCL contexts for the same application.
+
+To mark an OpenCL zone one must make sure that a valid OpenCL \texttt{cl\_event} object is available. The event will be the object that Tracy will use to query profiling information from the OpenCL driver. For this to work, all OpenCL queues must be created with the \texttt{CL\_QUEUE\_PROFILING\_ENABLE} property.
+
+OpenCL zones can be created with the \texttt{TracyCLZone(ctx, name)} where \texttt{name} will usually be a descriptive name for the operation represented by the \texttt{cl\_event}. Within the scope of the zone, you must call \texttt{TracyCLSetEvent(event)} for the event to be registered in Tracy.
+
+Similarly to Vulkan and OpenGL, you also need to periodically collect the OpenCL events using the \texttt{TracyCLCollect(ctx)} macro. A good place to perform this operation is after a \texttt{clFinish}, since this will ensure that any previous queued OpenCL commands will have finished by this point. 
+
 \subsubsection{Multiple zones in one scope}
 
 Putting more than one GPU zone macro in a single scope features the same issue as with the \texttt{ZoneScoped} macros, described in section~\ref{multizone} (but this time the variable name is \texttt{\_\_\_tracy\_gpu\_zone}).