[SYCL] Repurpose SYCL_CACHE_TRACE to enable fine-grained tracing of SYCL caches

[uditagarwal97]

Currently, we use SYCL_CACHE_TRACE for events in persistent cache only. This PR repurposes SYCL_CACHE_TRACE to also enable tracing of in-memory cache and kernel_compiler.

After this change, SYCL_CACHE_TRACE will accept the following bit-masks:

Bit-mask	Corresponding cache tracing
0x01	Enable tracing of persistent cache
0x02	Enable tracing of in-memory cache
0x04	Enable tracing of kernel_compiler cache

Any valid combination of the above bit-masks can be used to enable/disable tracing of the corresponding caches.

[cperkinsintel]

what is this, anyway? Doesn't it set the default values for these environment vars? But, if so, why was it set to 1 before?

[uditagarwal97]

That's a good question. From what I understand, the syntax is CONFIG(CONFIG_NAME, VALUE_MAX_SIZE_IN_BYTES, COMPILE_TIME_CONFIG_NAME) and VALUE_MAX_SIZE_IN_BYTES is the maximum amount of bytes to read when we read this environment variable from the configuration file.

I do not think there's a default - if I remove this line, I get the following error:

llvm/sycl/source/detail/config.hpp:711:30: error: ‘SYCL_CACHE_TRACE’ was not declared in this scope; did you mean ‘SYCL_UR_TRACE’?
  711 | template <> class SYCLConfig<SYCL_CACHE_TRACE> {

Now, regarding the size, I think it was 1 earlier because this flag was just accepting a boolean - to disable/enable tracing of disk cache. Now, it is accepting an integer so we need to updated the size accordingly. I used 16 bytes previously because I was copying what SYCL_UR_TRACE did. But, now that I think more, I guess 4 bytes should be sufficient.

[steffenlarsen]

Docs LGTM! Tag @jopperm & @sommerlukas for awareness.

[uditagarwal97]

@intel/llvm-gatekeepers the PR is ready to be merged.